dorsal/arxiv
View SchemaDefinitive heat of formation of methylenimine, CH2=NH, and of methylenimmonium ion, CH2NH2+, by means of W2 theory
| Authors | Glenisson de Oliveira, Jan M. L. Martin, Indira K. C. Silwal, Joel F. Liebman |
|---|---|
| Categories | |
| ArXiv ID | physics/0101051 |
| URL | https://arxiv.org/abs/physics/0101051 |
| Journal | Journal of Computational Chemistry 22, 1297-1305 (2001) |
Abstract
A long-standing controversy concerning the heat of formation of methylenimine has been addressed by means of the W2 (Weizmann-2) ab initio thermochemical approach. Our best calculated values, DeltaHf298(CH2NH)=21.1+/-0.5 kcal/mol and DeltaHf298(CH2NH2+)=179.4+/-0.5 kcal/mol, are in good agreement with the most recent measurements but carry a much smaller uncertainty. As a by-product, we obtain the first-ever accurate anharmonic force field for methylenimine: upon consideration of the appropriate resonances, the experimental gas-phase band origins are all reproduced to better than 10 cm-1. Consideration of the difference between a fully anharmonic zero-point vibrational energy and B3LYP/cc-pVTZ harmonic frequencies scaled by 0.985 suggests that the calculation of anharmonic zero-point vibrational energies can generally be dispensed with, even in benchmark work, for rigid molecules.
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"abstract": "A long-standing controversy concerning the heat of formation of methylenimine\nhas been addressed by means of the W2 (Weizmann-2) ab initio thermochemical\napproach. Our best calculated values, DeltaHf298(CH2NH)=21.1+/-0.5 kcal/mol and\nDeltaHf298(CH2NH2+)=179.4+/-0.5 kcal/mol, are in good agreement with the most\nrecent measurements but carry a much smaller uncertainty. As a by-product, we\nobtain the first-ever accurate anharmonic force field for methylenimine: upon\nconsideration of the appropriate resonances, the experimental gas-phase band\norigins are all reproduced to better than 10 cm-1. Consideration of the\ndifference between a fully anharmonic zero-point vibrational energy and\nB3LYP/cc-pVTZ harmonic frequencies scaled by 0.985 suggests that the\ncalculation of anharmonic zero-point vibrational energies can generally be\ndispensed with, even in benchmark work, for rigid molecules.",
"arxiv_id": "physics/0101051",
"authors": [
"Glenisson de Oliveira",
"Jan M. L. Martin",
"Indira K. C. Silwal",
"Joel F. Liebman"
],
"categories": [
"physics.chem-ph",
"physics.comp-ph"
],
"journal_ref": "Journal of Computational Chemistry 22, 1297-1305 (2001)",
"title": "Definitive heat of formation of methylenimine, CH2=NH, and of methylenimmonium ion, CH2NH2+, by means of W2 theory",
"url": "https://arxiv.org/abs/physics/0101051"
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