Study Toluene P-xylene And M-xylene Chloromethylation Catalysted By Ionic Liquids

Room-temperature ionic liquids as a new type of environmentally friendlysolvents and catalysts was known and accepted. In comparison with VOCs, ILs as areaction media or catalyzer has no vaportension and can be reused, the process is alsosignificant from the viewpoint of pollution control of VOCs and while the ionicliquids can be recycled.In this paper, a series of ILs were synthesized. These ILs are [C₂mim]Br,[C₃mim] Br, [C₄mim] Br, [C₅mim] Br, [C₆mim] Br, [C₇mim] Br, [C₈mim] Br, [C₁₂mim] Br, [C₄mim]BF₄,[Hmim]Br, [Hmim]Cl, [C₄mim]C₄F₉SO₃.Furthermore, We have investigated the use of room temperature ionic liquids ascatalytic for the Blanc reaction of toluene, p-xylene and m-xylene. The effects oftemperature, time and the amount of ILs were investigated. The reaction was found toproceed under relatively mild conditions with excellent conversion and selectivity.The toluene's reaction was found to proceed with high conversion (up to 90%) underrelatively shorter reaction times(10h), lower temperatures (65℃) and lower amountof [C₁₂mim]Br catalyst (4%mol) to give the desired methylbenzyl chroride as the soleproduct. The p-xylene's reaction was found to proceed with high conversion (up to88.5%) under relatively shorter reaction times(10h), lower temperatures (65℃) andlower amount of [C₁₂mim]Br catalyst (4%mol) to give the desired 2,5-dimethylbenzylchloride as the sole product. The m-xylene's reaction was found to proceed with highconversion (up to 91.5%) under relatively shorter reaction times(10h), lowertemperatures (65℃) and lower amount of [C₁₂mim]Br catalyst (4%mol) to give thedesired 2,4-dimethylbenzyl chloride as the sole product. It was found that the long ofalkyl of cations effect the conversion of toluene. The longer the long of alkyl was thehigher the conversion of toluene was. The 1-alkyl-3-methyl-imidazolium bromide hasbetter behavior than other used ionic liquids. When the cation is same, the anion isalso important for the Blanc reaction. It is seemly that Br is better than other anion.The ionic liquid layer was concentrated under reduced pressure to remove water andthe resulting liquid was dried in vacuum. The ionic liquid can be recycled and reusedwithout loss of chemical yield concerning the chloromethylation product after reused6 times.In conclusion, we have demonstrated that ionic liquids can be successfully used for Blanc reactions of toluene, p-xylene and m-xylene.