MC test: Stereoisomerism

Multiple choice test on 20.3 Stereoisomerism

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. You will need access to a periodic table (Section 6 of the IB data booklet). Note that this quiz covers both electrophilic addition and electrophilic substitution reactions.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

Which are correct statements about conformational isomers?

I. A 50:50 mixture of two different conformational isomers is known as a racemic mixture.

II. Different conformational isomers often cannot be isolated as they interconvert too rapidly.

III. Conformational isomers interconvert by rotation about a σ bond.

A racemic mixture is a 50:50 mixture of two enantiomers which are configurational isomers.

 

Which are correct statements about configurational isomers?

I. All configurational isomers interconvert only by breaking and reforming a bond.

II. All configurational isomers differ in the way substituents are arranged around two carbon atoms that are bonded by one σ and one π bond.

III. Configurational isomerism is sub-divided into cis-trans and E/Z isomerism and optical isomerism.

Optical isomerism and cis-trans isomerism in cyclic compounds do not involve π bonds so II is only true for cis-trans and E/Z isomerism in asymmetric alkenes.

 

Which isomer is a cis- and E isomer?

The correct answer is cis-2-bromo-but-2-ene which is also E-2-bromo-but-2-ene as Br has a higher CIP priority than CH3.

 

Which isomer is a trans- and E isomer?

The correct answer is trans-but-2-ene which is also the E isomer as CH3 has a higher CIP priority than H.

 

How many different isomers of dichlorcyclobutane exist that retain the four-membered carbon ring and are not an enantiomer of one of the other isomers?

cis- and trans-1,2-dichlorocyclobutane, cis- and trans-1,3-dichlorocyclobutane and 1,1-dichlorocyclobutane. (The trans-1,2-dichlorocyclobutane isomer exists as two enantiomers).

 

Which compound can exist as enantiomers?

Only butan-2-ol contains an asymmetric carbon atom, H3CCH2C*H(OH)CH3

 

Which is the correct description of optical isomerism?

It is the plane of plane-polarized light that is rotated by the same amount - not the polarized light itself.

 

What instrument is used to detect and measure optical activity?

The angle of rotation can be measure by rotating the analyser of the polarimeter until light of maximum intensity is seen.

 

Which statement is correct about enantiomers and diastereomers?

Both enantiomers and diastereomers can be formed when a compound has more than one chiral centre. Diastereomers are not mirror images of each other and their physical (and chemical properties) are different.

 

How many isomers exist with the molecular formula C4H10O?

There are four alcohols, butan-1-ol, butan-2-ol, 2-methylpropan-1-ol and 2-methyl propan-2-ol. Butan-2-ol exist in two enantiomeric forms as it has a chiral carbon atom. There are also three ethers, CH3CH2CH2OCH3, CH3CH(CH3)OCH3 and C2H5OC2H5 making a total of 8 isomers.

 

Total Score:
All materials on this website are for the exclusive use of teachers and students at subscribing schools for the period of their subscription. Any unauthorised copying or posting of materials on other websites is an infringement of our copyright and could result in your account being blocked and legal action being taken against you.