The Fourier transform-infrared spectrum of 3-methylsulfanilic acid was recorded and analyzed. The vibrational wavenumbers of the compound have been computed using the Hartree-Fock/6-31G* basis and compared with the experimental values. The first hyperpolarizability, predicted infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar structures and is an attractive object for future studies of non linear optics. Optimized geometrical parameters of the title compound are in agreement with similar reported structures.

The vibrational frequencies of anilinium nitrate were calculated using Gaussian03 software package and the fundamental modes are assigned. The calculated frequencies are in agreement with the reported experimental values. The calculated geometrical parameters are compared with the geometrical parameters of similar derivatives. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non linear optics.

Fourier transform infrared (FT-IR) and Fourier transform (FT) Raman spectra of aniline acetate were recorded and analyzed. The vibrational frequencies of aniline acetate were calculated using Gaussian03 software package and the fundamental modes are assigned. The calculated frequencies are in agreement with the experimental values. The calculated geometrical parameters are compared with the geometrical parameters of similar derivatives. The first hyperpolarizability, infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non linear optics

The vibrational frequencies of 2-hydroxy-4-methyl pyrimidine were calculated using Gaussian 03 software package and the fundamental modes are assigned. The calculated frequencies are in agreement with the reported experimental values. The calculated geometrical parameters are compared with the geometrical parameters of similar derivatives. The calculated first hyperpolarizability is comparable with the reported values of similar derivatives and is an attractive object for future studies of non linear optics.