Chemiluminescent and non-chemiluminescent ozonations of selected electron-rich alkynes in halomethanes

Alkynes of sufficiently high nucleophilicity react with electrophilic O-3 u nder conversion of the alkyne function to a vicinal dicarbonyl function. Co ntrary to earlier investigations with alkylated or arylated acetylene, prod ucts of complete C-C cleavage were not found as primary products, and, beyo nd that, peroxidic reaction products were absent. Trimethylsilylated alkyne s reacted with O-3 either by uptake of two or three O-atoms, but again with out C-C cleavage or formation of peroxides. Two particularly electron-rich, symmetrically substituted alkynes revealed strong chemiluminescence during ozonation at low temperature, whereas this behavior was not observed with unsymmetrically substituted alkynes. The results are summarized in terms of a mechanistic discussion.