Chemical ionization mass spectra of acetals of beta-D-glycopyranosylnitromethanes

O-Isopropylidene and O-benzylidene acetals of common 2, 6-anhydro-1-deoxy-1-nitroalditols (beta-D-glycopyranosylnitromethanes) derived from D-glucose, D-galactose and D-mannose were studied by chemical ionization mass spectrometry (CIMS) using methane, isobutane, ammonia or pyridine as reaction gas. Production of [M+H](+) adduct ions dominates in the case of methane or isobutane possessing proton affinity values PA = 552 or 683 kJ mol(-1), respectively. The collision-induced dissociation time-of-flight product ion spectra of [M+H](+) ions differ characteristically according the stereochemical arrangement of the pyranoid ring. These differences can be helpful when assigning stereochemical arrangements for the pyranoid ring. The dominant process in ammonia (PA = 853 kJ mol(-1)) CIMS for most of the compounds studied is the production of the cluster ions [M+NH(4)](+). The cluster [M+pyridineH](+) ions are observable only for substances possessing the O-benzylidene group (PA of pyridine = 924 kJ mol(-1)). Copyright 2000 John Wiley & Sons, Ltd.     

Chemical ionization mass spectra of some 2-norbornyl derivatives

Chemical ionization mass spectra of exo- and endo-2-norbornanols and their phenylurethane derivatives have been obtained with several reactant ions. Small differences are noted in the abundances of norbornyl and [M+H]⁺ ions for the phenylurethane derivatives: more norbornyl ions with the exo compounds. Relative rate constants for decomposition of [M+H]⁺ ions, k_exo/k_endo ? 1-2. No evidence was found for s?-participation in the decomposition of these ions. The i-C₄H₁₀ chemical ionization spectrum of endo-2-norbornanol contains a much greater abundance of [M-H]⁺ ions than the i-C₄H₁₀ chemical ionization spectrum of exo-2-norbornanol. This difference presumably results from steric hindrance toward attack of the endo hydrogen.     

Chemical ionization mass spectra of alkylphenol and linear alcohol polyethoxylates

The chemical ionization mass spectra of some tert-octylphenol ethoxylates and linear alcohol ethoxylates have been determined using methane and ammonia as reactant gases. Proton, [C₂H₅]⁺ and [C₃H₅]⁺ adducts were observed with attachment on the ring as well as on the oxyethylene chain for the tertiary octylphenol ethoxylates. Proton and [NH₄]⁺ addition reactions were also observed. Alkyl ion and olefin displacement reactions were also important fragmentations. Hydride abstraction and proton, [C₂H₅]⁺, [C₃H₅]⁺ and [NH₄]⁺ attachment were the most important reactions occurring for the linear alcohol ethoxylates.     

Chemical ionization mass spectra of 2, 4, 6-trinitroaromatic compounds

The methane and isobutane chemical ionization mass spectra of ten 2,4,6-trinitroaromatic compounds have been recorded. The mass spectra contain intense [M + 1]⁺ ions and usually little fragmentation. However, in some cases major fragmentation processes have been observed. Some unusual adduct ions have been found with isobutane as the reagent and their temperature dependence has been studied.     

Chemical ionization mass spectra of natural monohydroxy- and monoacyloxy-substituted dihydropyranocoumarins and dihydrofurocoumarins

Summary The chemical ionization mass spectra of ten compounds of the group of natural monohydroxy and monoacyloxy derivatives of dihydropyranocoumarins and dihydrofurocoumarins have been studied. Their difference from the electron impact mass spectra has been shown. The structural-analytical possibilities of the method of chemical ionization for this series of substances has been determined.M. V. Lomonosov Moscow State University. Patrice Lumumba International Friendship University, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 508–512, July–August, 1977.     

Chemical ionization mass spectra of selected C3H6O compounds

The chemical ionization mass spectra of five isomers of C₃H₆O (acetone, propionaldehyde, oxetane, propylene oxide and allyl alcohol) have been determined using a variety of reagent gases (H₂, D₂, N₂/H₂, CO₂/H₂ and CO/H₂). The [C₃H₇O]⁺ ions produced by protonation of these isomers undergo very similar reactions to those reported for analogous [C₃H₇O]⁺ metastable ions; however, decomposing ions generated by chemical ionization appear to have somewhat higher internal energies. The results of ²H labelling studies (D₂ reagent gas or labelled analogues of C₃H₆O) indicate that protonation occurs mainly on oxygen and are consistent with previous investigations of metastable oxonium ions. The protonated acetone ion is particularly stable, in agreement with the higher activation energies for fragmentation of this isomer than for other [C₃H₇O]⁺ structures. As the calculated heat of protonation of C₃H₆O is reduced by changing the reagent gas, so the extent to which fragmentation occurs decreases. This is discussed in the context of competition between fragmentation and collisional stabilization of the excited [C₃H₇O]⁺* ion. It is concluded that on average a large fraction (approaching 1) of the exothermicity of the protonation reaction resides in the [C₃H₇O]⁺* ions produced initially.     

Rearrangements in chemical ionization mass spectra

Rearrangements reported in the literature for positive ions formed by chemical ionization are briefly reviewed, with particular emphasis on illustrative examples of hydrogen and skeletal rearrangements.     

Chemical ionization mass spectrometry of bifunctional cyclopentanes and cyclohexanes. A correlation between stereochemistry and chemical ionization spectra

A correlation has been fround between the stereochemistry of 3-methoxyeyclopentyl and 3-methoxyccyelohexyl acetic acid esters and their methane or isobutane themical ionizaion spectra: only the cis compounds yield quasimolecular ions and the [MH? CH₃OH]⁺ ions are more abundant for the trans isomers. A similar situation occurs in the iow temperature methane chemical ionization spectra of the coresponding trimethylsilylethers.     

Chemical ionization and electron impact mass spectra of symmetrical S-alkyl alkanesulfonothioates (thiosulfonates)

The chemical ionization (CI) and electron impact (EI) mass spectra of eight symmetrical S-alkyl alkanesulfonothioates (thiosulfonates) are reported.     

Chemical ionization and electron impact mass spectra of alicyclic substituted 2-aryl-1,3-dithianes

The methane and isobutane chemical ionization mass spectra of alicyclic substituted 2-aryl-1,3-dithianes were examined by gas chromatography mass spectrometry. The protonated molecular ion was found to be of low abundance in the methane spectra, while a protonated cyclic sulfide cation (m/z 107) appeared as the base peak. A protonated molecular ion was the base peak when isobutane was used as the reagent gas. Electron impact mass spectra displayed weak molecular ions and were characterized by the m/z 106 fragment.     

Chemical ionization and electron impact mass spectra of thiosulfinates,thiosulfonates and sulfinyl sulfones

The chemical ionization and electron impact mass spectra of some thiosulfinates, thiosulfonates and sulfinyl sulfones have been studied. The electron impact mass spectra of four of the six thiosulfonates show molecular ions of less than 1%. Inconclusive evidence was obtained for sulfenyl sulfinate type intermediates in the electron impact spectra of thiosulfonates. The electron impact spectra of thiosulfonates were similar to those of thiosulfonates. The chemical ionization (isobutane) mass spectra of thiosulfinates and thiosulfonates generally show protonated molecular ions [MH]⁺ as base peaks and [MH+1]⁺ and [MH+2]⁺ peaks.     

Electron ionization mass spectra of alkylated sulfabenzamides

Mono‐, di‐ and trialkyl derivatives of 'sulfabenzamide' (N‐4‐aminophenylsulfonylbenzamide) have been prepared and their electron ionization (EI) mass spectra examined. It is found that the fragmentation of N‐alkylsulfabenzamides (alkyl = CH₃ to n‐C₅H₁₁) proceeds via a very specific rearrangement process. The proposed mechanism involves an intermediate formation of distonic molecular ions, and the driving force for this process is the formation of stable N‐alkylphenylcyanide cations [R‐N⁺ ? CC₆H₅]. The findings are confirmed by exact mass measurements, tandem mass spectrometry (MS/MS) experiments and deuterium labeling. Published in 2011 by John Wiley & Sons, Ltd.     

Chemical ionization mass spectrum of peroxyacetylnitrate

The chemical ionization mass spectrum of peroxyacetylnitrate, a major component of photochemical smog highly toxic to man and plants, was obtained using both methane and isobutane as reagent gas. The spectrum contains a [M + H]⁺ ion at m/e 122, intense fragment ions at m/e 43 [CH,CO]⁺ and m/e 46 [NO₂]⁺, and less intense ions at m/e 61 [CH,ONO]⁺, m/e 77 [CH30NOz]⁺ and m/e 88 [⁺O?CCH₂ONO] formed by internal rearrangements. These results confirm the commonly accepted structure for peroxyacetylnitrate, CH₃(CO)OONO₂.     

Chemical ionization mass spectrometry of nitrosamines

The mass spectra of eight nitrosamines have been recorded, with excitation by chemical ionization (CI) and electron impact (EI). Comparison of the intensities of the base peaks under CI and El conditions gives intensity ratios in the range 1.4-1.9 for low resolution measurements and up to 10 for high resolution measurements, confirming the enhanced sensitivity available in the CI mode.     

Chemical ionization and electron impact mass spectra of S-1-chloroalkyl alkanesulfonothioates (thiosulfonates)

The chemical ionization (CI) and electron impact (El) mass spectra of six S-1-chloroalkyl alkanesulfonothioates (thiosulfonates) are reported.     

Field ionization mass spectra of photopolymers of thymine

The field ionization mass spectra of cis-syn thymine dimer, tymine-thymine adduct and a new thymine phototrimer have been measured. Results are presented to illustrate that this technique is more efficacious than the electron impact method in structural elucidation of photopolymers of thymine and related compounds.