1,6-Hexanedithiol is a linear α,ω-bifunctional thiol that remains liquid down to –21 °C and distils at 184–185 °C (760 mm Hg; flash-point 90 °C). It is practically immiscible with water (< 0.1 g L⁻¹) but dissolves readily in ethanol, acetone, toluene and chloroform. The product is marketed as FEMA-GRAS 3495 and is used at 0.05–1 mg kg⁻¹ to impart a “boiled-meat” note to savoury food flavours; in perfumery it acts as a trace burnt-citrus modifier. Its main outlet, however, is polymer chemistry: the two terminal –SH groups undergo oxidative poly-condensation with oxygen, Fe³⁺ or Cu²⁺ to give poly(hexamethylene disulfide), an elastomeric polysulfide with –S–S– cross-links that shows excellent gasoline and ozone resistance and is employed as a sealant in aviation fuel tanks. 1,6-Hexanedithiol is also a chain-transfer agent in the emulsion polymerisation of chloroprene, regulating molar mass and reducing gel. At room temperature the compound slowly oxidises to the cyclic disulfide; it should therefore be stored under nitrogen at 2–8 °C. Contact with strong bases or oxidisers generates heat and may release toxic H₂S. The liquid is harmful if swallowed (rat oral LD₅₀ 560 mg kg⁻¹) and is irritating to skin and eyes; appropriate gloves and goggles are recommended during handling.
