Thiols, Sulfides, and Sulfonium Ions

Question 1

Formation of a Sulfonium Ion

Answer 1

Reactant: Dimethyl suflide CH₃SCH₃

Reagents: CH₃I

Product: Trimethyl sulfonium iodide or the sulfonium ion

⁺S(CH₃)₃

Question 2

Sulfonium Ion Reaction

Answer 2

Reactant: Sulfonium Ion

Reagent: 1. strong base (^-OH)

Product: varies

Mechanism: SN2

The reaction works best if the group undergoing nucleophilic attack is a methyl group or primary alkyl group.

Question 3

Thiol Reaction

Answer 3

Reactant: Thiol

Reagent: 1. Strong base (-OH)

2. Alkyl halide

Product: varies

Mechanism: SN2

The less substituted of the 2 R groups should be the alkyl halide and the more substituted should be the the thiol.

A tertiary halide cannot undergo SN2, so it must be the thiol.

A benzene ring cannot undergo backside attack so it must be the thiol.