Joel F. Liebman

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

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.

Heat capacity corrections to a standard state: a comparison of new and some literature methods for organic liquids and solids

The estimation methods commonly used to correct phase change enthalpies to the standard state are compared where possible to experimental measurements. Heat capacity corrections for liquid-gas equilibria are found to correlate with molecular structure, and we suggest an improved method for estimating these corrections using group methods. A similar improvement for estimating heat capacity corrections for solid-gas equilibria using group methods is also proposed. Heat capacity corrections for liquid-solid equilibria are examined. These corrections were found to be comparable in magnitude to the experimental error associated with heat capacity measurements, so it was not possible to obtain any meaningful correlations.

A Group Additivity Approach for the Estimation of Heat Capacities of Organic Liquids and Solids at 298 K

A group additivity method is described which provides heat capacity estimates of the condensed phase. The data base consists of 810 liquids and 446 solids. Group values for carbon in various common substitution and hybridization states and for 47 functional groups are provided. The standard error of estimation using this approach on this data base is 19.5 (liquids) and 26.9 J/ (mole K) (solids). This can be compared to typical experimental uncertainties of 8.12 and 23,4 J/ (mole K) associated with these measurements, respectively. Experimental uncertainties were estimated from the numerical differences obtained for a given substance from multiple independent literature reports.

Active oxygen in biochemistry

Biological reactions of dioxygen - an introduction - Raymond Y.N. Ho, Joel F. Liebman, Joan Selverstone Valentine Oxygen activation by flavins and pterins - Bruce A. Palfey, David P. Ballou, Vincent Massey Reactions of dioxgen and its reduced forms with heme proteins and model porphyrin complexes - Teddy G. Traylor, Patricia S. Traylor Dioxygen reactivity in copper proteins and complexes - Stephen Fox, Kenneth Karlin Oxygen activation at nonheme iron centers - Lawrence Que Jr. The mechanism of lipoxygenases - Mark J. Nelson, Steven P. Scitz The biological significance of oxygen-derivative species - Barry Halliwell Metal-complex-catalyzed cleavage of biopolymers - Claude F. Meares, Rosemary A. Marusak Exploration of selected pathways for metabolic oxidative ring opening of benzene based upon estimates of molecular energetics - Arthur Greenberg The role of oxidized lipids in cardiovascular disease - Judith A. Berliner, Andrew D. Watson.

Energetics of Organic Free Radicals

Preface. Series Preface. Contributors. Free Radical Reactions C. Walling. Heats of Formation of Organic Free Radicals by Kinetic Mehods Wing Tsang. Thermochemical Data for Free Radicals From Studies of Ions J.C Traeger, B.M. Kompe. Theoretical Studies of the Energetics of Free Radicals J.S. Francisco, J.A. Montgomery Jr. Photoacoustic Calorimetry of Radicals and Biradicals. J.L. Goodman. A Short and Illustrated Guide to Metal-Alkyl Bonding Energetics F.J.A. Martinho Simoes, M.E. Minas da Piedade. Resonance and 1,2 Rearrangements in Radicals: From Alkyl Radicals to Alkylcobalamins A. Greenberg, J.F. Liebman. Solvent Effects in the Reactions of Neutral Free Radicals J.M. Tanko, N. Kamrudin Suleman. Index.

Estimating Solid-Liquid Phase Change Enthalpies and Entropies

A group additivity method based on molecular structure is described that can be used to estimate solid–liquid total phase change entropy (Δ0TfusStpce) and enthalpy (Δ0TfusHtpce) of organic molecules. The estimation of these phase changes is described and numerous examples are provided to guide the user in evaluating these properties for a broad range of organic structures. A total of 1858 compounds were used in deriving the group values and these values are tested on a database of 260 additional compounds. The absolute average and relative errors between experimental and calculated values for these 1858 compounds are 9.9 J⋅mol−1⋅K−1 and 3.52 kJ⋅mol−1, and 0.154 and 0.17 for Δ0TfusStpce and Δ0TfusHtpce, respectively. For the 260 test compounds, standard deviations of ±13.0 J⋅mol−1⋅K−1(Δ0TfusStpce) and ±4.88 kJ mol−1(Δ0TfusHtpce) between experimental and calculated values were obtained. Estimations are provided for both databases. Fusion enthalpies for some additional compounds not included in the statistic...

The Chemistry of Cyclobutanes

1 Cyclobutane-physical properties and theoretical studies (Kenneth B. Wiberg). 2 Antiaromaticity and aromaticity in carbocyclic four-membered rings (M. Eckert-Maksic and Z. B. Maksic). 3 Stereochemical aspects-conformation and configuration (Ulf Berg). 4 Thermochemistry of cyclobutane and its derivatives (Joel F. Liebman and Suzanne W. Slayden). 5 Acidity and basicity of cyclobutanes (Esther Quintanilla, Juan Z. Davalos, Jos-e Luis M. Abboud and Ibon Alkorta). 6 NMR spectroscopy of cyclobutanes (Peter Rudolf Seidl and Jacques Fernandes Dias). 7 Mass spectrometry and gas-phase ion chemistry of cyclobutanes (Dietmar Kuck). 8 Synthesis of cyclobutanes (E. Lee-Ruff). 9 The application of cyclobutane derivatives in organic synthesis (Nan-Yan Fu, Siu-Hin Chan and Henry N. C. Wong). 10 Structural effects of the cyclobutyl group on reactivity and properties (Marvin Charton). 11 Rearrangements of cyclobutanes (J. M. Tanko). 12 Cyclobutyl, cyclobutyl-substituted and related carbocations (Hans-Ullrich Siehl). 13 Cation radicals in the synthesis and reactions of cyclobutanes (Nathan L. Bauld). 14 Highly unsaturated cyclobutane derivatives (Richard P. Johnson). 15 Cyclobutarenes (Amnon Stanger). 16 Organometallic derivatives (Holger Butenschon) 17 Photochemistry of cyclobutanes: Synthesis and reactivity (William M. Horspool). 18 Solvent-free photosynthesis of cyclobutanes: Photodimerization of crystalline olefins (Arunkumar Natarajan and V. Ramamurthy). 19 Chemistry of cubane and other prismanes (A. Bashir-Hashemi and Hiroyuki Higuchi). 20 Bicyclo[2.1.0]pentanes and bicyclo[2.2.0]hexanes (Barry K. Carpenter). 21 Fluorinated cyclobutanes and their derivatives (David M. Lemal and Xudong Chen). 22 Cyclobutane pyrimidine dimers as UV-induced DNA lesions (Marcus G. Friedel, Johannes Gierlich and Thomas Carell). 23 Cubanes, fenestranes, ladderanes, prismanes, staffanes and other oligocyclobutanoids (Henning Hopf, Joel F. Liebman and H. Mark Perks). Author index. Subject index.

Definitive heat of formation of methylenimine, CH2NH, and of methylenimmonium ion, CH2NH2+, by means of W2 theory

A long‐standing controversy concerning the heat of formation of methylenimine has been addressed by means of the W2 (Weizmann‐2) thermochemical approach. Our best calculated values, ΔH°f,298(CH2NH) = 21.1±0.5 kcal/mol and ΔH°f,298(CH2NH2+) = 179.4±0.5 kcal/mol, are in good agreement with the most recent measurements but carry a much smaller uncertainty. As a byproduct, 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.

The thermodynamic effect of fluorine as a substituent: Vinylic CF2 and CFH and allylic CF2C

Abstract I 2 -catalyzed isomerizations of 3-fluoropropene and 3,3 - difluoropropene, and a Cope rearrangement of 1,1 - difluoro - 1,5 - hexadiene provide thermodynamic data which allow the determination of a number of important group values for contributions to ΔH o f which when combined with those determined in the preceding paper allow the calculations of ΔH o f s of most simple F-substituted hydrocarbons: [C d (F)(H)] = − 38.4, [C d (F) 2 ] = − 88.0, [C(F) 2 (C)(C d )] = − 103.9, [C(F) 2 (C) 2 ] = − 104.9 kcal/mole. A kinetic study of the conversion of 1,1 - difluoro- to 3,3 - difluoro - 1,5 - hexadiene provided activation parameters for the process: Log A = 10.8, E a = 33.0 kcal/mole and ΔS ≠ = − 12.2 e.u. Incremental geminal stabilizations of F and other substituents are discussed and contrasted.

The origin of rotational barriers in amides and esters

Abstract We discuss in this article the origin and magnitude of the single bond rotational barrier in amides and esters. The high rotational barrier of amides is biochemically manifested in the limited conformational freedom of proteins, Since there are only two instead of three bonds to rotate about per arnino acid residue. On the basis of thermochemical estimates with model compounds, we find that the resonance energy of esters is somewhat higher than that of amides. However, the experimental rotational barrier for the former is considerably lower than the latter. We suggest esters have lower rotational barriers than the corresponding amides because they retain a large fraction of the resonance energy in the transition state. Justification is offerred using an orbital delocalization argument.