Metastable ion study of organosilicon compounds. Part I—Diethoxydimethylsilane

Electron impact induced fragmentations of diethoxydimethylsilane (1) and its deuterium-labelled analogues (2 and 3) were investigated by mass-analysed ion kinetic energy spectrometry. The principal fragmentation processes of compound 1 are dominated by silicenium ions which undergo consecutive losses of ethylene and aldehyde molecules. The fragmentations of 1 led to the formation of protonated silanoic acid [CH₃Si(OH)₂]⁺ and protonated dimethyl-silanone [(CH₃)₂Si = OH]⁺, and their unimolecular reacdvities were clarified. The fragmentation characteristics of compound 1 are compared with those of the carbon analogue, acetone diethyl acetal (4).     

Gas-phase ion–molecule reactions in dilute mixtures of dimethyl ether in krypton. Bimolecular and clustering reactions

The results of high-pressure variable-temperature and variable ionizing electron energy studies of gas-phase ion-molecule reactions of dimethyl ether in krypton are presented. Near the ionization threshold a series of peaks corresponding to (CH₃OCH₃)_nH⁺ (n = 1-4) clusters are observed. At higher ionizing electron energies, two new series of peaks appear, corresponding to [CH₃OCH₂]⁺(CH₃OCH₃)_n and [(CH₃)₃O]⁺ (CH₃OCH₃)_n clusters. The onium ion, [(CH₃)₃O]⁺, has been previously reported at elevated temperatures under methane chemical ionization conditions. It was suggested that the onium ion is formed by reaction of (CH₃)₂OH⁺ with CH₃OCH₃ with subsequent elimination of methanel, i.e. by fragmentation of an adduct ion. The present results strongly suggest that, under our conditions, [CH₃OCH₂]⁺ rather than thermal (CH₃)₃OH⁺, is the precursor to [(CH₃)₃O]⁺.     

Beitrag zur Massenspektrometrie substituierter α, ω-Alkandiamine. 29. Mitteilung über massenspektrometrische Untersuchungen

Contribution to the mass spectrometry of substituted α,ω-alkane diamines The main mass spectral fragmentation pattern of compounds of types 1 to 4 is discussed. After loss of C₆H₅ · CH₂ · from the molecular ion the acid correspondin to the N,N-disubstituted residue is splitted off. The mechanism of this fragmentation reaction depends on the member of CH₂-groups between the two nitrogen atoms (Schemes 1 and 3) and on the substitution pattern of both nitrogens (Scheme 2).     

Radical reaction of ethyl orthoacetate with 3,3,3-trifluoropropene

Summary The reaction of 3,3,3-trifluoropropene with ethyl orthoacetate leads to the formation of an acetate CH₃C(O)OCH(CH₃)CH₂CH₂CF₃ and a ketone CH₃C(O)CH₂CH(CF₃)CH₂CH₂CF₃. A reaction mechanism is proposed which involves rearrangement of the radicals CR₃C(OC₂H₅)₂OCH(CH₃) (CH₂CHCF₃) _n ^. with 1,7- and 1,5-migration of an H atom and stabilization by fragmentation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1583–1586, July, 1986.     

Zum Verhalten von Trimethylalkoxysilanen bei Elektronenstoss

The mass spectra of trimethylalkoxy silanes (CH₃)₃Si? O? (CH₂)_n? CH₃ (n = 0-8) and (CH₃)₃Si? O? (CH₂)_n? CH(CH₃)₂ (n = 0-3) have been investigated and most of the fragmentations, induced by electron-impact, have been identified by metastable ions. The fragmentation mechanisms of trimethylpentoxysilane, established by Diekman, Thomson and Djerassi, are also observed in the mass spectra of these trimethylalkoxy silanes. Characteristic features of these reactions in the mass spectra of compounds with smaller and longer alkoxy groups, together with some additional fragmentations, are discussed.     

Mass spectrometric study of μ4-oxohexa-μ-acetatotetrazinc,Zn4O(CH3CO2)6

The electron impact mass spectrum of Zn₄O(CH₃CO₂)₆ isostructural to Be₄O(CH₃CO₂)₆ studied earlier is reported. The principal fragmentation paths of both compounds involve the elimination of M(CH₃CO₂)₂ where M is Zn, Be, or (CH₃CO)₂O. Further fragmentations proceed by the losses of CH₂CO and H₂O. The spectrum of Zn₄O(CH₃CO₂)₆ contains intense doubly charged ions. The results obtained are interpreted in terms of stereochemical considerations.     

Complexes of bidentate group VB chelates : XIX. Mass spectral studies on some methyl-substituted bidentate group VB donor ligands

The fragmentation patterns of seven bidentate and two tridentate Group VB donor ligands are reported. For these methyl-substituted ligands the initial fragmentation is essentially loss of methyl radicals. Phenyl, but not methyl, migration occurs for the bis(phenylmethylarsino)alkanes, but methyl migration is evident in the all aliphatic bidentate chelates. The tridentate ligands PhE(CH₂CH₂CH₂AsMe₂)2 (E = P, As) show similar fragmentation routes, but are more complex. The long chain diarsine, Me₂As(CH₂)₁₂AsMe₂, exhibits a tendency to cyclise and lose C₂H₄ fragments progressively.     

PHOTOFRAGMENTATION OF HYDROXYACETONE, 1.3-DIHYDROXYACETONE, AND 1.3-DICARBOXYACETONE IN AQUEOUS SOLUTION. AN EPR STUDY

Abstract —On photoexcitation, hydroxyacetone undergoes a Norrish-type-1 fragmentation to yield CH₃CO and CH₂OH. CH₂OH is identified by its EPR spectrum. The existence of CH₃CO is inferred from the presence of diacetyl and acetaldehyde in irradiated solutions. Above pH 5, in addition to CH₂OH, the cis and trans forms of the hydroxyacetone enediol radical anion, CH₃C(O^-)=C(O***)H, are detected. 1.3-Dihydroxyacetone is photodecomposed to HOCH₂C?O and C?H₂OH. The former radical decarbonylates to yield CH₂OH and CO. At 254 nm the overall quantum yield of CO production is 0.75. Above pH 5, in addition to CH₂OH, the cis and trans forms of the 1.3-dihydroxyacetone enediol radical anion, HOCH₂C(O^-)C(O***)H, are observed. Electronically excited hydroxyacetone and 1.3-dihydroxyacetone react exclusively by C-C fragmentation, and no H-abstraction from H-donors is observed. In contrast, electronically excited 1.3-dicarboxyacetone shows H-abstraction from H-donors in competition with C-C fragmentation. In the absence of H-donors, fragmentation resulting in CH₂CO₂^- and ^-O₂CCH₂C?O occurs followed by decarbonylation of ^-O₂H₂C?O. At 254 nm the quantum yield of CO production is 0.02. In the presence of H-donors, H-abstraction, yielding HO₂CCH₂C(OH)CH₂CO₂, predominates.     

Fluordiazadiphosphetidine. 21. Mitt. Die Photochemische Chlorierung von 2,2,2,4,4,4-Hexafluoro-1,3-diethyl (und dipropyl)-1,3,2λ5,4λ5-diazadiphosphetidin und die Herstellung von 2,2,2,4,4,4-Hexafluoro-1-(cyanometyl)-3-methyl-1,3,2λ5,4λ5-diazadiphosphetidin

Summary The result of the chlorination of (CH₃CH₂NPF₃)₂ and (CH₃CH₂CH₂NPF₃)₂ with chlorine under UV-radiation were the new compounds CH₃CH₂(NPF₃)₂CH₂CH₂Cl and CH₃CH₂CH₂(NPF₃)₂CH₂CH₂CH₂Cl. The reaction of CH₃(NPF₃)₂CH₂Cl with KCN and crown-ether gave the new compound CH₃(NPF₃)₂CH₂CN.

     

Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen. XVI—hydrid-Wanderungen bei der Fragmentierung von αω-Dimethoxyalkyl-Ionen

The isomerization and fragmentation of α,ω-dimethoxyalkyl ions a (CH₃OCH₂(CH₂)_n- CH⁺OCH₃, n = 1-6) has been investigated by deuterium labelling. It is shown that a isomerizes to ion a' by hydride transfer from the ω-CH₂ group to the positive charge at the α-C-atom before elimination of methanol. Both methoxy groups are lost as methanol. The amount of isomerization can be deduced from alkene elimination from [a ? CH₃OH]+ ions in deuterated derivatives of a. On average at 70 eV three rearrangement steps involving hydride transfer are observed.     

Elektronenstoss-induzierter zerfall substituierter titanocendihalogenide

The electron impact mass spectra of the [1]titanocenophane dihalides (CH₃)₂Si(C₅H₄)₂TiX₂ (X = Cl, Br, I) and of [(CH₃)₃EC₅H₄]₂TiCl₂ complexes (E = C, Si, Ge) are described. The fragmentation of the compounds is highly influenced by the substituents at the cyclopentadienyl rings and shows several interesting rearrangements, e.g. elimination of (CH₃)₂SiX₂ in the case of the [1]titanocenophane complexes.     

The mass spectra of phosphorus esters. I. Bicyclic phosphites

The mass spectra of bicyclic phosphites of the type P(OCH₂)₃CR, where R = CH₃, C₂H₅, and C₃H₇ and NO₂, are reported, and their fragmentation patterns analyzed. Unlike trialkyl phosphites, these cyclic phosphites do not yield a large number of phosphorus-containing fragment ions resulting from hydrogen rearrangement.     

Bifunctional even-electron ions. III. Fragmentation behaviour of aliphatic hydroxonium ions containing an additional carbomethoxy group

The primary and subsequent fragmentations of the bifunctional oxonium ions \documentclass{article}\pagestyle{empty}\begin{document}${\rm R} \!-\! \mathop {\rm C}\limits^ + ({\rm OH})\! -\! ({\rm CH}_2)_n \! - \! {\rm COOCH}_3 $\end{document} (n = 0?5), a, are dominated by functional group interactions. Loss of CH₃OH is the only appreciable primary fragmentation of the higher homoiogues, but for the lowest homologue (a₀) this reaction is missing. Instead, CO loss is observed. The next homologue (a₁) shov.s loss of CH₂CO besides loss of CH₃OH. The mode of the subsequent fragmentations is dependent on the chain length separating the functional group, and formation of cyclic ions is typical of the fragmentation behaviour of a₂ and a₃. Evidence for proton transfer from the carbonyl oxygen to the methoxy group of a protonated ester group is presented.     

Mass spectra of monosubstituted trans-stilbenes

The mass spectra of twenty-eight monosubstituted trans-stilbenes in ortho, meta, para and alpha positions with ? N(CH₃)₂, ? NH₂, ? OCH₃, ? OH, ? Br, ? Cl, ? F, ? CH₃, ? COOH, ? CN and ? NO₂ groups as substituents have been studied. A detailed fragmentation pathway is given for stilbene. This fragmentation, characteristic for most of the substituted stilbenes, takes place either from the molecular or from the [M - Substituent] ion. In o-nitro-, o-methoxy-,α-carboxyl- and α-methylstilbene, however, rearrangement reactions prior to fragmentation influence the fragmentation pattern.     

Collisionally induced dissociative ionization of neutral products from unimolecular ion fragmentations. 1—Neutral product structures

A method is described for the investigation of the structure of neutral products from the unimolecular (metastable) dissociative ionizations of mass selected ions, by means of the collisionally induced dissociative ionization of the neutral species themselves. The neutral species, with kilovolt translational energies, enter a positively charged collision cell situated in the second field free region of a standard ZAB-2F mass spectrometer. Dissociative ionization of the neutrals results therein from their collisions with He target gas. The resulting ions are analysed by means of the electric sector and the relative ion abundances are shown to be structure characteristic. For such experiments the neutral flux should be c. ≥ 0.5% of the selected precursor ion flux; the collision gas pressure must be insufficient to cause significant precursor ion fragmentation in the field free region preceding the collision cell. It was shown that HNC is generated in the fragmentation of aniline molecular ions, whereas HCN is the neutral product in the dissociative ionizations of pyridine, benzonitrile and benzyl cyanide. The neutral radical [C, H₃, O˙] formed together with [CH₃CO]⁺ from ionized methyl acetate has the structure ˙CH₂OH, but that from the analogous fragmentation of the methyl propanoate molecular ion has the structure CH₃O˙. Allyl radicals were shown to be generated from [(CH₃)₂CHCH₂OH]⁺˙ together with [CH₃OH₂]⁺ ions.     

Die komplexchemie polyfunktioneller liganden : XXVIII. Über die selektive spaltung von arsenphenyl-bindungen mit jodwasserstoff in nichtwässrigen systemen

The phenylalkyl arsines (CH₃)₂AsC₆H₅, CH₃As(C₆H₅)₂, C₂H₅As(C₆H₅)₂, (CH₂)_n [As(C₆H₅)₂]₂ (n = 1, 2), and C[CH₂As(C₆H₅)₂]₄ react with liquid or gaseous HI in nonaqueous solvents by selective cleavage of the arsenicphenyl bonds yielding (CH₃)₂AsI, CH₃AsI₂, C₂H₅AsI₂, (CH₂)_n(AsI₂)₂ and C(CH₂AsI₂)₄. The latter forms the tetradentate ligand C[CH₂As(CH₃)₂]₄ with CH₃MgI. The electron impact mass spectra of these compounds show clear fragmentation patterns resulting mainly from the formation of fragments with AsAs bonds or (As)_n clusters (_n = 3, 4). From CH₃AsI₂ and C₂H₅AsI₂ the iodine-free cycloarsines (AsCH₃)₃, (AsC₂H₅)₃, (AsC₂H₅)₄, As₃(C₂H₅)₂CH₃ and As₄(C₂H₅)₃CH₃ are formed by thermal secondary reactions in the high temperature inlet systems of the mass spectrometer. The fragmentations of the cycloarsines and the other compounds are discussed. The infrared spectral absorptions of all the alkyl iodoarsines can be completely assigned in the range of 4000 – 250 cm^?1. The IR data of C₂H₅AsI₂ indicate the existence of trans and gauche rotational isomers.     

Mass spectra of piperidines with a shielded nitrogen atom

2,2,6,6-Tetramethylpiperidines with various substituants attached to the C₄ atom [R=H, OH, CN, CH₂COOH, C₆H₅, N(CH₃)₂, N(COCH₃)CH₂C₆H₅, N(CH₂)₅, and N(CH₂CH₂)O] were studied by means of mass spectrometry. The peculiarities of the fragmentation of the piperidine ring with a shielded electron pair at the heteroatom as a function of the type of substituent attached to the C₄, atom are discussed. The fragmentation was studied with the use of high-resolution mass spectrometry, lowvoltage mass spectra, and deuterium labeling.Communication 8 from the series Application of Mass Spectrometry in Structural and Chemical Investigations. See [1] for communication 7.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 507–512, April, 1979.     

Silicium-stickstoff-fluorverbidungen: V. Darstellung neuer silylaminofluorsilane

Compounds of the composition RR′SiFNR″Si(CH₃)₃ (R = H, F, CH₃, C₂H₅, C₃H₇, C₂H₃, C₆H₅, C(CH₃)₃; R = F, CH₃, C₆H₅; R″ = CH₃, C(CH₃)₃, Si(CH₃)₃) are obtained by the reaction of silicontetrafluoride or organo-substituted silicon-fluorides with the lithium salts of alkylsilylamines in a molar ratio of $\text{1}\text{1}$. The disubstituted compounds RSiF(NR′Si(CH₃)₃)₂ (R = H, F, CH₃, C₂H₃, C₆H₅; R′ = CH₃, C(CH₃)₃) result when the reactants are in a $\text{1}\text{2}$ molar-ratio. Likewise the unsymmetrical siliconfluorsilylamines of the formulae F₂Si(NRSi(CH₃)₃) (NR′Si(CH₃)₃) (R = CH₃, R′ = C(CH₃)₃), as well as the trisubstituted compounds FSi(NCH₃Si(CH₃)₃)₃ and FSi(NCH₃Si(CH₃)₃)₂(N(Si(CH₃)₃)₂) were made. By reacting phenyltrifluorsilane with dialkylamines ($\text{1}\text{2}$) C₆H₅SiF₂NR₂(R = CH₃, C₂H₅) was obtained. The IR-, mass-, ¹H and ¹⁹F NMR spectra of the above-mentioned compounds are reported.     

Four-centred rearrangements in the mass spectra of aliphatic ethers

The [CH₃O?CHCH₃]⁺ ions observed in the mass spectra of ethers of formula CH₃OCH (CH₃)R(R = H or alkyl) undergo two rearrangement fragmentation reactions to form [C₂H₅]⁺ and [CH₂OH]⁺. The scope of the rearrangements has been investigated and it is shown that enlargement of the alkyl group on either side of the ether linkage leads to alternative fragmentation routes. From a study of metastable intensities it is concluded that the fragmentations probably occur directly from the [CH₃O?CHCH₃]⁺ structure through four centred rearrangements rather than through the intermediacy of the [C₂H₅O?CH₂]⁺ ion.     

Beiträge zur Chemie der Alkylverbindungen von Übergangsmetallen. XXXIV. Darstellung und Eigenschaften von 3-(N,N-Dialkylamino)-propylmangan-Verbindungen

Contributions to the Chemistry of Transition Metal Alkyl Compounds. XXXIV. Synthesis and Properties of 3-(N,N-dialkylamino)propyl Manganese Compounds MnCl₂ reacts with lithium organyls of the type R₂N(CH₂)₃Li with formation of definite organomanganese complexes. The pure [(CH₃)₂N(CH₂)₃]₂Mn, [(C₂H₅)₂N(CH₂)₃]₂Mn, [(CH₂)₅N(CH₂)₃]₂Mn and the complexes [(CH₃)₂N(CH₂)₃]₂Mn · LiCl and Li{Mn[(CH₂)₃N(CH₃)₂]₃} · 1,5 THF were isolated. [(CH₃)₂N(CH₂)₃]₂Mn · 2 Li(acac) was obtained as a result of reactions of Mn(acac)₂ and Mn(acac)₃ with the corresponding lithium organyl. The σ-organomanganese(II) derivatives were characterized in detail by elementary analysis, molecular weight determination, ESR- and IR-spectra, conductivity measurements and the magnetic moments.