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Versatility of the Cyano Group in Intermolecular Interactions.

ABSTRACT: Several cyano groups are added to an alkane, alkene, and alkyne group so as to construct a Lewis acid molecule with a positive region of electrostatic potential in the area adjoining these substituents. Although each individual cyano group produces only a weak ?-hole, when two or more such groups are properly situated, they can pool their ?-holes into one much more intense positive region that is located midway between them. A NH3 base is attracted to this site, where it forms a strong noncovalent bond to the Lewis acid, amounting to as much as 13.6 kcal/mol. The precise nature of the bonding varies a bit from one complex to the next but typically contains a tetrel bond to the C atoms of the cyano groups or the C atoms of the linkage connecting the C?N substituents. The placement of the cyano groups on a cyclic system like cyclopropane or cyclobutane has a mild weakening effect upon the binding. Although F is comparable to C?N in terms of electron-withdrawing power, the replacement of cyano by F substituents substantially weakens the binding with NH3.

SUBMITTER: Scheiner S

PROVIDER: S-EPMC7582283 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Versatility of the Cyano Group in Intermolecular Interactions.

Scheiner Steve S

Molecules (Basel, Switzerland) 20200930 19

Several cyano groups are added to an alkane, alkene, and alkyne group so as to construct a Lewis acid molecule with a positive region of electrostatic potential in the area adjoining these substituents. Although each individual cyano group produces only a weak π-hole, when two or more such groups are properly situated, they can pool their π-holes into one much more intense positive region that is located midway between them. A NH<sub>3</sub> base is attracted to this site, where it forms a stron ...[more]

PMID: 33007991

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