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 17.09.2011   Карта сайта     Language По-русски По-английски
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17.09.2011

Overcoming lability of extremely long alkane carbon–carbon bonds through dispersion forces





Journal name:

Nature

Volume:

477,

Pages:

308–311

Date published:

(15 September 2011)

DOI:

doi:10.1038/nature10367


Received


Accepted


Published online







Steric effects in chemistry are a consequence of the space required to accommodate the atoms and groups within a molecule, and are often thought to be dominated by repulsive forces arising from overlapping electron densities (Pauli repulsion). An appreciation of attractive interactions such as van der Waals forces (which include London dispersion forces) is necessary to understand chemical bonding and reactivity fully. This is evident from, for example, the strongly debated origin of the higher stability of branched alkanes relative to linear alkanes1, 2 and the possibility of constructing hydrocarbons with extraordinarily long C–C single bonds through steric crowding3. Although empirical bond distance/bond strength relationships have been established for C–C bonds4 (longer C–C bonds have smaller bond dissociation energies), these have no present theoretical basis5. Nevertheless, these empirical considerations are fundamental to structural and energetic evaluations in chemistry6, 7, as summarized by Pauling8 as early as 1960 and confirmed more recently4. Here we report the preparation of hydrocarbons with extremely long C–C bonds (up to 1.704Å), the longest such bonds observed so far in alkanes. The prepared compounds are unexpectedly stable—noticeable decomposition occurs only above 200°C. We prepared the alkanes by coupling nanometre-sized, diamond-like, highly rigid structures known as diamondoids9. The extraordinary stability of the coupling products is due to overall attractive dispersion interactions between the intramolecular H•••H contact surfaces, as is evident from density functional theory computations with10 and without inclusion of dispersion corrections.


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  • Chen Wev .  honorary member of ISSC science council

  • Harton Vladislav Vadim  honorary member of ISSC science council

  • Lichtenstain Alexandr Iosif  honorary member of ISSC science council

  • Novikov Dimirtii Leonid  honorary member of ISSC science council

  • Yakushev Mikhail Vasilii  honorary member of ISSC science council

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