Studies of the formation of N-substituted pyridinium mesylates: A theoretical approach

► 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. ► MPW1K/6-31+G** level activation barriers are slightly higher than those from B3LYP/6-31+G**. ► The activation barriers found in solution are lower than those in the gas phase by about 5-10 kcal mol−1.