Chapter 8: Q.30 (page 326)

Label each pair of alkenes as constitutional isomers, stereoisomers, or identical.
a.
b.
c.
d.

Short Answer

Expert verified

For a. the pairs are constitutional isomers.

For b. the pairs are stereoisomers.

For c. the pairs are stereoisomers.

For d. the pairs are stereoisomers.

Step by step solution

Constitutional isomers, stereoisomers, and identical structures

Constitutional isomers are molecules having the same molecular formula, but the difference lies in bonding and molecular structure.These structures differ due to different orientations of the carbon atoms.

Stereoisomers isomers are isomers with same molecular formula. Their structures are the same but with different spatial arrangements.They are two kinds – cis/Z and trans/E.

Identical structures are those structures upon rotation resemble the same structure as its counterpart.

Identification of the double bond

The double-bonded carbons are identified first.

Representation of the double bond

Identification based on definitions

Based on the definition it is found that in the case of (a) constitutional isomers are present since the molecular formula is the same, but the position of the double bond is different.

For (b), (c) and (d) the high priority groups are lying in the opposite directions, hence they are considered to be stereoisomers.

For a. the pairs are constitutional isomers.

Pair of constitutional isomers