Characteristic Vibrations of CHClF2

(Cs symmetry)

CHClF2 (chlorodifluoromethane, also known as HCFC-22 or Freon-22) is roughly tetrahedral, like the other halogen-substituted methanes (e.g., CFC-11, CFC-13). There are no significant natural sources of this molecule, and it is as a result of human activity that the present atmosphere contains ~0.132 ppb of CHClF2. CHClF2 has been used as a more ozone-friendly substitute for CFC's in refrigeration, and as a propellant. HCFC's like CHClF2 break down relative quickly in the atmosphere (with a lifetime of roughly 10 years), and so will not accumulate in the stratosphere as easily as the more durable CFC's, which last 50-100 years. However, CHClF2 does have significant ozone-destroying potential, and production will eventually be scaled back. CHClF2 is a slight contributor to the human-induced strengthening of Earth's greenhouse effect, adding a radiative forcing ≈ 0.03 Watts/m2 (IPCC).
Since both stable isotopes of chlorine are common (35Cl - 75.77%, 37Cl - 24.23%), atmospheric CHClF2 is a mixture of 12C1H35Cl19F2 (~75%) and 12C1H37Cl19F2 (~24%). Both isotopic forms of the molecule have Cs point-group symmetry. All nine characteristic vibrational modes can interact with infrared light, scattering or absorbing heat radiation from the Earth before it escapes to space. The normal modes depicted below were modeled using hybrid density functional theory (B3LYP) and the cc-pVTZ basis set. Vibrational frequencies, tabulated by Snels and D'Amico (2001, J. Mol. Spectrosc. 209:1-10), are also shown -- values for the 12C1H35Cl19F2, isotopologue are listed first, with values for 12C1H37Cl19F2 underneath. These are the fundamental frequencies, and have not been corrected for anharmonicity.

o1 = 3021.6 cm-1 (35Cl)
3021.4 cm-1 (37Cl)
A' Symmetry

o2 = 1313.2 cm-1 (35Cl)
N/A cm-1 (37Cl)
A' Symmetry

o3 = 1108.7 cm-1 (35Cl)
1108.7 cm-1 (37Cl)
A' Symmetry
CHClF2_nu1.gif CHClF2_nu2.gif CHClF2_nu3.gif

o4 = 809.7 cm-1 (35Cl)
804.5 cm-1 (37Cl)
A' Symmetry

o5 = 596.4 cm-1 (35Cl)
595.4 cm-1 (37Cl)
A' Symmetry

o6 = 412.9 cm-1 (35Cl)
407.9 cm-1 (37Cl)
A' Symmetry
CHClF2_nu4.gif CHClF2_nu5.gif CHClF2_nu6.gif

o7 = 1351.3 cm-1 (35Cl)
N/A cm-1 (37Cl)
A'' Symmetry

o8 = 1127.3 cm-1 (35Cl)
1127.1 cm-1 (37Cl)
A'' Symmetry

o9 = 366.2 cm-1 (35Cl)
364.3 cm-1 (37Cl)
A'' Symmetry
CHClF2_nu7.gif CHClF2_nu8.gif CHClF2_nu9.gif

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