Mass Spectrometry in Structural and Stereochemical Problems. CXIV.¹ Electron Impact Induced Rearrangement of Thiocarbonates, Carbamates, and Thiocarbamates²

Abstract

The mass spectra of all possible methyl phenyl, and diphenyl mono-, di-, and trithiocarbonates and of a number of methyl-and phenyl-substituted carbamates and mono-and dithiocarbamates have been examined in order to compare the possible elimination of CS, COS, or CSZ with the well-documented one of C O and COP. Rearrangement, with elimination of the central portion of the molecu1e;'is insignificant in the case of the carbamates and thiocarbamates, In the case of the thiocarbonates, loss of CS or of CSz is negligible. Significant loss of COS requires the presence of the group CSOCH, while expulsion of COz is important in the presence of the group COOCH3. In CBH~XCOYR (X = 0 or S; Y = 0 or S; R = CH, or C B H~) COZ is lost when X = Y = 0 or when Y = 0 and R = CH,; otherwise CO is eliminated. A preliminary rearrangement of the molecular ion of compounds with the group CsH60CS, to C6HsSC0, is observed.

Electron‐impact‐induced ion fragmentation of polyfunctional N‐cyclohexylcarbamates

“…Infrared spectra are consistent with the proposed structure which was confirmed by elemental analysis: Found: C, 39.36; H, 5 …”

Electron ionization mass spectra of indolenines obtained using sector and ion trap mass spectrometers

“…( vi ) and CO ( v ) from ion a ( m/z 302). In contrast, loss of 132 u from 5 to give the abundant ion g ( m/z 170) could be explained by neutral losses of CH 3 OH ( i ), CO ( ii ), and CO 2 +CH 2 CH 2 from the N ‐carbethoxy group ( viii ), with concomitant transfer of a γ ‐hydrogen atom in a hexacyclic transition state 15. These proposals are supported by accurate mass data (Table 3).…”

“…As a result of the elimination of an alkoxy radical from ion c , even‐electron ion e is formed. In general, such a fragmentation pathway has commonly been observed during the mass fragmentation of carbamates, thiocarbamates and aromatic esters 15–17…”

Mass–spectra Studies of Disperse Dyes

“…The mass spectra of lg and Ih show no molecular ion, the ion of highest molecular weight occurring at m/e 361, C Z 1 H 1 5 N 0 3 S , corresponding to Ib. Loss of RNCO from N-carbamoylamino derivatives is likely to be thermally induced [30] and is particularly apparent in carbamates in which the N-substituent is phenyl [31,32]. We have observed similar loss in 4-(N-alkyl-N-carbamoyl)amino-@-dicyanostyrenes and ethyliu-4-N-carbamoylaminocinnamates [ 291 and in 4-N-carbamoylaminoazobenzenes [ 331 .…”