Question

Draw the structure of the starting material needed to make 2-methylhept-3-yne using sodium amide in liquid ammonia, followed by 1-bromopropane. The starting hydrocarbon must have no more than five carbons. 1) NaNH2, NH3(l) 2) CH3CH2CH2Br + NaBr

Answer 1

Concepts and reason

The concept used to solve this problem is to draw the starting material (alkyne) using the given base, alkyl halide and products.

The alkynes are converted to acetylide ion with a strong base, which is capable of reacting with the electrophiles (alkyl halides and epoxides).

Fundamentals

Sodium amide, is a strong base which abstracts the proton.

Acetylide ions react with the unhindered alkyl halide and forms the substitution product.

The mechanism of the nucleophilic substitution is ${{\rm{S}}_{\rm{N}}}{\rm{2}}$ .

The retrosynthesis is as follows:

The reaction is as follows:

The reaction is as follows:

Ans:

The required alkyne is as follows: