Raman study of the concentration dependence of the frequency shifts and linewidth changes in a(3Cl-pyridine + methanol) system

The frequency shifts and linewidth changes of the two vibrational bands of 3Cl-pyridine (3Cl-p) at ≈ 729 and ≈1031 cm−1 have been studied in a binary mixture of (3Cl-p + CH3 OH) with varying concentrations of 3Cl-p in mole fractionsC = 0.1, 0.2, 0.3, 0.5, 0.7, 0.8 and 0.9. A plot of linewidth vs.C depicts a minimum aroundC = 0.7 which has been explained in terms of two competing phenomena, namely diffusion and motional narrowing. The frequency shifts, which exhibit almost negligibly small changes with varyingC, are most probably caused due to opposing effects of the CI substituent at position 3 and an N atom sitting in the ring.