Q.65. - Organic Chemistry

Question

Question: Devise a synthesis of (E)-hex-2-ene from pent-1-ene and any needed organic compounds or inorganic reagents.

Step-by-Step Solution

Answer

Answer

Step 1: Conversion of 1-pentene to 1-pentyne

An alkene can be converted to an alkyne via a geminal dihalide intermediate. A strong base like   can be used for the conversion of dihalide to the desired alkyne. The reaction is shown below:

Conversion of 1-pentene to 1-pentyne

Step 2: Conversion of 1-pentyne to 1-hexyne

The 1-pentyne formed in a previous step is treated with a strong base for its corresponding acetylide anion to form, which is further treated with bromomethane to form 2-hexyne.The reaction is shown below:

Conversion of 1-pentyne to 1-hexyne

Step 3: Formation of (2E)-2-hexene from 2-hexyne

The anti-addition of hydrogen to 2-hexyne can be performed using the reagent sodium in liquid ammonia. The reaction is known as Birch reduction. The reaction is given below:

Formation of (2E)-2-hexene