Question

Predict the product and provide the complete electron-pushing mechanism for the following two-step synthetic processes:

Short answer

(a)

(b)

(c)

Step-by-step solution

Step 1:General mechanism for addition of NaNH2 into alkyne

Addition of acetylene into ${\mathbf{\text{NaNH}}}_{\mathbf{2}}$lead to abstraction of acidic hydrogen. Finally the reaction of haloalkane $\mathbf{\left(}{\mathbf{RCH}}_{\mathbf{2}}\mathbf{Br}\mathbf{\right)}$with anionic intermediate leads to the addition alkane group into the alkyne.

Formation of product in part (a)

Reaction of given reactant with ${\text{NaNH}}_2$results into a formation of anionic intermediate

In the second step addition of methyl iodide takes place. Nucleophilic attack of methyl iodide ${\text{(CH}}_3\text{I)}$and then addition of a methyl group into acetylene.

Formation of product in part (b)

Reaction of given reactant with ${\text{NaNH}}_2$results into a formation of anionic intermediate

In the second step addition of Benzyl iodide ${\text{(PhCH}}_2\text{I)}$takes place. Nucleophilic attack of Benzyl iodide and then addition of a Benzyl group into reactant.

Formation of product in part (c)

Reaction of given reactant with ${\text{NaNH}}_2$results into a formation of anionic intermediate.

In the second step addition of methyl iodide ${\text{(PhCH}}_2\text{I)}$takes place. Nucleophilic attack of Benzyl iodide and then addition of a benzyl group into butylene.