H-D isotope effects in the decomposition of acetylene by electron impact

Haarhoff, P.C.

doi:10.1080/00268976400100061

Cited by 12 publications

(1 citation statement)

References 22 publications

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“…Here the assignment to the two possible reactants is easy: (19) must be due to C2H3D2+; (20) and (21) are probably predominantly due to C2HDa+; possible contributions from C2H 3 D2+ should be weaker than the intensity of (19) found for mass 32 (5.5 and 167, respectively) and would thus be negligible. The observed ratio of 55 between the intensities of Reactions (20) and (21) again reflects primarily the isotope effect in C2HD3+ (the corresponding HD/D 2 ratio observed for mass 32 is 167/5.5= 30), while structural effects cannot be ruled out (the C-C ruptures discussed above indicated that scrambling may be incomplete).…”

Section: Mass 31mentioning

confidence: 98%

Metastable Ions in the Mass Spectra of CD3CH3 and C2H6

Löhle

Ottinger

1969

The Journal of Chemical Physics

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Articles you may be interested inIon-molecule reaction mechanisms: Thermal energy gas phase reactions of 12C+ and 13C+ ions with CH4, C2H4, C2H6, C3H6, C3H8, and CD3CH2CD3The mass spectra of CDaCHa and C2Ha were searched for metastable tran~iti~ns ';Ising a mass spectromet~r with high sensitivity. With a detection limit of about 3X1()-ll of the totallOnlzatIon, 54 metastable transItions in CDaCHa and 19 in C2H& were found. Allo(these were checked for possible collision-induced contributions by adritting krypton to the analyzer tube. The CHaCDa decompositions are classified as (a) C-C ruptures, (b) H2, HD, and D2 eliminations, and (c) loss of an H or I? ato~. The first category'provide~ information about D-H scrambling. The rate constant for D-H scramblmg pnor to C-C rupture IS 5X10 sec 1 for parent ions, but very much larger in fragment ions, with the possible exception of CH 2 CD2+. The second category gives information about the isotope effect between H2, HD, and D,loss. Compared to the loss of H2 the elinlination of HD is diminished about fivefold and that of D2 by a factor of about 150. In the parent ion much less (if any) D-H scrambling occurs prior to the HD elimination than prior to the C-C rupture, in accord with the expected dependence of the scrambling rate on internal energy. Practically no H2 and D2 loss from the parent ion is found, indicating that the mass-28 ion of ethane has the ethylene structure. The Hand D losses provide only a few, but very convincing, examples of the strong isotope effect whiclt suppresses D loss in the presence of H by a factor of at least 600. Furthermore, evidence is seen for a secondary isotope effect which slows down the loss of H from CH2CD 2 + as compared to C2H.+.

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Section: Mass 31mentioning

confidence: 98%

Metastable Ions in the Mass Spectra of CD3CH3 and C2H6

Löhle

Ottinger

1969

The Journal of Chemical Physics

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Calculation of Statistical Complexions of Polyatomic Molecules and Ions

Lin

1971

Advances in Chemical Physics

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Effets Isotopiques dans la Fragmentation par Impact Électronique de Méthanols Deutériés

Corval

Masclet

1972

Org. Mass Spectrom.

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The mass spectra of the CH,OH, CH,DOH, CD,OH, CH,OD and CD,OD methanols have been recorded at nominal electron energies ranging from 11 to 35 eV. Curves are given for the variation of the isotope effects related to the molecular ion stability and bond cleavage probabilities as a function of the electron energy, and are compared with apriori calculations. A simple distribution function and a value for the number of oscillators equal to half the theoretical figure give fairly satisfactory agreement, except as concerns the molecular ion stability. The form of the curves for the latter could be explained by the existence of an electronic state of the molecular ion other than the ground state.R6sumB-Les spectres de masse des mCthanols CH,OH, CH,DOH, CHD,OH, CD,OH, CH,OD et CD,OD ont etB enregistres pour des Bnergies norninales des Clectrons allant de 11 a 35 eV. Les courbes qui representent la variation, en fonction de l'bnergie des Blectrons, des effets d'isotopie relatifs a la stabilite des ions molkculaires et aux probabilites de coupure des liaisons sont comparkes a celles dkterminees par un calcul a priori. En adoptant une fonction simple de distribution de 1'Cnergie d'excitation et un nombre d'oscillateurs moitiB du nornbre thkorique, l'accord obtenu est dans I'ensemble satisfaisant, sauf en ce qui concerne la stabilitk des ions molkculaires, pour laquelle la forme des courbes pourrait s'interprkter par I'intervention d'un ktat Blectronique de I'ion molkculaire autre que 1'6tat fondamental. I N T R O D U C T I O NDANS une Ctude prCcCdente,l nous avons montrC que la thCorie statistique des spectres de masse sous sa forme la plus simple2e3 permet, dans le cas de 1'Cthanol substituC par le deutCrium dans diffkrentes positions, de rendre compte des effets d'isotopie observts lors du bombardement par des Clectrons de 70eV. En effet, une partie des difficultis auxquelles se heurte I'application de cette thkorie se trouvent Ccarttes dans la mesure OG certaines approximations ont une incidence bien moindre lorsqu'on s'intkresse au calcul des effets d'isotopie plut6t qu'a celui du spectre de masse. I1 s'agit en particulier du choix des valeurs numtriques des grandeurs qui interviennent dans l'expression des constantes de vitesse de dCcomposition de l'ion moltculaire : le nombre effectif d'oscillateurs auxquels on assimile I'ion molCculaire et la fonction de distribution de 1'Cnergie interne de cet ion ont une influence trks limitCe sur les valeurs calculCes des effets d'isotopie pour des Clectrons de 70 eV. I1 nous a paru que la confrontation des valeurs exptrimentales des effets d'isotopie et des valeurs calculCes, dans une gamme d'tnergie allant du potentiel d'ionisation de la moltcule B quelques dizaines d'ilectrons-volts, pourrait constituer un test plus significatif de la validitt de la thCorie statistique, aussi bien que du choix du nombre effectif d'oscillateurs et de la fonction de distribution de 1'Cnergie. Notre ttude concerne six espkces isotopiques du mCthanol: t Les spectres de masse des Bchantillons de mtth...

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H-D isotope effects in the decomposition of acetylene by electron impact

Cited by 12 publications

References 22 publications

Metastable Ions in the Mass Spectra of CD3CH3 and C2H6

Metastable Ions in the Mass Spectra of CD3CH3 and C2H6

Calculation of Statistical Complexions of Polyatomic Molecules and Ions

Effets Isotopiques dans la Fragmentation par Impact Électronique de Méthanols Deutériés

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