The polarization data and concentration dependence of the Raman spectra of aqueous solutions of tetramethyl ammonium chloride in the region 2700–3100 cm^-1 are studied. Group theoretically consistent assignments reveal that the C₄N₊-skeleton acquires a dynamic distortion to C_3v symmetry due to outof-phase combinations of the four CH₃,-stretching oscillations.

The usefulness of Raman spectroscopy as a powerful non-contact, nondestructive analytical tool has been well-demonstrated. A bird’s eye-view of various techniques used for the study of various types of structural phase transitions is given. A few modern applications of laser Raman spectroscopic studies have been mentioned. Thermal variations near critical transition region in the position, halfwidths, intensities and shapes of few thermo-sensitive bands in a few organic and inorganic salts and complexes have been used to deduce the critical exponents β and the activation energyU for orientational disorder of NCS⁻ ions and CH₃NH₃ type groups.