40422-05-7Relevant articles and documents
Intermediacy of ion neutral complexes in the fragmentation of short-chain dialkyl sulfides
Filsak,Budzikiewicz
, p. 601 - 610 (2007/10/03)
The main fragmentation processes after electron ionization of butyl methyl and butyl ethyl sulfides are rationalized by the intermediacy of the ion neutral complex [RSH · methylcyclopropane](+·) as demonstrated by extensive labeling and collision activation studies.
Side-chain Effects on the Fragmentation Behaviour of Alkylthiophenes
Lange, D.,Budzikiewicz, H.
, p. 432 - 438 (2007/10/02)
The processes leading to the fragment ions formed from alkylthiophene molecule ions by benzylic cleavage without and with transfer of one hydrogen from the side-chain to the ring and the influence of additional methyl groups on the relative importance of these two fragmentation reactions were investigated.
A McLafferty Rearrangement in an Even-electron System: C3H6 Elimination from the α-Cleavage Product of Tri-n-butylamine
Budzikiewicz, Herbert,Bold, Peter
, p. 709 - 712 (2007/10/02)
It is shown by deuterium labelling, linked-scan measurements and collision activation that the .>+ (α-cleavage) ion in the electron impact ionization spectrum of tributylamine loses C3H6 with transfer of one hydrogen specifically from the γ-position.The experimental data point towards a mechanism which involves the intermediate formation of a distonic diradical ion from an excited α-cleavage ion which the eliminates the neutral alkene.
Ion-Neutral Complexes as Intermediates in the Decompositions of C5H10O2.+ Isomers
McAdoo, David J.,Hudson, Charles E.,Skyiepal, Mark,Broido, Ellen,Griffin, Lawrence L.
, p. 7648 - 7653 (2007/10/02)
Ionized pentanoic acid, 3-methylbutanoic acid, and the enol isomer of ionized isopropyl acetate are shown to pass in part through common intermediates before decomposing to CH3C.HC(OH)2+ (7) and the "McLafferty + 1" ion CH3C(OH)2+ (10).The H transfer to form the methyl of CH3C(OH)2+ and the joining of two CH2 groups to form the C-C bond in the ethylene eliminated to produce CH3C.HC(OH)2+ are both attributed to reactions of the ion-neutral complex .H2C(OH)2+>.The McLafferty + 1 ion is also formed, especially from ionized esters, by another pathway in which complexes may or may not be intermediates.The intermediacy of the ion-neutral complexes is supported by energetic considerations, isotope effects, and the decomposition patterns of labeled ions.The latter correlate with a preference for hydrogen transfer from the end carbons of the C3 partner in other reactions proposed to be complex-mediated.Unification of the McLafferty rearrangement, the McLafferty + 1 rearrangement, and the McLafferty rearrangement with charge reversal by a common initial γ-hydrogen rearrangement followed by dissociation or isomerization in ion-neutral complexes is proposed.Group migration by 1,2-shifts, possibly by dissociation to form a double bond in one partner in an ion-neutral complex followed by addition at the opposite end of the double bond, is shown to be a general reaction of ions in the gas phase.
Deuterium and Carbon-13 NMR of the Solid Polymorphism of Benzenehexoyl Hexa-n-hexanoate
Lifshitz, E.,Goldfarb, D.,Vega, S.,Luz, Z.,Zimmermann, H.
, p. 7280 - 7286 (2007/10/02)
Deuterium and carbon-13 NMR of specifically labeled benzenehexoyl hexa-n-hexanoate in the various solid-state phases are reported.The spectra exhibit dynamic line shapes which change discontinuously at the phase transitions.The results are interpreted in terms of sequential "melting" of the side chains on going from the low-temperature solid phases IV, III, etc., toward the liquid.In phase IV the molecules are very nearly static, except for fast rotation of the methyl groups about their C3 axes.The results in phase III were quantitatively interpreted in terms of a two-site isomerization process ivolving simultaneous rotation by 95 deg about C1-C1 and transition from gtg to g'g't (or equivalently g'tg' to ggt) for the rest of the chain.The specific rate of this reaction at 0 deg C is ca. 1E5 s-1.In phase II additional chain isomerization processes set-in which were, however, not analyzed quantitatively.Further motional modes, involving reorintation of whole chains about their Car-O bonds, appear on going to phase I.In all solid phases the benzene ring remains static.
THE rs STRUCTURES OF PROPYL FLUORIDE AND DIFFERENCES IN STRUCTURES BETWEEN ROTATIONAL ISOMERS
Hayashi, Michiro,Fujitake, Masaharu
, p. 9 - 24 (2007/10/02)
Microwave spectra of trans and gauche propyl fluoride and its isotopically substituted species have been measured.The rs structures of the trans and gauche isomers of this molecule are determined from the observed moments of inertia.It is found that the CCC angle values are largely different between two isomers, while the CCF angle values stay unchanged.The rs structures of ethyl fluorosilane and ethylmethyl sulfide are re-examined in order to compare the results with those of propyl fluoride.The differences in the structural parameter values between the rotational isomers are discussed for the present molecules and the analogous molecules such as ethanethiol and ethaneselenol.
ESR, Structure, and reactions of Specifically Deuterium-Labeled Pentane Cations in X-Irradiated Freon Matrices
Dolivo, G.,Lund, A.
, p. 3977 - 3984 (2007/10/02)
Solutions of 1-2 mol percent of pentane, pentane-3-d2, pentane-2,4-d4, and pentane-1,5-d6 in CFCl3, CF3CCl3, and CF2ClClFCl2 have been X irradiated at 77 K.ESR spectra of the molecular ions were recorded at temperatures between 77 K and either the glass transition temperature for CF3CCl3 (140 K) and CF2ClClFCl2 (about 110 K) or the melting point for CFCl3 (162 K).It was found that the pentane molecular ions in these matrices have not only the structure of an extended chain, but also that of several gauche conformers.Their identity and proportions depend on the matrix and on the labeling.INDO calculations were made to elucidate the detailed structure of the conformers of the pentane molecular ions in these matrices.Tilting both methyl groups toward the central-CH2- leads to a significant decrease in the energy of the ion with a minimum at about 90 deg and to significant changes in hyperfine coupling constants, giving a much better agreement with experimental data.Isotope effects were discovered for the deprotonation reaction in CF2ClCFCl2 and especially for the photofragmentation in CF3CCl3.
The Reactions of Metastable +. Ions with the Oxygen on the Second Carbon
McAdoo, David J.,Hudson, Charles E.,McLafferty, Fred W.,Parks, Terry E.
, p. 353 - 362 (2007/10/02)
Nearly all +.> isomers with the oxygen on the second carbon are shown to interconvert with each other and lose methyl and ethylene at the threshold for dissociation.The methyls contain the carbon from the 1- and 5-positions with about equal frequency, and C(3) or perhaps C(4) about half as often as either terminal carbon.CH3CH2CH2CO+ is formed by loss of the C(1) methyl and CH2=CHC(O+H)CH3 by loss of the C(5) methyl.Hydrogen transfer between C(5) and the oxygen and between the oxygen and C(4) are facile, and 1,2-hydrogen transfers between C(3) and C(4) occur with high frequency.Extensive skeletal rearrangements also take place by 1,2-shifts between C(2), C(3) and C(4).We attribute the occurence of the three-center shifts between C(2), C(3) and C(4) to the presence of considerable charge density on C(2) and C(3) in many of the +. isomers.The isomerizations of +. can be considered a mixture of free radical and carbocation reactions.Strong similarities exist between the isomerizations of metastable +. ions with the oxygen on the second carbon and those of isomers of ionized butanoic acid, methyl butanoate and n-butanal.
Pseudo One-Step Cleavage of C-C Bonds in the Decomposition of Ionized Carboxyclic Acids. Radical Like Reactions in Mass Spectrometry
Weiske, Thomas,Schwarz, Helmut
, p. 323 - 347 (2007/10/02)
Metastable molecular ions of hexanoic acid (1) decompose unimolecularly to C2H5. and protonated methacrylic acid (5-H+)(92percent rel. abund.).Investigation of the mechanism reveals that 1) the branched cation radical 11 must be regarded as the essential intermediate in the course of the rearrangement/dissociation reaction and 2) the process commences with intramolecular hydrogen transfer from either C-3 or C-5 to the ionized carbonyl oxygen ("hidden" hydrogen migration).Hydrogen transfer from C-4, which would correspond to the well-known McLafferty rearrangement, is of no importance in the C2H5.-elimination from 1.The same conclusion applies for various alternative mechanisms, as for example a SRi type reaction, 1 -> 2-H+.The gas phase chemistry of the cation radical of 1, and in particular the hydrogen exchange processes between the methylene groups C-2/C-3 and C-5/C-6, is in surprisingly close correspondence to the chemistry of free alkyl radicals. - The syntheses of various 13C and 2H-labelled model compounds are described.
Electrolysis of Potassium Butyrate in Acetonitrile. A Deuterium NMR Study
Laurent, Eliane,Thomalla, Marc,Marquet, Bernard,Burger, Ulrich
, p. 4193 - 4198 (2007/10/02)
The anodic oxidation of 2,2-dideuteriobutyrate ion in acetonitrile gives rise to radical-derived and cation-derived C3 products.By 2H FT NMR spectroscopy, the radical-derived propane and propene are found to be formed without scrambling of the label.Similarly, the products derived from the intermediate isopropyl cation, i.e., the remainder of the propene and N-isopropylamides, bear deuterium only at the terminal C-1 and C-3 positions of the C3 fragment.However, the 1:1:1 label distribution found in the N-n-propylamides and the formation of cyclopropane strongly suggest that ring closure of the n-propyl cation to rapidly scrambling pr otonated cyclopropane is an important reaction pathway.Atom scrambling at the level of protonated cyclopropane shows a large H/D isotope effect.
