Abstract:

The chiral shift mechanism of ibuprofen molecule in water was researched at the B3LYP/6-31+g(d,p) level, which is based on density functional theory. In addition, the structures of transition states and intermediates during the shift process from Stype to Rtype ibuprofen molecules were searched in water. At the MP2/631++g(d,p) level, the single point energies of transition states and intermediates were calculated, as well as zero point vibrational energies of the whole system were amended to get a higher energy. Then the potential energy surfaces of hydrogen transfer and the heterogeneous processes of intermediates on the chiral transition path of ibuprofen molecules in water were drawn. The results show that there are two paths to achieve chiral transition of ibuprofen molecule in water. The process of hydrogen transfer can be achieved with single or two water molecules as bridge. The highest energy barriers of the two paths both come from the transfer processes of hydrogen on the chiral carbon transfers to the oxygen on the carbonyl.

Key words: chiral, ibuprofen, density functional, transition state