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1.
Molecular structures and energies have been calculated in the MNDO approximation, for P4S3 and its molecular ion P4S3+, and for the mass spectral fragment pairs: (P3S3+ + P), (P3S2+ + PS), (P3S+ + PS2), (P2S3+ + P2), (P2S2+ + P2S), (P2S+ + P2S2), (P2S2), PS3+ + P3), (PS2+ + P3S), (PS+ + P3S2), and (PS+ + P2S + PS). Three distinct energy minima were found for each of P2S2+ and P2S2, and two minima for each of P2S+, P2S, PS3+, PS3+, PS2+, PS2, P3+ and P3. The fragments arising from P4 and P4+ were also investigated. The structures are discussed in terms of the Jahn—Teller effect, whose predictions are fulfilled without exception.  相似文献   

2.
Structures and energies have been calculated, in the MNDO approximation, for xanthan hydride (C2H2N2S3) and its molecular cation, and for the mass spectral fragment ions H2NCNCS+, HNCNCS+, CS2+, H2N2CS+ (two isomers), HN2CS+, S2+, H2NCS+ (three isomers), HNCS+ (two isomers), H3N2C2+ (four isomers), CS+ and HNCS+2 (two isomers), together with the corresponding neutral fragments.  相似文献   

3.
Molecular structures and energies have been calculated, in the MINDO/3 approximation, for neutral singlets and triplets, and for molecular cations and anions of benzene and seven of its valence isomers.  相似文献   

4.
Calculations have been made using MINDO/3 of the structures and energies of four conformations of ethyl acetate, of four isomeric forms of its molecular ion, and of all the fragment and rearrangement ions in the mass spectrum together with those of the corresponding neutral fragments.  相似文献   

5.
Molecular geometries and heats of formation are calculated, using MINDO/3, for the following mass-spectral fragment pairs derived from formic acid: X(2A')(HCOOH)+; (HCOO)+ + Hxxx; (HCO)+ + OH; HCO + (OH)+; (CO)+ + H2O; (CO2)+ + H2. The activation energy for the reaction (HCOOH)+ → (HCOO)+ + Hxxx is 75 kJ mol?1. A correlation is made of the symmetry classes of the electronic states of (HCOOH)+, accessible by single electron excitation, and those of the mass-spectral fragments: it is shown that, despite their closely similar appearance potentials, the ions (HCOO)+ and (HCO)+ arise from different states of (HCOOH)+. The structure of (HCOOH)2+ is also reported.  相似文献   

6.
Molecular geometries and heats of formation have been calculated, using MINDO/3, for mass spectral fragment pairs (A+ + B) derived from formamide. There are five stable isomeric forms of the molecular ion: [H2NC(OH)]+, (H3NCO)+, [HNC(OH2)]+, [NCH(OH2)]+, and (NCOH3)+ (in order of increasing
, but no isomer (H2NCHO)+. There are three isomeric forms of (M—H)+: (H2NCO)+ (HNCOH)+, and (NCOH2)+: the only stable form of (M—2H)+ is (NCOH)+. Other (A/B)+ fragment pairs calculated are (CO/NH3)+, (HCO/NH2)+, (H2O/HCN)+, (H2O/HNC)+ [HO. + (HCNH)+], and [HO. + (H2NC)+]. The structure of the doubly charged ion M2+ is also reported.  相似文献   

7.
Structures and energies have been calculated, in the MNDO approximation, for PH3, P2H4, P2H2, and P3H5, for their molecular cations, for all the ions in their mass spectra, and for the corresponding neutral mass spectral fragments. With the exception of the conformation of P2H4, which is calculated to be anti rather than gauche, the calculated structures and energies are in good agreement with those found experimentally, where these are known. Appearance potentials have been calculated, and allow deductions to be made concerning fragmentation pathways.  相似文献   

8.
The electrochemical oxidation of various substituted chrysoidines was studied by cyclic voltammetry, to determine which have stable oxidation products. Only 4-hydroxy-chrysoidine has a stable product; the apparent oxidation potential is 0.779 V vs. NHE. 4-Methoxy- and 4-ethoxy-chrysoidine rapidly lose methanol or ethanol, respectively, so that the 4-hydroxychrysoidine wave appears on subsequent scans. All the other chrysoidines studied are irreversible. The results indicate that a hydroxy group in the 4-position is necessary for stability; the 4-alkoxychrysoidines can achieve the stable quinoidal structure by cleavage of the alkoxy group after nucleophilic attack.  相似文献   

9.
MINDO/3 calculations have been made of the molecular structures and energies of seven isomeric forms of the molecular cation (CCl4)+, of the mass spectral fragment pairs:
and also of a number of neutral fragment pairs. Reaction energy profiles have been calculated for two fragmentations of (CCl4)+, into [(CCl2)+ + Cl2], and into [(CCl3)+ + Cl?], in the latter of which the reaction proceeds via a rather stable intermediate; for the fragmentation of three electronic states of (CCl3)+ into [(CCl2)+ + Cl?], where the ground singlet state and first triplet state of (CCl3+ yield the ground doublet state of (CCl2)+, but the first excited singlet of (CCl3)+ yields the first excited doublet of (CCl2)+ ; and for the fragmentation of the ground state of (CCl3)+ into [(CCl)+ + Cl2].  相似文献   

10.
Azido-nitrosyl complexes and their derivatives of the types [Cr(NO)(N3)5]3? and [Cr(NO)(N3)2(L-L)] [L-L = 2,2′bipyridine (bipy) and 1,10 phenanthroline (phen)] were synthesised directly from chromate ion using hydroxylamine hydrochloride, azide ion and hydroxyl ion and other appropriate ligands virtually in a single step process in an aqueous aerobic medium. The compounds are characterised by IR, molecular weight, molar conductance, magnetic susceptibility, esr and electronic spectral data.  相似文献   

11.
The performance of the VN—1 potential model at the INDO/2 level of approximation in the calculation of transition energy, singlet—triplet splitting, change in molecular structure, inversion barrier and electron-density distribution in the excited electronic states of a few simple carbonyls is analysed. The method turns out to be reasonably successful in many ways.  相似文献   

12.
Structural investigation, mainly by mass spectrometry and X-ray crystallography, of the product obtained from the reaction of propylenediamine and N3P3Cl6 shows it to have a monospiro structure. It is demonstrated that in this case data collected through indirect structural methods such as IR or NMR spectroscopy could not provide a priori the right answer.  相似文献   

13.
Tan YL  Quanci JF 《Talanta》1985,32(7):577-578
A packed-column gas-chromatograph/mass-spectrometer (GC/MS), Hewlett-Packard 5982, was modified to accommodate fused silica capillary columns. The original GC/MS interface and chemical-ionization sample-line in the ion-source were changed to allow the end of a fused silica capillary column to enter the ion-chamber directly. For chemical-ionization operation, the reagent gas was brought into the MS through the direct-insertion probe port. The calibration compound was introduced through the electron-impact sample-inlet, which simplified the operation. The modified system yields higher sensitivity and more efficient separation, as well as simpler operation, without sacrificing any original instrument functions.  相似文献   

14.
The action of thorium or uranium tetrachloride with octaethylporphyrin [(oep)H2] affords the dichlorometal (IV) complexes [M(IV)(oep)Cl2, Ln] (M(IV) = Th or U, L = benzonitrile, tetrahydrofuran or pyridine). Spectral properties of these complexes are in good agreement with a cis octa-coordination.  相似文献   

15.
MINDO/3 calculations have been made for the activation enthalpies, and the transition state structures for the following equilibria between isomers of the formamide molecular cation, M+: (NCOH3)+ ? (NCHOH2)+ ? (HNCOH2)+? (H2NCOH)+? (H3NCC)+ for the following equilibria between the isomers of (M-H)+: (NCOH2)+ ? (HNCOH)+ ? (H2NCO)+ and for seven decomposition reactions of general type: M+ → (M-H)+ + H? Rate constants have been deduced using calculated enthalpies of activation, and estimated A factors. All the processes are symmetry-allowed.  相似文献   

16.
Morphological studies on graphite tube surfaces by scanning electron microscopy are presented for unused and corroded tubes from various endurance experiments in electrothermal AAS.Tubes always break in their center as this is the hottest part; tube thinning occurs predominantly at the outside. The inner surface of tubes coated with pyrographite is usually only slightly corroded, unless highly aggressive reagents are applied. Deposition of carbon in thin layers as well as in nodules is observed in the hot central zone.  相似文献   

17.
The photoluminescence spectra of hydrated and anhydrous uranyl sulfates have been studied under conditions of high resolution at cryogenic temperatures. All uranyl sulfate systems were found to yield nonequivalent spectra: the energies for the electronic and vibronic origins were found to vary with the system, and certain uranyl vibrational frequencies exhibited a dependence on environment. These differences must reflect the various ways in which the uranyl centers are linked by the bridging sulfate groups, as this linking is the main difference between the various structures.  相似文献   

18.
19.
Dittrich K  Shkinev VM  Spivakov BV 《Talanta》1985,32(11):1019-1022
The determination of traces of fluoride by means of the molecular absorption of AlF volatilized in graphite cuvettes is described. An extraction method for separation and preconcentration of the fluoride has been developed, to avoid matrix effects. The fluoride is extracted with 10(-3)M triphenylantimony(V) dihydroxide in M1BK, and stripped with 0.025M barium hydroxide. The method is sensitive and specific for fluoride. The detection limit is about 0.3 ng of fluoride, and the fluoride content of 6 ml of 10(-7)M solution can be determined. The determination is possible in presence of various ions, but it is estimated that usage of trace matrix separation leads to a considerable improvement in the relative detection limits (by 2-3 orders of magnitude), levels as low as 0.01 ppm being detectable in some matrices.  相似文献   

20.
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