Abstract
Near-UV irradiation of solutions of (Bu
4N)AuCl
4 in aerated ethanol-stabilized chloroform causes the continuous decomposition of chloroform, as evidenced by the production
of many equivalents of HCl and peroxides. At the outset of irradiation, most of the AuCl
4
− is reduced to AuCl
2
−, but the reduction stops and is reversed. The same experiments done in ethanol-free chloroform cause chloroform decomposition
only until the irreversible reduction of the gold is complete. In deoxygenated ethanol-free chloroform, irreversible reduction
to AuCl
2
− is accompanied by the formation of HCl and CCl
4, while the main decomposition products in deoxygenated ethanol-stabilized chloroform are HCl and C
2Cl
6. It is proposed that, in ethanol-free chloroform, photoreduction of AuCl
4
− begins with the concerted elimination of HCl from an association complex of CHCl
3 with AuCl
4
−, and that ethanol suppresses
{ \text
CHCl3 ·\text
AuCl4 - } \{ {\text{CHCl}}_{3} \cdot {\text{AuCl}}_{4}^{ - } \} complex formation, leaving a slower radical process to carry out the photoreduction of AuCl
4
− in ethanol-stabilized chloroform. In the presence of oxygen, the radical process causes a build-up of CCl
3OOH, which reoxidizes AuCl
2
− to AuCl
4
− and allows the photodecomposition of CHCl
3 to continue indefinitely.
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