Isomerism: structural, cis‑trans, enantiomerism：練習問題

Which of the following properties is most likely to differ between two enantiomers under non-chiral conditions?

How many structural isomers are possible for the molecular formula \(C_5H_{12}\)?

Consider the compound 2,4-dibromopentane ($$CH_3CHBrCH_2CHBrCH_3$$). How many distinct stereoisomers (including enantiomers and meso compounds) are possible for this compound?

What type of isomerism is shown by the pair pentan-2-ol and pentan-3-ol?

How many structural isomers exist for the molecular formula \( \text{C}_3\text{H}_6\text{Cl}_2 \)?

What specific arrangement of groups around a carbon atom defines it as a chiral centre (or stereocentre)?

How many chiral carbon atoms are present in the molecule 2-butanol (\(CH_3CH(OH)CH_2CH_3\))?

Explain why cis-1,2-dichloroethene has a higher boiling point than trans-1,2-dichloroethene by comparing their molecular polarities and the resulting intermolecular forces.

A compound with the molecular formula \(C_4H_9Br\) exists in several isomeric forms.

(a) Draw the structural formulae and give the systematic names for two structural isomers of this compound that are chain isomers of each other. (2 marks)

(b) Identify which structural isomer of \(C_4H_9Br\) contains a chiral carbon. Draw its 3D structure to show the two enantiomers. (1 mark)

The existence of cis-trans isomerism is closely related to the structural features of a molecule.

(a) Explain why 1,2-dichloroethene exists as a pair of cis-trans isomers, while 1,2-dichloroethane does not. (2 marks)

(b) Draw the 3D structural formulae for the cis and trans isomers of 1,2-dichloroethene. Label each isomer clearly. (2 marks)