Conjugation of reduced glutathione to a wide number of exogenous and endogenous hydrophobic electrophiles (PubMed:3277162, PubMed:3532034). Involved in the detoxification of certain herbicides (PubMed:3532034). glutathione + RX = a halide anion + an S-substituted glutathione + H(+) Homodimer. Belongs to the GST superfamily. Phi family.