Question

What product do you predict from the reaction of \(\mathrm{SCl}_{2}\) with benzene in the presence of \(\mathrm{AlCl}_{3}\) ? What product results if diphenyl ether is treated with \(\mathrm{SCl}_{2}\) and \(\mathrm{AlCl}_{3}\) ?

Short answer

Question: Predict the products of the following reactions: (a) Benzene reacts with \(\mathrm{SCl}_{2}\) in the presence of \(\mathrm{AlCl}_{3}\). (b) Diphenyl ether reacts with \(\mathrm{SCl}_{2}\) and \(\mathrm{AlCl}_{3}\). Answer: (a) The product of the reaction between benzene and \(\mathrm{SCl}_{2}\) in the presence of \(\mathrm{AlCl}_{3}\) is chlorobenzene sulfenyl chloride, \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{SCl}_{2}\). (b) For the reaction between diphenyl ether and \(\mathrm{SCl}_{2}\) in the presence of \(\mathrm{AlCl}_{3}\), the products are the ortho and para isomers of chlorophenyl sulfenyl chloride substituted diphenyl ether, \(\mathrm{o}\)-\(\mathrm{(SCl}_{2}\mathrm{)}\mathrm{C}_{6}\mathrm{H}_{4}\mathrm{OC}_{6}\mathrm{H}_{5}\) and \(\mathrm{p}\)-\(\mathrm{(SCl}_{2}\mathrm{)}\mathrm{C}_{6}\mathrm{H}_{4}\mathrm{OC}_{6}\mathrm{H}_{5}\), respectively.

Step-by-step solution

Understand electrophilic aromatic substitution

Benzene is an electron-rich aromatic compound that can undergo electrophilic aromatic substitution reactions. In these reactions, an electrophile E+ reacts with the benzene ring to substitute a hydrogen atom, resulting in a substituted benzene ring. The presence of a Lewis acid, \(\mathrm{AlCl}_{3}\), in this case, usually helps to generate the electrophile from the other reagent.

Identify the electrophile in the first reaction

In the first reaction, the benzene ring reacts with \(\mathrm{SCl}_{2}\) in the presence of \(\mathrm{AlCl}_{3}\). The Lewis acid, \(\mathrm{AlCl}_{3}\), reacts with \(\mathrm{SCl}_{2}\) to generate a more electrophilic species, \(\mathrm{SCl}_{2}^+\). This electrophilic species will react with the benzene ring.

Predict the product of the first reaction

In the presence of the Lewis acid, the electrophilic species \(\mathrm{SCl}_{2}^+\) will be attracted to the electron-rich benzene ring. An electrophilic aromatic substitution reaction will occur, and one of the hydrogen atoms on the benzene ring will be replaced by the electrophile, \(\mathrm{SCl}_{2}^+\). The product of this reaction will be chlorobenzene sulfenyl chloride, \(\mathrm{C}_{6}\mathrm{H}_{5}\mathrm{SCl}_{2}\).

Identify the electrophile in the second reaction

In the second reaction, diphenyl ether reacts with \(\mathrm{SCl}_{2}\) in the presence of \(\mathrm{AlCl}_{3}\). Just like in the first reaction, the Lewis acid, \(\mathrm{AlCl}_{3}\), reacts with \(\mathrm{SCl}_{2}\) to generate the electrophilic species, \(\mathrm{SCl}_{2}^+\).

Predict the product of the second reaction

The second reaction is a bit different due to the presence of diphenyl ether, where the phenyl rings are connected by an oxygen (O) atom. Due to the electron-donating effect of the oxygen atom, the electrophilic aromatic substitution reaction will occur ortho or para to the oxygen atom in phenyl rings. The product of this reaction will be \(\mathrm{o}\)-\(\mathrm{(SCl}_{2}\mathrm{)}\mathrm{C}_{6}\mathrm{H}_{4}\mathrm{OC}_{6}\mathrm{H}_{5}\) and \(\mathrm{p}\)-\(\mathrm{(SCl}_{2}\mathrm{)}\mathrm{C}_{6}\mathrm{H}_{4}\mathrm{OC}_{6}\mathrm{H}_{5}\), the ortho and para isomers of chlorophenyl sulfenyl chloride substituted diphenyl ether, respectively.