Ozonolysis of Tetramethylethylene: Characterization of Cyclic and Open-Chain Oligoperoxidic Products.

The ozonolysis of tetramethylethylene (TME) in soln. to high conversion in nonparticipating solvents at -60 °C yields predominantly oligoperoxides. For the first time, these products have been characterized using electrospray ionization mass spectrometry (ESI-MS) under soft ionization conditions. The predominant structure formed in reactions carried out in pentane (up to 2.0 M TME) is shown to be the cyclic hexamer of acetone carbonyl oxide (oligocarbonyl oxide with d.p., n = 6), but cyclic structures with n up to 19 are obsd. A small proportion of the oligoperoxides formed are open-chain compds. with end groups that suggest that chain termination of oligocarbonyl oxides can occur through reaction with either water or hydrogen peroxide. Ozonolysis in dried Bu acetate similarly produces mainly cyclic oligoperoxides. However, ozonolyzes carried out in undried Bu acetate yield mainly open-chain oligoperoxides, confirming that propagating carbonyl oxide chains are readily terminated by water. Relative amts. of the open-chain oligomers so-formed suggest that undried Bu acetate contains ca. 0.1% wt./wt. water. The ozonolysis of TME in the participating solvent, methanol, at -60 °C yields 2-methoxyprop-2-yl hydroperoxide via reaction of acetone carbonyl oxide with methanol; no oligoperoxidic products are formed in this case. [on SciFinder(R)]