We don't have synonyms for sulphonating yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are sulphonation, sulfonating and sulphurating.
(n) :
(British spelling, chemistry) Alternative spelling of sulfonate. [(American spelling, chemistry) Any salt or ester of a sulfonic acid.]
(v) :
(British spelling, chemistry) Alternative spelling of sulfonate. [To treat or react with a sulfonic acid, or to introduce such a group into a compound.]
(n) :
(British spelling, chemistry) Alternative spelling of sulfonate. [(American spelling, chemistry) Any salt or ester of a sulfonic acid.]
(v) :
(British spelling, chemistry) Alternative spelling of sulfonate. [To treat or react with a sulfonic acid, or to introduce such a group into a compound.]