Dipole Moment Derivatives of Free and Hydrogen Bonded O-H Bond of Methanol

Infrared intensities of fundamental and first overtone bands of O-H stretching mode of methanol are reported in a few hydrogen bonding solvents. From these intensity data the first and second dipole moment derivatives have been computed. It is noticed that the intensity of the fundamental band increases appreciably on hydrogen bonding whereas the first overtone does not show much change in intensity. Two sets of dipole moment derivatives obtained from ++ and -+ combinations of the transition moment matrix elements R10 and R20 are considered, the values for – and -+ combinations are equal in magnitude to those of ++ and +- combinations respectively and opposite in signs. It is observed that in all the case studied both the dipole moment derivatives of O-H bond increase on hydrogen bonding. It is shown that with an increase in the values of both the dipole moment derivatives not only one can explain an appreciable increase in