Question

In addition to using ${\mathbf{CHX}}_{\mathbf{3}}$and base to synthesize dihalocarbenes (Section 26.4), dichlorocarbene $\left({\mathrm{CCL}}_2\right)$can be prepared by heating sodium trichloroacetate. Draw a stepwise mechanism for this reaction.

Short answer

Answer

Mechanism

Step-by-step solution

 α-elimination reaction

The 1,1-elimination or $\alpha$-elimination reaction involves the elimination of two groups from the same carbon atom.

Stability  

The dichlorocarbene compound is more stable than the trichloromethanide ion, as the dichlorocarbene compound is neutral.

Mechanism of the given reaction

Sodium trichloroacetate, upon heating, loses a carboxyl $\left(\mathrm{COO}\right)$group, resulting in the formation of sodium-trichloromethanide. The trichloride ion loses a chloride ion to achieve greater stability and form dichlorocarbene.

The mechanism of the given reaction is shown below.

Mechanism