Pyrolysis of organomercury compounds: investigation by the method of matrix isolation

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 degrees K to form a matrix that was subsequently studied by infrared spectroscopy. In the case of C(6)H(5)HgCCl(3), we found that pyrolysis in the temperature range 220-400 degrees 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 C(6)H(5)HgCl. In general, the same reactive intermediates, CCl(2) and CCl(3), were found from pyrolysis of Hg(CCl(3))(2) in the temperature range 250-500 degrees C, along with CCl(3)HgCl and HgCl(2). The identity of CCl(2) and CCl(2) was demonstrated by measurement of the relative intensities and isotopic splittings of stretching vibrations due to the chlorine isotopes. Isotopic patterns found for CCl(2) are: v(3) (745.8, 744.0, 741.8 cm(-1)), v(1) (719.5, 717.0, 714.9 cm(-1)) and for CCl(3) are: v(3) (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 CCl(2) and CCl(3) spectral bands and an increase of bands due to C(2)Cl(4), C(2)Cl(6), and other products. These results show the usefulness of matrix isolation in the study of such reactive species as CCl(2) produced by pyrolysis in the gas phase.