Which alcohol is unaffected by Jones reagent ($\mathrm{CrO}{}_3$/$\mathrm{H}{}_2\mathrm{SO}{}_4$/acetone) at room temperature?

Chromic acid oxidation needs a hydrogen on the carbinol carbon, because the chromate ester loses that H in the elimination step. 2-Methylpropan-2-ol is tertiary and has none, so it is unaffected. The primary alcohols give acids and butan-2-ol gives a ketone.