Video Transcript
The following equation describes how benzene can be reacted with chloromethane to make toluene and hydrogen chloride products. Which of the following substances is ordinarily used to speed up and facilitate this reaction process? (A) Concentrated sulfuric acid, (B) concentrated hydrochloric acid, (C) aluminum chloride, (D) iron metal, (E) nickel metal.
Let’s begin by examining the given reaction. The reactants are benzene and chloromethane. Chloromethane is a type of organic molecule known as a chloroalkane. The products are toluene and hydrogen chloride. Toluene is a monosubstituted arene, which means that one of the hydrogen atoms of the benzene ring was replaced with another group during the reaction. To form toluene, a hydrogen atom must have been replaced with a methyl group.
When parts of a molecule are removed and replaced with alkyl groups, such as methyl groups, the reaction is known as an alkyl substitution reaction. More specifically, the reaction in this problem is known as the Friedel–Crafts alkylation of benzene. In this type of alkylation, benzene is reacted with a chloroalkane in the presence of a Lewis acid catalyst to produce an alkyl benzene and hydrogen chloride. The Lewis acid catalyst weakens the carbon-chlorine single bond in the chloroalkane, which accelerates the reaction with benzene. The alkyl portion of the chloroalkane replaces a hydrogen atom on the benzene ring. And the hydrogen atom that was removed combines with chlorine to form hydrogen chloride.
Now, there are many options for reactants and catalysts for a Friedel–Crafts alkylation. However, two of the most commonly used catalysts are iron(III) chloride and aluminum chloride. In conclusion, one of the substances that is ordinarily used to speed up and facilitate the reaction process shown in this question is aluminum chloride or answer choice (C).
