Theoretical studies of the formation of quaternary pyridinium mesylates

► The reaction pathway of the formation of four quaternary pyridinium salts was investigated at the DFT level. ► Structures were optimized in the vacuum, single point PCM calculations were done in chloroform, ethanol and water. ► B3LYP/6-31+G** activation barrier increases when a hydrogen atom in the methyl group is replaced by a tetrahydrofuran ring. ► MPW1K/6-31+G** level activation barriers are slightly higher than those from B3LYP/6-31+G**.