MASS SPECTROMETRY IN STRUCTURAL AND STEREOCHEMICAL PROBLEMS .183. A STUDY OF ELECTRON IMPACT INDUCED FRAGMENTATION OF ALIPHATIC ALDEHYDES

In spite of the importance of the aldehyde functionality in organic chemistry, no investigation of the mass spectral behavior of aliphatic aldehydes has as yet been performed using the techniques of isotopic labeling, exact mass measurement, and metastable peak analysis. The present study, utilizing hexanal and all of its possible deuterated analogs as substrates as well as several pertinent labeled heptanals, has shed new light on the electron impact induced behavior of aliphatic aldehydes. Several interesting observations have been made, including the origin of the hydrogen atoms in the loss of water (Tables III and IV), the multiple, and yet not indiscriminate, expulsion of ethylene (Schemes I and II), the apparent nonspecificity of the “McLafferty” rearrangement leading to an ionized olefin (Scheme IV), and the reciprocal hydrogen transfer (Scheme VI) associated with the loss of a propyl radical. © 1969, American Chemical Society. All rights reserved.