Read the following passage given below and answer the question.

Andehydes and ketones undergo nucleophilic addition reactions. A nucleophile attacks the electrophilic carbon atom of polar carbonyl group from perpendicular to plane of \(sp^2\) hybridized orbitals of carbonyl carbon. The hybridization of carbon changes from \(sp^2\) \(sp^3\) and a tetrahedral alkoxide intermediate is formed. This captures \(H^+\) to give neutral product. In carboxylic acids, carbonyl carbon is less electrophilic than carbonyl carbon carbon of aldehydes and ketones.

The correct order of reactivity for addition reaction of following carbonyl compounds with \(C_2H_5MgI\) is

(I) Methanal

(II) Propan-2-one

(III) Ethanal

(IV) 2,2,4,4-Tetramethylpentan-3-one

Choose the correct answer from the option given below:

I > III > II > IV

The correct answer is option 1. I > III > II > IV.

The reactivity of carbonyl compounds towards nucleophilic addition with C₂H₅MgI depends on:

• Electrophilicity of the carbonyl carbon

• Steric hindrance around the carbonyl group

(I) Methanal (HCHO): Methanal has no alkyl group attached to the carbonyl carbon. Hence, there is no +I effect and no steric hindrance. The carbonyl carbon is highly electrophilic. ∴ Most reactive.

(III) Ethanal (CH₃CHO): Ethanal has one alkyl group which shows +I effect, reducing electrophilicity slightly compared to methanal. However, steric hindrance is still low. ∴ Less reactive than methanal but more reactive than ketones.

(II) Propan-2-one (CH₃COCH₃): It has two alkyl groups, increasing +I effect and steric hindrance, which decreases electrophilicity of the carbonyl carbon. ∴ Less reactive than aldehydes.

(IV) 2,2,4,4-Tetramethylpentan-3-one: This ketone is highly bulky due to four methyl groups near the carbonyl carbon. This creates very high steric hindrance, making nucleophilic attack difficult. ∴ Least reactive. 

Final order of reactivity: Methanal > Ethanal > Propan-2-one > 2,2,4,4-Tetramethylpentan-3-one

Hence, I > III > II > IV