AbstractFor Abstract see ChemInform Abstract in Full Text.

The reactions of the water solvated ammonia radical cation [NH3·+, H2O] with a variety of aldehydes and ketones were investigated. The reactions observed differ from those of low energy aldehydes and ketones radical cations, although electron transfer from the keto compound to ionized ammonia is thermodynamically allowed within the terbody complexes initially formed. The main process yields an ammonia solvated enol with loss of water and an alkene. This process corresponds formally to a McLafferty fragmentation within a complex. With aldehydes, another reaction can take place, namely the transfer of the hydrogen from the CHO group to ammonia, leading to the proton bound dimer of ammonia and water, and to the NH4+ cation. Comparison between the available experimental results leads to the conclusion that the McLafferty fragmentation occurs within the terbody complex initially formed, with no prior ligand exchange, the water molecule acting as a spectator partner.

Gas basicities (GBs) and proton affinities (PAs) of CH3SiHO, CH3CH2SiHO, (CH3)2SiO (CH3CH2)2SiO, were determined by using the kinetic method as well as calculations. From experiment, GB of these molecules were respectively measured to be 203.3, 206.3, 213.4 and 218.0kcalmol−1. The precision is estimated to be 0.5kcalmol−1. Calculations are in excellent agreement with experiment.

Journal of Mass SpectrometryVolume 36, Issue 1 p. 102-104 JMS Letter Spontaneous and catalyzed isomerizations of the acetamide radical cation Philippe Mourgues, Corresponding Author Philippe Mourgues [email protected] DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceDCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, France===Search for more papers by this authorJulia Chamot-Rooke, Julia Chamot-Rooke DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceSearch for more papers by this authorHristo Nedev, Hristo Nedev DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceSearch for more papers by this authorHenri-Edouard Audier, Henri-Edouard Audier DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceSearch for more papers by this author Philippe Mourgues, Corresponding Author Philippe Mourgues [email protected] DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceDCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, France===Search for more papers by this authorJulia Chamot-Rooke, Julia Chamot-Rooke DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceSearch for more papers by this authorHristo Nedev, Hristo Nedev DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceSearch for more papers by this authorHenri-Edouard Audier, Henri-Edouard Audier DCMR, Ecole Polytechnique, UMR-CNRS 7651, 91128 Palaiseau, FranceSearch for more papers by this author First published: 24 January 2001 https://doi.org/10.1002/jms.106Citations: 26Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume36, Issue1January 2001Pages 102-104 RelatedInformation

In the gas phase, the CH 2 CHOH .+ enol radical cation 1 as well as its higher homologues CH 3 CHCHOH .+ 2 and (CH 3 ) 2 CCHOH .+ 3 , undergo exactly the same sequence of reactions with tert-butanol, leading to the losses of isobutene, water and water plus alkene. Fourier transform ion cyclotron resonance (FT-ICR) experiments using labeled reactants as well as ab initio calculations show that independent pathways can be proposed to explain the observed reactivity. For ion 1 , taken as the simplest model, the first step of the reaction is formation of a proton bound complex which gives, by a simple exothermic proton transfer, the ter-body intermediate [CH 2 CHO . , H 2 O, C(CH 3 ) 3 + ]. This complex, which was shown to possess a significant lifetime, is the key intermediate which undergoes three reactions. First, it can collapse to yield tert -butylvinyl ether with elimination of water. Second, by a regiospecific proton transfer, this complex can isomerize into three different ter-body complexes formed of water, isobutene and ionized enol. Within one of these complexes, which does not interconvert with the others, elimination of isobutene leads to the formation of a solvated enol ion. Within the others, a cycloaddition—cycloreversion process can proceed to yield the ionized enol 3 (loss of water and ethylene channel).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPreparation and Reactivity of Solvated Distonic Ions and Ionized Enols in the Gas PhaseV. Troude, G. van der Rest, P. Mourgues, and H. E. AudierView Author Information Laboratoire des Mécanismes Réactionnels, URA CNRS 1307 Ecole Polytechnique, F-91128 Palaiseau Cedex, France Cite this: J. Am. Chem. Soc. 1997, 119, 39, 9287–9288Publication Date (Web):October 1, 1997Publication History Received7 March 1997Published online1 October 1997Published inissue 1 October 1997https://doi.org/10.1021/ja9707365Copyright © 1997 American Chemical SocietyRequest reuse permissionsArticle Views48Altmetric-Citations12LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (93 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Alcohols,Cations,Ions,Molecules,Reactivity Get e-Alerts

Studies of unimolecular dissociation (MIKES) of ions formed in a chemical ionization ion source show that under CI conditions, the reaction of CH3+ with CH3OH or CH3OCH3 leads to the covalent structures (CH3)(2)-OH+ or(CH3O+. In contrast a FT-ICR study indicates that these reactions lead either to covalent structures by C-O bond formation and to [CH3+/CH3OH] or [CH3+/CH3OCH3] ion-neutral complexes. Ab initio calculations confirm that such complexes correspond to minima on the potential energy surface. Their geometries correspond to a species in which a hydrogen of the CH3+ cation is weakly bonded to the oxygen of the neutral. The interaction energies are similar to 20 kcal/mol.

Studies of unimolecular dissociation (MIKES) of ions formed in a chemical ionization ion source show that under CI conditions, the reaction of CH3+ with CH3OH or CH3OCH3 leads to the covalent structures (CH3)2OH+ or (CH3)3O+. In contrast a FT-ICR study indicates that these reactions lead either to covalent structures by C−O bond formation and to [CH3+/CH3OH] or [CH3+/CH3OCH3] ion−neutral complexes. Ab initio calculations confirm that such complexes correspond to minima on the potential energy surface. Their geometries correspond to a species in which a hydrogen of the CH3+ cation is weakly bonded to the oxygen of the neutral. The interaction energies are ∼20 kcal/mol.

La reactivite bimoleculaire en phase gazeuse des ions β-distoniques CH 2 CH 2 XH + 1-4 (X = OH, OCH 3 , OC 2 H 5 , NH 2 ) a ete etudiee en spectrometrie de masse par resonance cyclotronique ionique et transforme de Fourier. La substitution du groupe XH par un neutre est generalement consideree comme etant la reaction la plus caracteristique de ces ions. Ce travail montre que la substitution depend fortement de la nature de l'ion β-distonique. En particulier, la substitution thermoneutre du groupe XH par le neutre marque * XH est rapide pour l'ion.CH 2 CH 2 OH 2 + (1) mais n'est pas observee pour l'ion.CH 2 CH 2 NH 3 + (4). Le comportement des ions CH 2 CH 2 OH + CH 3 (2) et CH 2 CH 2 OH + C 2 H 5 (3) est intermediaire. Les calculs ab initio au niveau MP2(FU)/6-31G * permettent de rationaliser ces observations : la structure de l'etat de transition pour la substitution possede une energie inferieure a celle des reactifs pour X = OH (ion 1), mais superieure a celle des reactifs pour X = NH 2 (ion 4).

The proton affinity at the heteroatom PAX of four α-radicals (CH2OH, CH3CHOH, CH2OCH3 and CH2NH2) was measured by studying the deprotonation of the corresponding α-distonic ions in the cell of a FTICR spectrometer. This method can only be used for α-distonic ions which are more stable than their molecular ion counterpart. It was found that the PAX of the CH2OH, CH3CHOH, CH2OCH3 and CH2NH2 α-radicals lies respectively 15.7, 14.5, 10.1 and 17.2 kcal mol−1 under that of CH3OH, CH3CH2OH, CH3OCH3 and CH3NH2. These results are in good agreement with the PA obtained by high level ab initio calculations.

In the gas phase, the unimolecular reactions of metastable protonated alkyl arenes lead to alkyl cation formation with arene loss, protonated arene formation with alkene loss, and benzylic cation formation with alkane elimination. The dissociations are often preceded by an exchange between the hydrogen atoms of the chain and those of the ring, which can be rationalized by an interconversion between [arene alkyl cation] and [protonated arene alkene] ion-neutral complexes. By comparing the reactions of the metastable protonated alkyl arenes and those of their isomeric adducts (arene/alkyl cation) generated in the ion source by ion-molecule reaction, we show that ct-complexes [arene alkyl cation] have a significant lifetime. By ab initio calculations, [C6H6 iso-C3H7+] and [C6H7+ C3H6] ion-neutral complexes are shown to be energy minima on the potential energy surface. They correspond therefore to stable structures. Two methods, namely, ab initio and semiempirical calculations, are used to calculate the interaction energies of [arene alkyl cation] complexes. The smallest stabilization energy (49 kJ/mol) corresponds to [C6H6 tert-C4H9+] and the largest (65 kJ/mol) corresponds to [p-CH3C6H4CH(3) iso-C3H7+] The [protonated arene alkene] complexes are less stabilized (ca. 25 kJ/mol). The calculations also indicate that [arene alkyl cation] complexes have pi-structures, but do not correspond to electron donor-acceptor (EDA) systems since, among the components of their interaction energy, the charge exchange term is negligible. Finally, these results are used to propose energy diagrams and fragmentation pathways.

AbstractIn the gas phase, π‐complexes are common intermediates in unimolecular reactions of metastable protonated alkylbenzenes. The transient formation of two π‐complexes generated from protonated dialikylbenzenes has been proposed in the Literature, even when the substitution degree of the two benzylic carbons is different. For metastable tert‐C4H9C6H5R+ cations (R ‐ n‐C4H9, sec‐C4H9, iso‐C4H9), we demonstrate in this paper that the [tert‐C4H, C6H5‐R] π‐complex is produced and does not interconvert into the [tert‐C4H9C6H5, R+] π‐complex prior to fragmentation.

The reaction of the ˙CH2CH2OHCH3+ distonic ion with CH2O was studied by Fourier transform ion cyclotron resonance spectrometry. The process is induced by an initial regiospecific attack of the carbon CH2O at the radical site of the distonic ion, leading to an intermediate adduct ion which loses water. The mechanism was demonstrated by labelling, by studying the structure of the product ion and by examining independently the behaviour of the putative intermediate radical cation.

In the gas phase, sc-complexes are common intermediates in unimolecular reactions of metastable protonated alkylbenzenes. The transient formation of two sc-complexes generated from protonated dialkylbenzenes has been proposed in the Literature, even when the substitution degree of the two benzylic carbons is different, For metastable tert-C4H9-C6H5-R(+) cations (R = n-C4H9, sec-C4H9, iso-C4H9), we demonstrate in this paper that the [tert-C4H9+ C6H5-R] pi-complex is produced and does not interconvert into the [tert-C4H9-C6H5, R(+)] pi-complex prior to fragmentation.