Nonempirical LCAO MO SCF and CI Studies of the Isomers of CH3O+

Haney, Max A.; Patel, Jashbhai C.; Hayes, Edward F.

doi:10.1063/1.1673892

Cited by 14 publications

(5 citation statements)

References 10 publications

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“…After correction of the PIE spectrum for CH2OH, 13CH20, and CHDO, essentially no residual signal remained.53•54 This negative result is consistent with the failure to observe CH3O when it was generated via CH3 + N02 (mentioned above), and it is consistent with negative results reported previously.278•28 It is also interesting to note that the early calculations of Haney et a/. 14 (1) predicted that CH3O4" should be unstable and that it should dissociatively ionize to form HCO"1" + H2 and (2) were apparently the first to establish that the ionic ground state of CH3O was a triplet rather Photoion efficiency spectrum for HCO+ from dissociative ionization of CH3O (corrected for a small amount of HCO+ formed from direct ionization of HCO). The threshold, indicated by the dashed line, at 142.0 nm gives an appearance energy of 8.73 eV.…”

Section: Cd2hodsupporting

confidence: 70%

Photoionization of Hydroxymethyl (CD2OH and CD2OD) and Methoxy (CD3O) Radicals: Photoion Efficiency Spectra, Ionization Energies, and Thermochemistry

Kuo¹,

Zhang²,

Klemm³

et al. 1994

J. Phys. Chem.

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Section: Cd2hodsupporting

confidence: 70%

Photoionization of Hydroxymethyl (CD2OH and CD2OD) and Methoxy (CD3O) Radicals: Photoion Efficiency Spectra, Ionization Energies, and Thermochemistry

Kuo¹,

Zhang²,

Klemm³

et al. 1994

J. Phys. Chem.

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“…For all molecules, AE‐CCSD(T)/aug‐cc‐pCVQZ equilibrium structures were used as reference geometries in our FPA computations. Simple expectation, measurements 126, and even early simple ab initio electronic structure computations 127–131 of enthalpies of formation showed that the most stable isomer of H 2 COH + has the proton on O. Therefore, only this form was considered in the present study.…”

Section: Resultsmentioning

confidence: 99%

“…Simple expectation, measurements [126], and even early simple ab initio electronic structure computations [127][128][129][130][131] of enthalpies of formation showed that the most stable isomer of H 2 COH ϩ has the proton on O. Therefore, only this form was considered in the present study.…”

Section: Reference Structuresmentioning

confidence: 99%

Proton affinity and enthalpy of formation of formaldehyde

Czakó

Nagy

Tasi

et al. 2009

Int J of Quantum Chemistry

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The proton affinity and the enthalpy of formation of the prototypical carbonyl, formaldehyde, have been determined by the first-principles composite focalpoint analysis (FPA) approach. The electronic structure computations employed the allelectron coupled-cluster method with up to single, double, triple, quadruple, and even pentuple excitations. In these computations the aug-cc-p(C)VXZ [X ϭ 2(D), 3(T), 4(Q), 5, and 6] correlation-consistent Gaussian basis sets for C and O were used in conjunction with the corresponding aug-cc-pVXZ (X ϭ 2-6) sets for H. The basis set limit values have been confirmed via explicitly correlated computations. Our FPA study supersedes previous computational work for the proton affinity and to some extent the enthalpy of formation of formaldehyde by accounting for (a) electron correlation beyond the "gold standard" CCSD(T) level; (b) the non-additivity of core electron correlation effects; (c) scalar relativity; (d) diagonal Born-Oppenheimer corrections computed at a correlated level; (e) anharmonicity of zero-point vibrational energies, based on global potential energy surfaces and variational vibrational computations; and (f) thermal corrections to enthalpies by direct summation over rovibrational energy levels. Our final proton affinities at 298.15 (0.0) K are ⌬ pa H o (H 2 CO) ϭ 711.02 (704.98) Ϯ 0.39 kJ mol Ϫ1 . Our final enthalpies of formation at 298.15 (0.0) K are ⌬ f H o (H 2 CO) ϭ Ϫ109.23 (Ϫ105.42) Ϯ 0.33 kJ mol Ϫ1 .The latter values are based on the enthalpy of the H 2 ϩ CO 3 H 2 CO reaction but supported by two further reaction schemes, H 2 O ϩ C 3 H 2 CO and 2H ϩ C ϩ O 3 H 2 CO. These values, especially ⌬ pa H o (H 2 CO), have better accuracy and considerably lower uncertainty than the best previous recommendations and thus should be employed in future studies.

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“…As expected from previous work, protonated formaldehyde is far more stable than either the methoxy or oxonio-methylene ions; the relative energies of the three isomers are completely consistent with previous results. [22][23][24][25]28,30,33,36,40 We have not investigated the energies of the singlet/triplet curve crossing for methoxy/protonated formaldehyde but use here the previous results of Schwarz and co-workers. 40 The oxonio-methylene energetics shown are those from Radom and co-workers.…”

Section: ■ Experimental Detailsmentioning

confidence: 99%

“…The ion at m / z = 31 is produced as an abundant fragment in the ionization of methanol, ethanol, dimethyl ether, and other small oxygen-containing molecules . This ion has been the subject of much study and discussion in the mass spectrometry community for many years. − Two important structures are recognized, the CH 2 OH + protonated formaldehyde ion and the CH 3 O + methoxy cation. The HCOH 2 + oxonio-methylene ion was also proposed on the basis of computational studies, but there is apparently no experimental evidence for this species.…”

Section: Introductionmentioning

confidence: 99%

Infrared Spectroscopy of the Mass 31 Cation: Protonated Formaldehyde vs Methoxy

et al. 2012

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Pulsed discharges containing methanol or ethanol produce ions having the nominal formula [C,H(3),O](+), i.e. m/z = 31. Similar ions resulting from electron impact ionization in mass spectrometers are long recognized to have either the CH(2)OH(+) protonated formaldehyde or CH(3)O(+) methoxy cation structures. The H(2)OCH(+) oxonio-methylene structure has also been suggested by computational chemistry. To investigate these structures, ions are expanded in a supersonic beam, mass-selected in a time-of-flight spectrometer, and studied with infrared laser photodissociation spectroscopy. Sharp bands in the O-H and C-H stretching and fingerprint regions are compared to computational predictions for the three isomeric structures and their vibrational spectra. Protonated formaldehyde is the most abundant isomer, but methoxy is also formed with significant abundance. The branching ratio of these two ion species varies with precursors and formation conditions.

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Nonempirical LCAO MO SCF and CI Studies of the Isomers of CH3O+

Cited by 14 publications

References 10 publications

Photoionization of Hydroxymethyl (CD2OH and CD2OD) and Methoxy (CD3O) Radicals: Photoion Efficiency Spectra, Ionization Energies, and Thermochemistry

Photoionization of Hydroxymethyl (CD2OH and CD2OD) and Methoxy (CD3O) Radicals: Photoion Efficiency Spectra, Ionization Energies, and Thermochemistry

Proton affinity and enthalpy of formation of formaldehyde

Infrared Spectroscopy of the Mass 31 Cation: Protonated Formaldehyde vs Methoxy

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