Gas‐Chromatographie und Massenspektrometrie der Trimethylsilyl‐enoläther von 5α‐ und 5β‐Cholestan‐3‐on
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Abstract:
Abstract Trimethylsilyl‐enolethers of 5α‐ and 5β‐cholestan‐3‐on were investigated by gas chromatography and mass spectrometry. These derivatives are readily prepared and well suited for gas chromatographic analysis. In the mass spectrum they show fairly intense fragmentation, which appears to be characteristic for some structural elements in the surroundings of the functional group (excluding stereochemistry). This fragmentation may be useful for the structure elucidation of 3‐oxo‐steroids and related compounds. For comparison purposes the corresponding enolacetates were also investigated.Keywords:
Trimethylsilyl
Fragmentation
The mass spectra of 8, 8-dicyanoheptafulvene and its derivatives, which are considered to belong to a non-benzenoid aromatic compound, were measured. The high degree of aromaticity of 8, 8-dicyanoheptafulvenes was made clear by mass spectrometry. Low mass regions of dicyanoheptafulvene showed the elimination of hydrogen cyanide from parent ion and rearrangement to phenylpropiolonitrile ion. The mass spectra of methoxy dicyanoheptafulvenes showed fragmentation quite different from that of 8, 8-dicyanoheptafulvenes. The structures and fragmentation processes of dicyanoheptafulvenes were discussed.
Fragmentation
Hydrogen cyanide
Mass
High mass
Polyatomic ion
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The mass spectra of 8, 8-dicyanoheptafulvene and its derivatives, which are considered to belong to a nonbenzenoid aromatic compound, were measured. The high degree of aromaticity of8, 8-dicyanotheptafulvene was made clear by masss pectrometry. Low mass regions of dicyanoheptofalvene showed the elimination of HCN from parent ion and rearrangement to phenvlpropiolonitrile ion. The mass spectra of methoxy-dicyanoheptafulvenes showed fragmentation quite different from that 8, 8-dieyanoheptafulvenes. The structure and fragmentation processes of dieyanoheptafulvenes were discussed.
Fragmentation
Polyatomic ion
High mass
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Trimethylsilyl
Carbon fibers
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The preparation and gas chromatographic mass spectrometric properties of a number of vinyldimethylsilyl ethers of steroids and cannabinoids are reported. Gas-liquid chromatographic retention increments for the vinyldimethylsilyl ethers were about 1 methylene unit higher than those of the corresponding trimethylsilyl ethers for each derivatized hydroxyl group. The mass spectra were very similar to those of the correspondig trimethylsilyl derivatives with, in many cases, enhancement of the abundance of both the molecular ions and diagnostic fragment ions containing silicon. These properties made vinyldimethylsilyl derivatives useful for: (a) mass spectral interpretation by the shift technique; (b) correlating spectra with those of the trimethylsilyl derivativeds when vinyldimethylsilyl derivatives were used to shift diols from monohydroxy compounds in gas chromatograms; and (c) for determining the major site of RMe2SiOH loss in the mass spectra of mixed trimethylsilyl/vinyldimethylsilyl derivatives.
Trimethylsilyl
Methylene
Polyatomic ion
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The mass spectral fragmentation of the cyclodipeptides were investigated. The main fragmentation processes for the peptides were almost the same. In the case of compounds that have the large side chains, the cyclic skeletal ions generated by the loss of the side chain group were followed by the further fragmentations. The important ions arising from cycloglycylglycine in 70 eV-mass spectrum were of m/z 86 [M-CO] and of m/z 71 [M-NHCO] from which further fragmentations occurred. The metastable ion spectrum by B/E linked scan method indicated that the m/z 30 (the most abundant ion in 70 eV-mass spectrum) was formed from the process via the ion of m/z 86.
Fragmentation
Metastability
Polyatomic ion
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The doubly charged ion mass spectra of anhydropisatin, 4-methoxyanhydropisatin, 3, 8, 9-trimethoxypterocarpen and 3, 4, 8, 9-tetramethoxypterocarpen were determined, and the fragmentation was explained by assuming that the paired electrons were partially localized in the fragmentations and by comparing the spectra with that of 3-(CD3)-anhydropisatin. Conventional mass spectra of these compounds were very simple, but the doubly charged ion spectra were sufficiently characteristic for the reliable identification.
Fragmentation
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Abstract An ion formed by loss of 56 mass units from the molecular ion is often seen in mass spectra of trimethylsilyl ethers of C 19 and C 21 steroids having a 3β‐hydroxy‐Δ 5 structure and an oxo group at C‐17 or C‐20. The nature of this fragment was investigated by the use of perdeuteriotrimethylsilyl ether derivatives and of [4‐ 14 C], [3‐ 18 O], [4,4‐ 2 H 2 ] and [2,2,4,4‐ 2 H] labelled derivatives of 3β‐hydroxy‐5‐androsten‐17‐one and 3β‐hydroxy‐5‐pregnen‐20‐one. Evidence is presented to show that the neutral fragment of mass 56 is composed of carbon atoms 1, 2 and 3, the oxygen at C‐3 and four hydrogen atoms. During the fragmentation process, the trimethylsilyl group and one of the hydrogens at C‐2 are transferred to the fragment that carries the charge.
Fragmentation
Trimethylsilyl
Polyatomic ion
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The mass spectra of several γ-substituted β-keto esters have been recorded and interpreted. The fragmentation patterns are compared to those of α-substituted β-keto esters and are found to be very useful in differentiating the α- and γ-substituted isomers. The mass spectral fragmentation schemes are dominated by cleavages α to the carbonyl groups and by McLafferty rearrangements.
Fragmentation
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Abstract Ketones are reported to be conveniently converted into their α-tolylsulfinylated derivatives. This new procedure is based on the reaction of their corresponding trimethylsilyl enol ethers with p-toluenesulfinyl p-tolylsulfone in the presence of tris(dimethylamino)sulfur trimethylsilyldifluoride (TAS-F). Considering that β-ketosulfoxides are key intermediates for the preparation of α,β-unsaturated ketones, this procedure turns out to be of rather broad synthetic relevance.
Trimethylsilyl
Enol ether
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