Dihydrogen contacts in alkanes are subtle but not faint

Departament de Química Inorgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
Nature Chemistry (Impact Factor: 25.33). 04/2011; 3(4):323-30. DOI: 10.1038/nchem.1004
Source: PubMed


Alkane molecules are held together in the crystal state by purportedly weak homonuclear R-H···H-R dihydrogen interactions. In an apparent contradiction, the high melting points and vaporization enthalpies of polyhedranes in condensed phases require quite strong intermolecular interactions. Two questions arise: 'How strong can a weak C-H···H-C bond be?' and 'How do the size and topology of the carbon skeleton affect these bonding interactions?' A systematic computational study of intermolecular interactions in dimers of n-alkanes and polyhedranes, such as tetrahedrane, cubane, octahedrane or dodecahedrane, showed that attractive C-H···H-C interactions are stronger than usually thought. We identified factors that account for the strength of these interactions, including the tertiary nature of the carbon atoms and their low pyramidality. An alkane with a bowl shape was designed in the search for stronger dihydrogen intermolecular bonding, and a dissociation energy as high as 12 kJ mol⁻¹ is predicted by our calculations.

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Available from: Gabriel Aullón, Oct 13, 2014
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    • "Much latter Desiraju introduced the term " weak hydrogen bonds " for C H· · ·O [10], and C H· · ·C(sp 2 ) interactions [11] in polynuclear aromatic hydrocarbons. Alvarez et al. supported this idea regarding the attractive di-hydrogen CH· · ·HC interactions in alkanes with both linear and polyhedral structure [12] [13] [14]. After much debate, the nature of halogen–halogen interactions in organic crystals is also now defined as a type of donor–acceptor interaction [15]. "
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