Q24E - Organic Chemistry (Mcmurry)

Question

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

Step-by-Step Solution

Answer

(a)

(b) 

(c) 

Step 1:General mechanism for addition of NaNH 2 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.

Step 2: 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.

Step 3: 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.

Step 4: 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.