64118-37-2Relevant articles and documents
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.
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.
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.
