Pyrolysis of Organomercury Compounds: Investigation by the Method of Matrix Isolation

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The method of matrix isolation has been used to investigate mechanisms of gas-phase chemical reactions, in particular the pyrolysis of some organomercury compounds. A molecular beam of pyrolysis products was condensed simultaneously with a large excess of rare gas at temperatures from 5 to 15°K to form a matrix that was subsequently studied by infrared spectroscopy. In the case of C6H5HgCCl3, we found that pyrolysis in the temperature range 220-400°C produced mainly dichlorocarbene. In addition, some trichloromethyl radical was observed and increased in relative importance at increased temperatures. Another identified product of pyrolysis was C6H5HgCl. In general, the same reactive intermediates, CCl2 and CCl3, were found from pyrolysis of Hg(CCl3)2 in the temperature range 250-500°C, along with CCl3HgCl and HgCl2. The identity of CCl2 and CCl2 was demonstrated by measurement of the relative intensities and isotopic splittings of stretching vibrations due to the chlorine isotopes. Isotopic patterns found for CCl2 are: v3 (745.8, 744.0, 741.8 cm-1), v1 (719.5, 717.0, 714.9 cm-1) and for CCl3 are: v3 (897.8, 896.4, 895.2, 893.9 cm-1). Less dilution with the rare gas or warming of the matrix produced a decrease of CCl2 and CCl3 spectral bands and an increase of bands due to C2Cl4, C2Cl6, and other products. These results show the usefulness of matrix isolation in the study of such reactive species as CCl2 produced by pyrolysis in the gas phase.

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