Reaction of Cyclohexene with Sulfur in the Presence of Heat

When cyclohexene reacts with sulfur in the presence of heat, the major product formed is 1,2-dithiocyclohexane. This reaction is a type of addition reaction known as a sulfurization reaction. Let's break down the reaction and explain it in detail.

Reaction Mechanism:

The reaction starts with the addition of sulfur to the double bond of cyclohexene. The pi electrons of the double bond attack one of the sulfur atoms, resulting in the formation of a new bond between carbon and sulfur. This leads to the formation of a three-membered ring intermediate called episulfonium ion.

Formation of Episulfonium Ion:

The episulfonium ion is a cycliconium ion intermediate that contains a positively charged sulfur atom. It is formed due to the nucleophilic attack of the double bond on sulfur. The positive charge is delocalized over the carbon atoms adjacent to the sulfur atom.

Rearrangement of Episulfonium Ion:

The episulfonium ion undergoes rearrangement to form a more stable intermediate called a carbocation. This rearrangement involves the migration of a hydrogen atom from one of the carbon atoms adjacent to the sulfur atom to the positively charged carbon atom. This results in the formation of a new double bond between the carbon atoms.

Formation of 1,2-Dithiocyclohexane:

Finally, the carbocation reacts with another sulfur molecule to form 1,2-dithiocyclohexane. The nucleophilic sulfur attacks the positively charged carbon atom, leading to the formation of a new bond and the expulsion of a proton. This results in the formation of the desired product, 1,2-dithiocyclohexane.

Overall, the reaction of cyclohexene with sulfur in the presence of heat proceeds through the formation of episulfonium ion and subsequent rearrangement to form a carbocation. The carbocation then reacts with sulfur to yield 1,2-dithiocyclohexane as the major product.