Phenylacetyl disulfide is used as a sulfurizing reagent in the chemical synthesis of oligonucleotides particularly in phosphoramidite-based DNA and RNA synthesis. It is used to convert phosphite triester linkages into phosphorothioate linkages in the growing oligonucleotide chain.

The purpose of phenylacetyl disulfide is to introduce a sulfur atom in place of the non-bridging oxygen of the phosphate group.

Phenylacetyl disulfide is an organosulfur compound that acts as a sulfur-transfer reagent during oligonucleotide synthesis. After the phosphoramidite coupling step it reacts with the phosphorus-containing intermediate to form the desired phosphorothioate linkage.