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1.
The structures of gas-phase [C4H6O]+· radical cations and their daughter ions of composition [C2H2O]+· and [C3H6]+· were investigated by using collisionally activated dissociation, metastable ion measurement, kinetic energy release and collisional ionization tandem mass spectrometric techniques. Electron ionization (70 eV) of ethoxyacetylene, methyl vinyl ketone, crotonaldehyde and 1-methoxyallene yields stable [C4H6O]+· ions, whereas the cyclic C4H6O compounds undergo ring opening to stable distonic ions. The structures of [C2H3O]+· ions produced by 70-eV ionization of several C4H6O compounds are identical with that of the ketene radical cation. The [C3H6]+· ions generated from crotonaldehyde, methacrylaldehyde, and cyclopropanecarboxaldehyde have structures similar to that of the propene radical cations, whereas those ions generated from the remainder of the [C4H6O]+· ions studied here produced a mixed population of cyclopropane and propene radical cations. 相似文献
2.
The non-empirical generalized Kirkwood, Unsöld, and the single-Δ Unsöld methods (with double-zeta quality SCF wave-functions) are used to calculate isotropic dispersion (and induction) energy coefficients C2n, with n ? 5, for interactions involving ground state CH4, C2H6, C3H8, n-C4H10 and cyclo-C3H6. Results are also given for the related multipole polarizabilities αl, multipole sums S1/(0) and S1(?1) which are evaluated using sum rules, and the permanent multipole moments. for l = 1 (dipole) to l = 3 (octupole). Estimates of the reliability of the non-empirical methods, for the type of molecules considered, are obtained by a comparison with accurate literature values of α1S1(?1) and C6. This, and the asymptotic properties of the multipolar expansion of the dispersion energy, the use to discuss recommended representation for the isotropic long range interaction energies through R?10 where R is the intermolecular separation. 相似文献
3.
The C8H9+-ion, formed from the molecular ions of 2-phenyl-1-bromoethane, 1-phenyl-1-bromoethane and of 1-phenyl-1-nitroethane by loss of the bromine atom and of the nitro group, splits off a molecule of acetylene after an almost complete randomization of hydrogens, as proved by deuteration. An eight-membered ring structure for the C8H9+-ion is proposed to explain these results. By loss of the nitro group from the molecular ions of 1-phenyl-1-nitropropane and of 1-phenyl-2-nitropropane the well-known phenylated cyclopropane ion3 (C9H11)+ is generated. Mass spectra of analogues, specifically deuterated in the side-chain, show that in this ion a randomization of hydrogen atoms in the cyclopropane ring as well as a hydride transfer from the cyclopropane ring to the phenyl cation occur. 相似文献
4.
John L. Holmes John K. Terlouw Peter C. Vijfhuizen Cor A'Campo 《Journal of mass spectrometry : JMS》1979,14(4):204-212
Metastable peak characteristics, ionization and appearance energy data and isotopic labelling experiments have been applied to a study of the fragmentation behaviour of the molecular ions of the isomeric C4H6O2C acids, cis and trans-crotonic acids, methacrylic acid, butenoic acid and cyclopropane carboxylic acid. Prior to the losses of H2O and CH3, all the metastable molecular ions rearrange to [cis-crotonic acid]+? ions. Loss of H2O, which generates a composite metastable peak, is proposed to yield vinylketene and/or cyclobutenone molecular ions. Detailed mechanisms are presented for the isomerizations of the various molecular ions and for the above fragmentations. Ionized 3-butenoic and cyclopropane carboxylic acids display a major loss of CO from their metastable ions, a minor process in the other isomers. The metastable peaks consist of two components and these are ascribed to the formation of propen-1-ol and allyl alcohol as daughter ions. Some comparative data are presented for the isomeric C5H8O2 acids, tiglic acid, angelic acid and senecioic acid. 相似文献
5.
The mechanisms of formation of m/z 73 ions in the mass spectrum of the ionized title compound were investigated by deuterium substitution and by examining the decompositions of metastable ions. Two routes to the [C4H9O]+ ions were found in the normal spectrum. The ethyl lost by the major pathway contains the α- and β-hydrogens and a γ-hydrogen from the butyl group. The minor route involves the loss of ethylene from the [M? H]+ ion. There were metastable peaks for losses of ethyl, ethanol and methyl from the molecular ion. The ethyl contains the α- and β-methylenes and a γ-hydrogen, while the methyl is the δ-methyl of the butyl group. The labeling data rule out a previous mechanistic proposal for the loss of ethyl and support a mechanism involving stepwise isomerization to the sec-butyl ethyl ether molecular ion. However, the metastable ion chemistries of the molecular ions from the n- and sec-butyl ethyl ethers are highly dissimilar, perhaps due to decompositions from different electronic states. The n-pentyl methyl ether ions loses both ethyl and propyl, apparently following rearrangements to the 3-pentyl and 2-pentyl ether ions. Di n-butyl and n-butyl methyl ethers also give metastable peaks for loss of methyl, ethyl and the shorter chain alcohol. 相似文献
6.
J. R. Cao M. George John L. Holmes 《Journal of the American Society for Mass Spectrometry》1992,3(2):99-107
The fragmentation mechanisms of metastable ionized 1? and 3?methoxypropene have been examined in detail by using ionization and appearance energy measurements, metastable ion and collisional activation mass spectra, and a variety of isotopically labeled molecules. These metastable C4H8O+? ions fragment by loss of H; CH3, and H2CO, and the experimental observations allowed the construction of the potential energy diagram which describes their interconversion and the participation of four other distonic and carbene C4H8O+? ions. It was found that these two methyl alkenyl ether ions had no common reaction channel with either the 2?methoxy isomer or with any of the alcohol, keto, or enol C4H8On+? isomers which previously have been extensively studied. 相似文献
7.
The formation of [CH2OH]+. by fragmentation of [C3H7O]+. ions in the electron-impact mass spectra of 2-methyl-2-propanol and 2-propanol has been investigated using 13C labeling, deuterium labeling and metastable studies. The similar fragmentation reaction in the chemical ionization mass spectrum of acetone has been studied. It is concluded that the fragmentation reaction does not involve complete randomization of the carbon atoms and therefore does not proceed through formation of a hydroxylated cyclopropane intermediate. Alternative mechanisms are discussed. 相似文献
8.
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. 相似文献
9.
Robert Flammang Philippe Meyrant Andr Maquestiau Eric E. Kingston John H. Beynon 《Journal of mass spectrometry : JMS》1985,20(3):253-257
Charge-stripping spectra have been used to differentiate ionized cyclopentadiene from its acyclic isomers. The minimum amounts of translational energy lost during the charge-stripping processes and the relative charge-stripping efficiencies, which are also structurally important parameters, have been measured for these ionic species. [C5H6]+˙ ions, formed by dissociative ionization of various precursors in the ion source are found, usually, to be a mixture of cyclic and acyclic ions. In contrast, [C5H6]+˙ ions, derived from the dissociation of metastable molecular ions from a series of organic compounds, have the cyclopentadienyl structure. This structure was confirmed by collision-induced dissociation of ions formed in the first field-free region of a triple sector mass spectrometer. 相似文献
10.
Guo Yu Xing Fan Xue‐Ming Dong Rui‐Yu Wang Yun‐Peng Zhao Hong‐Cun Bai Tian‐Sheng Zhao Qing‐Jie Guo Xian‐Yong Wei 《Journal of separation science》2020,43(4):839-846
Dayan lignite was subjected to thermal dissolution sequentially with cyclohexane, acetone, and methanol. Each thermal dissolution extract was subjected to further separation/enrichment using column chromatography, which was sequentially eluted with petroleum ether, a mixture of ethyl acetate and petroleum ether (vol:vol = 1:1), and ethyl acetate. The three thermal dissolution extracts and nine enrichment subfractions were characterized by an Orbitrap mass spectrometry equipped with an atmospheric pressure chemical ionization ion source. The mass spectrometry data were also statistically analyzed by principal component analysis, which can reduce the dimensionality of data and classify multiple samples according to principal components. Identified compounds in the extracts and subfractions are classified into eight classes according to the heteroatom distribution. Hydrocarbon class is mainly presented in the petroleum ether fraction, and oxygen class, nitrogen class, and oxygen‐nitrogen class are distributed in both petroleum ether/ethyl acetate and ethyl acetate subfractions. The combination of different analytical methods enhances the understanding of coal at the molecular level and provides important data for downstream refining processes. 相似文献
11.
Frank W. Crow Michael L. Gross Maurice M. Bursey 《Journal of mass spectrometry : JMS》1981,16(7):309-311
Collisional activation of the molecular ions of 1-propanol, 2-propanol and methyl ethyl ether, and of the m/z 60 ion from 1,2-dimethoxyethane provides evidence for four distinct forms of [C3H8O]+˙. Collision induced decompositions may be explained either by simple cleavages, by cyclic processes involving adjacent substituents, or by bicyclic processes of adjacent substituents. Evidence for a form of [C3H8O]+˙ in which charge and radical site are separate is assembled from the spectra. 相似文献
12.
Free, unsolvated phenylium ions formed by the spontaneous β decay of a constituent atom of multitritiated benzene have been allowed to react with gaseous propene and cyclopropane in the pressure range from 10 to 700 torr. Phenylium ions attack efficiently both the C-H and the C-C bonds of cyclopropane, yielding respectively tritiated cyclopropylbenzene and indane as the major products. Selective attack of phenylium ions on the π bond of propene is suggested by the composition of tritiated products, isomeric phenylpropenes and isopropylbenzene. The different behavior of propene and cyclopropane toward gaseous phenylium ions is consistent with the results of related radiolytic investigations concerning gaseous systems at nearly atmospheric pressure. The reactivity pattern of the isomeric C3H6 hydrocarbons toward gaseous phenylium ions is discussed and compared with pertinent mass spectrometric data. 相似文献
13.
J. W. Dallinga N. M. M. Nibbering G. J. Louter 《Journal of mass spectrometry : JMS》1981,16(4):183-187
The structure and formation of [C8H8O]+. ions generated from phenylcyclopropylcarbinol and 1-phenyl-1-hydroxymethylcyclopropane upon electron impact, have been studied using kinetic energy release measurements, by determination of ionization and appearance energies and by collisional activation. It is shown that the non-decomposing [C8H8O]+˙ ions have exclusively the structure of the enol ion of phenylacetaldehyde, although it is less stable than the enol ion of acetophenone by about 45 kJ mol?1. This has been interpreted as an indication that the [C8H8O]+˙ ions from phenylcyclopropylcarbinol are formed by an attack of either the phenyl ring or the hydroxyl group upon the C-1? C-2 (or C-1? C-3) bond of the cyclopropane ring under a simultaneous expulsion of ethene and migration of the attacking group to the C-1 position. The [C8H8O]+˙ ion from 1-phenyl-1-(hydroxymethyl)cyclopropane is formed by opening of the cyclopropane ring via a benzylic cleavage. A kinetically controlled hydrogen shift in the resulting ring opened ion prior to or during ethene loss then leads to the formation of [C8H8O]+˙ ions which have the structure of the enol ion of phenylacetaldehyde. 相似文献
14.
Dr. Peter Krenmayr 《Monatshefte für Chemie / Chemical Monthly》1975,106(4):925-939
Abundance ratios of C2H4 and CO loss (CH4 and O loss) in the field-free region of a mass spectrometer have been determined by mass resolution of metastable peaks. Using the method ofShannon andMcLafferty the abundance ratios have been applied to characterize the structure of metastable ions. C3H5O+ ions from 10 compounds and C4H7O+ ions from 14 compounds have been examined. In the case of C3H5O+, three types of structurally different isomers are present. C4H7O+ ions represent a not equilibrating mixture of different. structures in some cases. From examination of 2-pentanone-1,1,1,3,3-d 5, metastable C4H7O+ ions from 2-pentanone have been shown to consist of two structurally distinct types of ions which are assumed to be $$\begin{array}{*{20}c} {CH_2 - O^ + } \\ {\begin{array}{*{20}c} | & {||} \\ \end{array} } \\ {CH_2 - C - CH_3 } \\ \end{array}$$ and butyryl ion. 相似文献
15.
N. S. Mirzabekova N. E. Kuzmina E. S. Osipova O. I. Lukashov 《Journal of Structural Chemistry》2008,49(4):644-649
The spatial isomers of the new synthetic analogs of ethyl permithrinic ether and permethrin were investigated by NMR (1H, 13C, DEPT (distortionless enhancement by polarization transfer), COSY (correlation spectroscopy), CHCORR (heteronuclear (C, H) shift correlation spectroscopy), ROESY (rotating-frame Overhauser effect spectroscopy)). Several tendencies were revealed in the 1H and 13C chemical shifts of the α atoms of the substituents in the 2nd and 3rd positions of the cyclopropane ring. For substituents cis-orientated relative to the ester group, the spectra show a paramagnetic shift of the 1H signals and the diamagnetic shift of the 13C signals relative to the trans-orientated substituents. The 1H and 13C chemical shifts of the α atoms of the substituents in the 2nd and 3rd positions of the cyclopropane ring permit an unambiguous determination of the stereochemistry of ethyl permethrinic ether and permethrin analogs. 相似文献
16.
Vanessa Gallardo Hilkka I. Kenttämaa 《Rapid communications in mass spectrometry : RCM》2012,26(8):940-942
The reactivity of ClMn(H2O)+ towards small organic compounds (L) was examined in a Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometer. The organic compounds studied are aliphatic and aromatic alcohols, aliphatic amines, ketones, an epoxide, an ether, a thiol and a phosphine. All the reactions lead to the formation of the ClMn(H2O)(L)+ complex, which dissociates by loss of the H2O molecule. In general, the reactions were found to occur with high efficiencies (>85%), indicating them to be exothermic. Electron transfer was also observed between ClMn(H2O)+ and compounds with low ionization energies (IE), to form the molecular ion (L+?) of the analyte. Based on these observations, the IE of ClMn(H2O)+ is approximated to be 8.1 ± 0.1 eV. Thus, the utility of ClMn(H2O)+ as a chemical ionization reagent in mass spectrometry is expected to be limited to organic compounds with IEs greater than 8 eV. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1988,44(12):1333-1334
The most stable conformation of cyclopropylamine is the one in which the cyclopropane ring is oriented cis to the nitrogen lone-pair electrons and trans to the plane of the amino group. 相似文献
18.
《Journal of membrane science》1988,35(3):339-345
Neutral crown ethers do not transport trivalent lanthanide cations in a H2O-CHCl3-H2O liquid membrane system. With the addition of a carboxylate group to a macrocyclic polyether, as in the case of sym-dibenzo-16-crown-5-oxyacetic acid, high efficiencies of transporting trivalent lanthanides were observed across the H2O-CHCl3-H2O liquid membrane. The crown ether carboxylic acid also showed significant selectivity for the lanthanides studied in this system. 相似文献
19.
H. E. Audier G. Bouchoux Y. Hoppilliard A. Milliet 《Journal of mass spectrometry : JMS》1982,17(8):382-385
It is demonstrated by means of metastable ions characteristics, collisional activation, deuterium labelling and appearance energy measurements that ionized ethyl isobutyl ether and ethyl n-butyl ether isomerize prior to decomposition. The lower critical energy fragmentation gives [CH3CH2OCHCH3]+ ions. A mechanism of isomerization is proposed in which 1,4 hydrogen migration on the oxygen atom is coupled with rearrangement of the butyl chain. 相似文献
20.
Yuhai Jiang Jinfeng Sun Linde Wan 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,34(1):29-33
A model complex optical potential (composed of static, exchange, polarization and absorption terms) is employed to calculate the total (elastic and inelastic) electron-atom scattering cross sections from the corresponding atomic wave function at the Hartree-Fock level. The total cross sections (TCS) for electron scattering by their corresponding molecules (C2H2, C2H4, C2H6, C3H6, C3H8 and C4H8) are firstly obtained by the use of the additivity rule over an incident energy range of 10–1000 eV. The qualitative molecular results are compared with experimental data and other calculations wherever available, good agreement is obtained in intermediate-and high-energy region. 相似文献