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1.
Electron impact mass spectra of 2-diphenylmethyl-3-aryl-4(3H)-quinazolinones display ions arising from migrations of different aryl groups in the molecular and [M? H]+ ions. The most abundant ion due to rearrangement, [C13H9NO]+˙, is formed by migration of a phenyl from the benzhydryl group onto N-1 and subsequent cleavage of the heterocyclic ring. Other rearrangements involve initial migration of the N-3 aryl group to the benzylic carbon. The mechanisms of migrations were elucidated by means of deuterium and 15N labelling and are supported by metastable spectra. 相似文献
2.
K. K. Zhigulev S. D. Sokolov R. A. Khmel'nitskii 《Chemistry of Heterocyclic Compounds》1974,10(6):654-657
The effect of charge migration in the molecular ion on the dissociative ionization of isoxazole derivatives was examined. It is shown that charge redistribution between the substituent in the 3 position and the oxygen atom of the heteroring precedes isomerization of the molecular ion and its disintegration. The intensity of the peaks of the RCO+ ions in the mass spectra of 5-R-3-arylisoxazoles increases as the acceptor effect of the aryl substituent becomes stronger. It is shown that the average internal energy with which the nitrobenzoyl ions are formed decreases as the probability of their formation increases, i.e., as the intensity of charge migration from the aryl substituent to the oxygen atom increases. 相似文献
3.
M. M. Aleksankin I. P. Samchenko L. I. Fileleeva 《Theoretical and Experimental Chemistry》1985,21(6):694-699
A new type of fragmentation of organic cation radicals of sulfides, sulfoxides, and sulfones, leading to the elimination of S+, SO+ and SO
2
+
ions, respectively, has been discovered, and the possible mechanisms of their formation have been proposed. The most probable is a mechanism by which a cleavage of two C-S bonds takes place in the cyclic transition complex and formation of one C-C bond due to the recombination of the radicals. The line of the ion with a mass of 32 amu present in the spectra of almost all the sulfoxides studied, was assigned to the sulfur ion, formed by a similar mechanism after the displacement of alkyl or aryl residue in the molecular ion from sulfur to oxygen. Signs of such a migration also appear in the mass spectra of certain sulfones.Translated from Teoreticheskaya i Éksperimental'naya Khimia, Vol. 21, No. 6, pp. 730–735, November–December, 1986. 相似文献
4.
D. R. Dakternieks I. W. Fraser J. L. Garnett I. K. Gregor 《Journal of mass spectrometry : JMS》1977,12(6):370-374
Electron capture processes in a series of copper (II) β-diketonate complexes of formula Cu[R1COCHCOR2]2 (where R1 is an alkyl, perfluoroalkyl or aryl group and R2 either an alkyl or aryl group) have been examined. Molecular anions, ligand ions and some novel rearrangement ions have been observed with these compounds. Relative intensities of fragment ions were dependent on the substituents R1, R2 as well as the electron energy and compound pressure in the ion source. By operating the mass spectrometer at compound pressures of c. 4×10?6 Torr and higher, reproducible negative ion mass spectra (free from any significant ion-molecule contributions) have been obtained for all compounds of the series. 相似文献
5.
K. P. Madhusudanan Shubhra Mittal S. Durani R. S. Kapil 《Journal of mass spectrometry : JMS》1985,20(3):215-222
The electron impact (EI) and chemical ionization (CI) mass spectra of certain 1,2,3-triaryl-2-propen-1-ones (TAPs) have been studied in detail with the help of exact mass measurements, deuterium labelling and metastable data. The E- and Z-isomeric pairs do not show any difference in their behaviour under EI or CH4 CI conditions. EI-induced rearangement reactions in the TAPs include aryl migration to carbonium ion centres. A study of the metastable transitions reveals aryl group interchange in the molecular ions prior to fragmentation. Under EI conditions loss of arene involves either C(2) or C(3) aryl groups while under CI conditions the C(1) aryl is lost as a neutral arene molecule. Mechanisms for the different fragmentation modes are given. 相似文献
6.
Dmitri V. Zagorevskii Yurii S. Nekrasov John L. Holmes 《Journal of the American Society for Mass Spectrometry》1993,4(3):216-222
The behavior of some substituted cyclopentadienylmanganese ions has been studied by tandem mass spectrometry. This metastable ion study showed that only C5H5Mn+ and (C5H4CN)Mn+ ions retain their nido-cluster structure (1), which is characterized by a simple metal-ligand bond cleavage. Other substituted ions, RXC5H4Mn+, rearrange to a different extent, depending on the nature of the substituent. The first rearrangement step is R radical migration to the central metal atom, leading to RMnC5H4X+-type ions (2). These ions decompose by elimination of X (for X=CO) or with formation of RMnX+, but further rearrangements can also occur. These are the reverse migration of R from the metal atom to the π-ligand (for R=H, Ph) and cyclopentadienyl ring expansion (for X=CH2). Collisional activation mass spectra contained an Mn+ ion peak, which can indicate the existence of stable type 1 structures for most cyclopentadienylmanganese ions. Carboxyl and hydroxymethyl derivatives exist, presumably as ions of type 2. The neutralization-reionization mass spectra of RXC5H4Mn+ ions are also discussed. 相似文献
7.
Robert E. Swaim William P. Weber Heinz G. Boettger Margaret Evans Frank M. Bockhoff 《Journal of mass spectrometry : JMS》1980,15(6):304-311
The mass spectra of arylpentamethyldisiloxanes, sym-diaryltetramethyldisiloxanes and 1,5-diaryl-1,1,3,3,5,5-hexamethyltrisiloxanes were examined. Isotopic labeling and peak matching were used to substantiate the proposed fragmentation mechanisms. Siliconium ions dominate the spectra. Loss of neutral fragments from the [M-15]+ ions is important. Phenylpentamethyldisiloxane, sym-tetramethyldiphenyldisiloxane and 1,1,3,3,5,5-hexamethyl-1,5-diphenyltrisiloxane are representative examples of the three classes of compounds discussed. The [M-15]+ ion of phenylpentamethyldisiloxane loses methane, dimethylsilanone [(CH3)2Si?O] and phenylmethylsilanone [PhCH3Si?O] to yield daughter siliconium ions. The [M-15]+ ion of sym-tetramethyldiphenyldisiloxane loses benzene, methane, dimethylsilanone and phenylmethylsilanone to yield daughter siliconium ions. The [M-15]+ ion of 1,1,3,3,5,5-hexamethyl-1,5-diphenyltrisiloxane loses benzene, tetramethylcyclodisiloxane and phenyltrimethylcyclodisiloxane to yield daughter siliconium ions. Finally, doubly charged ions are important in the mass spectra of the three series of aryl substituted di- and trisiloxanes discussed. 相似文献
8.
The CI mass spectra of aryl ketones, πCOR, were studied and found to give primarily [M + 29]+, [M + 1]+, [M ? 1]+, [πCO]+ and [RCO]+ ions. The major change in the spectra with increasing length of the aliphatic side chain was an increase in the [M ? 1]+/[M + 1]+ ratio. Increasing sample size was reflected primarily in the formation of [2M + 1]+ ions and a decrease in [M + 1]+ ions. Small amounts of water in the reactant gas reduced the extent of fragmentation action. 相似文献
9.
Miss Itawati Pratanata L. R. Williams R. N. Williams 《Journal of mass spectrometry : JMS》1974,9(4):418-421
When subjected to electron-impact, chloromethyl aryl sulphones (II, X = Cl) fragment predominantly by the loss of CH2Cl from the molecular ion followed by the loss of SO2 and in most cases the appropriate metastable peaks are present to confirm the transitions. In addition, alkyl–oxygen bond formation in the molecular ion was revealed by the presence of prominent peaks corresponding to the [R? ?-SO]+ ions. In most spectra no evidence for aryl–oxygen bond formation could be found and thus the presence of the chlorine atom was able to effectively reverse the direction of skeletal rearrangement reported for aryl methyl sulphones. 相似文献
10.
D. R. Dakternieks I. W. Fraser J. L. Garnett I. K. Gregor 《Journal of mass spectrometry : JMS》1979,14(12):676-680
Results of electron attachment reactions and negative ion mass spectra are presented for a group of selected nickel(II) β-diketonate complexes of formula Ni[R1COCHCOR2]2, where R1 is a perfluoroalkyl group and R2 either an alkyl or aryl group. Molecular negative ions together with ligand ions are the major contributors to the total ion currents for each compound, and the degree of fragmentation has been shown to be dependent on the substituents R1 and R2. Fragmentation schemes have been elucidated for all the major ion decomposition pathways, and all significant ions have been identified in the negative ion mass spectra of each compound. Bis(1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedionato) nickel(II), with R1?CF3 and R2?tert-butyl is the complex which shows considerable potential for analytical quantitation in the negative ion mode, because of the stability of its negative molecular ion, the high negative ion yield given after electron attachment, as well as the volatility of the compound. 相似文献
11.
《Journal of solid state chemistry》1986,62(3):317-327
Luminescence and energy transfer properties of Gd2Ti2O7: Eu and Eu2Ti2O7 are reported. Transfer between unperturbed (intrinsic) Eu3+ ions and perturbed (extrinsic) Eu3+ ions has been observed. At low temperatures the emission spectra of Eu2Ti2O7 are dominated by trap emission, due to direct energy transfer from the intrinsic Eu3+ ions to the extrinsic Eu3+ ions. Above 10 K energy migration among the Eu3+ ions to quenching centers occurs. The interaction between the Eu3+ ions is probably exchange in character. The nature of the extrinsic Eu3+ ions has been elucidated. 相似文献
12.
The 2-acetoxyethyl aryl sulphones were found to be unsuitable for a comparative study with the corresponding chlorides and alcohols as their predominant fragmentation involved cleavage of the aliphatic carbon-sulphur bond with charge retention on the aliphatic part of the molecule The expected McLafferty rearrangement to yield an intermediate vinyl species was only a minor fragmentation path. Indirect evidence for alkyl migration in the molecular ion was found in the spectrum of 2-acetoxyethyl 1-paranitro phenyl sulphone. The spectra of the aryl vinyl sulphones revealed intense [Aryl SO]+ ions resulting from preferred migration of the vinyl group from sulphur to oxygen. 相似文献
13.
Joachim G. Liehr Richard M. Caprioli John H. Beynon Roger P. Morgan Wilhelm J. Richter 《Journal of mass spectrometry : JMS》1980,15(3):157-160
The oxygen rearrangement in molecular ions of 3-phenylpropionates has been investigated with the aid of mass analyzed ion kinetic energy spectra. Elimination of an allyl radical followed by expulsion of ketene from the molecular ion of allyl 3-phenylpropionate is shown to result in formation of protonated benzaldehyde. The oxygen rearrangement has been found to be inoperative in ionized methyl 3-methyl-3-phenylbutyrate. [M ? CH3 ? CH2CO]+ ions in the spectrum of the latter compound are formed by elimination of the 3-methyl substituent and subsequent methoxy migration. 相似文献
14.
A. S. Moskovkin N. N. Guseva L. A. Ignatova I. V. Miroshnichenko B. V. Unkovskii 《Chemistry of Heterocyclic Compounds》1983,19(9):1022-1026
In order to investigate the ring-chain tautomerism of substituted 4-hydroxyhexahydropyrimidine-2-thiones the mass spectra of a series of compounds of this group were studied. It is shown that equilibrium exists between the cyclic hydroxy form and the acyclic oxo form, which belongs to the oxoalkylthiourea class, in a series of 3-alkyl(aryl)-4,6,6-trimethyl derivatives in the gas phase. The mass spectra of these compounds contain intense peaks of [M-18]+ and [M-33]+ ions, which are formed as a result of the successive elimination of a water molecule and a methyl radical by the molecular ions. The fragmentation of 3-alkyl-4,5-dimethyl derivatives takes place from the open oxo form of the molecular ion with detachment of the terminal groups.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1273–1278, September, 1983. 相似文献
15.
G. Thielking U. Filges H. -Fr. Grützmacher 《Journal of the American Society for Mass Spectrometry》1992,3(4):417-426
Protonated aromatic aldehydes and methyl ketones 1a–10a, carrying initially the proton at the carbonyl group, are prepared by electron impact-induced loss of a methyl radical from 1?arylethanols and 2?aryl?2?propanols, respectively. The aryl moiety of the ions corresponds to a benzene group, a naphthalene group, a phenanthrene group, a biphenyl group, and a terphenyl group. respectively, each substituted by a CH3OCH2 side-chain as remote from the acyl substituent as possible. The characteristic reactions of the metastable ions, studied by mass-analyzed ion kinetic energy spectrometry, are the elimination of methanol, the formation of CH3OCH 2 + ions, and the elimination of an ester RCOOCH3 (R = H and CH3) . The mechanisms of these fragmentations were studied by using D-labeled derivatives. Confirming earlier results, it is shown that the ester elimination, at least from the protonated aryl methyl ketones, has to proceed by an intermediate [acyl cation/arylmethyl methyl ether]-complex. The relative abundances of the elimination of methanol and of the ester decrease and increase, respectively, with the size of the aromatic system. Clearly, the fragmentation via intermediate ion-neutral complexes is favored for the larger ions. Furthermore, the acyl cation of these complexes can move unrestricted over quite large molecular distances to react with the remote CH3OCH2-side-chain, contrasting the restricted migration of a proton by 1,2-shifts (“ring walk”) in these systems. 相似文献
16.
J. B. Westmore Denis C. K. Lin K. K. Ogilvie H. Wayborn J. Berestiansky 《Journal of mass spectrometry : JMS》1972,6(11):1243-1270
The mass spectra of 2,2′-anhydrouridine, 2,2′-anhydrothymidine and 2,2′-anhydro-4-thiouridine are reported. The acetyl, trifluoroacetyl, trityl, pivaloyl and trimethylsilyl ether derivatives were also studied. Deuterium labeling in acetyl and trimethylsilyl groups aided characterization of many ions in the spectra, as well as helping to clarify hydrogen migration processes. The anhydronucleosides and their derivatives are readily distinguished from natural nucleosides by the presence of an ion containing the base moiety plus the anhydro-ring plus one hydrogen atom from the rest of the molecule. As for natural nucleosides the [base + H]+ and [base + 2H]+ ions are usually prominent, but in contrast to natural nucleosides, ions characteristic of the sugar moiety do not retain the 2′-oxygen atom (i.e. the oxygen atom of the anhydro-ring). The mass spectra of deuterium labeled derivatives suggest a test for the presence of a 3′-O-acetyl function (the O-acetyl group is lost from the molecular ion much more readily from the 3′- than from the 5′-carbon atom). The trimethylsilyl derivatives showed evidence in their mass spectra for migration of trimethylsilyl groups in addition to hydrogen atoms. 相似文献
17.
The HO· fragment eliminated on electron impact (EI) from the molecular ions of o-nitrodiarylamines contains either the amine or the aryl hydrogen. Moreover, 2-phenylamino-3-nitropyridine loses H· from the phenyl group. As confirmed by collision-activated dissociation mass-analysed ion kinetic energy spectra, the fragmentation of such compounds involves the formation of carbazole radical cations. Such a process was not observed for the corresponding o-aminodiarylamines. 相似文献
18.
Tuula Kuivalainen Risto Kostiainen Rolf Uggla Markku R. Sundberg Heikki Björk 《Journal of the American Society for Mass Spectrometry》1996,7(2):189-197
The gas-phase ion chemistry of protonated O,O-diethyl O-aryl phosphorothionates was studied with tandem mass spectrometric and ab initio theoretical methods. Collision-activated dissociation (CAD) experiments were performed for the [M+H]+ ions on a triple quadrupole mass spectrometer. Various amounts of internal energy were deposited into the ions upon CAD by variation of the collision energy and collision gas pressure. In addition to isobutane, deuterated isobutane C4D10 also was used as reagent gas in chemical ionization. The daughter ions [M+H?C2H4]+ and [M+H?2C2H4]+ dominate the CAD spectra. These fragments arise via various pathways, each of which involves γ-proton migration. Formation of the terminal ions [M+H?2C2H4?H2O]+, [M+H?2C2H4?H2S]+, [ZPhOH2]+, [ZPhSH2]+, and [ZPhS]+ [Z = substituent(s) on the benzene ring] suggests that (1) the fragmenting [M+H]+ ions of O,O-diethyl O-aryl phosphorothionates have protons attached on the oxygen of an ethoxy group and on the oxygen of the phenoxy group; (2) thiono-thiolo rearrangement by aryl migration to sulfur occurs; (3) the fragmenting rear-ranged [M+H]+ ions have protons attached on the oxygen of an ethoxy group and on the sulfur of the thiophenoxy group. To get additional support for our interpretation of the mass spectrometric results, some characteristics of three protomers of O,O-diethyl O-phenyl phosphorothionate were investigated by carrying out ab initio molecular orbital calculations at the RHF/3–21G* level of theory. 相似文献
19.
Ring cleavage α to the oxygen function leads to [C3H5O]+ and [C4H7O]+ ions in the mass spectra of 4-arylcyclohexanols and their methyl ethers, respectively. Cleavage α to the aryl group gives rise to [C3H7O]+ (from the alcohols), [C4H9O]+ (from the ethers) and [ArC3H4]+ (from both) ions. The competition between the two ring cleavages explains the effect of the substituents of the aryl groups on the relative abundances of the resulting ions. 相似文献
20.
F. de Jong H. J. M. Sinnige Matthijs J. Janssen 《Journal of mass spectrometry : JMS》1970,3(12):1539-1548
The mass spectra of 13C-labelled thiophenes were studied and the label-distributions for the C3H3⊕, HCS⊕, C2H2S⊕ and [M ? CH3]⊕ ions are interpreted in terms of a carbon skeletal rearrangement. From a comparison of the results of 13C-labelling and D-labelling, a concurrent hydrogen migration process is demonstrated. The production of HCS⊕ ions is preceded by partial carbon scrambling and hydrogen migration is of minor importance. In contrast, hydrogen scrambling predominates over carbon scrambling in the loss of acetylene. 相似文献