Redetermination of mass spectra of deuteromethanes

Abstract

Mass spectra of the four deuteromethanes have been re~easu~ed uS.ing samples of improved isotopic purity. The relative abundances of fragment lOns myolvmg loss of I~ 0: D atoms from the molec ules CH3D, CH2D2, and CHD3 are not proportlOnal to the a pnon probabilities of removing H or D atoms but have been expressed in t erms of the a priori probabil ity times a weighting factor. The weighting ~a~tor for remo,:"ing one H or D ~tom from these mol ec ul es can be roughly expressed as posItIve and negahve powers of a slDgle constant 1.19 ±O.015 and the same power law holds for the relative abundances of H+ and D +. Weighting factors for removing two or more hydrogenic atoms are not consistent with this power law.

Mass spectra of some deuteroethanes

“…This is qualitatively consistent with experiments with other deuterohydrocarbons. The weighting factors for removing H and D, 1.67 and 0.86 are of the magnitudes found for CHD 3 [ 5 ] and C 2 HD 3 [ 6 ]. There is, however, no regular trend in weighting factors for removing 1, 2, 3, etc., atoms from C 2 HD 5 such as was found in the deuteroethylene spectra [ 6 ].…”

“…The mass spectra of deuteroethylenes [ 6 ] and deuteromethanes [ 5 ] show a regular trend in the probability of removing H and D atoms from molecules with increasing numbers of D atoms in the molecule. In the C 2 range there is no appreciable difference between the patterns of symmetrical and unsymmetrical dideuteroethylenes.…”

Highly dispersed silica-supported iridium and iridium–aluminium catalysts for methane activation prepared via surface organometallic chemistry

“…The precise amount of each isotopomer was determined as a function of methane conversion (Figure 4) according to the fragmentation models given by Dibeler and Mohler. 27 To consolidate these results, the isotopic distribution was also determined by a complementary mathematical approach developed by Schoofs and his team. 28 From these data, it is possible to calculate the deuteration rate of methane -noted τ thereafter -by using the following relation: τ = 0.25CH 3 D + 0.5CH 2 D 2 + 0.75CHD 3 + CD 4 .…”

Raman spectroscopic and mass spectrometric investigations of the hydrogen isotopes and isotopically labelled methane

“…29 through 3 1) and compared with values from the literature [48]." The peak heights are normatized to the parent peak, which was arbitrarily set to equal 100%.…”