The ionic liquids containing trichloride ion, 1-methyl-3-n-hexylimadazolium trichloride ([HeMIM][Cl₃]) and 1-methyl-3-n-octylimadazolium trichloride ([OcMIM][Cl₃]), were synthesized by bubbling purified chlorine gas into the ionic liquids containing chloride ion, 1-methyl-3-n-hexylimadazolium chloride ([HeMIM]Cl) and 1-methyl-3-n-octylimadazolium chloride ([OcMIM]Cl), at room temperature and possess an excellent performance as chlorinating agent for the chlorination of some organic substrates including alkenes, ketones and arenes. The experimental results indicate that the ionic liquids, [HeMIM]Cl and [OcMIM]Cl, are the ideal medium for absorption of chlorine, their maximum absorption contents of active chloride are 25.9% and 23.1% (w/w), respectively, and these ionic liquids can be recycled for the absorption of chlorine as absorption medium and for the chlorination reaction as chlorinating agent.

Key words: ionic liquid, chlorine, chlorination, trichloride