Question

multiple choice 2 points
which of the following alkenes can show geometric isomerism: 2,3 - dichloro - 2 - pentene, 4 - chloro - 3 - ethyl - 3 - hexene, 3 - chloro - 2 - methyl - 2 - butene, and 3 - chloro - 2 - methyl - 1 - butene?
2,3 - dichloro - 2 - pentene
3 - chloro - 2 - methyl - 2 - butene
3 - chloro - 2 - methyl - 1 - butene
4 - chloro - 3 - ethyl - 3 - hexene

Explanation:

Step1: Recall geometric isomerism condition

For an alkene to show geometric isomerism, each carbon of the double bond must have two different groups attached.

Step2: Analyze 2,3 - dichloro - 2 - pentene

The second carbon of the double bond has two similar groups (chloro), so no geometric isomerism.

Step3: Analyze 3 - chloro - 2 - methyl - 2 - butene

The second carbon of the double bond has two similar groups (methyl), so no geometric isomerism.

Step4: Analyze 3 - chloro - 2 - methyl - 1 - butene

The first carbon of the double bond has hydrogen and methyl, the second carbon has chloro and isopropyl. Different groups, so geometric isomerism possible.

Step5: Analyze 4 - chloro - 3 - ethyl - 3 - hexene

The third carbon of the double bond has two similar groups (ethyl), so no geometric isomerism.

Answer:

C. 3 - chloro - 2 - methyl - 1 - butene