Final answer:
The reactivity order for nucleophilic addition reactions of carbonyl compounds with ethyl magnesium iodide is aldehyde > ketone > ester. Aldehydes are the most reactive due to less steric hindrance, while esters are the least reactive due to steric hindrance and electron-withdrawing effects.
Step-by-step explanation:
The reactivity of carbonyl compounds in nucleophilic addition reactions with ethyl magnesium iodide can be understood by considering the electronic and steric factors affecting the carbonyl carbon. In general, the reactivity order for carbonyl compounds towards nucleophilic addition is aldehyde > ketone > ester.
This is because aldehydes have less steric hindrance and no additional electron-withdrawing groups compared to ketones and esters, making the carbonyl carbon more accessible and electrophilic for nucleophilic attack. Ketones are generally less reactive than aldehydes due to their additional alkyl group which introduces steric hindrance. Esters have both steric hindrance and the electron-withdrawing effect of the alkoxy group, which reduces the electrophilicity of the carbonyl carbon, thus making them the least reactive among the three.