Chemical shifts of 1 H and 13 C NMR of series of methylimidazolium salts (MIM + , X=Br − , BF 4 − and PF 6 − ) function on the length of alkyl groups on the ring, type of solvents and the concentration. The bromides series demonstrate more chemical shift variation on H2 upon the change of solvents and concentration. Unexpected H–D exchange reactions were also observed in the MIM + Br − by using CD 3 OD and D 2 O. The exchange rates strongly depend on the length of the alkyl group, which could cause more steric factor to reduce the interaction between deuterium atom from solvent and C2 of the ring.