Birge–Sponer Estimation of the C–H Bond Dissociation Energy in Chloroform Using Infrared, Near-Infrared, and Visible Absorption Spectroscopy. An Experiment in Physical Chemistry

Abstract

The fundamental and overtone vibrational absorption spectroscopy of the C–H unit in CHCl3 is measured for transitions from the ν = 0 energy level to ν = 1 through ν = 5 energy levels. The energies of the transitions exhibit a linearly-decreasing spacing between adjacent vibrational levels as the vibrational quantum number increases. These data are used as the basis for Birge–Sponer estimation of the dissociation energy, D0, for the C–H bond in chloroform. The value obtained from the first 5 transitions is D0 = 459 ± 8 kJ mol-1 (95% confident interval), compared to a literature value of the bond dissociation energy for this bond of 401 kJ mol-1. The error of 14.5% results from sampling only the most harmonic energy levels in the vibrational potential well.