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AbstractThe charge‐stripping mass spectra of the ten C5H10 isomers and of cyclopropane and propene have been re‐evaluated. Oxygen is the preferred collision gas for the former group and helium for the latter pair. A con bined study of the low‐energy mass spectra, charge‐stripping mass spectra and appearance energy measurements had to the conclusion that loss of H2O from ionized pentan‐1‐ol and loss of HCl from ionized 1‐chloropentane both predominantly produce ionized ethylcyclopropane as the fragment ion. For the alcohol, a 1,4‐elimination followed by an energetically favoured 1,2‐H shift is involved, whereas for the halide a direct 1,3‐elimination obtains.

It is shown that it is possible to distinguish between menthol, isomenthol, neomenthol and neoisomenthol and their methyl ethers by measuring M+/[M-HOR]+ (R = H for the menthols, R = Me for the ethers) at an electron ionizing energy of ca. 12 eV and at a source temperature of ca. 350 K. The low-energy, low-temperature mass spectra are reported.

AbstractA series of dioxabicyclo[n.2.2]alkanes (n = 1,2,3 and 4) and dioxabicyclo[n.2.2]alkenes were studied under electron impact ionization. The fragmentation pathways were elucidated with the aid of accurate mass measurements, metastable scan techniojei and deuterium labelling. The preferential fragmentation of molecular ions in dioxabicyclo[n.2.2]alkanes corresponds to the loss of hydroperoxyl radical ·OOH. Hydrogens that are participating in this elimination come primarily from the syn position on the two‐membered carbon bridge. The dioxabicyclo[n.2.2]alkenes undergo the retro‐Diels–Alder process, which produces dioxygen and 1,3‐cycloalkadiene. In both saturated and unsatutated peroxides subsequent fragmentation of the hydrocarbon ring depends upon the value of n.

AbstractThe low‐energy, low‐temperature mass spectra of thirteen alkanals are reported and their predominant modes of fragmentation discussed in terms of energetics. Characteristic of this class of compounds is the very high proportion of odd‐electron ions in the mass spectra, namely [M  CMH2m]+˙, [M  H2O]+˙ and [M  H2O  CmH2m]+˙.

Organic Mass SpectrometryVolume 21, Issue 8 p. 519-519 Book Review J. R.Chapman. Practical organic mass spectrometry. John Wiley & Sons, Chichester, 1985. No. of pages: 208. ISBN 0-471-0906 964. Price £ 19.50, $ 31.10 Margaret N. Mruzek, Margaret N. Mruzek Department of Chemistry, University College London March 1986.Search for more papers by this author Margaret N. Mruzek, Margaret N. Mruzek Department of Chemistry, University College London March 1986.Search for more papers by this author First published: August 1986 https://doi.org/10.1002/oms.1210210813AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume21, Issue8August 1986Pages 519-519 RelatedInformation

Mass spectrometric fragmentation of cyclophosphamide (CP) has been studied in detail using linked field scanning, isotope labelling, low energy ionization and accurate mass measurements. The molecular ion is of low abundance and it favours loss of HCI and ·CH2CI to form the base peak at m/z 211. All the other ions are formed by sequential fragmentation processes. The direct bond rupture between phosphorus and the N-chloroethyl group produces two ions m/z 120 and m/z 92. The ion m/z 56 is a triplet. Many of the ions in the spectrum are produced by several competing pathways. Several of the rearrangement mechanisms involve a single hydrogen transfer. Quantitative differences between two commercial CP preparations were observed in the linked field scanning spectra. Differences in the abundances of the metastable ions strongly suggest that there is an intense isomeric competition in the decomposition pathways. The experimental evidence supports the conclusion that the two CP preparations differ in their isomeric composition and these differences are related to their stereoisomers. The rates of the individual fragmentation pathways are dependent upon the isomeric structure of the parent molecule and might also be reflected by different rates of metabolism of the isomers of the drug in vivo.

Abstract13C labelling has been used to study isoquinoline molecular ions undergoing breakdown by HCN elimination in a mass spectrometer. For otherwise stable ions caused to fragment by collisional activation, there is no skeletal rearrangement prior to HCN loss. Of the ions formed by 70 eV electron impact, 69% of those which fragment in the ion source by HCN loss retain their structural integrity, as do 44% of the metastable ions. Of the ions that eliminate HCN without prior arrangement, approximately two‐thirds eliminate C‐1 and one‐third eliminate C‐3. Critical energies are reported for the elimination of HCN from pyridine and isoquinoline molecular ions.

Organic Mass SpectrometryVolume 17, Issue 1 p. 54-54 Book Review U. P. Schlunegger. Advanced mass spectrometry: Applications in organic and analytical chemistry. Pergamon Press, Oxford, 1980. pp. 143. £12.25 U. P. Suchlunegger, U. P. SuchluneggerSearch for more papers by this authorMargaret N. Mruzek, Margaret N. Mruzek University College LondonSearch for more papers by this author U. P. Suchlunegger, U. P. SuchluneggerSearch for more papers by this authorMargaret N. Mruzek, Margaret N. Mruzek University College LondonSearch for more papers by this author First published: January 1982 https://doi.org/10.1002/oms.1210170111AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue1January 1982Pages 54-54 RelatedInformation

Chlorine kinetic isotope effects in the thermolysis of 2-chloropropane and 2-chloro-2-methyl-propane have been measured at temperatures between 250 and 441 °C. The isotope effects are primary and they show normal temperature dependence. They increase with increasing methyl substitution on the central carbon atom. Model calculations using the heavy atom approximation theory show satisfactory agreement with the experimental data and with the observed temperature dependence. The participation of chlorine in the activated complex is the same for primary, secondary and tertiary alkyl chlorides and involves a combination of C—Cl stretching (3 %), C—C—Cl bending (2.7 %) and C—CH3 shortening (4 %) from the ground state values.

Chlorine kinetic isotope effects have been investigated for the pyrolysis of 1-chloroethane in a static system in the temperature range 395–482°C. The temperature dependence of the kinetic isotope effects has been determined. The mass spectrometric isotope ratio analysis was made on the hydrogen chloride produced. A model for the chlorine involvement in the four-centre activated complex is advanced and various alternative geometries are evaluated in terms of heavy-atom approximation and first-order high temperature kinetic isotope effects. Best agreement with the experimentally determined values of k35/k37 is given by a model of the activated complex which involves chlorine participation in the reaction coordinate with three degrees of freedom. The effect of the individual geometric parameters that includes the C—Cl stretching, the C—C—Cl bending and the C—CH3 stretching and their combination, is evaluated.

A study of 35k/37k for the gas-phase elimination of hydrogen chloride from ethyl chloride is reported. The value found at 723 K is 1.001 5 ± 0.000 2. Heavy atom kinetic isotope theory is applied in an attempt to characterise the transition state. It is concluded that there is only a moderate lengthening of the carbon-chlorine bond, and only a little motion of the chlorine atom in the transition state.