Formation of the exceptional [M - H]+ cation in atmospheric pressure ionization mass spectrometry analysis of 2-(diphenylsilyl) cyclopropanecarboxylate esters.

The favorable formation of [M - H]+ ions in these compounds is attributed to the unique diphenylhydrosilyl group in their structure. The [M + H]+ ion formed easily underwent H2 elimination to produce the [1 - H]+ ion in the API source, and thus, acidification of the ESI solvent apparently accelerates the formation of the [1 - H]+ ion.