Arrange the following in increasing order of their reactivity towards $\overset{Θ}{O}H$.

A. Benzophenone

B. Acetophenone

C. Ethanal

D. Acetone

Choose the correct answer from the options given below:

A<B<D<C

The correct answer is Option (1) → A < B < D < C.

To explain the reactivity of the compounds toward \( \text{OH}^- \) (hydroxide ion) in nucleophilic addition reactions, let’s analyze each compound's structure, substituents, and how these factors influence electrophilicity at the carbonyl carbon.

A. Benzophenone 

The carbonyl carbon is bonded to two aromatic rings, which are electron-donating due to resonance. The electron-donating nature of the phenyl groups decreases the positive character of the carbonyl carbon, making it less electrophilic and, thus, less reactive toward nucleophiles like \( \text{OH}^- \).

B. Acetophenone

This compound has one electron-donating phenyl group and one electron-donating methyl group. The methyl group slightly increases the electron density at the carbonyl carbon, making it more reactive than benzophenone because the steric hindrance is lower compared to having two bulky phenyl groups.

C. Ethanal

Ethanal has no bulky substituents, allowing the carbonyl carbon to be more electrophilic. The absence of stabilizing groups means that the carbonyl carbon is more susceptible to nucleophilic attack, making ethanal highly reactive toward \( \text{OH}^- \).

D. Acetone

Acetone is a simple ketone with two electron-donating methyl groups. While the presence of two methyl groups provides some electron density, they also create steric hindrance, which can slightly reduce the reactivity compared to ethanal, but acetone is generally still more reactive than benzophenone and acetophenone

Reactivity Summary:

Electrophilicity: The ability of the carbonyl carbon to attract nucleophiles is key. The more electron-donating substituents there are around the carbonyl carbon, the less electrophilic it becomes.

Steric Effects: Bulky substituents can hinder the approach of nucleophiles to the carbonyl carbon.

The increasing order of reactivity toward \( \text{OH}^- \) is A < B < D < C.

This analysis leads to the conclusion that Benzophenone < Acetophenone < Acetone < Ethanal in terms of their reactivity toward nucleophilic addition.