Hydrogen sulfide reactivity with thiols in the presence of copper(II) in hydroalcoholic solutions cognac brandies: Formation of symmetrical and unsymmetrical dialkyl trisulfides

In the presence of copper(II), hydrogen sulfide reacts with thiols (methanethiol and ethanethiol) to yield symmetrical or unsymmetrical trisulfides (dimethyl trisulfide, diethyl trisulfide, and ethyl methyl trisulfide). In alcoholic beverages, these compounds are known for their nauseous character reminiscent of onion smell, and for their low detection levels (dimethyl trisulfide: 0.1 mu g/L). A mechanism for trisulfide formation is proposed that involves a two-step redox reaction.