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In chemistry, homoconjugation has two unrelated meanings: In acid–base chemistry, homoconjugation is an alternate name for the phenomenon of homoassociation . In organic chemistry, homoconjugation is a type of conjugated system where two π-systems are separated by one non-conjugating group.
In acid–base chemistry, homoassociation (an IUPAC term) [2] is an association between a base and its conjugate acid through a hydrogen bond. [1]Most commonly, homoassociation leads to the enhancement of the acidity of an acid by itself.
An acid may also form hydrogen bonds to its conjugate base. This process, known as homoconjugation, has the effect of enhancing the acidity of acids, lowering their effective pK a values, by stabilizing the conjugate base. Homoconjugation enhances the proton-donating power of toluenesulfonic acid in acetonitrile solution by a factor of nearly ...
Hyperconjugation can be used to rationalize a variety of chemical phenomena, including the anomeric effect, the gauche effect, the rotational barrier of ethane, the beta-silicon effect, the vibrational frequency of exocyclic carbonyl groups, and the relative stability of substituted carbocations and substituted carbon centred radicals, and the thermodynamic Zaitsev's rule for alkene stability.
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The last sentence says that homoconjugation does not occur in aqueous solutions because the oligomers cannot form; this doesn't sound like an explanation, based on the earlier sentences, which made it appear that oligomers and homoconjugation are different, though both are dependent on hydrogen bonds.
Also because of homoconjugation, the following statement might be incorrect "Unlike other hydrohalic acids, such as hydrochloric acid, hydrogen fluoride is only a weak acid in water solution" The pK a depends on concentration. Most importantly, thank you for your editing. --Smokefoot 20:31, 12 May 2013 (UTC)
Hydrofluoric acid is complicated because its strength depends on the concentration owing to the effects of homoconjugation. As solutions in non-aqueous solvents, such as acetonitrile, the hydrogen halides are only modestly acidic however. Similarly, the hydrogen halides react with ammonia (and other bases), forming ammonium halides: