An unknown has a chemical formula of C4H10O. When chromic acid was added to the unknown, it turned green. When the Lucas reagent was added to a separate portion of the unknown, it turned cloudy in 5 minutes. When NaOH and KI/iodine was added to the unknown, a yellow precipitate formed. What is the structure of the unknown compound?

The structure of the unknown compound is 2-butanol.

Explanation:

Chromic acid reagent is the most efficient procedure for oxidizing secondary alcohols. Chromic acid in aqueous sulfuric acid and acetone solution is known as Jones reagent, which oxidizes primary and secondary alcohols to carboxylic acids and ketones, respectively.

Lucas reagent reacts with primary, secondary and tertiary alcohols with fairly predictable rates, and these rates can be used to distinguish between the three types of alcohols.  If the solution becomes cloudy in 3 to 5 minutes it indicates the presence of a secondary alcohol.

These two methods indicate the presence of a secondary alcohol, but the iodoform test indicates a specific structural unit.