Computational chemistry data demonstrating the intersection of hyperconjugation and polarizability in organic chemistry.

<p dir="ltr">Hyperconjugation and polarizability are two models that are used to explain the stabilisation of charge in organic molecules. We are proposing that there is considerable overlap between these two models, such that it would be almost impossible to assign an experimental observation exclusively to one effect or the other.</p><p dir="ltr">The dataset is organised in the following way:</p><p dir="ltr">Hexane - Gaussian calculations using a computationally applied field cause polarisation of the molecule. This polarization is reflected in the hyperconjugation interactions, which clearly shows that there is at least overlap between these two effects.</p><p dir="ltr">Fluoropentane - Calculations on fluoropentane with an applied field show similar changes to those above. In this case, fluorine introduces an asymmetry within the structure, so that the effects in different directions (with and against the direction of F) will inevitably differ. The hyperconjugation interactions associated with fluorine are well described in the organic chemistry literature. What we are able to show is that the hyperconjugation interactions can be modulated in a systematic way by application of an applied field. That is, polarisation affects hyperconjugation.</p><p dir="ltr">Alcohols - we compare the charge distribution of alcohols and their corresponding alkoxides using Gaussian calculations, including NBO analysis. The NBO interactions change in a systematic way upon deprotonation, and this is in line with the charge redistribution. Hyperconjugation interactions can be considered as a type of donor-acceptor interaction, so this is reasonable.</p><p dir="ltr">Carbocations - here, we take the same approach with positive charge. A carbocation accepts electron-density from other parts of the molecule. We quantify this using charge analysis, and find that the changes in charge are consistent with the hyperconjugation NBO interactions as above.</p><p dir="ltr">Pentylamine - as an example of an amine that can be protonated, we find exactly the same as above. Protonation of the amine causes polarisation of the pentyl chain, and this can also be seen in changes to hyperconjugation interactions.</p>