Question

Question: You will often return to nucleophilic substitution, in particular the S_N2 reaction, in subsequent chapters and concentrate on the nucleophile rather than the alkyl halide. By using different nucleophiles, nucleophilic substitution allows the synthesis of a wide variety of organic compounds with many different functional groups. With this in mind, draw the products of each two-step sequence. (Hint: Step [1] in each part involves an acid-base reaction that removes the most acidic hydrogen from the starting material.)

a.

b.

c.

Short answer

a.

b.

c.

Step-by-step solution

Alkyl halide

The alkyl halide contains the alkyl group and the halogen atom (F, Cl, Br, I).

The halogen atoms attract the electron of the carbon. Therefore, it generates the electrophile at the location of the C-X bond.

Alkoxide

The alkoxide contains the alkyl group and an oxide ion. The oxide ion has three lone pairs of electrons.Therefore, the alkoxide acts as a nucleophile. The nucleophile forms the bond with the electrophile.

Mechanism 

a. In the given reaction, the alcohol contains acidic hydrogen, which is abstracted by the base NaH. This reaction gives an alkoxide which attacks at the alkyl halide and forms the desired product, as shown below:

Nucleophilic substitution reaction in a

b. In the given reaction, the terminal alkyne contains acidic hydrogen, which is abstracted by the base . This reaction gives a nucleophile that attacks at the alkyl halide and forms the desired product, as shown below:

Nucleophilic substitution reaction in b

c. In the given reaction, the anhydride contains acidic hydrogen which is abstracted by the base sodium ethoxide. This reaction gives a nucleophile that attacks at the alkyl halide and forms the desired product, as shown below:

Nucleophilic substitution reaction in c