Mass spectra of the deuteromethanes

Abstract

The fou r d euteromethan e have been sy nthesized and t heir mass spect ra ob tain ed w ith a Consolidat.ed mass spectrometer. The se nsitivities of t he molecu le ions of CH , a nd o f CD, are eq ual wi thin t he estimated un certainty. The total ionization is the same fo r CH " CHaD, and CHzD z but is signifi ca ntly Jow for C D ,. The m ass spectra of the de ute romet ha nes ar e not predictable from CH, by statistical co nsiderations alone. In agreem e nt with pre viously p ublished data o n CH aD , p robabili ty fac to rs of 1.18 and 0.45 we re obse rv ed for t he cLi ssoc iation of an H atom or a D atom compared wi th t he dissociation of an H atom from CH •. \Vhereas these facto rs re main a pproximately constant for subsequent dissociations in the sam e molec ule, they differ markedly for th e t hree protiodeu tero methanes. ' Vide diverge nce is obser ved for some probabili ty factors obtained in di ssociatio ns of two or more atoms.

Redetermination of mass spectra of deuteromethanes

“…Thus both CH2+ and CD+ contribute to the 14 peak and 1-12 and D contribute to the 2 peak. In table 3 the abundancc of ions heavier than mass number 12 has been computed on the assumption that the probability of r emoving one, two, or three hydrogenic atoms from t~~ dcutcromethane is proportional to the probablhty of removing H , 2H, and 3H from methane [1). The ions CH+ and CHzD + from CH3D and CH+, CHD+, and CHD2+ of CHzD2 are observed, and with the above assumption the abundances of thc othcr ions are derived.…”

“…It is a rough approximation for some but not all of the weighting factors. Thus al for CHsD, CH2D 2 , and CHDa is 1 1.17-3 , and 1.14-2 • Weighting factors for removing two or three atoms are in some cases roughly consistent with the power law, but in general the agreement is poor. Values enclosed in parentheses do not fit, and values for C+ and for all of the CD4 spectrum do not vary in the manner found for C2+ of the ethylenes and for the C2D 4 spectrum.…”

“…A paper by this title by Dibeler and Mohl~r [1]1 was publishcd in 1950 and at about the same tIme a paper by Schissler, Thompson, and Turkevich [2) also includcd mass spectra of the four deuteromethanes. There are some discrcpancics between the mass spectra reported in the two papers, and in both researches thc isotopic purity of thc molecules CHzDz and CHD3 1eft much to bc desired.…”

Mass spectra of deuteroacetylenes, monodeuterobenzene, and deuteronaphthalenes

“…There have been a number of papers published on th~ .mass spectra of the simpler hydrocarbons contammg one or more deuterium atoms [1,2,3).1 In ?ompounds containing both D and H , the probabilIty. of removing H is greater and that of removing D IS less than the probability of removing H in the hydrogen compound.…”

“…of removing H is greater and that of removing D IS less than the probability of removing H in the hydrogen compound. Thus in CH3D [3], the probability of removing H is increased by a factor, 1.18, and that of removing D is decreased by a factor, 0.45 , as compared with the a priori probabilities of re~?ving H or D . In general, in compounds contammg two or more carbon atoms with several H a~oms on each carbon atom, it is impossible to predICt what the spectrum will be when one deuterium atom is in a given position in the molecule.…”