Question

In each reaction box, place the best reagent and conditions from the list below. in each reaction box, place the best reagent and conditions from the list below.

Answer 1

Concepts and reason

The concepts used for the formation of given products from propyne are based on the deprotonation of alkynes with soda amide, alkylation of acetylides, hydrogenation of alkynes with , Lindlar’s catalyst, epoxidation and opening of epoxide ring.

Initially, the complete reaction steps for the formation of the products is determined. Lastly, all the reagents that are used for the given reaction are identified.

Fundamentals

Deprotonation of alkynes: In this reaction, the formation of acetylides takes place. The reagent used for deprotonation of the alkyne is soda amide. It is a strong base and a good nucleophile. The reaction is given as follows.

Alkylation of acetylides: The acetylides can be alkylated on reaction with an alkyl halide. It is the nucleophilic substitution reaction. The general reaction is given as follows.

Here, .

Hydrogenation of alkynes: It means the addition of hydrogen to the alkyne. The alkyne is hydrogenated to cis-alkene with the use of , Lindlar’s catalyst. The reaction is as follows.

Epoxidation of alkenes: In this reaction, the epoxide is formed from an alkene. The reaction takes place in the presence of peracids. The most commonly used peracid is meta-chloroperbenzoic acid . The reaction is given as follows.

Opening of epoxide ring: The ring opening can be processed via either or mechanism. In the hydrolysis of asymmetric epoxide, the ring-opening occurs by mechanism and a nucleophile attacks at the less substituted carbon of epoxide ring. The reaction is given as follows.

The formation of given products from propyne can be illustrated by the following chemical reactions.

The sequential order of reagents and conditions that are required for the formation of pentanediol are the following:

1.For deprotonation of alkyne: .

2.For the substitution: .

3.For the conversion of alkyne to alkene: .

4.For the formation of epoxide: .

5.For the opening of the epoxide ring:

Ans:

The sequential order of reagents and the conditions that are required for the formation of pentanediol are shown below.