ez isomerism homework

E -1-bromo-1-chloro-2-fluoro-2-iodoethene

The skeletal formulae would be written as   NOTE : The IUPAC recommend that the terms geometrical/geometric isomerism are NOT used   but to use the stereoisomerism classification terms E/Z stereoisomerism or E-Z isomerism . The E/Z notation is replacing the limited cis/trans notation in assigning names to a particular stereoisomer. However cis/trans nomenclature is in widespread use so it will be acknowledged in parallel with the E/Z convention where appropriate.

TOP OF PAGE and sub-index

14.2(d) E/Z isomers of some hydrocarbon alkenes and halogenated alkenes

Note : cis-trans  isomerism is sometimes defined as a special type of  E / Z isomerism  in which there is a non-hydrogen group and a hydrogen atom attached to each C of a C=C double bond. This means the cis isomer is the Z  isomer with the H atoms on each carbon on the same side and the trans isomer will be the E isomer with the hydrogens on opposite sides of the double bond. BUT, the terms cis and trans are sometimes applied to where there are only two substituents like cis/trans 1,2-dichloroethene (above) and cis/trans but-2-ene. At other times, if the same substituent is on both carbon atoms of the C=C bond, if both of these substituents are on the same side its the cis isomer, if diagonally across the double bond its the trans isomer. The terms cis/trans have been quite loosely used, which is why the E/Z system is the best and recommended by the IUPAC, so you must know how to use the E/Z rules and correctly designate the E or Z isomer , it covers anything you will come across.

I've started off by repeated the but-2-ene example in more detail.

(priority -CH 3 > -H)

(ball and stick model 2), and the

(ball and stick model 1)

both E/Z isomeric forms of but-2-ene

However, in order for E/Z stereoisomers to exist there must be two different atoms/groups attached to both carbon atoms of the C=C carbon double bond or two adjacent carbons in a substituted cycloalkane.

Note that E-but-2-ene and Z-but-2-ene are NOT mirror images of each other.

If the groups are not different, they have the same priority!

This is why structural isomer methylpropene (model 3 above) cannot exhibit E/Z isomerism, both carbon atoms of the double bond have the same two atoms/groups attached to them.

Again, this is why but-1-ene   , with two hydrogens on the right-hand carbon of the double bond, cannot exhibit E/Z isomerism, but it is a structural isomer of the E/Z isomers of but-2-ene and methylpropene.

The same argument applies to 2-methylbut-2-ene It has two methyl groups attached to the same right-hand carbon atom of the C=C double bond, you cannot make two spatially different molecules. However the isomeric pent-2-ene would exhibit E/Z isomerism.

(i) that you cannot superimpose one E/Z isomer on the other - proof they are spatially different isomers. (ii) the structural formula cannot be used to indicate E/Z isomers, the molecule must be represented by the full displayed 2D/3D structural formula.

The three most common situations you are likely to encounter are > C=C < or a > C=N - double bond and around a C-C single bond in cycloalkanes . In both cases the energy required is too high to allow free rotation around the double bond BUT free rotation is possible around single bonds (C-C, C-O etc.) e.g. alkyl groups around the C-C single bonds in non-cyclo linear/branched alkanes. If two identical atoms/groups are attached to the same carbon atom of a C=C double bond, you cannot have geometrical isomers e.g. those with R 2 C=C< or R 2 C=N- where R = R. See the diagram below. The 'old' nomenclature term cis often means the same substituents are on the same side of the double bond and trans when they are on opposite sides. Under the E/Z notation cis is now Z and trans is now E . In a sense cis/trans isomers were a special case of a substituent and a hydrogen atom on each carbon of the C=C double bond. E/Z configuration assignment is absolutely necessary when there 3 or 4 different substituents on the C=C group (again, see the diagram below) Shown below are some more i ntroductory exemplar diagrams to illustrate whether E-Z isomers can exist or not and how to use the modern E/Z isomerism notation-designation-assignment of absolute configuration.

Lower left example: (E)-1-bromo-1-chloropropene and (Z)-1-bromo-1-chloropropene Lower right example: E-3-methylpent-2-ene and Z-3-methylpent-2-ene (repeated further down with skeletal formulae) To understand the two lower left and right examples apply the Priority Rules to alkenes for E/Z ('geometrical') isomerism: For each carbon of the double bond the higher priority atom/group is worked out. The Z isomer is where both highest priority groups are on the same side of the double bond (includes all cis configurations of the old convention). The E isomer is where the two highest priority atoms/groups are diagonally opposite each other on different sides of the plane of the double bond system (includes all trans isomers of the old convention). (Note: In terms of the two highest priority atoms or groups, E, ' on opposite sides ', comes from the German word entgegen , meaning 'opposite' and the Z ' on the same side ' comes from the German word zusammen meaning 'together') More alkene examples of E/Z isomerism 3-methylpent-2-ene , can be drawn as E/Z isomers using structural and skeletal formula   , , E-3-methylpent-2-ene and   , Z-3-methylpent-2-ene Note the priority order CH 3 CH 2 > CH 3 > H from the Cahn-Ingold-Prelog priority rules  ( 6 C 6 C > 6 C > 1 H)

the E/Z isomers of

Z-hept-2-ene and E-hept-2-ene (cis and trans hept-2-ene) Cahn-Ingold-Prelog priority rule:  CH 3 CH 2 CH 2 CH 2 > CH 3 > H

and the E/Z isomers of E-3-methylhex-3-ene     and    Z-3-methylhex-3-ene Cahn-Ingold-Prelog priority rule:  CH 3 CH 2 > CH 3 > H  ( 6 C 6 C > 6 C > 1 H)

4-methylpent-2-ene , , has E/Z isomers: Z /cis- , , E /trans- , Cahn-Ingold-Prelog priority rule: (CH 3 ) 2 CH- > CH 3 - > H-  ( 6 C 6 C > 6 C > 1 H) Z-4-methylpent-2-ene and E-4-methylpent-2-ene

3,4-dimethylpent-2-ene , has two E/Z isomers: E -3,4-dimethylpent-2-ene , and Z -3,4-dimethylpent-2-ene Cahn-Ingold-Prelog priority rule: (CH 3 ) 2 CH- > CH 3 - > H-  ( 6 C 6 C > 6 C > 1 H)

4,4-dimethylpent-2-ene ,   E/Z isomers: Z /cis- , and E /trans- Cahn-Ingold-Prelog priority rule: (CH 3 ) 3 CH- > CH 3 - > H-  ( 6 C 6 C > 6 C > 1 H)

3-ethylpent-2-ene , ,   no E/Z isomers because there are two identical (ethyl) groups attached to the same (left) carbon of the double bond

Hex-2-ene , Z-hex-2-ene / cis-hex-2-ene , , and E-hex-2-ene /  trans-hex-2-ene , ,   Cahn-Ingold-Prelog priority rule: CH 3 CH 2 CH 2 - > CH 3 - > H-  ( 6 C 6 C > 6 C > 1 H)

hept-3-ene , , has two E/Z isomers: Z-hept-3-ene / cis-hept-3-ene and E-hept-3-ene / trans-hept-3-ene   Cahn-Ingold-Prelog priority rule: CH 3 CH 2 CH 2 - > CH 3 CH 2 - > H-  ( 6 C 6 C 6 C > 6 C 6 C > 1 H)

14.2(e) Further case studies of E/Z stereoisomerism

BUT, now including discussing similarities & difference in physical & chemical properties of the E/Z isomers

Case studies of E/Z (geometric) isomerism:

2a.1 C 4 H 8 *  2a.2 HOOC-CH=CH-COOH * 2a.3 ClCH=CHCl   *  2a.4 di-substituted cycloalkanes

2a.5 azo (-N=N-) and R 2 C=N-X compounds   *  2a.6 Dienes   *  2a.7 Trans fats

2a.8 But-2-enoic acid and 2-methylbut-2-enoic acid   *  2a.9 Organic analogues of the anti-cancer drug cis-platin

2a.10  Cis/trans retinal - biochemistry of the eye   *  Definition of diastereoisomers

Case study 2a.1 Isomers of C 4 H 8 , cis/trans or Z/E-but-2-ene and other alkenes

Ball and stick models for three isomers of C 4 H 8 1. Z-but-2-ene (cis isomer),   2. E-but-2-ene (trans isomer),  3-methylpropene (cannot exhibit E/Z isomerism) Priority order: -CH 3 > H (since at. no. of carbon 6 > 1 for hydrogen) (1) Z-but-2-ene (cis) (bpt 4 o C)   , , (Z-2-butene) The Z isomer has the two highest priority groups on the same side of the plane of the C=C double bond. (2) E-but-2-ene (trans) (bpt 1 o C) , , (E-2-butene) The E isomer has the two highest priority groups on opposite sides of the carbon = carbon double bond. (1) and (2) are very similar physically (e.g. colourless gases and very low bpt) and chemically (e.g. alkene electrophilic addition reactions). Note that there are four other physically similar isomers of C 4 H 8 namely, (3) 2-methylpropene (bpt -7 o C, chain isomer) (4) but-1-ene (bpt -6 o C, position of C=C isomer) (5) methylcyclopropane and (6) cyclobutane (bpts 5 o C and 13 o C, and are alkane functional group isomers of alkenes 1 to 4) BUT non of (3) to (6) can form E/Z isomers . (3) and (4) would be chemically similar to (1) and (2) being alkenes and undergo many addition reactions, but (5) and (6) have no 'alkene' chemistry but just the limited chemistry of alkanes e.g. uv chlorination as well as the combustion, which they all readily undergo!

Similarly ...

, , E-3-methylpent-2-ene

and   , Z-3-methylpent-2-ene

BUT , 2-methyl-2-pentene does NOT exhibit E/Z isomerism because two identical (CH 3 ) groups are attached to the same carbon atom of the double bond.

4,4-dimethylpent-2-ene ,   has two E/Z isomers: Z-4,4-dimethylpent-2-ene (cis), and E- 4,4-dimethylpent-2-ene (trans)

Case study 2a.2  trans/cis or Z/E-but-2-ene-1,4-dioic acid, HOOC-CH=CH-COOH

(butenedioic acids, old names given below ). Substituent group priority -COOH > H On heating the trans form (1) fumaric acid ) now called E-but-2-ene-1,4-dioc acid , it proves difficult to change it into the cyclic anhydride (3) below. Z-but-2-ene-1,4-dioc acid (2) cis form, maleic acid (3)   + H 2 O

The skeletal formulae of the three molecules mentioned

However, if the Z (cis) form (2) is heated, it readily changes into the cyclic acid anhydride (3). Not only does the restricted rotation about the C=C bond cause the existence of E/Z geometrical isomers, but in this case you can only readily get the elimination of water when the two -OH groups are on the same side of the planar >C=C< system, as in the cis/Z form (2). In the trans/E form (1) the elimination reaction is stereochemically hindered because the -OH so far apart. However, both (1) and (2) undergo the same electrophilic addition reactions of the 'alkene' double bond, >C=C< and the same reactions of the carboxylic acid group -COOH.

Some physical differences.

* Sometimes the trans isomer has the higher symmetry and packs more closely into a crystal lattice, increasing the intermolecular forces, and this tends to increase melting points and density but decrease solubility as solvation is not as energetically favourable. The physical differences may be partially explained by the different polarities of the molecules and the orientation of hydrogen bonding, either in the crystal lattice or when dissolved in water. ( * unfortunately, there are many exceptions to this 'rough rule of thumb', so beware ). (1) The E/trans form: d = 1.64 gcm -3 , solubility in water 0.7g/100 cm 3 at 25 o C, melting point 287 o C,  (2) The Z/cis form: d = 1.59 gcm -3 , solubility in water 78.8g/100 cm 3 at 25 o C, melting point 130 o C,

Case study 2a.3   Physical properties of cis/trans or Z/E-1,2-dichloroethene

Ball and stick models of halogenated ethene molecules. 1. 1,2-dichloroethene H 2 C=CCl 2 ,    2. 2-bromo-1,1-dichloroethene CCl 2 C=CHBr (neither can exhibit E/Z isomerism) 3. E-1,2-dichloroethene (trans stereoisomer of ClCH=CHCl ),   4. Z-1,2-dichloroethene (cis isomer of ClCH=CHCl ) The C δ+ -Cl δ- bond is polar due to the difference in electronegativity between carbon and chlorine (Cl > C) and this partially accounts for the small differences in physical properties.

Cahn-Ingold-Prelog priority rule:  17 Cl > 1 H

and there is positional isomer (3) shown below.

The skeletal formulae of the three molecules mentioned. All three isomers are chemically similar e.g. the electrophilic addition reactions of alkenes.

Case study 2a.4   of E/Z isomerism with 1,2- or 1,3-disubstituted cycloalkanes - examples based on cyclopropane, cyclobutane, cyclopentane and cyclohexane

E/Z isomers can exist in 1,2-disubstituted cyclopropanes * and cyclobutanes * because the -C-C- ring structure inhibits rotation about the C-C bonds. These are alicyclic compounds - cyclo-aliphatic compounds with a carbon chain ring of =>3 carbon atoms. In order to change from one E/Z isomer to another, you would have to break at least one strong covalent bond e.g. the C-C bond of the ring itself.   * Alicyclic compounds means cyclo-aliphatic. If the 1,2-substituents are on the same side of the plane of the triangle/square of carbon atoms you get the Z (cis) form, if the are on opposite sides you get the E (trans) form. Disubstituted cyclopropanes (1) 1,2-dichlorocyclopropane can give E/Z isomers and the group priority is Cl > H   Z-1,2-dichlorocyclopropane (cis), both highest priority groups on the same side of the 'plane' of the cyclopropane ring. Cahn-Ingold-Prelog priority rule:  17 Cl > 1 H

and E-1,2-dichlorocyclopropane (trans), the highest priority groups are on opposite sides of the 'plane' of the cyclopropane ring.   to help you think in 3D !

(2) 1,1-dichlorocyclopropane is a positional isomer of C 3 H 4 Cl 2 , and cannot exhibit geometrical isomerism.   Dis ubstituted cyclobutanes (3) 1,2-dibromocyclobutane , likewise can give ...     ( Z isomer , cis) and (7) ( E isomer, trans)

(4) or (9) 1,1-dibromocyclobutane, is a positional isomer of C 4 H 6 Br 2 and cannot exhibit E/Z (geometrical) isomerism because the two bromine atoms are attached to the same carbon.   (5) 1,3-dibromocyclobutane is also positional isomer of C 4 H 6 Br 2 and can exhibit E/Z (geometric) isomerism.   Z/cis , with the two Br atoms on same side of the plane of the C4 ring, and E/trans with the two Br atoms on each side of the plane of the cyclobutane ring. Note 1: The molecular formulae C 3 H 4 Cl 2 and C 4 H 6 Br 2 can theoretically give rise to other functional group/positional/E/Z (trans/cis) isomers in the form of non-cyclic alkenes e.g. (6) ClCH 2 CH=CHCl (1,3-dichloropropene) or (7) CH 3 CHBr=CHBrCH 3 (2,3-dibromobut-2-ene) etc. etc! both of which can exhibit E/Z isomerism.

Note 2 : Strictly speaking the 4 carbon ring of cyclobutanes is NOT planar, in fact the 'V' of two of the carbon atoms is bent at 26 o from the 'V' of the other two carbons. However, using planar projections it is possible to work out and illustrate the E/Z isomers of cyclobutanes.

Disubstituted cyclopentanes - dichlorocyclopentanes (ball and stick models below)

1. Chlorocyclopentane C 5 H 9 Cl : This has no stereoisomers, but is structurally isomeric with monochloropentenes. 2. 1,1-dichlorocyclopentane C 5 H 8 Cl 2 : This almost has a plane of symmetry and does not have any stereoisomers, but it is a positional structural isomer of C 5 H 8 Cl 2 . For 3. and 4. the restricted rotation about the single C-C bonds allows E/Z stereoisomers to exist, they are also structural isomers of C 5 H 8 Cl 2 .

3. Z-1,2-dichlorocyclopentane C 5 H 8 Cl 2 :

This is the Z isomer (cis in old terms). Both chlorine atoms are above the 'almost' flat plane of the ring of five carbon atoms. The carbon atoms of the C-Cl bonds are also chiral , so the molecule can exhibit R/S isomerism .

4. E-1,2-dichlorocyclopentane C 5 H 8 Cl 2 :

This is an E isomer (trans in old terms). One chlorine atom is above the plane of the carbon atom ring and the other chlorine is below the plane. Again, the carbon atoms of the C-Cl bonds are also chiral , so the molecule can exhibit R/S isomerism .

3. and 4. are formed when chlorine electrophilically adds to cyclopentene.

+ Cl 2   ====> 

More advanced note:

The two C-Cl stereocentres give rise to E/Z isomerism, but they are also chiral carbon stereocentres which means there are R/S isomers .

Disubstituted cyclohexanes

e.g. the E/Z isomers of 1,2-dibromocyclohexane.   +  Br 2   ===>  Unsaturated cyclohexene readily undergoes electrophilic addition of bromine to yield saturated 1,2-dibromocyclohexane.  However, the 'flat' skeletal formula doesn't tell the whole story. Just like the other 1,2 or 1,3 disubstituted cycloalkanes, the product can exhibit E/Z isomerism. Priority here is: 35 Br  >  6 C  >  1 H   but only the Br and H need be considered.

A good excuse to play with my model kit, its the only toy I possess! chair confirmation diagrams?

A conventional simplified 2D diagram, but remember the hexagonal ring of carbon atoms is NOT planar (more 'chair' shaped), never-the-less it is ok to talk about and 'above' and 'below' the ring to distinguish the spatial positions of the bromine atoms.

The Z (cis) and E (trans) isomers of 1,2-dibromohexane. The two bromine atoms have the highest priority. 2D diagram For both diagrams: on the left is Z-1,2-dibromocyclohexane, with both two bromine atoms above the hexagonal ring (which isn't quite planar - in fact all the C-C-C, C-C-H, H-C-H, C-C-Br and H-C-Br bond angles are ~109 o ). On the right is  E-1,2-dibromocyclohexane, with one bromine atom above the hexagonal ring and one bromine atom below the hexagonal ring. Similar to the previous example, the two C-Br stereocentre carbon atoms give rise to E/Z isomers, but they are also chiral carbon stereocentres which means there are R/S isomers too. In fact both E/Z isomers have the two R/S isomers (enantiomers) and this applies to all 1,2-disubstituted cyclohexane molecules,  so things are quite complicated and a full analysis is beyond the scope of pre-university organic chemistry.

Case study 2a.5   Isomerism in azo (-N=N-) and R 2 C=N-X compounds

Organic (or inorganic) compounds of the structure R-N=N-R' (e.g. aromatic azo dyes) can exist as cis and trans isomers in just the same way as alkenes, where R or R' = H, alkyl, aryl group etc. R can be different or the same as R' . Stereochemically, the lone pairs on the nitrogen effectively behave as an atom bonding pair of electrons in determining the trigonal planar orientation of the -N= bonds and the lone pair of electrons on the nitrogen . Three groups of electrons around an atom X, always give a trigonal planar arrangement around the central atom >X-. The double bond, N=N or C=N, ensures that too high an energy is required for ready rotation about the double bond . The Z/cis and E/trans forms will have different physical properties such as melting/boiling points. Examples of -N=N- systems : (1) ( Z/cis ) and (2) ( E/trans )   ( all R-N=N-R' bond angles are about 120 o ) Examples of >C=N- systems Carbonyl compounds like aldehydes and ketones undergo condensation reactions of the type RR'C=O + H 2 N- X ==> RR'C=N- X + H 2 O   where R is different to R' and = H , alkyl or aryl etc. geometrical isomers can occur . and when X = H (ammonia), alkyl (aliphatic primary amine), aryl (aromatic primary amine), OH (hydroxylamine), NH 2 (hydrazine), NHC 6 H 3 (NO 2 ) 2 (2,4-dinitrophenylhydrazine). If for (3) and (4) if in priority R' > R (e.g. CH 3 CH 2 > CH 3 )

(i.e. R' as a higher ranking group than R) When R = R' i.e. (5) geometrical isomerism is not possible . ( Note: all >C=N- X angles are about 120 o )

Case Study 2a.6 Dienes can also exhibit E/Z stereoisomerism

, Z -buta-1,3-diene (cis), unstable, 2%, low activation of rotation to give the E isomer. and , E -buta-1,3-diene (trans), much more stable, 98%, in dynamic equilibrium with the Z isomer. In this case the E/Z designation is based on the central C-C single carbon-carbon bond and therefore rotation is much easier and the E stereoisomer is the more stable configuration.

Case study 2a.7 Trans fats

Many natural oils and fats are esters of propane-1,2,3-triol (glycerol) and long saturated and unsaturated chain fatty acids - sometimes referred to as triglyceride esters. Animal fats can be mainly saturated, but vegetable oils are unsaturated. Any unsaturated fats or oils can exist as E/Z isomers (trans/cis isomers). The terms mono, di or tri-unsaturated fatty acids refer to the number of alkene groups in the fatty acid. In the natural oils the component fatty acids are the Z isomers (cis isomers) and are considered to be healthy in your diet. Each carbon of the C=C double bond has one hydrogen atom attached to it. However, when an unsaturated oil or fat is partially hydrogenated with a nickel catalyst some of the double bonds are broken. This allows rotation around a single carbon-carbon bond, the double bond reforms and the E isomer (trans isomer) is formed - the more unhealthy E/Z isomer! These trans fatty acids are considered more harmful in your diet than the original cis fatty acids. Diagram showing the structure of a typical triglyceride ester of saturated, monounsaturated and polyunsaturated fatty acids. A possible change from the Z- (cis) linkage to an E- (trans) linkage is shown.

Comparison of oil and fat structures not showing the stereochemical structure Animal fats are mainly saturated fats with no carbon = carbon double bonds in the fatty acid chain and are low melting solids at room temperature.

The 'long–chain fatty acids' can be unsaturated , with one or more C=C double bonds , and so forming unsaturated oils or fats e.g. the triglyceride formed from oleic acid. Vegetable oils are usually viscous liquid at room temperature.

A simple (non-stereochemical) diagram showing several points of 'unsaturation' - the C=C carbon-carbon double bonds in the fatty acid chain.

Case study 2a.8 But-2-enoic acid and 2-methylbut-2-enoic acid

These are monounsaturated monocarboxylic acids. The E/Z isomers of but-2-enoic acid: The E/Z (trans/cis) isomers of but-2-enoic acid, structural formula, CH 3 CH=CHCOOH

The priority rule for E/Z assignment:  8 O 6 C (COOH)  >  6 C (CH 3 )  >  1 H E-but-2-enoic acid (trans isomer), melting point 70-73 o C, boiling point 185-189 o C, density 1.02 g/cm 3 , pK a = 4.69 It has the higher melting point because the molecules can pack more closely together than the Z isomer, so increasing the intermolecular forces, hence increase in both melting and boiling point.

Z-but-2-enoic acid (cis isomer), melting point 15 o C, boiling point 168-169 o C, density 1.03 g/cm 3 , pK a = ?

It has the lower melting point because the molecules cannot pack more closely together than the E isomers, so decreasing the intermolecular forces - with both the methyl group and the carboxylic acid group on the same side of the >C=C< bond the molecules are pushed a bit further apart.

The E/Z isomers of but-2-enoic acid will have different crystal structures, with differences in intermolecular forces, leading to different physical properties like melting point, boiling point and density, but the solubility in water would remain the same.

You would expect them to have very similar chemical reactions e/g/ of the alkene group or carboxylic acid group.

The E/Z isomers of but-2-enoic acid: a similar situation to but-2-enoic acid

The E/Z (trans/cis) isomers of 2-methylbut-2-enoic acid, structural formula, CH 3 CH=C(CH 3 )COOH The priority rule for E/Z assignment:  8 O 6 C (COOH)  >  6 C (CH 3 )  >  1 H E-2-methylbut-2-enoic acid (trans form, commonly known as Tiglic acid ) Tiglic acid is found in croton oil (from the seeds of the Croton tiglium tree) and is volatile crystallisable material with a sweet, warm and spicy odour. It is carcinogenic and is used in cancer research. Tiglic acid melts at 64 o C, higher than Angelic acid , pK a = 4.96, slightly soluble in cold water.

Z-2-methylbut-2-enoic acid (cis form, commonly known as Angelic acid )

Angelic acid is found as the acid or as an ester in the roots of the Angelica archangelica plant. Angelic esters are active components in many herbal medicines for gout, fevers and pains. It readily isomerises to give the trans Tiglic acid . Angelic acid is a volatile solid with a biting taste and pungent sour odour and forms colourless crystals. Angelic acid is a volatile solid with a biting taste and pungent sour odour and forms colourless. It melts at 46 o C and pK a = 4.97, both isomers of similar weak acid strength, slightly soluble in hot water. Angelic acid melts at a lower temperature than Tiglic acid because its molecules cannot pack as closely together as those in Tiglic acid . The decreasing the intermolecular forces - with both the methyl group and the carboxylic acid group on the same side of the >C=C< bond, the molecules are pushed a bit further apart, reducing the intermolecular forces, reducing the energy needed for any phase change.

Tiglic acid and Angelic acid are both produced in the defensive secretions of many beetles.

Its amazing how the same molecules crop in quite different living organisms - molecular evolution!

2a.9 Organic analogues of the anti-cancer drug cis-platin

Platinum(II) complexes are used to prepare anti–cancer drugs used in chemotherapy.  One example is the compound cis–diamminedichloroplatinum(II), [Pt(NH 3 ) 2 Cl 2 ] 0 , (known as cisplatin).  Cisplatin is a much more effective anti-cancer drug than transplatin.

Cis-platin (Z-platin) and trans-platin (E-platin), square planar neutral complexes.  The square planar bond arrangement allows the existence of E/Z isomers , which would not exist if the bonds around the platinum ion where arranged tetrahedrally. For more see my Transition metal notes on platinum Many organic analogues have, and are, being tested for their anti-cancer properties, by replacing  the ammonia group with an aliphatic amine or more complex amines that can act as an electron pair donating ligand. A huge number of Pt(II) complexes have been synthesised, many with the general formula [(RR'HN:) 2 PtCl 2 ], where R and R' are organic groups, R and R' can be the same e.g. the 'simple' E (trans) and Z (cis) complexes with ethylamine and 1,2-diaminoethane (monodentate and bidentate ligand) shown below, but many have much more complicated organic ligands.

In most case the Z (cis) E/Z isomer is the most effective as an anti-cancer chemotherapeutic agent but the medical situations are complex and chemotherapy has its obvious side-effects like loss of hair. A bit of biochemistry: These complexes interfere with the DNA repair mechanisms in a cell and the DNA damage causes the cancer cell to undergo apoptosis - a kind of cell death, thus preventing cell division.

2a.10   Cis/trans retinal - a biochemistry aspect of the eye   (amazing! - fascinating!)

Retinal (retinaldehyde) is a complex unsaturated aliphatic aldehyde that is found in the receptor cells of the retina in the human eye. In retinal photoreceptor cells, the 'polyene' chromophore molecule retinal bound to proteins called opsins Opsins are the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision) in the retinal photoreceptor cells.   The extended alternating C-C single and C=C double bond system in retinal forms the basis of the conjugated chromophore - in fact the pi orbital overlaps will also include the C=O bond of the aldehyde group too.

Retinal is an example of where E/Z isomerisation has an important biological role and involves the interchange of the E and Z isomers (trans and cis) of retinal.

Retinal is the light-sensitive component of rod and cone photoreceptors in the retina of the eye.

When cis-retinal absorbs a photon of visible light the pi bond breaks and trans-retinal is formed (in 2 x 10 -11 seconds).

This configuration change pushes against an opsin protein in the retina, which triggers a chemical signalling cascade, which can result in perception of light or images by the human brain. In other words the change in shape of the retinal molecules causes a nerve impulse to be sent to the brain.

The above simplified diagram (adapted from Wikipedia) shows the molecular, and reversible, transformation between Z-retinal (cis-retinal) and E-retinal (trans-retinal) triggered by a single photon. An enzyme can then transform the trans-retinal back into cis-retinal, which can then interact again with another incoming photon of visible light impacting on the retina. The absorbance spectrum of the chromophore depends on its interactions with the opsin protein to which it is bound, so that different retinal-opsin complexes will absorb photons of different wavelengths (i.e., different colours of light). See the absorption spectra of the rod and cone photopigments of the eye .

Diastereomers (in case you come across the terms):

Diastereomers (diastereoisomers) are a type of a stereoisomer. Diastereomers are defined as non-mirror image non-identical stereoisomers Diastereomerism occurs when two or more stereoisomers of a compound have different configurations at one or more of the equivalent stereocenters and are NOT mirror images of each other . E/Z isomers are examples of diastereoisomers, and, as you will see, they are NOT mirror images of each other (BUT R/S isomerism does involve non-superimposable mirror image molecules. I will not being using these terms again on this page and I don't think they are needed for UK A Level Chemistry.

what is stereoisomerism in organic chemistry? what are cis/trans isomers? why can E/Z isomers exist? why is the interconversion of cis/trans isomers difficult? describe how to use the Cahn-Ingold-Prelog priority sequence rules for E/Z (sis/trans isomers), how do you define stereoisomerism for E/Z or cis/trans isomers of a given molecular formula? give the names and structures of the E/Z cis/trans isomers of molecular formula C4H8 butenes, give the names and structures of the E/Z cis/trans isomers of molecular formula C3H4BrCl, give the names and structures of the E/Z cis/trans isomers of molecular formula C6H12 alkenes, give the names and structures of the E/Z cis/trans isomers of molecular formula C7H14 heptenes, give the names and structures of the E/Z cis/trans isomers of molecular formula C4H4O4 unsaturated dicarboxylic acids, give the names and structures of the E/Z cis/trans isomers of molecular formula C2H2Cl2 dichloroethene, give the names and structures of the E/Z cis/trans isomers of disubstituted cycloalkanes of molecular formula C3H4Cl2 dichlorocyclopropane, give the names and structures of the E/Z cis/trans isomers of molecular formula C4H6Br2 dibromocyclobutane, give the names and structures of the E/Z cis/trans isomerism of the isomers of azo compounds advanced level chemistry Cahn-Ingold-Prelog Priority Rules for AQA AS chemistry, Cahn-Ingold-Prelog Priority Rules for Edexcel A level AS chemistry, Cahn-Ingold-Prelog Priority Rules for A level OCR AS chemistry A, Cahn-Ingold-Prelog Priority Rules for OCR Salters AS chemistry B, Cahn-Ingold-Prelog Priority Rules for AQA A level chemistry, Cahn-Ingold-Prelog Priority Rules for A level Edexcel A level chemistry, Cahn-Ingold-Prelog Priority Rules for OCR A level chemistry A, Cahn-Ingold-Prelog Priority Rules for A level OCR Salters A level chemistry B Cahn-Ingold-Prelog Priority Rules for US Honours grade 11 grade 12 Cahn-Ingold-Prelog Priority Rules for pre-university chemistry courses pre-university A level revision notes for Cahn-Ingold-Prelog Priority Rules  A level guide notes on Cahn-Ingold-Prelog Priority Rules for schools colleges academies science course tutors images pictures diagrams for Cahn-Ingold-Prelog Priority Rules A level chemistry revision notes on Cahn-Ingold-Prelog Priority Rules for revising module topics notes to help on understanding of Cahn-Ingold-Prelog Priority Rules university courses in science careers in science jobs in the industry laboratory assistant apprenticeships technical internships USA US grade 11 grade 11 AQA A level chemistry notes on Cahn-Ingold-Prelog Priority Rules Edexcel A level chemistry notes on Cahn-Ingold-Prelog Priority Rules for OCR A level chemistry notes WJEC A level chemistry notes on Cahn-Ingold-Prelog Priority Rules CCEA/CEA A level chemistry notes on Cahn-Ingold-Prelog Priority Rules for university entrance examinations with advanced level chemistry

Personalised lessons and regular feedback to ensure you ace your exams! Book a free consultation today

100+ Video Tutorials, Flashcards and Weekly Seminars

Gain hands-on experience of how physics is used in different fields. Experience life as a uni student and boost your university application with our summer programme!

• Revision notes >
• A-level Chemistry Revision Notes >
• AQA A-Level Chemistry Revision Notes

Introduction to Organic Chemistry - E/Z Isomerism (A-Level Chemistry)

E/z isomerism, stereoisomerism.

Stereoisomers are molecules with the same molecular formula but differing positions in space. There are two types of stereoisomerism: E/Z isomerism (which we will cover in more detail in this chapter) and optical isomerism (which you will meet later).

• E/Z isomerism occurs in alkenes. Alkanes are unsaturated hydrocarbons with C=C bonds and general formula CnH2n.
• E/Z isomerism occurs due to restricted rotation about C=C double. C=C double bonds contain both σ and π bonds . The π bonds arise as a result of the overlap of 2p orbitals from both C atoms in the formation of the covalent bond. The overlap occurs above and below the C atoms, preventing free rotation of the groups about the double bond.

• E/Z isomerism only occurs if the groups bonded to each carbon atom in the C=C bond are different. Due to the restricted rotation about the planar C=C double bond, the position of the groups bonded to the carbons in the double bond cannot be interchanged. Therefore, different isomers exist.

The Z-isomer has the groups with priority (more on this later) together , either above or below the carbon, carbon double bond.

The E-isomer occurs when the groups with priority are on opposite sides of the double bond.

CIP Rules for E/Z Stereoisomers

CIP stands for Cahn-Ingold-Prelog priority rules. These are the rules which determine whether a molecule is an E or a Z isomer.

Even when the C=C in a molecule is next to more than two unique groups, it can show E/Z isomerism.

There are some key rules to remember to work out if a molecule is an E or a Z isomer. These refer to the atom or atoms bonded to the two carbons in the double bond.

• For single atoms, a higher atomic mass gives a molecule higher priority. For example, bromine has a higher atomic mass than hydrogen and so has higher priority.
• For groups of atoms, look at the atom directly bonded to the carbons in the double bond. Whichever carbon is bonded to the atom with the highest atomic mass will have priority. If these are the same (for example if both are carbons), look down the chain.

If the groups with higher priority are on the same side , then it is a Z isomer .

If they are on opposite sides , then it is an E isomer .

Cis-Trans Isomerism

Cis-Trans isomerism is a special type of E/Z isomerism in which both of the carbon atoms of the C=C group have at least one substituent group in common.

Cis isomers will have the equal groups on the same side and trans isomers will have the equal groups on different sides.

Drawing E/Z Isomers

To draw this form of isomers:

• Draw the longest chain described in the name of the compound. Refer back to chapter 72 if you do not remember the different stems used to name carbon compounds of different chain lengths.
• Number the carbons. The main chain will be numbered in such a way the substituents are given the lowest number as possible.
• Add the functional groups to the carbons described in the name. The carbon to which the functional group is bonded to will be indicated with a number in the name.
• Ensure that the groups are in the correct arrangement across the double bond. In Z isomers the high priority groups will be on the same side and in E isomers they will be on opposite sides.

Worked example: 3-methylpent-2-ene exists as E and Z isomers. Draw the structure of Z-3-methlypent-2-ene.

1) Draw the C=C and then add the side chains from each atom around it as shown.

2) Identify and draw the groups with the highest masses on the same side of the double bond (Z isomer)

Organic chemistry is the study of the structure, properties, and reactions of organic compounds, which are compounds that contain carbon atoms.

In an E isomer, the two highest priority groups (i.e., those with the highest atomic number) on each carbon atom are on opposite sides of the double bond. “E” stands for “entgegen,” which is German for “opposite.” In a Z isomer, the two highest priority groups on each carbon atom are on the same side of the double bond. “Z” stands for “zusammen,” which is German for “together.” The E and Z notation is commonly used in organic chemistry to describe the stereochemistry of double bonds. It is important because the different spatial arrangements of E and Z isomers can affect their physical and chemical properties, including reactivity and biological activity.

E and Z isomerism is a type of stereoisomerism, which is a type of isomerism that arises due to differences in the spatial arrangement of atoms in molecules. Steroisomers have the same molecular formula and connectivity of atoms, but differ in their three-dimensional orientation or arrangement. In the case of E and Z isomers, they differ in the orientation of groups around a double bond, which is a type of geometric isomerism.

E isomers have a trans arrangement of substituents on a double bond, while Z isomers have a cis arrangement.

To draw E and Z isomers, follow these steps: Identify the carbon atoms that are double bonded. Determine the priority of the groups attached to each carbon atom based on their atomic number. The group with the highest atomic number is assigned the highest priority, and the group with the lowest atomic number is assigned the lowest priority. Draw a horizontal line between the two carbon atoms to represent the double bond. Draw the groups attached to each carbon atom on either side of the double bond, with the highest priority group at the top and the lowest priority group at the bottom. Determine whether the two highest priority groups on each carbon atom are on the same side (Z) or opposite sides (E) of the double bond. If the two highest priority groups on each carbon atom are on the same side of the double bond, it is a Z isomer. If they are on opposite sides, it is an E isomer.

To determine whether a molecule is an E or Z isomer, you need to consider the priority of the substituents attached to the double bond. The substituent with the highest priority should be on the same side of the double bond.

Understanding E/Z isomerism is important in A-Level Chemistry as it helps to explain the stereochemistry of organic compounds and the different properties that result from the different arrangements of atoms in space.

E/Z isomerism affects the properties of organic compounds, such as their physical and chemical properties, as the different arrangements of atoms in space result in different molecular shapes and interactions.

Cis-trans isomerism is a type of stereoisomerism that arises due to the restricted rotation around a double bond or a ring in a molecule. It occurs when two substituents attached to the double bond or ring are different, and their relative positions cannot be interchanged by rotation around the bond or ring. In cis-trans isomerism, the two stereoisomers are referred to as cis and trans isomers. Cis isomers have the two substituents on the same side of the double bond or ring, whereas trans isomers have the two substituents on opposite sides of the double bond or ring. Cis-trans isomerism is commonly seen in organic molecules that contain a carbon-carbon double bond or a cyclic structure, such as alkenes, cycloalkanes, and some aromatic compounds. It can affect the physical and chemical properties of the molecules, including their reactivity, biological activity, and solubility, among others.

E/Z isomerism can impact the reaction of organic compounds as the different arrangements of atoms in space can affect the reactivity of the molecule. This is because different isomers can have different orientations of functional groups and different interactions with reactants and products.

Still got a question? Leave a comment

Leave a comment, cancel reply.

Save my name, email, and website in this browser for the next time I comment.

AQA 3.1.1 Atomic structure

Ionisation energies (a-level chemistry), atomic structure – electron arrangement (a-level chemistry), atomic structure – electrons in atoms (a-level chemistry), atomic structure – mass spectrometry (a-level chemistry), atomic structure – element isotopes (a-level chemistry), atomic structure – atomic and mass number (a-level chemistry), atomic structure – subatomic particles (a-level chemistry), aqa 3.1.10 equilibrium constant kp for homogeneous systems, equilibrium constant for homogenous systems – le chatelier’s principle in gas equilibria (a-level chemistry), equilibrium constant for homogenous systems – gas equilibria and kp (a-level chemistry), equilibrium constant for homogeneous system – changing kp (a-level chemistry), equilibrium constant for homogenous systems – gas partial pressures (a-level chemistry), aqa 3.1.11 electrode potentials and electrochemical cells, acids and bases – drawing ph curves (a-level chemistry), acids and bases – acid-base indicators (a-level chemistry), acids and bases – dilutions and ph (a-level chemistry), electrode potentials and electrochemical cells – commercial applications of fuel cells (a-level chemistry), electrode potentials and electrochemical cells – electrochemical cells reactions (a-level chemistry), electrode potentials and electrochemical cells – representing electrochemical cells (a-level chemistry), electrode potentials and electrochemical cells – electrode potentials (a-level chemistry), electrode potentials and electrochemical cells – half cells and full cells (a-level chemistry), aqa 3.1.12 acids and bases, acids and bases – titrations (a-level chemistry), acids and bases – buffer action (a-level chemistry), acids and bases – ph of strong bases (a-level chemistry), acids and bases – ionic product of water (a-level chemistry), acids and bases – more ka calculations (a-level chemistry), acids and bases – the acid dissociation constant, ka (a-level chemistry), acids and bases – the ph scale and strong acids (a-level chemistry), acids and bases – neutralisation reactions (a-level chemistry), acids and bases – acid and base strength (a-level chemistry), acids and bases – the brønsted-lowry acid-base theory (a-level chemistry), aqa 3.1.2 amount of substance, amount of substance – percentage atom economy (a-level chemistry), amount of substance – calculating percentage yields (a-level chemistry), amount of substance – stoichiometric calculations (a-level chemistry), amount of substance – balancing chemical equations (a-level chemistry), amount of substance – empirical and molecular formulae (a-level chemistry), amount of substance – further mole calculations (a-level chemistry), amount of substance- the mole and the avogadro constant (a-level chemistry), amount of substance – measuring relative masses (a-level chemistry), amount of substance – the ideal gas equation (a-level chemistry), aqa 3.1.3 bonding, periodicity – classification (a-level chemistry), bonding – hydrogen bonding in water (a-level chemistry), bonding – forces between molecules (a-level chemistry), bonding – bond polarity (a-level chemistry), bonding – molecular shapes (a-level chemistry), bonding – predicting structures (a-level chemistry), bonding – carbon allotropes (a-level chemistry), bonding – properties of metallic bonding (a-level chemistry), bonding – properties of covalent structures (a-level chemistry), bonding – covalent bonds (a-level chemistry), aqa 3.1.4 energetics, aqa 3.1.5 kinetics, kinetics – the maxwell–boltzmann distribution and catalysts (a-level chemistry), kinetics – the collision theory and reaction rates (a-level chemistry), aqa 3.1.6 chemical equilibria, calculations with equilibrium constants (a-level chemistry), chemical equilibria applied to industry (a-level chemistry), chemical equilibria and le chatelier’s principle (a-level chemistry), aqa 3.1.7 oxidation, reduction and redox, oxidation, reduction and redox equations – balancing redox equations (a-level chemistry), oxidation, reduction and redox equations – redox processes (a-level chemistry), oxidation, reduction and redox equations – oxidation states (a-level chemistry), aqa 3.1.8 thermodynamics, thermodynamic – calculations involving free energy (a-level chemistry), thermodynamic – gibbs free energy (a-level chemistry), thermodynamic – entropy change predictions (a-level chemistry), thermodynamic – total entropy changes (a-level chemistry), thermodynamic – introduction to entropy (a-level chemistry), thermodynamic – calculating enthalpy changes of solution (a-level chemistry), thermodynamic – enthalpy of solution (a-level chemistry), thermodynamic – enthalpy of hydration (a-level chemistry), thermodynamic – calculations involving born-haber cycles (a-level chemistry), thermodynamic – construction of born-haber cycles (a-level chemistry), aqa 3.1.9 rate equations, rate equations – reaction determining steps (a-level chemistry), rate equations – reaction half lives (a-level chemistry), rate equations – uses of clock reactions (a-level chemistry), rate equations – determining orders of reactions graphically (a-level chemistry), rate equations – determining order of reaction experimentally (a-level chemistry), rate equations – temperature changes and the rate constant (a-level chemistry), rate equations – the rate constant (a-level chemistry), rate equations – introduction to orders of reactions (a-level chemistry), rate equations – the rate equation (a-level chemistry), rate equations – measuring rate of reaction (a-level chemistry), aqa 3.2.1 periodicity, periodicity – trends along period 3 (a-level chemistry), aqa 3.2.2 group 2, the alkaline earth metals, uses of group 2 elements and their compounds (a-level chemistry), reactions of group 2 elements (a-level chemistry), group 2, the alkaline earth metals (a-level chemistry), aqa 3.2.3 group 7(17), the halogens, the halogens -halide ions and their reactions (a-level chemistry), the halogens – disproportionation reactions in halogens (a-level chemistry), the halogens – reactions with halogens (a-level chemistry), the halogens – group 7, the halogens (a-level chemistry), aqa 3.2.4 properties of period 3 elements, properties of period 3 elements – properties of period 3 compounds (a-level chemistry), properties of period 3 elements – reactivity of period 3 elements (a-level chemistry), aqa 3.2.5 transition metals, transition metals – autocatalysis of transition metals (a-level chemistry), transition metals – transition metals as homogeneous catalysts (a-level chemistry), transition metals – transition metals as heterogeneous catalysts (a-level chemistry), transition metals – examples of redox reactions in transition metals (a-level chemistry), transition metals – iodine-sodium thiosulfate titrations (a-level chemistry), transition metals – carrying titrations with potassium permanganate (a-level chemistry), transition metals – redox titrations (a-level chemistry), transition metals – redox potentials (a-level chemistry), transition metals – redox reactions revisited (a-level chemistry), transition metals – ligand substitution reactions (a-level chemistry), aqa 3.2.6 reactions of ions in aqueous solution, reactions of ions in aqueous solutions – metal ions in solution (a-level chemistry), aqa 3.3.1 introduction to organic chemistry, introduction to organic chemistry – structural isomers (a-level chemistry), introduction to organic chemistry – e/z isomerism (a-level chemistry), introduction to organic chemistry – reaction mechanisms in organic chemistry (a-level chemistry), introduction to organic chemistry – general formulae (a-level chemistry), introduction to organic chemistry – introduction to functional groups (a-level chemistry), introduction to organic chemistry – naming and representing organic compounds (a-level chemistry), aqa 3.3.10 aromatic chemistry, aromatic chemistry – friedel-crafts acylation and alkylation (a-level chemistry), aromatic chemistry – halogenation reactions in benzene (a-level chemistry), aromatic chemistry – electrophilic substitution reactions in benzene (a-level chemistry), aromatic chemistry – improved benzene model (a-level chemistry), aromatic chemistry – introduction to benzene (a-level chemistry), aqa 3.3.11 amines, amines – nitriles (a-level chemistry), amines – properties and reactivity of amines (a-level chemistry), amines – amine synthesis (a-level chemistry), amines – introduction to amines (a-level chemistry), aqa 3.3.12 polymers, polymer disposal (a-level chemistry), polymer biodegradability (a-level chemistry), condensation polymers (a-level chemistry), polyamide formation (a-level chemistry), aqa 3.3.13 amino acids, amino acids, proteins and dna – dna replication (a-level chemistry), amino acids, proteins and dna – dna (a-level chemistry), amino acids, proteins and dna – enzyme action (a-level chemistry), amino acids, proteins and dna – structure of proteins (a-level chemistry), amino acids, proteins and dna – structure of amino acids (a-level chemistry), aqa 3.3.14 organic synthesis, organic synthesis – considerations in organic synthesis (a-level chemistry), organic synthesis – organic synthesis: aromatic compounds (a-level chemistry), organic synthesis – organic synthesis: aliphatic compounds (a-level chemistry), aqa 3.3.15 nmr, analytical techniques – high resolution ¹h nmr (a-level chemistry), analytical techniques – types of nmr: hydrogen (a-level chemistry), analytical techniques – types of nmr: carbon 13 (a-level chemistry), analytical techniques – nmr samples and standards (a-level chemistry), analytical techniques – nuclear magnetic resonance spectroscopy (a-level chemistry), aqa 3.3.16 chromatography, analytical techniques – different types of chromatography (a-level chemistry), analytical techniques – chromatography (a-level chemistry), aqa 3.3.2 alkanes, alkanes – obtaining alkanes (a-level chemistry), alkanes – alkanes: properties and reactivity (a-level chemistry), aqa 3.3.3 halogenoalkanes, halogenoalkanes – environmental impact of halogenalkanes (a-level chemistry), halogenoalkanes – reactivity of halogenoalkanes (a-level chemistry), halogenoalkanes – introduction to halogenoalkanes (a-level chemistry), aqa 3.3.4 alkenes, alkenes – addition polymerisation in alkenes (a-level chemistry), alkenes – alkene structure and reactivity (a-level chemistry), aqa 3.3.5 alcohols, alcohols – industrial production of alcohols (a-level chemistry), alcohols – alcohol reactivity (a-level chemistry), alcohols – alcohol oxidation (a-level chemistry), alcohols – introduction to alcohols (a-level chemistry), aqa 3.3.6 organic analysis, organic analysis – infrared (ir) spectroscopy (a-level chemistry), organic analysis – identification of functional groups (a-level chemistry), aqa 3.3.7 optical isomerism, optical isomerism (a-level chemistry), aqa 3.3.8 aldehydes and ketones, aldehydes and ketones – reactions to increase carbon chain length (a-level chemistry), aldehydes and ketones – testing for carbonyl compounds (a-level chemistry), aldehydes and ketones – reactivity of carbonyl compunds (a-level chemistry), aldehydes and ketones – carbonyl compounds (a-level chemistry), aqa 3.3.9 carboxylic acids, carboxylic acids and derivatives – structure of amides (a-level chemistry), carboxylic acids and derivatives – acyl groups (a-level chemistry), carboxylic acids and derivatives – properties and reactivity of esters (a-level chemistry), carboxylic acids and derivatives – properties and reactivity of carboxylic acids (a-level chemistry), 21: organic synthesis, 29: intro to organic chemistry, aromatic chemistry – benzene nomenclature (a-level chemistry), cie 1: atomic structure, bonding – ion formation (a-level chemistry), cie 10: group 2, cie 11: group 17, cie 13: intro to as organic chemistry, cie 14: hydrocarbons, cie 15: halogen compounds, cie 16: hydroxy compounds, cie 17: carbonyl compounds, cie 18: carboxylic acids and derivatives, cie 19: nitrogen compounds, cie 2: atoms, molecules and stoichiometry, cie 20: polymerisation, cie 22: analytical techniques, cie 23: chemical energetics, cie 24: electrochemistry, cie 25: equilibria, cie 27: group 2 elements, cie 28: chemistry of transition elements, transition metals – colour in transition metal ions (a-level chemistry), transition metals – optical isomerism in complex ions (a-level chemistry), transition metals – cis-trans isomerism in complex ions (a-level chemistry), transition metals – complex ion shape (a-level chemistry), transition metals – ligands (a-level chemistry), transition metals – introduction to complex ions (a-level chemistry), cie 3: chemical bonding, bonding – properties of ionic bonding (a-level chemistry), cie 30: hydrocarbons, aromatic chemistry – reactivity of substituted benzene (a-level chemistry), cie 31: halogen compounds, cie 32: hydroxy compounds, cie 33: carboxylic acids and derivatives, cie 34: nitrogen compounds, cie 35: polymerisation, cie 36: organic synthesis, cie 37: analytic techniques, analytical techniques – deuterium use in ¹h nmr (a-level chemistry), cie 4: states of matter, cie 6: electrochemistry, cie 7: equilibria, cie 8: reaction kinetics, cie 9: the periodic table, cie: 26: reaction kinetics, catalysts, edexcel topic 1: atomic structure and the periodic table, edexcel topic 10: equlibrium 1, edexcel topic 11: equilibrium 2, edexcel topic 12: acid-base equilibria, edexcel topic 13: energetics 2, edexcel topic 14: redox 2, edexcel topic 15: transition metals, edexcel topic 16: kinetics 2, edexcel topic 17: organic chemistry 2, edexcel topic 18: organic chemistry 3, organic synthesis – practical purification techniques (a-level chemistry), organic synthesis – practical preparation techniques (a-level chemistry), edexcel topic 19: modern analytical techniques 2, edexcel topic 2a & b: bonding and structure, edexcel topic 3: redox 1, edexcel topic 4: inorganic chemistry & the periodic table, the halogens – testing for ions (a-level chemistry), edexcel topic 5: formulae, equations and amounts of substance, edexcel topic 6: organic chemistry 1, edexcel topic 7: modern analytical techniques 1, edexcel topic 8, edexcel topic 9: kinetics 1, ocr 2.1.1 atomic structure and isotopes, ocr 2.1.2 compounds, formulae and equations, ocr 2.1.3 amount of substance, ocr 2.1.4 acids, ocr 2.1.5 redox, ocr 2.2.1 electron structure, ocr 2.2.2 bonding and structure, ocr 3.1.1 periodicity, ocr 3.1.2 group 2, ocr 3.1.3 the halogens, ocr 3.1.4 qualitative analysis, ocr 3.2.2 reaction rates, ocr 3.2.3 chemical equilibrium, ocr 4.1.1 basic concepts of organic chemistry, ocr 4.1.2 alkanes, ocr 4.1.3 alkenes, ocr 4.2.1 alcohols, ocr 4.2.2 haloalkanes, ocr 4.2.3 organic synthesis, ocr 4.2.4 analytical techniques, ocr 5.1.1 rates, equilibrium and ph, ocr 5.1.2 how fast, ocr 5.1.3 acids, bases and buffers, ocr 5.2.1 lattice enthalpy, thermodynamic – enthalpy key terms (a-level chemistry), thermodynamic – lattice enthalpies (a-level chemistry), ocr 5.2.2 enthalpy and entropy, ocr 5.2.3 redox and electrode potentials, ocr 5.3.1 transition elements, precipitation reactions of metal ions in solution (a-level chemistry), ocr 5.3.2 qualitative analysis, ocr 6.1.1 aromatic compounds, ocr 6.1.2 carbonyl compounds, ocr 6.1.3 carboxylic acids and esters, ocr 6.2.1 amines, ocr 6.2.2 amino acids, amides and chirality, ocr 6.2.3 polyesters and polyamides, ocr 6.2.4 carbon–carbon bond formation, ocr 6.2.5 organic synthesis, ocr 6.3.1 chromatography and qualitative analysis, ocr 6.3.2 spectroscopy, related links.

• A-level Chemistry Past Papers

Boost your A-Level Chemistry Performance

Get a 9 in A-Level Chemistry with our Trusted 1-1 Tutors. Enquire now.

100+ Video Tutorials, Flashcards and Weekly Seminars. 100% Money Back Guarantee

Gain hands-on experience of how physics is used in different fields. Boost your university application with our summer programme!

Learn live with other students and gain expert tips and advice to boost your score.

Let's get acquainted ? What is your name?

Nice to meet you, {{name}} what is your preferred e-mail address, nice to meet you, {{name}} what is your preferred phone number, what is your preferred phone number, just to check, what are you interested in, when should we call you.

It would be great to have a 15m chat to discuss a personalised plan and answer any questions

What time works best for you? (UK Time)

Pick a time-slot that works best for you ?

How many hours of 1-1 tutoring are you looking for?

My whatsapp number is..., for our safeguarding policy, please confirm....

Please provide the mobile number of a guardian/parent

Which online course are you interested in?

What is your query, you can apply for a bursary by clicking this link, sure, what is your query, thank you for your response. we will aim to get back to you within 12-24 hours., lock in a 2 hour 1-1 tutoring lesson now.

If you're ready and keen to get started click the button below to book your first 2 hour 1-1 tutoring lesson with us. Connect with a tutor from a university of your choice in minutes. (Use FAST5 to get 5% Off!)

• International
• Education Jobs
• Schools directory
• Resources Education Jobs Schools directory News Search

E-Z isomerism h/w

Subject: Chemistry

Age range: 16+

Resource type: Worksheet/Activity

Last updated

9 December 2013

• Share through email
• Share through twitter
• Share through linkedin
• Share through facebook
• Share through pinterest

Tes classic free licence

Your rating is required to reflect your happiness.

It's good to leave some feedback.

Something went wrong, please try again later.

Very similar to one I posted- I like it!

Empty reply does not make any sense for the end user

Report this resource to let us know if it violates our terms and conditions. Our customer service team will review your report and will be in touch.

Not quite what you were looking for? Search by keyword to find the right resource:

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings
• My Bibliography
• Collections
• Citation manager

Save citation to file

Email citation, add to collections.

• Create a new collection
• Add to an existing collection

Add to My Bibliography

Your saved search, create a file for external citation management software, your rss feed.

• Search in PubMed
• Search in NLM Catalog
• Add to Search

Identification and interconversion of isomeric 4,5-functionalized 1,2,3-thiadiazoles and 1,2,3-triazoles in conditions of electrospray ionization

Affiliations.

• 1 Lomonosov Moscow State University, Organic Chemistry Department, 119992 Moscow, Russia.
• 2 Ural Federal University, Technology of Organic Synthesis Department, 620002, Yekaterinburg, Russia.
• 3 Lomonosov Moscow State University, Organic Chemistry Department, 119992 Moscow, Russia. Electronic address: [email protected].
• PMID: 28709128
• DOI: 10.1016/j.jpba.2017.06.064

1,2,3-Triazoles and 1,2,3-thiadiazoles have been receiving permanent interest due to their exciting chemical reactivity and interesting biological properties including antibacterial, anticancer and antiviral activities. There are four compounds bearing 1H-1,2,3-triazole core in clinical studies which may appear in the market of drugs in nearest future. Definitely reliable methods of their identification and quantification should be developed by that time. Mass spectrometry showed itself as the most reliable method of analysis when dealing with trace levels of organic compounds in the mixtures and in the most complex matrices, including biological ones. In the present study tandem mass spectrometry was used to study fragmentation pathways of protonated and deprotonated molecules of isomeric 4,5-functionalized 1,2,3-thiadiazoles and 1,2,3-triazoles in conditions of electrospray ionization (ESI). A group of marker ions allowing differentiation between the targeted isomeric compounds was established. Besides, interconversion of these isomers into one another was studied in the gas phase in conditions mimicking these processes in solution.

Keywords: 1,2,3-thiadiazoles; 1,2,3-triazoles; Electrospray ionization; Isomer identification; Mass spectrometry.

Copyright © 2017 Elsevier B.V. All rights reserved.

PubMed Disclaimer

Similar articles

• Differentiation between Isomeric 4,5-Functionalized 1,2,3-Thiadiazoles and 1,2,3-Triazoles by ESI-HRMS and IR Ion Spectroscopy. Mazur DM, Piacentino EL, Berden G, Oomens J, Ryzhov V, Bakulev VA, Lebedev AT. Mazur DM, et al. Molecules. 2023 Jan 18;28(3):977. doi: 10.3390/molecules28030977. Molecules. 2023. PMID: 36770641 Free PMC article.
• Fragmentation characteristics and isomeric differentiation of flavonol O-rhamnosides using negative ion electrospray ionization tandem mass spectrometry. Ablajan K, Tuoheti A. Ablajan K, et al. Rapid Commun Mass Spectrom. 2013 Feb 15;27(3):451-60. doi: 10.1002/rcm.6476. Rapid Commun Mass Spectrom. 2013. PMID: 23280977
• Electrospray ionization tandem mass spectrometry of protonated and alkali-cationized Boc-N-protected hybrid peptides containing repeats of D-Ala-APyC and APyC-D-Ala: formation of [b(n-1) + OCH3 + Na]+ and [b(n-1) + OH + Na]+ ions. Raju G, Purna Chander C, Srinivas Reddy K, Srinivas R, Sharma GV. Raju G, et al. Rapid Commun Mass Spectrom. 2012 Nov 30;26(22):2591-600. doi: 10.1002/rcm.6381. Rapid Commun Mass Spectrom. 2012. PMID: 23059875
• Fluorinated triazoles as privileged potential candidates in drug development-focusing on their biological and pharmaceutical properties. Ullah I, Ilyas M, Omer M, Alamzeb M, Adnan, Sohail M. Ullah I, et al. Front Chem. 2022 Aug 9;10:926723. doi: 10.3389/fchem.2022.926723. eCollection 2022. Front Chem. 2022. PMID: 36017163 Free PMC article. Review.
• An updated review on 1,2,3-/1,2,4-triazoles: synthesis and diverse range of biological potential. Raman APS, Aslam M, Awasthi A, Ansari A, Jain P, Lal K, Bahadur I, Singh P, Kumari K. Raman APS, et al. Mol Divers. 2024 Jul 27. doi: 10.1007/s11030-024-10858-0. Online ahead of print. Mol Divers. 2024. PMID: 39066993 Review.
• Search in MeSH

Related information

• PubChem Compound (MeSH Keyword)

LinkOut - more resources

Full text sources.

• Elsevier Science
• Ovid Technologies, Inc.

Other Literature Sources

• scite Smart Citations
• Citation Manager

NCBI Literature Resources

MeSH PMC Bookshelf Disclaimer

The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Unauthorized use of these marks is strictly prohibited.

Optical isomerism and biological activity of pharmaceutical preparations

• Published: 07 August 2012
• Volume 67 , pages 95–102, ( 2012 )

Cite this article

• I. G. Smirnova 1 ,
• G. N. Gil’deeva 2 &
• V. G. Kukes 2  

235 Accesses

8 Citations

3 Altmetric

Explore all metrics

The paper considers the relationship between optical isomerism and the pharmacological activity of pharmaceutical preparations.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save.

• Get 10 units per month
• Download Article/Chapter or eBook
• 1 Unit = 1 Article or 1 Chapter
• Cancel anytime

Price includes VAT (Russian Federation)

Instant access to the full article PDF.

Rent this article via DeepDyve

Institutional subscriptions

Similar content being viewed by others

Spectral data of porphyrin derivative C24H26N4

Physicochemical Properties of a Phenyltetrahydroquinolinedione Derivative with TRPA1 Antagonist Activity

Refractive index of 1-methylpiperazine

Lehninger, A. and Cox, N., Principles of Biochemistry , New York: World Publishers, 1993, p. 58.

Google Scholar  

Golikov, S.N., Kuznetsov, S.G., and Zatsepin, E.P., Stereospetsifichnost’ Deistviya Lekarstvennykh Veshchestv (Stereospecificity of the Action of Medical Compounds), Leningrad: Meditsina, 1973.

Williams, K. and Lee, E., Drugs , 1985, vol. 30, p. 333.

Article   CAS   Google Scholar  

Alekseev, V.V., Sorovskii Obrazovatel’nyi Zh. , 1998, no. 1, p. 49.

Yanitskii, P.K., Reverskii, V., and Gumulka, V., Novosti Farmatsii i Meditsiny , 1991, nos. 4–5, p. 98.

Dunina, V.V. and Beletskaya, I.P., Zh. Org. Khim. , 1992, p. 1929.

Roberts, J.D., Caserio, M., Basic Principles of Organic Chemistry . New York: W. A. Benjamin, 1977.

Fieser, L. and Fieser, M., Advanced Organic Chemistry , New York: Reinhold, 1961.

Netshchesku, K.D., Organicheskaya Khimiya. T. 2 (Organic Chemistry, vol. 2), Moscow, 1967, p. 148.

Velluz L., Legrand M., and Grosjean M., Optical Circular Dichroism: Principles, Measurements, and Applications , Weinheim: Verlag Chemie, 1965.

Gordon, A. and Ford, R., Chemists’s Companion , New York: Wiley, 1972.

Adler, A.I., Greenfield, N.I., and Fasman, G.D., Methods in Enzymology. 27D , Hirs C.H.W. and Timasheff S.N., Ed., New York: Academic Press, 1973, p. 675.

Freifelder, D., Physical Biochemistry , Boston: Bartlett Publishers, 1982.

Snatske, G., Djerassi, C., in Optical Rotatory Dispersion and Circular Dichroism in Organic Chemistry , Snatske G., Ed., London: Herden and Sons, 1967.

Cantor, Ch. and Shimmel, P., Biophysical Chemistry , San Francisco: Freeman, 1980.

Serdyuk I.N., Zaccai N., and Zaccai J., Methods in molecular biophysics: Structure, function, dynamics , Cambridge: Cambridge Univ. Press, 2007.

Chichibabin, A.E., Osnovnye Nachala Organicheskoi Khimii. T. 1 . (Basics of Organic Chemsitry), Moscow: GosKhimIzdat, 1953, p. 506.

Boyle, P.H., Quart. Rev. , 1971, p. 323.

Wilen, S., Resolving Agents and Resolutions in Organic Chemistry. Topics in Stereochemistry , New York: Wiley, 1971, vol.6, p. 107.

Raban M., Misow K., Topics in Stereochemicstry , New York: Wiley, 1967., vol. 2, p. 199.

Book   Google Scholar  

Sargeson A.M., Chelating Agents and Metal Chelates , F.P. Dwyer, D.P. Mellor, Ed., New York: Academic Press, 1964, p. 193.

Morrison J. and Mosher H., Asymmetric Organic Reactions , Engelwood Cliffs, New Jersey: Prentice Hall, 1971.

Rogozhin S.V. and Davankov V.A., Usp. Khim. , 1968, vol. 37, p. 1327.

CAS   Google Scholar  

Hais I.M. and Macek K., Paper Chromatography , London: Academic Press, 1963, pp. 450, 580.

Marini-Bettolo G., Thin Layer Chromatography , New York: Elsevier, 1964, p. 9.

Download references

Author information

Authors and affiliations.

Department of Chemistry, Moscow State University, Moscow, Russia

I. G. Smirnova

Sechenov Moscow State Medical University, Moscow, Russia

G. N. Gil’deeva & V. G. Kukes

You can also search for this author in PubMed   Google Scholar

Corresponding author

Correspondence to I. G. Smirnova .

Additional information

Original Russian Text © I.G. Smirnova, G.N. Gil’deeva, V.G. Kukes, 2012, published in Vestnik Moskovskogo Universiteta. Khimiya, 2012, No. 3, pp. 147–156.

About this article

Smirnova, I.G., Gil’deeva, G.N. & Kukes, V.G. Optical isomerism and biological activity of pharmaceutical preparations. Moscow Univ. Chem. Bull. 67 , 95–102 (2012). https://doi.org/10.3103/S002713141203008X

Download citation

Received : 01 February 2012

Published : 07 August 2012

Issue Date : May 2012

DOI : https://doi.org/10.3103/S002713141203008X

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• pharmaceutical preparations
• optical isomerism
• UV-spectroscopy
• circular dichroism
• pharmacological activity
• Find a journal
• Publish with us
• Track your research