The Raman spectra of a number of polychloro compounds

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Abstract
The Raman spectra are given of the following compounds, for the greater part prepared by Prins and put by him at our disposal: CCl3. CHCl2 (P), C3Cl8, CCl3.CHCl.CCl3 (P), CCl3.CCl2. CHCl2, CCl3. CHCl. CHCl2. CHCl2. CCl2. CHCl2. CHCl2. CHCl. CHCl2, CHCl2. CCl2. CHCl. CHCl2, CHCl2. CHCl. CHCl. CH2Cl (liquid and solid), CHCl2. CCl2. CCl2. CCl2. CCl2. CHCl2, CCl2 = CCl. CCl3, CCl2 = CCl. CHCl2, CHCl = CCl. CHCl2 (cis and trans), CCl2 = CCl. CCl2. CHCl. CCl3, CCl2 = CCl. CHCl. CCl2. CCl3, CCl2 = CCl. CCl2. CHCl. CHCl2, CHCl = CCl. CHCl. CHCl. CCl2. CHCl2, CCl2 = CCl. CCl = CCl. CCl3 (P), CCl2 = CCl. CCl2. CCl2. CCl = CCl2 (P) and CCl3. CCl = CCl. CCl = CCl. CCl3 (P).Hydrogen vibrational frequencies (in particular valency frequencies) may be distinguished, which are characteristic for the groups —CHCl2, —CHCl— and CH2Cl— in saturated polychloro compounds (in which these groups are attached to chains of varying lengths with masses considerably exceeding that of chlorine). The valency frequency v(CH) in CHCl2— is about 40—50 cm−1 higher than that in ‐CHCl‐. It is probable that this difference must be ascribed to mutual interactions between hydrogen with chlorine of the same group and with chlorine atoms attached to neighbouring carbon atoms.v(CH) for H attached to C = C in unsaturated compounds is considerably higher than v(CH) in saturated compounds. This increase must apparently be ascribed to a direct influence which the C = C double bond exerts on the C ‐ H bond (electron displacements). v(CH) vibrations in groups CHCl2‐ and ‐CHCl‐ retain in general about the values they possessed in the same groups in saturated compounds. Some general remarks are made regarding the influence of a continued substitution of H by Cl in methane on the sign and the magnitude of the charge present on the atoms of hydrogen.Chain vibrational frequencies “v(C‐C)” in saturated, “v(CC)” and “v(C‐C)” in unsaturated compounds are discussed. The introduction of a double bond in a saturated polychloro compound results in an increase of the “v(C ‐ C)” chain vibrational frequencies also.A comparison of “v(C ‐ Cl)” for Cl bound to C = C with “v(C ‐ Cl)” for Cl attached to C ‐ C in otherwise identical compounds containing only one atom of chlorine (or halogen), permits us to draw the conclusion that v(C ‐ Cl) is larger for Cl bound to C = C than for Cl at C ‐ C. The phenomenon of resonance in the unsaturated halogen compounds is at least partially responsible for this increase, as it causes the C‐Cl bond in the unsaturated compounds to possess a certain amount of double bond character.In general we did not meet indications of the presence of rotational isomers caused by a restricted rotation around the C ‐ C single bond. Exception must be made for CHCl = CCl. CHCl2 (“cis”) and for the compounds C5Cl8 and C5Cl10, where such a hindered rotation plays a role in all probability.

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