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Your search keyword '"Liebman, J. F."' showing total 141 results
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141 results on '"Liebman, J. F."'

1. Tetrahedral Units: For Dodecahedral Super-Structures

Author

Ortiz, Y., Klein, D. J., and Liebman, J. F.

Subjects
Physics - Chemical Physics
Abstract

Different novel organic-chemical possibilities for tetrahedral building units are considered, with attention to their utility in constructing different super-structures. As a representative construction we consider the use of sets of 20 such identical tetrahedral units to form a super-dodecahedron.

Published
2016

2. Workshop on „the Applications of Quantum Mechanical Methods in Gas Phase Ion Chemistry“

Author

HruŠák, J., primary, Liebman, J. F., additional, Gaspar, P. P., additional, Berger, D. J., additional, Oiestad, E. Leere, additional, Oiestad, A. Leere, additional, Skaane, H., additional, Ruud, K., additional, Helgaker, T., additional, Uggerud, E., additional, Vulpius, T., additional, Squires, R. R., additional, Mcgibbon, G. A., additional, Terlouw, J. K., additional, Hrusák, J., additional, Schwarz, H., additional, and Hrusšák, J., additional

Published
1999
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4. Gas-phase ion chemistry of organic peroxides

Author

Marek, I, Liebman, J F, Rappoport, Z, Kato, Shuji, Blanksby, Stephen, Marek, I, Liebman, J F, Rappoport, Z, Kato, Shuji, and Blanksby, Stephen

Abstract

Over the last 30 years, mass spectrometry and allied technologies have provided significant new insights into the intrinsic, gas phase properties of organic peroxides. In this chapter, the formation and interrogation of neutral peroxides, and their ionized analogues in the gas phase are discussed for several key classes of organic peroxides. Methods for the formation of intact, gas phase cations and anions from labile, often nonvolatile, peroxides using conventional and contemporary soft ionization techniques are described. Studies of the unimolecular dissociation of these ionized peroxides are shown to yield new understanding of energetics and bonding as well as providing diagnostic markers for the elucidation of molecular structure. The bimolecular chemistries of peroxides in the gas phase are considered in two categories: (i) reactions of ions with neutral peroxides; and (ii) the reactions of deprotonated organic hydroperoxides with neutral substrates. Advanced topics cover analytical applications of chemical ionization to the detection of peroxides and peroxyl radicals along with the synthesis of distonic peroxyl radical ions. Studies of the gas phase spectroscopy of organic peroxides that exploit the ionized forms of the peroxides are reviewed including negative-ion photoelectron spectroscopy, infrared multiple photon dissociation and action spectroscopy.

Published
2014

5. The annular tautomerism of imidazoles and pyrazoles: The possible existence of nonaromatic forms

Author

Alkorta, Ibon, Elguero, José, Liebman, J. F., Alkorta, Ibon, Elguero, José, and Liebman, J. F.

Abstract

DFT (B3LYP/6-31G*) and G3//B3LYP (usually referred as G3B3 in the literature) calculations have been carried out on annular tautomers of C- and/or N-functionalized imidazoles (both the aromatic 1H- and nonaromatic 2H-) and pyrazoles (the aromatic 1H- and 2H-, and nonaromatic 3H- and 4H-). The aromaticity of 1H-imidazole and 1H- and 2H-pyrazole results in these species being more stable than their nonaromatic tautomers. However, this stability is reversed when the hydrogen on the azole nitrogen or methylene carbon is substituted by OH or by F, e.g., in increasing order of stability we find 1-fluoro-1H-imidazole <2-fluoro-2H-imidazole (<2-fluoro-1H-imidazole). These results are related to a recent report of a highly substituted imidazole that exists in the >nonaromatic> 2H-tautomeric form, and discussed subsequently in a purely thermochemical context. © 2006 Springer Science+Business Media, LLC.

Published
2006

22. ChemInform Abstract: Interrelations of the Energetics of Amides and Alkenes: Enthalpies of Formation of N,N‐Dimethyl Derivatives of Pivalamide, 1‐ Adamantylcarboxamide and Benzamide, and of Styrene and Its α‐, trans‐β‐ and β,β‐Methylated Derivatives.

Author

ABBOUD, J.‐L. M., primary, JIMENEZ, P., additional, ROUX, M. V., additional, TURRION, C., additional, LOPEZ‐MARDOMINGO, C., additional, PODOSENIN, A., additional, ROGERS, D. W., additional, and LIEBMAN, J. F., additional

Published
1995
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31. Response Reactions:  A Mathematical Well-Defined Way to Obtain Accurate Thermochemistry from ab Initio Calculations

Author

Fishtik, I., Datta, R., and Liebman, J. F.

Abstract

The concept of stoichiometrically unique reactions referred to as response reactions (RERs), earlier deduced by us in applications of chemical thermodynamics and kinetics, is extended to isodesmic reactions. Namely, it is shown that the additional stoichiometric constraints according to which the number and type of chemical bonds in a multiple chemical reaction system are conserved may be formally appended to the conventional RERs formalism. As a result, one can define and generate a stoichiometrically unique class of isodesmic RERs. Along with the conventional RERs, the newly defined isodesmic RERs are shown to be effective in converting the total enthalpies of the species obtained from ab initio calculations into accurate values of the standard enthalpies of formations for large species.

Published
2003

33. MBPT and DFT Study of Hydrogen Cyanide Borane(1) Oligomers and Dehydrogenated Analogues

Author

Pappova, A., Cernusak, I., Urban, M., and Liebman, J. F.

Abstract

Geometry optimizations and fragmentation energies of the series of hydrogen cyanide borane(1) oligomers (up to hexamers) and their dehydrogenated analogues are presented. Structural parameters are examined at different computational levels:  MBPT(2) (second-order many-body perturbation theory), SDQ-MBPT(4) (fourth-order many-body perturbation theory limited to singly-, doubly-, and quadruply excited configurations), and DFT-B3LYP (density functional theory with Becke's three-parameter hybrid functional using the Lee−Yang−Parr correlation functional). These oligomers seem to be suitable input for the models of the polymer chain because of their periodic structure emerging from successive HCNBH or HCNB addition. The stability of the oligomers in terms of initial “cracking” of the weakest bond is fairly high, ranging from 97 to 443 kJ/mol for the HCNBH series and from 329 to 589 kJ/mol for the HCNB series.

Published
2000

35. Enthalpies of Formation of N-Substituted Pyrazoles and Imidazoles

Author

Mo, O., Yanez, M., Roux, M. V., Jimenez, P., Davalos, J. Z., Silva, Ribeiro da, V., M. A., Silva, Ribeiro da, C., M. D. M., Matos, M. A. R., Amaral, L. M. P. F., Sanchez-Migallon, A., Cabildo, P., Claramunt, R., Elguero, J., and Liebman, J. F.

Abstract

Accurate experimental enthalpies of formation measured using static bomb combustion calorimetry, the “vacuum sublimation” drop calorimetry method, and the Knudsen-effusion method are reported for the first time for four azoles:  1-methylimidazole (1MeIMI), 1-methylpyrazole (1MePYR), 1-benzylimidazole (1BnIMI), and 1-benzylpyrazole (1BnPYR). These values and those corresponding to imidazole (1HIMI), pyrazole (1HPYR), 1-ethylimidazole (1EtIMI), 1-ethylpyrazole (1EtPYR), 1-phenylimidazole (1PhIMI), and 1-phenylpyrazole (1PhPYR) are compared with theoretical values using the G2(MP2) and the B3LYP/6-311*G(3df,2p)//6-31G(d) approaches. In general, there is a very good agreement between calculated and experimental values for the series of N-substituted imidazoles, while the agreement is less good for the series of the N-substituted pyrazoles. Experimentally, the gap between the enthalpies of formation of imidazoles and pyrazoles decreases significantly upon N-substitution, while the theoretical estimates indicate that this decrease is smaller.

Published
1999

40. Evaluated Gas Phase Basicities and Proton Affinities of Molecules; Heats of Formation of Protonated Molecules

Author

NATIONAL STANDARD REFERENCE DATA SYSTEM, Lias, S G, Liebman, J F, Levin, R D, NATIONAL STANDARD REFERENCE DATA SYSTEM, Lias, S G, Liebman, J F, and Levin, R D

Abstract

The gas phase basicity and proton affinity of a molecule, M, are both defined in terms of the hypothetical reaction: M + H(+) yields MH(+). The gas phase basicity is the negative of the corresponding enthalpy change. The available data on gas phase basicities and proton affinities of molecules are compiled and evaluated. Tables giving the molecules ordered (1) according to proton affinity and (2) according to empirical formula, sorted alphabetically are provided. The heats of formation of the molecules and the corresponding protonated species are also listed. Originator supplied keywords include: Basicity; Heats of formation; Ion-molecule reaction; Proton affinity; and Proton transfer., Reprint no. 254 from Jnl. of Physical and Chemical Reference Data, v13 n3 p695-808 1984.

Published
1984

41. The Conjugation Stabilization of 1,3-Butadiyne Is Zero

Author

Rogers, D. W., Matsunaga, N., Zavitsas, A. A., McLafferty, F. J., and Liebman, J. F.

Abstract

In contrast to 1,3-butadiene, the textbook example of “conjugation stabilization”, G3(MP2) calculations yielding the enthalpy of hydrogenation ΔhydH298 of 1,3-butadiyne indicate that it is not stabilized by the conjugated configuration of its triple bonds. Differences between ethylenic and acetylenic π bonds are examined in the light of CAS-MCSCF calculations on 1,3-butadiene and 1,3-butadiyne.

Published
2003

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