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The adiabatic ionization energies and COOH+ appearance energies for a series of carboxylic acids have been measured by dissociative photoionization mass Spectrometry. Using the stationary electron convention, a heat of formation of 143.5 ± 0.7 kcal mol?1 (1 kcal = 4.184 kJ) at 298 K is derived for the carboxyl cation in the gas phase, which corresponds to an absolute proton affinity for carbon dioxide of 128.1 ± 0.7 kcal mol?1. 相似文献
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LoSecco JM Bionta RM Biewitt G Bratton CB Casper D Chrysicopoulou P Claus R Cortez BG Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG Lehmann E Park HS Reines F Schultz J Seidel S Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R van der Velde JC Wuest C 《Physical review letters》1985,54(21):2299-2301
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Phillip T. Mead John C. Traeger John R. Christie Peter. J. Derrick 《Journal of mass spectrometry : JMS》1978,13(7):386-388
The internal energies of [C3H7]+ ions contributing to the metastable peak [C3H7]+ → [C3H5]+ + H2 are higher (by perhaps > 100 kJ mol?1) than those of the ion contributing to the threshold current in appearance energy measurements on [C3H5]+. The measured appearance energy may lead to an underestimation of the activation energy, i.e. negative ‘kinetic shift’, due to quantum, mechanical tunnelling. The distribution of energy released in the decomposition can be explained on the basis that much of the reverse activation energy and a statistical proportion of the excess energy is released as translation. 相似文献
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John C. Traeger Charles E. Hudson David J. McAdoo 《Journal of the American Society for Mass Spectrometry》1992,3(3):183-187
Formation of the 3-pentanone ion (3) from ionized propyl propanoate through the complex [C2H5CO+ ?OC3H7] is proposed based on data obtained by photoionization. The threshold and energy dependence for forming 3 relative to those for related processes support this proposal. The threshold for forming 3 coincides with that predicted for forming [CH3CH2CO+ ?CH2CH3], suggesting that that complex is also an intermediate in the pathway to 3. 3-Pentanone ion formation is important much further above threshold than is alkane elimination through [RCO+ ?R] complexes. This adds to evidence that reactions between the partners in ion-dipole complexes take place over a wider energy range than do such reactions in complexes containing nonpolar neutral partners. 相似文献
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John C. Traeger 《Journal of mass spectrometry : JMS》1984,19(10):514-516
Photoionization mass spectrometry has been used to measure the appearance energies for [C2H5]+ from ethanethiol, [C3H7]+ from 2-propanethiol and [C3H5]+ from 2-methylthiirane. From the known thermochemistry of these cations and their precursor molecules, a 298 K heat of formation of 138.6±0.4 kJ mol?1 for the SH radical has been derived. 相似文献
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