4-hydroxy-2,5-dimethylphenyl-benzophenone: conformational stability, FT-IR and Raman investigation

In this paper we have studied the 4-hydroxyl-2,5 dimethylphenyl-benzophenone. Also, it was analyzed the vibrational assignment (FT-IR and Raman) in conjunction with computational results. The conformational analysis showed three barrier heights where two are due to the dihedral rotation and the other one is attributed to hydroxyl rotation. While the high dihedral rotational barrier (TS1) is 6.06-7.22 kcal mol(-1), the lower one (TS2) is almost three times smaller. The variations with the change of basis set is 5-8% to TS1, and 3-15% in the values predicted to TS2. In the case of OH rotational barrier, the values range from 3.70 to 4.86 kcal mol(-1), and it is also observed that this transition state is less sensitive to the change of basis set and to the method. Two isomers was detected due to the changes in the OH rotation with the gap energy lower than 0.7 kcal mol(-1), and at this point is seen that semi-empirical methods fail into describe the most stable conformation which may be due to the small energy gap. The enthalpy formation at 0 K and 298 K was 111.71 and 102.20 kcal mol(-1), respectively.