The [C4H6O]+˙ ion of structure [CH2?CHCH?CHOH]+˙ (a) is generated by loss of C4H8 from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔHf of [CH2?CHCH?CHOH]+˙ was estimated to be 736 kJ mol?1. The isomeric ion [CH2?C(OH)CH?CH2]+˙ (b) was shown to have ΔHf, ? 761 kJ mol?1, 54 kJ mol?1 less than that of its keto analogue [CH3COCH?CH2]+˙. Ion [CH2?C(OH)CH?CH2]+˙ may be generated by loss of C2H4 from ionized hex-1-en-3-one or by loss of C4H8 from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C4H6O]+˙ ion generated by loss of C2H4 from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH2?CHCH?CHOH]+˙ and [CH2?C(OH)CH?CH2]+˙ ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH3˙ and CO, [CH2?CHCH?CHOH]+˙ and [CH2?C(OH)CH?CH2]+˙ do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C4H6O]+˙ ion [CH2?C?CHCH2OH]+˙ are also reported. 相似文献
The potential energy surface for the [CH5N]+˙ system has been investigated using ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence-electron correlation. Two [CH5N]+˙ isomers can be distinguished: the well known methylamine radical cation, [CH3NH2]+˙, and the less familiar methylenammonium radical cation, [CH2NH3]+˙. The latter is calculated to lie 8 kJ mol?1 lower in energy. A substantial barrier (176 kJ mol?1) is predicted for rearrangement of [CH2NH3]+˙ to [CH3NH2]+˙. In addition, a large barrier (202 kJ mol?1) is found for loss of a hydrogen radical from [CH2NH3]+˙ via direct N—H bond cleavage to give the aminomethyl cation [CH2NH2]+. These results are consistent with the existence of the methylenammonium ion [CH2NH3]+˙ as a stable observable species. The barrier to loss of a hydrogen radical from [CH3NH2]+˙ is calculated to be 140 kJ mol?1. 相似文献
The collision induced dissociation/mass analysed ion kinetic energy mass spectra of 2,5-diphenyltetrazole demonstrate the decay sequence [diphenyltetrazole]+˙→ [diphenylnitrile imine]+˙→ m/z 91. The m/z 91 ion was shown to be identical to the ion formed by loss of N2 from the phenyl azide radical cation, thus suggesting the phenylnitrene structure for the m/z 91 ion. 相似文献
Ab initio molecular orbital calculations with large, polarization basis sets and incorporating valence electron correlation have been employed to examine the [C2H2O]+˙ potential energy surface. Four [C2H2O]+˙ isomers have been identified as potentially stable, observable ions. These are the experimentally well-known ketene radical cation, [CH2?C?O]+˙ (a), and the presently unknown ethynol radical cation, [CH2?C? OH]+˙ (b), the oxirene radical cation (c) and an ion resembling a complex of CO with [CH2]+˙, (d). The calculated energies of b, c and d relative to a are 189, 257 and 259 kJ mol?1, respectively. Dissociation of ions a and d is found to occur without reverse activation energy. 相似文献
Methyl 2-oxocycIoalkane carboxylate structures are proposed lor the [M ? MeOH]+˙ ions from dimethyl adipate, pimelate, suberate and azelate. This proposal is based on a comparison of the metastable ion mass spectra and the kinetic energy releases for the major fragmentation reaction of these species with the same data for the molecular ions of authentic cyclic β-keto esters. The mass spectra of α,α,α′,α′-d4-pimelic acid and its dimethyl ester indicate that the α-hydrogens are involved only to a minor extent in the formation of [M ? ROH]+˙ and [M ? 2ROH]+˙ ions, while these α-hydrogens are involved almost exclusively in the loss of ROH from the [M ? RO˙]+ ions (R = H or CH3). The molecules XCO(CH2)7COOMe (X = OH, Cl) form abundant ions in their mass spectra with the same structure as the [M ? 2MeOH]+˙ ions from dimethyl azelate. 相似文献
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
The N2 negative ion chemical ionization (NICI) mass spectra of aniline, aminonaphthalenes, aminobiphenyls and aminoanthracenes show an unexpected addition appearing at [M + 11]?˙. This addition is also observed in the N2 positive chemical ionization (PCI) mass spectra. An ion at [M – 15]? is found in the NICI spectra of aminoaromatics such as aniline, 1- and 2-aminonaphthalene and 1- and 2-aminoanthracene. Ion formation was studied using labeled reagents, variation of ion source pressure and temperature and examination of ion chromatograms. These experiments indicate that the [M + 11]?˙, [M – 15]?˙ and [M + 11]+˙ ions result from the ionization of analytes altered by surface-assisted reactions. Experiments with 15N2, [15N] aniline, [2,3,4,5,6-2H5] aniline and [13C6] aniline show that the [M + 11]?˙ ion corresponds to [M + N – 3H]?˙. The added nitrogen originates from the N2 buffer gas and the addition occurs with loss of one ring and two amino group hydrogens. Fragmentation patterns in the N2 PCI mass spectrum of aniline suggest that the neutral product of the surface-assisted reaction is 1,4-dicyanobuta-1,3-diene. Experiments with diamino-substituted aromatics show analogous reactions resulting in the formation of [M – 4H]?˙ ions for aromatics with ortho-amino groups. Experiments with methylsubstituted aminoaromatics indicate that unsubstituted sites ortho to the amino group facilitate nitrogen addition, and that methyl groups provide additional sites for nitrogen addition. 相似文献
Three new uranyl polyphosphates, α‐K[(UO2)(P3O9)] ( 1 ), β‐K[(UO2)(P3O9)] ( 2 ), and K[(UO2)2(P3O10)] ( 3 ), were prepared by high‐temperature solid‐state reactions. The crystal structures of the compounds have been solved by direct methods: 1 – monoclinic, P21/m, a = 8.497(1), b = 15.1150(1), c = 14.7890(1) Å, β = 91.911(5)°, V = 1898.3(3) Å3, Z = 4, R1 = 0.0734 for 4181 unique reflections with |F0| ≥ 4σF; 2 – monoclinic, P21/n, a = 8.607(1), b = 14.842(2), c = 14.951(1) Å, β = 95.829(5)°, V = 1900.0(4) Å3, Z = 4, R1 = 0.0787 for 3185 unique reflections with |F0| ≥ 4σF; 3 – Pbcn, a = 10.632(1), b = 10.325(1), c = 11.209(1) Å, V = 1230.5(2) Å3, Z = 4, R1 = 0.0364 for 1338 unique reflections with |F0| ≥ 4σF. In the structures of 1 and 2 , phosphate tetrahedra share corners to form infinite [PO3]? chains, whereas, in the structure of 3 , tetrahedra form linear [P3O10]5? trimers. The structures are based upon 3‐D frameworks of U and P polyhedra linked by sharing common O corners. The infinite [PO3]? chains in the structures of 1 and 2 are parallel to [100] and [–101], respectively. The uranyl polyphosphate frameworks are occupied by host K+ cations. 相似文献
The extent of isomerization of [C9H10]+˙ ions, with lifetimes of approximately 10?11 and 10?6 s has been investigated using field ionization, collisionally activated dissociation and charge stripping techniques. The [C9H10]+˙ ions which were investigated included the molecular ions of α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, indan, cyclopropylbenzene, allylbenzene and the product of water loss from 3-phenylpropanol. The field ionization spectra of all the C9H10 hydrocarbons were different indicating that isomerization to a common ion structure had not occurred to a measurable extent for ions with lifetimes of approximately 10?11 s. Collisionally activated dissociation and charge stripping results indicated that most of the [C9H10]+˙ ions continued to maintain unique ion structures (or mixtures of structures) at ion lifetimes of 10?6 s. Possible exceptions are the [C9H10]+˙ ions from allylbenzene and cyclopropylbenzene which gave indistinguishable collisionally activated dissociation and charge stripping spectra. 相似文献
Unstable 2-hydroxpropene was prepared by retro-Diels-Alder decomposition of 5-exo-methyl-5-norbornenol at 800°C/2 × 10?6 Torr. The ionization energy of 2-hydroxypropene was measured as 8.67±0.05 eV. Formation of [C2H3O]+ and [CH3]+ ions originating from different parts of the parent ion was examined by means of 13C and deuterium labelling. Threshold-energy [H2C?C(OH)? CH3]+˙ ions decompose to CH3CO++CH3˙ with appearance energy AE(CH3CO+) = 11.03 ± 0.03 eV. Higher energy ions also form CH2?C?OH+ + CH3 with appearance energy AE(CH2?C?OH+) = 12.2–12.3 eV. The fragmentation competes with hydrogen migration between C(1) and C(3) in the parent ion. [C2H3O]+ ions containing the original methyl group and [CH3]+ ions incorporating the former methylene and the hydroxyl hydrogen atom are formed preferentially, compared with their corresponding counterparts. This behaviour is due to rate-determining isomerization [H2C?C(OH)? CH3]+˙ →[CH3COCH3]+˙, followed by asymmetrical fragmentation of the latter ions. Effects of internal energy and isotope substitution are discussed. 相似文献
Phenyl vinyl ether (M1) has been copolymerized with its various ring-substituted derivatives (M2) in toluene at ?78°C with stannic tetrachloride as catalyst. The substituents investigated include p-CH3O, m-CH3O, p-CH3, m-CH3, p-Cl, and m-Cl. The course of copolymerization was followed by gas chromatographic determinations of residual monomers, and the monomer reactivity ratios were evaluated by use of the integral form of the Mayo-Lewis copolymerization equation. Except for the unusual case of the m-CH3O derivative, the observed values of log (1/r1) were found to be linearly correlated with Hammett's σ constants, the reaction constant being ρ = ?1.76 with the correlation coefficient r = 0.990. Comparisons of these results with the existing data for the styrene copolymerizations have enlightened the behavior of the oxygen atom in transmitting the electronic effects of ring substituents onto the reaction center. 相似文献
Kinetic and spectrophotometric measurements made during the Fe3+ ion catalyzed decomposition of H2O2 have been analyzed using the computer simulation method. Improved values of the rate constants of the “complex scheme” and of the molar absorptivities ofthe intermediates were obtained: k3/KM = 4.94 M?1 min?1, k4 = 193 M?1 min?1, εI/KM = 52.3 M?2 cm?1, εII = 25.7 M?1 cm?1. The simulation revealed details of the reaction which were unavailable by other means and which explained several features of its kinetics. The total amount of O2 evolved in the reaction using [H2O2] ~ 10?2 M has been calculated and found to be nearly stoichiometric. O2 evolution experiments in this region cannot, thus, distinguish between the “complex mechanism” predicting nearly stoichiometric evolution of O2 and the “free radical mechanism” predicting exactly stoichiometricamounts of O2. There are discrepancies within the “free radical scheme” with regard to the correct values of the rate constants to fit the reactions of H2O2 both with Fe2+ and Fe3+ ions, as well as other reactions assumed to proceed via free radicals. 相似文献