Dispersions of carbon nanotube salts prepared by treating single-walled carbon nanotubes (SWNTs) withlithium in liquid ammonia react with aryl and alkyl sulfides by single electron transfer (SET) to yield transientradical anions that dissociate into carbon-centered free radicals and mercaptide. The free radicals add to thesidewalls of the nanotubes or recombine with SWNT radical anions. AFM images indicate that the derivatizedSWNTs are partially debundled. Disulfides react with carbon nanotube salts to yield SWNTs functionalizedby sulfur-centered radicals.