Dissociation Dynamics of Sequential Ionic Reactions: Heats of Formation of Tri-, Di-, and Monoethylphosphine
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- 作者：James P. Kercher ; Zsolt Gengeliczki ; Bá ; lint Sztá ; ray ; Tomas Baer
- 刊名：Journal of Physical Chemistry A
- 出版年：2007
- 出版时间：January 11, 2007
- 年：2007
- 卷：111
- 期：1
- 页码：16 - 26
- 全文大小：384K
- 年卷期：v.111,no.1(January 11, 2007)
- ISSN：1520-5215
文摘
The sequential ethene (C2H4) loss channels of energy-selected ethylphosphine ions have been studied usingthreshold photoelectron photoion coincidence (TPEPICO) spectroscopy in which ion time-of-flight (TOF)distributions are recorded as a function of the photon energy. The ion TOF distributions and breakdowndiagrams have been modeled in terms of the statistical RRKM theory for unimolecular reactions, providing0 K dissociation onsets, E0, for the ethene loss channels. Three RRKM curves were used to model the fivemeasurements, since two of the reactions differ only by the internal energy of the parent ion. This series ofdissociations provides a detailed check of the calculation of the product energy distribution for sequentialreactions. From the determined E0's, the heats of formation of several ethylphosphine neutrals and ions havebeen determined: 
fH
298K[P(C2H5)3] = -152.7 ± 2.8 kJ/mol, fH298K[P(C2H5)3+] = 571.6 ± 4.0 kJ/mol,fH298K[HP(C2H5)2] = -89.6 ± 2.1 kJ/mol, fH298K[HP(C2H5)2+] = 669.9 ± 2.5 kJ/mol, fH298K[H2PC2H5] = -36.5 ± 1.5 kJ/mol, fH298K[H2PC2H5+] = 784.0 ± 1.9 kJ/mol. These values have been supportedby G2 and G3 calculations using isodesmic reactions. Coupled cluster calculations have been used to showthat the C2H4 loss channel, which involves a hydrogen transfer step, proceeds without a reverse energy barrier.
fH298K[P(C2H5)3] = -152.7 ± 2.8 kJ/mol, fH298K[P(C2H5)3+] = 571.6 ± 4.0 kJ/mol,fH298K[HP(C2H5)2] = -89.6 ± 2.1 kJ/mol, fH298K[HP(C2H5)2+] = 669.9 ± 2.5 kJ/mol, fH298K[H2PC2H5] = -36.5 ± 1.5 kJ/mol, fH298K[H2PC2H5+] = 784.0 ± 1.9 kJ/mol. These values have been supportedby G2 and G3 calculations using isodesmic reactions. Coupled cluster calculations have been used to showthat the C2H4 loss channel, which involves a hydrogen transfer step, proceeds without a reverse energy barrier.