Double Hydrogen Transfer Research Articles

Mass spectrometry in structural and stereochemical problems—CCXIX: Identification of an unidirectional quadruple hydrogen transfer process in 7‐phenylhept‐3‐en‐2‐one o‐methyl oxime ether

AbstractExtensive deuterium labeling of 7‐phenylhept‐3‐en‐2‐one O‐methyl oxime ether has made possible the first documentation of an unidirectional quadruple hydrogen transfer process. Three other double hydrogen transfer processes are also described. Several of these multiple hydrogen transfer processes must utilize either a seven‐ or eight‐membered transition state.

Studies in organic mass spectrometry. III. Adenosine 8‐Cyclonucleosides

AbstractThe mass spectra of purine 8‐cyclonucleosides have been determined and compared with those of purine nucleosides. The mass spectra of the former are characterized not only by the presence of an intense molecular ion but also by the presence of the peaks corresponding to 8‐oxy (or 8‐thio) adenine and its protonated form due to a double and triple hydrogen transfer.

Mass spectrometry in structural and stereochemical problems—CXCVIII: A study of the fragmentation processes of some α,β-unsaturated aliphatic ketones

In contrast to the numerous studies of the mass spectrometric fragmentation behavior of saturated aliphatic ketones, that of unsaturated ketones has received only scant attention. The present article is concerned with high resolution measurements and deuterium labeling studies of 17 α, β-unsaturated ketones in order to define their fragmentation modes after electron-impact. Several hitherto undescribed cleavage processes were thus uncovered. For instance α, β-unsaturated methyl ketones (type A) eliminate acetone from their molecular ions through a double hydrogen transfer process. Such a reaction is suppressed in the presence of an α-alkyl group (type B) where it is superseded by the loss of this alkyl substituent through an a prioriunfavorable rupture of a vinylic bond. In those α,β-unsaturated ketones (type C) which can undergo the McLafferty rearrangement, evidence is presented for the occurrence of subsequent methyl loss—a process which seems to be associated with the presence of the conjugated double bond. Whether this is due to prior ketonization of the enol, contrary to the behavior of saturated alicyclic ketones, remains to be determined.

Mass spectrometry and organic analysis—XII αβ‐Unsaturated secondary alcohols

AbstractThe fact that some αβ‐unsaturated alcohols give mass spectra that bear some similarity with the corresponding saturated ketones is discussed, and the double hydrogen transfer necessary to accommodate this is examined by deuterium labelling.