In diacetone alcohol, $CH X_{3} - CO - CH X_{2} - C (CH X_{3}) X_{2} - OH$ (4-hydroxy-4-methylpentan-2-one), treatment with $NaOH$ causes dehydration by E1cB. Count only the hydrogen atoms whose removal gives an enolate that can directly expel $OH X^{-}$ from the neighbouring carbon. How many such hydrogen atoms are there?

Numerical answer type, tolerance 0.5.

Answer: 2

The enolate that can expel

OH X^{-}

must have its carbanion carbon adjacent to the carbon bearing

OH

. That carbon is C-3, the

CH X_{2}

group, which has 2 hydrogens. The

CH X_{3}

hydrogens on C-1 also give an enolate, but it is on the wrong side and cannot expel

OH X^{-}

. Answer 2.