Splitting off of water from the molecular ions of steroidal cyclopropyl ketones

1980 ◽  
Vol 45 (11) ◽  
pp. 2985-2997 ◽  
Author(s):  
Alexander Kasal ◽  
Antonín Trka
Keyword(s):  
Water Molecule ◽  
Mass Spectra ◽  
Cyclopropane Ring ◽  
Molecular Ions ◽  
Keto Group ◽  
Hydrogen Atoms ◽  
Molecular Ion ◽  
Cyclopropyl Ketones

Mass spectra of 14 steroids containing a cyclopropane ring in the vicinity of a keto group were measured and the signals of the ions [M-H2O]+, [M-CH3]+ and [M-CO]+ were sought. Using models labelled selectively with deuterium it was shown that the water molecule, split off from the molecular ion of 3α,5-cyclo-5α-cholestan-6-one (I) is formed from the hydrogen atoms located in the positions 2β and 9α.

The mass spectrum of exo-2-norbornyl chloride; the elucidation of the fragmentation mechanism and ion structures by metastable ion analysis

1970 ◽  
Vol 48 (18) ◽  
pp. 2791-2797 ◽  
Author(s):  
J. L. Holmes ◽  
D. McGillivray ◽  
N. S. Isaacs
Keyword(s):  
Mass Spectrum ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Fragmentation Mechanism ◽  
Hydrogen Atoms ◽  
Ethylene Molecule ◽  
Molecular Ion ◽  
Carbonium Ions ◽  
Ion Analysis

The mass spectra of exo-2-norbornyl chloride and several deuterated analogues have been examined in detail with particular regard to metastable peaks involving the molecular ions and norbornyl cations. The molecular ion does not undergo Wagner–Meerwein isomerization prior to fragmentation; in the norbornyl cation the hydrogen atoms have lost their identity as shown by random H and D loss when the ion ejects an ethylene molecule. Metastable ion analysis is proposed as a method for studying the participation of norbornyl carbonium ions in the preparation of 2-norbornyl chloride.

Studies in Mass Spectrometry. VII. Triterpenoids: Ifflaionic Acid

1963 ◽  
Vol 16 (4) ◽  
pp. 683 ◽  
Author(s):  
JS Shannon
Keyword(s):  
Mass Spectrometry ◽  
Methyl Ester ◽  
Functional Groups ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Keto Group ◽  
Chemical Derivatives ◽  
Pentacyclic Triterpenoid

The mass spectra of the methyl ester of the new unsaturated pentacyclic triterpenoid ifflaionic acid (urs-12-en-3-on-30-oic acid) and some of its chemical derivatives are presented. These may be used to assign position C-20 to the carbomethoxy and C-3 or C-7 to the keto group. Mechanistic proposals for, and the effect of functional groups on, the main fragmentation of the molecular ions (cleavage through ring C) are discussed.

The Fragmentation Mechanism of Cyclobutanol

1973 ◽  
Vol 51 (14) ◽  
pp. 2342-2346 ◽  
Author(s):  
John L. Holmes ◽  
Robin T. B. Rye
Keyword(s):  
Hydrogen Atom ◽  
Mass Spectra ◽  
Fragmentation Mechanism ◽  
Hydrogen Atoms ◽  
Specific Mechanism ◽  
Molecular Ion ◽  
Random Manner ◽  
Hydroxyl Hydrogen

The mass spectra of cyclobutanol and three 2H labelled analogs have been studied. The losses of C2H4 and C2H5• from the molecular ion involve specific fragmentations. Only CH3• loss from the α-cleaved molecular ion2 clearly involves hydrogen atom scrambling; this fragmentation also proceeds by a specific mechanism involving C-2 and hydroxyl hydrogen atoms. Loss of water from the molecular ion involves all the hydrogen atoms but in a complex, non-random manner.

Mass Spectrometric Studies. XIV. Nitrochalcones

1979 ◽  
Vol 32 (10) ◽  
pp. 2249 ◽  
Author(s):  
J Baldas ◽  
QN Porter
Keyword(s):  
Oxygen Transfer ◽  
Mass Spectra ◽  
Nitro Compounds ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Hydrogen Atoms ◽  
Carbon Carbon Bond ◽  
Nitro Derivatives ◽  
Anchimeric Assistance ◽  
Hydroxy Groups

The mass spectra of chalcone, of its 2-, 2'-, 3-, 3'- and 4-nitro derivatives, and of a number of deuterated analogues, are described. Fragmentation of the 2-nitro isomer is very simple on account of anchimeric assistance to a carbon-carbon bond fission from the nitro group. The 2'-nitro isomer shows complex fragmentation resulting from oxygen transfer to the α,β-double bond. The 3-, 3'-, and 4-nitro compounds fragment in ways similar to that of chalcone itself, except for losses of hydroxy groups from their molecular ions. The origins of the transferred hydrogen atoms are shown by labelling experiments, and structures are suggested for the ions formed.

Studies in Mass Spectrometry. II. Random Hydrogen Rearrangement in Aromatic Molecular Ions

1962 ◽  
Vol 15 (4) ◽  
pp. 771 ◽  
Author(s):  
CG Macdonald ◽  
JS Shannon
Keyword(s):  
Mass Spectrometry ◽  
Aromatic Compounds ◽  
Mass Spectra ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Deuterium Exchange ◽  
Molecular Ion ◽  
Hydrogen Rearrangement ◽  
Aromatic Hydrogen

To provide data for investigations by, inter alia, mass-spectrometric methods into the deuterium exchange of the aromatic hydrogen of some coal fractions, a study was made which confirmed the occurrence of completely random hydrogen rearrangement prior to or during the elimination of C2H2 in the molecular ions of benzene-1,2,3-d3, benzene-l,3,5-d3, naphthalene-1,2,3,4-d4, naphthalene-1,4,5,8-d4, and phenanthrene-9,10-d2, and in the phenyl ions derived from o-bromobenzene-d, m-bromobenzene-d, and p-chlorobenzene-d, Similar but incomplete hydrogen rearrangement was found to occur in the molecular ion of carbazole-N-d prior to or during elimination of HCN. Such rearrangements, for which mechanistic considerations are presented, must be taken into account when the mass spectra of deuterium-substituted aromatic compounds are being interpreted.

Mass spectral studies of metal chelates. V. Mass spectra and appearance potentials of some fluorine-substituted acetylacetonates

1970 ◽  
Vol 48 (9) ◽  
pp. 1362-1370 ◽  
Author(s):  
C. Reichert ◽  
G. M. Bancroft ◽  
J. B. Westmore
Keyword(s):  
Mass Spectra ◽  
Molecular Ions ◽  
Metal Chelates ◽  
Spectral Studies ◽  
Molecular Ion ◽  
Mass Spectral ◽  
Fragment Ions ◽  
D Orbitals

The mass spectra of the hexafluoroacetylacetonates (hfacac) and trifluoroacetylacetonates (tfacac) of Al(III), Cr(III), Fe(III), Fe(II), Cu(II), and Zn(II) are reported. The main features of the spectra are discussed. Compared with the spectra of the acetylacetonates (acac), substitution of CF3 for CH3 in these complexes leads to more extensive fragmentation of the molecular ions. For example, ions corresponding to loss of •CF3 radicals are more abundant than those corresponding to loss of •CH3 radicals. The appearance potentials (a.p.'s) of the molecular ions and, where possible, of fragment ions formed from the molecular ion by loss of •CF3, •CH3, or ligand radicals are reported. The a.p.'s of the molecular ions are more sensitive to the nature of the ligand than to the metal. Thus, for the metal chelates studied here the a.p.'s of the molecular ions from ML2 and ML3 (L stands for ligand) were 9.95 ± 0.25 V for L = hfacac, 9.05 ± 0.35 V for L = tfacac, and 8.3 ± 0.35 V for L = acac. The energy required to dissociate a •CF3 or •CH3 radical from the molecular ion is sensitive to the nature and valency of the metal M, being low (relatively) for Al(III) and Fe(III), and high (relatively) for Cr(III) (inferred) and Fe(II). This variation is discussed in terms of the effect of substituent, and of interaction of metal d orbitals with the ligands.

Inductive effect in EI-mass spectra of some 5,6-dihalogenides and 5,6-halohydrins of 5α-cholestan-3β-ol and 3β-acetoxy-5α-cholestane

1982 ◽  
Vol 47 (11) ◽  
pp. 2946-2960 ◽  
Author(s):  
Antonín Trka ◽  
Alexander Kasal
Keyword(s):  
Mass Spectra ◽  
Inductive Effect ◽  
Molecular Ions ◽  
Hydroxyl Group ◽  
Halogen Atoms ◽  
Derivatives Of

Partial EI-mass spectra of 3β-hydroxy- and 3β-acetoxy-5α-cholestanes substituted in positions 5α-, 6β- or 5α,6β- with a hydroxyl group or halogen atoms (fluorine, chlorine, bromine) are presented. The molecular ions of 5α,6β-disubstituted derivatives of 3β-hydroxy-5α-cholestane (or of its 3-acetate) are considerably more stable than the corresponding monosubstituted derivatives if at least one of the pair of the vicinal substituents is chlorine or fluorine. This increase in stability, most striking in 5α- and 6β-fluoro compounds, is explained by the inductive effect.

Mass spectra of 4,4-dimethyl-A-homo-4a,6-cholestadien-3-ols, 4,4-dimethyl-A-homo-5-cholestene-3,4a-diols and their derivatives

1982 ◽  
Vol 47 (10) ◽  
pp. 2768-2778
Author(s):  
Antonín Trka ◽  
Helena Velgová
Keyword(s):  
Carbon Atom ◽  
Electron Impact ◽  
Mass Spectra ◽  
Molecular Ions

Partial electron impact induced mass spectra are given of 3α-hydroxy-, 3β-hydroxy-, 3β-methoxy-, 3α-acetoxy- and 3β-acetoxy-4,4-dimethyl-A-homo-4a,6-cholestadienes, 3α,5α-epoxy-4,4-dimethyl-A-homo-5-cholestane, isomeric 4,4-dimethyl-A-homo-5-cholestene-3α(β),4aα(β)-diols, their 3-acetoxy derivatives and 3-methyl ethers. The fragmentation of the molecular ions of these substances involves the usual elimination of substituents (in the form of H2O, CH3OH, CH3COOH, CH2CO), but the most abundant and characteristic ions are products of the contraction of ring A (to a six- or five-membered one), accompanied by expulsion of a fragment containing the carbon atom C(4) with both methyls.

scholarly journals Effect of ammonia and water molecule on OH + CH3OH reaction under tropospheric condition

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohamad Akbar Ali ◽  
M. Balaganesh ◽  
Faisal A. Al-Odail ◽  
K. C. Lin
Keyword(s):  
Water Molecule ◽  
Energy Surface ◽  
Rate Coefficient ◽  
Water Concentration ◽  
State Theory ◽  
Rate Coefficients ◽  
Hydrogen Atoms ◽  
Experimental And Theoretical Studies ◽  
Effective Reaction ◽  
Effective Reaction Rate

AbstractThe rate coefficients for OH + CH3OH and OH + CH3OH (+ X) (X = NH3, H2O) reactions were calculated using microcanonical, and canonical variational transition state theory (CVT) between 200 and 400 K based on potential energy surface constructed using CCSD(T)//M06-2X/6-311++G(3df,3pd). The results show that OH + CH3OH is dominated by the hydrogen atoms abstraction from CH3 position in both free and ammonia/water catalyzed ones. This result is in consistent with previous experimental and theoretical studies. The calculated rate coefficient for the OH + CH3OH (8.8 × 10−13 cm3 molecule−1 s−1), for OH + CH3OH (+ NH3) [1.9 × 10−21 cm3 molecule−1 s−1] and for OH + CH3OH (+ H2O) [8.1 × 10−16 cm3 molecule−1 s−1] at 300 K. The rate coefficient is at least 8 order magnitude [for OH + CH3OH(+ NH3) reaction] and 3 orders magnitude [OH + CH3OH (+ H2O)] are smaller than free OH + CH3OH reaction. Our calculations predict that the catalytic effect of single ammonia and water molecule on OH + CH3OH reaction has no effect under tropospheric conditions because the dominated ammonia and water-assisted reaction depends on ammonia and water concentration, respectively. As a result, the total effective reaction rate coefficients are smaller. The current study provides a comprehensive example of how basic and neutral catalysts effect the most important atmospheric prototype alcohol reactions.

Sign in / Sign up

Export Citation Format

Share Document