arylthiol

An arylthiol is an organosulfur compound in which a thiol group (−SH) is attached directly to an aryl ring. The simplest example is thiophenol (phenylthiol). Substituted arylthiols, such as 4-mercaptophenol, are also common. They are sometimes referred to as aryl mercaptans.

Properties and reactivity: The thiol hydrogen is moderately acidic; in water the pKa of thiophenol is about 6.6, making it more acidic than many aliphatic thiols. Deprotonation gives the arylthiolate anion (ArS−), which acts as a nucleophile in various reactions. The aryl ring delocalizes charge in the thiolate, influencing reactivity at sulfur. Arylthiols readily oxidize to disulfides (ArS–SAr) and, under stronger conditions, to higher oxidation products. They typically have strong, characteristic odors and are often used as odorants or odor cues in various contexts.

Preparation and occurrence: Arylthiols can be prepared by reducing diaryl disulfides, by thiolation of aryl halides under transition-metal catalysis, or by reduction of aryl sulfonyl chlorides. They occur in natural products and serve as versatile intermediates in organic synthesis.

Applications: Arylthiols are used as intermediates to form aryl thioethers and other sulfur-containing compounds. They also function as ligands in coordination chemistry and as components in fragrances and specialty chemicals. Safety considerations include their distinctive odors and potential toxicity, requiring appropriate handling and ventilation.