Unstable intermediates. Part LXXVII. Paramagnetic centres in γ-irradiated hydrogen chloride and caesium hydrogen chloride

Abstract

E.s.r. studies have revealed that the radical ion Cl₂^– is a major product of radiolysis of the title compounds at 77 K. The marked reduction in g⊥ compared with those for V_K centres in alkali-metal and alkaline-earth metal halides shows that Cl₂^–, especially in solid hydrogen chloride, is strongly hydrogen bonded. Hydrogen atoms are formed in good yield in CsHCl₂, but not in HCl. However, the hyperfine coupling of 495 G is unusually low and the g-value (2·0050) unusually high. These results, and the linewidths (ca. 17 G), are interpreted in terms of weak bonding to neighbouring chlorine atoms.

Of the other magnetic species formed, the most interesting is characterised by a well resolved 109 G doublet obtained from irradiated HCl. This was shown by use of DCl to be due to coupling to a single proton. A similar doublet, having a subsidiary structure consisting of four lines separated by ca. 10 G was partially concealed by the main doublet. After removal of the irradiated HCl, a broad doublet, was again given with a(H)ca. 139 G. It is postulated that these radicals are of the form HSi(OH)₂, HSiCl(OH), and HSi(O–)₂.

The mechanism of radiation damage is discussed.