Question

It is possible to generate sulfur ylides in a manner similar to that used to produce phosphonium ylides. For example, treating a sulfonium salt with a strong base gives the sulfur ylide.

Short answer

Question: Explain the process of generating sulfur ylides from a sulfonium salt using a strong base. Answer: To generate sulfur ylides from a sulfonium salt, follow these steps: 1. Identify the sulfonium salt and strong base: The sulfonium salt consists of a sulfur atom bonded to three organic substituents (R) with a positive charge on the sulfur atom. A strong base (B-) is required for deprotonation. 2. Formation of the sulfur ylide: The strong base extracts a proton (H+) from one of the organic substituents bonded to the sulfur atom. This leads to the breaking of one S-C bond and the transfer of the bond's electron pair to the sulfur atom, forming a sulfur ylide with a neutral sulfur atom, two organic substituents, and a lone pair of electrons. The general reaction is R_3S^(+) + B^(-) → R_2S: + HB. 3. Reaction of sulfur ylide with electrophiles: The sulfur ylide can react with various electrophiles, leading to the formation of different products depending on the reaction conditions. Sulfur ylides are useful in various synthetic transformations due to their nucleophilic properties.

Step-by-step solution

Identify the sulfonium salt and strong base

To generate the sulfur ylide, first identify the sulfonium salt and strong base to be used in the reaction. The sulfonium salt consists of a sulfur atom bonded to three organic substituents (R) and has a positive charge on the sulfur atom. A strong base (B-) is required to generate the ylide by deprotonation.

Formation of the sulfur ylide

Once the sulfonium salt and strong base are identified, the strong base extracts a proton (H+) from one of the organic substituents bonded to the sulfur atom. This causes the breaking of one S-C bond and the bond's electron pair being transferred to the sulfur atom, neutralizing its positive charge. The result of this deprotonation reaction is the formation of the sulfur ylide, which has a neutral sulfur atom bonded to two organic substituents and a lone pair of electrons. Here's the general reaction scheme for the formation of sulfur ylides: R_3S^(+) + B^(-) → R_2S: + HB R_3S^(+) represents the sulfonium salt, B^(-) is the strong base, R_2S: represents the sulfur ylide with a lone pair of electrons on the sulfur atom, and HB represents the conjugate acid of the base.

Reaction of sulfur ylide with electrophiles

After generating the sulfur ylide, it can react further with various electrophiles, leading to the formation of various products depending on the reaction conditions. These reactions are beyond the scope of this exercise, but it's worth mentioning that sulfur ylides can be employed in a range of synthetic transformations due to their nucleophilic properties.