Knowledge Bank

The integrated intensities of the fundamental absorption bands of $CHF3$ and $CDF3$ have been measured using the Wilson-Wells-Penner-Weber method. The results are in $CHF3,24.2\pm 0.9,12.3\pm 0.9,81.8\pm 1.1$, and $4.2\pm 0.3$ km $mol-1$ for the A modes at 3036 and $700cm-1$ and the E modes at 1372 and $507cm-1$, respectively, and $627\pm 10$ km $mol-1$ for the overlapping bands centered at $1150cm-1$, and in $CDF3,29.5\pm 2.0,76.7\pm 1.5,12.9\pm 0.4,579\pm 7,47.5\pm 4.0$ and $4.5\pm 0.2$ km $mol-1$ for the A modes at 2257, 1109 and $693cm-1$, and the E modes at 1209, 974 and $503cm-1$, respectively. The values of the hydrogen and fluorine atom affective charges derived from these data, making use of the concept of the atomic polar tensors, are $XH=0.049\pm 0.004$ e and $XF=0.6000\pm 0.004$ e, which are not only in good agreement with the SCF ab-initio calculation but also rather close to those of other fluoromethanes.