Mass spectral study on O,O-dialkyl N,N-dialkyl phosphoramidates under electron impact conditions

A series of O,O-dialkyl N,N-dialkyl phosphoramidates (1-25) were analyzed under GC-EIMS conditions. Clear-cut differences are found in the fragmentation of O,O-dialkyl N,N-dimethyl phosphoramidates (Series 1) and O,O-dimethyl N,N-dialkyl phosphoramidates (Series 2). The phosphoramidates comprising of mixed/crossed alkyl groups on nitrogen and oxygen (Series 3) showed mixed fragmentation pattern corresponding to both Series 1 and 2 depending on the nature of alkyl groups. All the possible isomers among the studied compounds showed distinguishable EI mass spectra. Although the major ions in the EI mass spectra for the isomers containing O-n-propyl or O-isopropyl and N,N-diethyl or N-isopropyl N-methyl are similar, the isomers could be distinguished by characteristic ions of low abundance at low mass region. The differences are prominent in the metastable ion spectra of characteristic ions.     

The electron-impact-induced fragmentation of some alkyl isocyanides and α-branched alkyl cyanides

The HRP mass spectra of some alkyl isocyanides (R? NC in which R equals CH₃, C₂H₅, n-C₃H₇, n-C₄H₉ and t-C₄H₉) and two methyl branched alkyl cyanides (R? CN in which R equals i-C₃H₇ and t-C₄H₉) have been studied. Using metastable ion transitions and appearance potentials, the fragmentation patterns and spectral characteristics of the isocyanides can be given. A comparison has been made with the mass spectral data of the corresponding cyanides. Although the mass spectra of alkyl cyanides and isocyanides show close relationship, evidence could be obtained that this resemblance is not caused by rearrangement of the isocyanide into cyanide molecules. The main difference between the spectra of both compounds is caused by the strength of the α-bond, being weaker in the case of the isocyanides. The abundance of ions formed by α-bond cleavage decreases with increasing size of the alkyl group.     

Mass spectra of some alkyl isoxazoles

The mass spectra of several compounds obtained during the process of Stork's isoxazole synthesis9 as well as the related isoxazoles have been investigated. The fragmentations of simple alkyl isoxazoles are nicely formulated via azirine intermediates. A striking difference between the spectra of isoxazoles and those of methylfurans as to the relative abundance of [M — l] peaks is noteworthy. The very low abundance of these peaks in the former reflects the unique character of isoxazole nucleus due to the preferential cleavage of N? O linkage rather than a benzylic C? H bond rupture. If an alkyl substituent is present at 4-position in 3,5-dimethylisoxazoles, strong peaks at m/e 110, 68 and 43 are common in their spectra. The analyses of metastable transitions and high resolution measurements have demonstrated that the formation of these ions can be interpreted by a mechanism involving the cleavage of N? O linkage.     

Recherches sur la formation et la transformation des esters LXXII. Aryl(ou aralcoyl ou alcoyl)amino-2-tétrahydro-m-thiazines ou aryl(ou aralcoyl ou alcoyl)amino-2-dihydro-Δ2-m-thiazines et dérivés

3-Aminopropanol reacts with aryl(or aralkyl or alkyl)isothiocyanates R? N?C?S to yield the corresponding thio-ureas R? NH? CS? NH? (CH₂)₃OH which, refluxed with hydrochloric acid, are cyclized by elimination of water. The cyclization products are identical with the hydrothiazines resulting by elimination of sulfate or phosphate from the sulfuric or phosphoric monoesters of these thio-ureas. The resulting hydrothiazines are either 2-(R-imino)-tetrahydro-m-thiazines (I) or 2-(R-amino)-dihydro-Δ²-m-thiazines (II). Their structure has been established by comparison of their spectra with those of model compounds in one of which the C?N double bond is certainly endocyclic (2-methyl-dihydro-Δ²-m-thiazine), the other presenting an exocyclic C?N double bond (3-methyl-2-phenylimino-tetrahydro-m-thiazine). When R is an aryl group, the C?N double bond is exocyclic (structure I with >C?N? Ar), and one may presume that this structure is stabilized by resonance. When R is an aralkyl or an alkyl group, the C?N double bond is endocyclic (structure II). The nmr spectra were taken with three types of solvent: CDCl₃ or CCl₄; (CD₃)₂SO; CF₃COOH. In CF₃COOH solution the benzylic protons of the hydrothiazine with R = pF? C₆H₄CH₂? couple with NH (J=5,5cps) which confirms the endocyclic position of the C?N double bond in this case.     

SYNTHESIS OF BRANCHED POLYETHYLENE USING (α-DIIMINE)NICKEL(Ⅱ)TiCl4 COMBINED AND SUPPORTED CATALYST*

(α-Diimine)nickel(Ⅱ) {[C6H5 -N = C(CH3)-C(CH3) = N -C6H5]NiBr2}-TiCl4 abbreviated as NiL-TiCl4 combined catalyst which is supported on MgCl2-SiO2 carrier has been prepared, by using alkyl aluminum (AIR3) as the cocatalyst in place of methylaluminoxane (MAO) to catalyze ethylene oligomerization and copolymerization in situ. The influences of procedure for supporting NiL-TiCI4, the molar ratio of NiL to TiCI4, cocatalyst type and polymerization temperature on the catalytic performance were studied. The degree of branching and the composition of the branched chain of polymers produced have been investigated by IR and ^13C-NMR spectra. The results show that the combined catalyst can synthesize the branched polyethylene with various banched chains .The polymerization reaction was monitored by gas chromatography and mass spectrometry (GC-MS). The results show that this catalyst promotes the oligomerization and copolymerization in situ for ethylene.     

Mass spectra of 1,2,4-triazoles—II: Alkyl 1,2,4-triazoles

The mass spectra of monomethyl 1,2,4-triazoles contain fragment ions produced by specific cleavage of the heterocyclic ring. A major fragmentation from many molecular ions involves the elimination of HCN, but loss of N₂ is either very small or completely absent. No N or H scrambling occurs within the triazole ring system, as evidenced by labelling studies. The loss of a hydrogen atom from the molecular ions of 3-alkyl-1,2,4-triazoles (alkyl ? C₂H₅) originates from hydrogens attached to the β carbon and nitrogen atoms.     

Mass spectrometric determination of the configuration of the 4-substituted 1,2-dimethyl-4-hydroxydecahydroquinolines

The mass spectra of a number of the epimeric 1,2-dimethyl-4-alkyl-4-hydroxydecahydroquinolines (alkyl: C?CH, CH?CH₂, C₂H₅ and COCH₃) have been studied. The configuration at C-2 and C-4 in these molecules is proposed on the basis of the data obtained. Some aspects of the fragmentation pathways under electron-impact are discussed.     

Über Chalkogenolate. 94. Untersuchungen über Trithioallophansäure 3. Ester der Trithioallophansäure [1]

On Chalcogenolates. 94. Studies on Trithioallophanic Acid. 3. Esters of Trithioallophanic Acid. The esters of trithioallophanic acid H₂N? CS? NH? CS(SR) with R = CH₃, CH₂C₆H₅ have been characterized by means of electron absorption spectra, infrared spectra, ¹H NMR spectra, and mass spectra.     

Über Chalkogenolate. 113 Umsetzung von Chloramin mit Kohlenstoffdisulfid und mit Methylestern von Dithiocarbamidsäuren

On Chalcogenolates. 113. Reactions of Chloramine with Carbon Disulfide and with Methylesters of Dithiocarbamic Acids The reactions of chloramine with CS₂ and with H₂N? CS? SCH₃, CH₃? NH? CS? SCH₃, and (CH₃)₂N? CS? SCH₃ have been studied. The reaction with the methylester of dithiocarbamic acid gives the known dimethyl perthiocyanate and the reaction with the methylester of N-methyldithiocarbamic acid leads to CH₃S? CS? N(CH₃)? C(?NCH₃)? SCH₃. The latter compound has been characterized by means of electron absorption spectra, infrared spectra, nuclear magnetic resonance spectra (¹H and ¹³C), and mass spectra.     

Effects of methyl substituents on the proton chemical shifts in the NMR spectra of the twenty methyl and ethyl substituted hydrazines. Electronegativity values for hydrazyl groups

The C? H proton NMR spectra of the twenty conceivable methyl and ethyl substituted hydrazines are presented and analyzed with respect to effects on chemical shifts of the C? H protons caused by replacement of hydrogen by methyl and ethyl groups on the C? N? N? C chain. Thirteen different methyl substituent effects and six different ethyl substituent effects are identified and evaluated. Most of the effects are shielding and in accordance with an electron-releasing inductive effect of alkyl groups. A deshielding effect (the ‘C? C bond effect’) is observed when a methyl group replaces the hydrogen on the carbon bearing the hydrogen in focus and primary hydrogen on the carbon bearing the hydrogen in focus and primary hydrogens become secondary, as observed in other systems. On the basis of their effects on the chemical shifts of methyl protons in CH₃X, eighteen different hydrazyl groups (× = ? NR₁NR₂R₃) fall into three classes: I (R₁ = H; R₂, R₃ = H or alkyl); II (R₁ = alkyl; R₂ and/or R₃ = H); III (R₁, R₂ and R₃ = alkyl), with slightly different electronegativities: 2·94, 2·83 and 2·74, respectively.     

Über Chalkogenolate. 100. Untersuchungen über Monothiocarbamidsäure. 2. S-Methyl- und O-Methylmonothiocarbamat, 2,4,5-Trioxo-thiazolidin-(1,3)

On Chalcogenolates. 100. Studies on Monothiocarbamic Acid. 2. S-Methyl and O-Methyl Monothiocarbamate, 2,4,5-Trioxo-thiazolidine-(1,3) The methyl esters of monothiocarbamic acid H₂N? CO? SCH₃ and H₂N? CS? OCH₃ as well as 2,4,5-trioxo-thiazolidine-(1,3) and its potassium salt have been prepared and characterized by means of electron absorption, infrared, ¹H-NMR, and mass spectra.     

Oxydationsprodukte von Thioharnstoff

Oxidation Products of Thiourea The oxidation of thiourea with hydrogen peroxide forms in dependence of test conditions thiourea S-dioxide (H₂N)₂C? SO₂ or in the presence of HCl dithiobisformamidinium dichloride [(H₂N)₂C? S? S? C(NH ₂)₂]Cl₂. Their electron absorption, infrared, nuclear magnetic resonance, and mass spectra are communicated. Both compounds as well as unstable bis(formamidine)disulfane do not react with carbon disulfide to produce the corresponding dithiocarbamate neither in the presence of help-bases. Also no reaction happens with alkyl esters of chlorodithioformic acid.     

Identification of esters by collisional charge inversion of their enolate ions

The collisional charge inversion and neutralization-reionization (^?NR) mass spectra of the enolate ions of m/z 115 derived from the four butyl acetates, the two propyl propionates, ethyl butyrate, ethyl isobutyrate, methyl valerate, methyl 2-methylbutyrate and methyl 3-methylbutyrate were recorded. The major primary fragmentation reactions of the unstable carbenium ion formed by charge inversion involve elimination of an alkoxy radical to form a ketene or alkylketene molecular ion and formation of an alkyl ion consisting of the R¹ group of RCOOR¹. A minor fragmentation reaction involves elimination of an alkyl radical by cleavage of a C? C bond α to the ether oxygen. The alkylketene ions fragment by β-cleavage eliminating an alkyl radical to form an olefinic acylium ion. In most cases the charge inversion mass spectra of the enolate ions allow identification of the ester.     

The mass spectra of diaziridinones

The electron-impact induced fragmentation of four N,N′-di-t-alkyl-substituted diaziridinones (I to IV) has been studied by both conventional and high resolution mass spectrometry. All diaziridinones exhibit weak molecular ions. Ejection of an alkyl isocyanate, corresponding to the N-alkyl substituent, from the molecular ion, is a dominant and general fragmentation process. Isocyanate-type odd-electron fragment ions occur only in III and IV (where at least one R group is phenyl) and are of low abundance. Elimination of a hydrocarbon radical from the tertiary alkyl substituents is observed in all compounds investigated. McLafferty rearrangement with elimination of a neutral alkene occurs in all compounds. Abundant even-electron hydrocarbon ions corresponding to the mass of the N-alkyl substituent are prevalent. The complete absence of elimination of carbon monoxide is noted. Loss of oxygen from the [M ? RCH²]+ species has been confirmed by accurate mass measurement. Several remarkable rearrangement reactions have been uncovered by high resolution studies and deuteration experiments.     

Radical addition approach to asymmetric amine synthesis: design, implementation, and comparison of chiral N-acylhydrazones

Intermolecular radical addition to C=N bonds with acyclic stereocontrol offers excellent potential as a mild, nonbasic carbon-carbon bond construction approach to chiral amines. Here, complete details of the first radical additions to chiral N-acylhydrazones as an approach to asymmetric amine synthesis are disclosed. Novel N-acylhydrazones were designed as chiral C=N radical acceptors with Lewis acid activation, restriction of conformational mobility, and commercial availability of precursors. Amination of 4-alkyl-2-oxazolidinones with O-(mesitylenesulfonyl)hydroxylamine or O-(p-nitrobenzoyl)hydroxylamine afforded N-aminooxazolidinones which were condensed with aldehydes to afford N-acylhydrazones 3-8. Three synthetic methods were developed, implementing these N-acylhydrazones in Lewis acid-promoted intermolecular radical additions to C=N bonds. First, additions of various secondary and tertiary alkyl iodides to propionaldehyde and benzaldehyde hydrazones (3 and 7) under tin hydride radical chain conditions in the presence of ZnCl2 gave N-acylhydrazine adducts with diastereomeric ratios ranging from 93:7 to 99:1. Radical additions to a series of N-acylhydrazones with different substituents on the oxazolidinone revealed that benzyl and diphenylmethyl were more effective stereocontrol elements than those with the aromatic ring directly attached to the oxazolidinone. Second, a tin-free method, exploiting dual functions of triethylborane for both initiation and chain propagation, enabled improved yields in addition of secondary alkyl iodides. Third, under photolytic conditions with hexamethylditin, primary radical addition could be achieved with ethyl iodide in the presence of diethyl ether as cosolvent; the 1-ethoxyethyl adduct was observed as a minor product. Chloromethyl addition was achieved under both the tin-free and photolytic conditions; in this case, the adduct bears alkyl chloride functionality with potential for further elaboration.     

The mass spectra of some alkyl and aryl oxazoles

The mass spectra of a variety of alkyl and aryl oxazoles have been determined and the spectra analyzed with the aid of deuterium labelling and high resolution mass spectrometry. In contrast to the corresponding benzenoid compounds, the mass spectra of isomeric alkyl oxazoles are distinctive and in this respect are akin to those of the corresponding pyridines. Further analogy to the pyridines is suggested by the unfavorable nature of a carbonium ion adjacent to the 2-position and this effect may be used to locate alkyl substituents attached to the oxazole nucleus. The loss of carbon monoxide from the molecular ions of 2,5-disubstituted oxazoles probably occurs with ring opening and migration of the C-5 substituent (e.g.Br) to the C-4 position.     

Mass spectra of sulfur compounds: Alkyl phenoxythioacetates

The mass spectra of some alkyl phenoxythioacetates have been examined. An unusual rearrangement ion [M ? C₆H₅O ? CO]⁺ was observed. The structure is confirmed by high resolution mass measurement and isotopic labeling studies.     

Mass spectra of ortho substituted 1-phenyl-2-thioureas

The mass spectra of some 1-(o-alkylphenyl)-2-thioureas have been investigated and deuterium labelling shows that the proton lost in the SH? abstraction originates from the α-hydrogens in the o-alkyl group. The intensity of the fragment ion formed by loss of the o-alkyl group increases with the stability of the corresponding alkyl radical.     

SYNTHESIS OF BRANCHED POLYETHYLENE USING (α-DIIMINE)NICKEL(Ⅱ) -TiCl4 COMBINED AND SUPPORTED CATALYST

(a-Diimine)nickel(Ⅱ) {[C6H5 - N = C(CH3) - C(CH3) = N - C6H5]NiBr2}-TiCl4 abbreviated as NiL-TiCl4combined catalyst which is supported on MgCl2-SiO2 carrier has been prepared, by using alkyl aluminum (AlR3) as the cocatalyst in place of methylaluminoxane (MAO) to catalyze ethylene oligomerization and copolymerization in situ. The influences of procedure for supporting NiL-TiCl4, the molar ratio of NiL to TiCl4, cocatalyst type and polymerization temperature on the catalytic performance were studied. The degree of branching and the composition of the branched chain of polymers produced have been investigated by IR and 13C-NMR spectra. The results show that the combined catalyst can synthesize the branched polyethylene with various banched chains .The polymerization reaction was monitored by gas chromatography and mass spectrometry (GC-MS). The results show that this catalyst promotes the oligomerization and copolymerization in situ for ethylene.     

Über Chalkogenolate. 184. Bis(thiocarbamoyl)- und Bis(N-methylthiocarbamoyl)sulfane

On Chalcogenolates. 184. Bis(thiocarbamoyl)- and Bis (N-methylthiocarbamoyl)sulfanes The sulfanes (H₂N? CS? )₂S₂ and (CH₃? NH? CS? )₂S_x with x = 1 and 2 have been characterized by means of electron absorption, infrared, nuclear magnetic resonance, and mass spectra. The decomposition of the N-methyl substituted compounds has been studied kinetically at 20°C in ethanolic solution.