OH have lone electron pair,so it can attract hydrogen cation.But in my book chemistry is writen,that hydroxy acid are not ampholytes.SO where is true?
Lone pairs on uncharged O are not very basic. They can accept H+
and become protonated, but only in the presence of strong acids. Note that the pKa of H3
is approximately -2, which means it is strongly acidic and it follows that H2
O is weakly basic. Alcohols behave similarly.
Your theory is absolutely correct though, the O lone pair can accept H+
, and indeed it is thought to do so in many chemical processes. The issue here is with the definition - as far as I know the definition is simply that it can "act as an acid or base" and I'm not sure this is within a defined pH range (I hope someone can comment on this). Generally speaking, a molecule is only considered ampholytic if it can accept H+
at moderately acidic pH and donate at moderately alkaline pH - an example would be an amino acid.
Under the broadest definition, almost every compound you can draw can both accept and donate H+
under extreme conditions.