The studyinvestigated the damage of ibuprofen molecules with two conformations induced by hydroxyl radical and the effect of water solvation in water vapor environment. The methods were density functional theory using the B3LYP functional

ab initio MP2 and Slovation Model Density (SMD) model method based on self consistent reaction field theory. The study showed that ibuprofen molecule damage had two mechanisms: α-H abstraction of hydroxyl radicals(water clusters) and hydroxyl radicals addition to benzene ring. The calculation of potential energy surface showed that

for ibuprofen conformation-1

the reaction channel of αH abstraction of hydroxyl radicals assisted by water molecular had an advantage

where the energy barrier of α-H abstraction was 34.68 kJ·mol

-1

. For ibuprofen conformation-2

the reaction channel of

α-

H abstraction of hydroxyl radicals had an advantage

where the energy barrier of α-H abstraction was 34.81 kJ·mol

-1

. In addition

the energy barrier of hydroxyl radicals addition to benzene ring was about 26.00 kJ·mol

-1



and damaged ibuprofen molecules were difficult to repair. The effect of water solvation had little effect on the ibuprofen molecules damage induced by αH abstraction of hydroxyl radicals(water clusters) and hydroxyl radicals addition to benzene ring.