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Theconformational space of 1,4-butanediol was examined at ωB97X-D/6-311+G(d,p).Of the 65 conformers examined, the seven lowest energy conformationshave an internal hydrogen bond. The strength of this hydrogen bondis estimated to be 4 kcal mol–1. A broad varietyof microsolvated configurations of both the open form 5oand hydrogen-bonded form 5rof 1,4-butanediol involvingone to four water molecules were located at ωB97X-D/6-311+G(d,p).When one to three water molecules are included in the clusters, thelowest energy configurations involve the hydrogen-bonded form 5r. With four water molecules, configurations involving theopen form 5oare favored enthalpically, but configurationswith the hydrogen bonded form 5rare the lowest in freeenergy. These calculations suggest that both 5rand 5owill coexist in aqueous solution. [ABSTRACT FROM AUTHOR]

Explicitlycorrelated CCSD(T) valence basis limit relative energies were obtainedfor the 65 conformers of butane-1,4-diol, a prototypical system witha strong internal hydrogen bond. The performance of a variety of abinitio and DFT methods (with and without empirical dispersion corrections)was assessed in detail. Consideration of all pairwise conformer energiesprovides a performance gauge for both H-bonds and van der Waals interactions,aside from internal strain of angles and bonds. In the post-HF realm,it was found that SCS(MI)CCSD-F12/cc-pVDZ-F12 can be a cost-effectivealternative to CCSD(T)/CBS, almost without any loss in accuracy. Inthe DFT arena, the double-hybrid DSD-PBEP86-D3BJ surpasses the accuracyof all other methods (except for SCS(MI)CCSD, but at a small fractionof its cost). Several hybrid functionals provide an acceptable accuracywith the def2-QZVP basis set, especially BMK, M06, LC-ωPBE-D3,and TPSS0-D3. With the more modest 6-311+G(d,p) basis set, the H-bondsare far from basis set completeness and, due to error compensation,the inclusion of a dispersion correction is generally counterproductive.Some functionals that represent “Pauling points” atthis level are LC-ωPBE, TPSS0, B1B95, BMK, TPSSh, PBE0, TPSS,and ωB97X. [ABSTRACT FROM AUTHOR]

The deprotonation energies of all possible lithiobenzenes (C6LinH6-n, n = 0-5) were computed at B3LYP/6-311+G(d,p). Based on natural population analysis, the conjugate bases can be thought of as salts between a polyanionic phenyl core and associated lithium cations. The most stable structures maximize the electrostatic attraction between these two species, typically by positioning the lithium cations to bridge in the ring plane across two adjacent carbanion centers. Favorable deprotonation occurs when the formal carbanion centers are adjacent to each other and then the proton is removed from an adjacent carbon. The deprotonation free energies range from 365.0 to 397.2 kcal mol-1, with most of them less than the deprotonation free energy of benzene (391.8 kcal mol-1). [ABSTRACT FROM AUTHOR]

The reaction of cyclo-L-cystine with thiolate is examined at the B3LYP/6-31+G[sup *] level. The two isomers of cyclo-l-cystine differ in their dihedral angle about the disulfide bond; the M isomer (with dihedral angle of -90.1°) is found to be slightly lower in energy. The nucleophilic substitution reaction at sulfur follows the addition-elimination mechanism, exemplified by the hypercoordinate sulfur intermediate on the reaction surface. The reaction is exergonic (ΔG = -6.16 kcal mol[sup -1]), and both the entrance and exit transition state lie below the reactant energies. [ABSTRACT FROM AUTHOR]

B3LYP/aug-cc-pVDZ and MP2/6-31+G[sup *] calculations of the reactions of HS with small cyclic disulfides (dithiirane, 1,2-dithietane, 1,2-dithiolane, and 1,2-dithiane) were performed to determine the reaction mechanismo For the five- and six-membered rings, the reaction proceeds via the addition-elimination pathway, consistent with acyclic analogues. The smaller, more strained threeand four-membered rings react by the S[sub N]2 mechanism. Addition of the nucleophile cannot be accommodated by the small rings without concomitant ring cleavage. [ABSTRACT FROM AUTHOR]

Examines the relative energies of polylithiated benzenes. Maximization on the electrostatic interactions between carbanions and lithium cations; Disproportionation reactions leading to polylithiated benzenes; Preparation of highly lithiated aromatic species.

Focuses on the critical evaluation of chemical publications. Limited terms of information on chemical publication of journals; Identification of cost, publishing, and libraries on the scholarly publication; Use of the Scholarly Publishing and Academic Resources Coalition services by the Association of Research Libraries on publishing.

Cyclopropa-, cyclopbutana-, and cyclobutena-annulated benzenes, pyridines, and phosphabenzenes are potentially aromatic compounds. The structures of all mono-, di- and tri-annulated variations are optimized at the B3LYP/aug-cc-pVDZ level. Their aromaticity is evaluated in terms of bond alternation, magnetic properties (NICS), and resonance energy. The cyclopropa systems are aromatic, the cyclobutanana systems express some aromaticity and the cyclobutena systems are not aromatic. [Copyright &y& Elsevier]

Examines the nucleophilic substitution reactions at two-coordinate sulfur. Elements used as nucleophile and leaving group in methylsulfenyl derivatives; Evidence for deprotonation involving hydroxide and amide; Presence of triple-well potential energy software.

Describes how the 'Internet Journal of Chemistry' came into existence and examines how many of the publication choices were made. Publishing of peer-reviewed articles in all areas of chemistry; Publication model employed by the journal; Significant advantages afforded by the electronic medium; Enhanced articles in user-customizable format.

Examines the Diels-Alder reaction of a series of substituted selenoaldehydes or selenoketones with 1,3-butadiene or 2-methoxy-1,3-butadiene to yield 3,6-dihydro-2H-selenopyrans using B3LYP with an altered 6-31G basis set. Comparison with results from several standard ab initio procedures; Electron-withdrawing groups.

Evaluates the nucleophilic substitution reactions of three trisulfides by thiolate at MP2(full)/6-31+G and MP4SDTQ(fc)/6-311+G**//MP2(full)/6-31+G&*. Gas-phase mechanism; Hydrogen bonding between the nucleophile and the trisulfide; Comparison of the mechanism of reaction 1 at HF and MP2.

Examines the reaction mechanism of the phosphaketene dimerization. Geometries; Energies; Electronic structures of the transition states.

Studies the Diels-Alder and Staudinger reactions between ketene and cyclopentadiene. Description of the computational method; Description of the results of the experiments; Products; Transition states.

Examines the keto-enol tautomerizations in formyl and diformylphoshine and compares them with the hydrocarbon analogues acetaldehyde and malonaldehyde. Structural parameters; Computational methods; Enol structures; Cis and trans conformers of the enol forms of diformylphosphine and malonaldehyde.

Examines the phospha-Cope rearrangement converting 1,6-diphospha-1,5-hexadiene into 3,4-diphospha-1,5-hexadiene. Energies; Computational methods; Geometries and electronic structures; C-C bond distances.