20. The Variety of Organic         Compounds   Previous PageNext Page

The alcohol functional group, -OH, looks misleadingly like the hydroxide group of a base, which might suggest that it dissociates from the rest of the molecule.

It cannot be emphasised too strongly that this is not so; an alcohol is held firmly together by covalent bonds and does not dissociate. This is because the oxygen atom and the carbon to which it is bonded in the hydrocarbon radical are of approximately the same electronegativity.

If the carbon were much less electronegative than the oxygen, then the oxygen of the -OH would pull the bonding electrons to itself and the molecule would ionize as a base does:


This happens with NaOH, but not with CHOH.


In contrast, if the carbon were much more elctronegative, then the alcohol would pull electrons away from the OH bond and release a proton, as an acid does:


This occurs with ONOH (nitric acid, HNO), but not with
HCOH (methanol).

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