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Browsing Chemistry by Subject "Bond dissociation energy"

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    Assessment of quantum chemical methods for the calculation of homolytic N–F bond dissociation energies
    (Chemical Data Collections, 2016-11-01) Akhmetova, Nuriya; Kaliyeva, Laura; O'Reilly, Robert J.; Nuriya, Akhmetova
    Abstract In this article, the performance of a wide range of conventional and double-hybrid DFT methods (in conjunction with Dunning basis sets of double-, triple- and quadruple-zeta quality), as well as a number of Gaussian-n thermochemical protocols are assessed for their ability to compute accurate homolytic N–F bond dissociation energies (BDEs). Their performance is evaluated against a previously reported set of 31 highly accurate gas-phase N–F BDEs obtained using the benchmark-quality W2w thermochemical protocol (See: R.J. O'Reilly, A. Karton, L. Radom, J. Phys. Chem. A2011, 115, 5496.). Out of all of the DFT/basis set combinations investigated, ωB97 and M06-2X (in conjunction with the aug'-cc-pVDZ basis set) offer the lowest mean absolute deviations (MADs= 2.4 and 2.7kJ mol–1, respectively). Of the Gaussian-n procedures, G3X offers the best performance (MAD= 1.4kJ mol–1), whilst the significantly more economical G3X(MP2)-RAD method also offers excellent performance (MAD= 1.8kJ mol–1).
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    A dataset of homolytic C–Cl bond dissociation energies obtained by means of W1w theory
    (Chemical Data Collections, 2016-08-01) Garifullina, Ainash; Mahboob, Abdulla; O'Reilly, Robert J.; Ainash, Garifullina
    Abstract We herein report a dataset of 28 homolytic C–Cl bond dissociation energies (BDEs) (to be known as the CCl28 dataset), obtained using the benchmark-quality W1w thermochemical protocol. This set contains chlorinated organic molecules that consist of either sp3-, sp2- or sp-hybridized C–Cl bonds. The species in this set have C–Cl BDEs (at 298K) that differ by as much as 168.4kJ mol–1, with allyl chloride having the lowest BDE (291.7kJ mol–1) and 1-chloroprop-1-yne having the largest (460.1kJ mol–1). Given the benchmark quality of the CCl28 dataset, it may serve as a useful reference for assessing the performance of more approximate quantum chemical methods, such as density functional theory (DFT) and double-hybrid DFT methods.
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    Homolytic C–Br bond dissociation energies obtained by means of the G4 thermochemical protocol
    (Chemical Data Collections, 2016-05-01) Kazakbayeva, Zhanna; Zhumagali, Shingis; Mahboob, Abdulla; O'Reilly, Robert J.; Zhanna, Kazakbayeva
    Abstract Knowledge of the energies required to induce homolytic cleavage of the C–Br bonds of brominated organic molecules, a process that affords carbon-centered radicals and Br•, is of fundamental importance. Although some data pertaining to the strength of C–Br bonds can already be found in the literature, the chemical diversity of the species for which bond dissociation energies (BDEs) are available is somewhat limited. In this data article, we report a comprehensive set of homolytic C–Br BDEs, obtained using the G4 thermochemical protocol, for brominated organic molecules with wide structural diversity. The species in this set have C–Br BDEs (at 298K) that differ by as much as 188.3kJmol–1, with α-bromoalanine having the lowest BDE (214.1kJmol–1) and 1-bromobut-1-yne having the largest (402.4kJmol–1). Of particular relevance to biological systems are the BDEs of 8-bromoguanine (345.3kJmol–1), 8-bromoadenine (345.6kJmol–1), 5-bromocytosine (348.8kJmol–1) and 5-bromouracil (350.3kJmol–1).