The number of -CH$$_2$$- (methylene) groups in the product formed from the following reaction sequence is _______.

The alcohol present at the end of the given sequence is tert-butyl alcohol, $$\left(CH_3\right)_3C\!-\!OH$$.

Recall that a methylene group is a carbon atom bearing exactly two hydrogen atoms (-CH$$_2$$-). In tert-butyl alcohol the central carbon is quaternary (no hydrogens) and each of the three peripheral carbons is a methyl carbon (-CH$$_3$$). None of the four carbons carries two hydrogens.

Hence the total number of methylene (-CH$$_2$$-) groups in the final product is $$0$$.

Answer: 0