Question

Rank the following compounds in order of increasing amount of hydrate present at equilibrium.

Short answer

The compounds in the increasing order amount of hydrate present at equilibrium is shown below.

Step-by-step solution

Stability of Hydrates of Carbonyl Compounds

When aldehyde is dissolved in water, a hydrate is formed. The aldehyde and its hydrate are in a state of equilibrium. The addition of water to most ketones, however, results in an unfavourable balance. A stable hydrate can be formed by compounds having strong electron-withdrawing groups linked to the carbonyl carbon. The hydrate is stabilised by the electron-withdrawing group. As a result, at equilibrium, aldehyde will have more hydrate than ketone. At equilibrium, an aldehyde with an electron-withdrawing group will have a higher hydrate.

Reaction of carbonyl compounds with water

The reaction for hydration of given compounds are shown below.

It is know that aldehyde with an electron withdrawing group will have a higher amount of hydrate. Here, compound (III) has an electron withdrawing group $(-\mathrm{Br})$at the alpha position. Therefore, compound (III) has a higher amount of hydrate present at equilibrium.

Now among compounds (I), (II), and (IV), compound (I) is aldehyde and (II) and (IV) are ketone. Therefore, the compound will have a higher amount of hydrate.

Now among (II) and (IV), compound (IV) has an electron withdrawing group $(-\mathrm{Br})$ at the alph position. Therefore, compound (IV) has a higher amount of hydrate present at the equilibrium.

Therefore, the compounds in the order of increasing amount of hydrate present at the equilibrium is shown below.