Mass spectral rearrangements in benzylidene hippuric esters

Abstract

The mass spectra of a series of hippuric esters have been determined. A variety of novel rearrangements induced by the presence of a formed benzyl carbonium ion has been rationalized with the aid of high resolution measurements and isotopic and substituent labeling. An eight centered rearrangement is proposed for the observed transfer of oxygen from a nitro group to a double bond.* This rearrangement ion (c), is also formed directly from the molecular ion as shown by the metastable at 105.1 in the spectrum of 11. Also, this [MI+' -+ c transition with its metastable exists at ionizing voltages too low to permit the direct cleavage to form b. (See Fig. Ib.)