(Aldol, benzoin, +I, -I, decreases, increases, cyanohydrin, lactic acid, tartaric acid, yellow, white, acetone, penta-3-one, `PCl_(3)`, PCl, benzal chloride, methanol, propanoic acid, ethanol, KOH, KCN, `alpha`-hydrogen atoms, no `alpha`-hydrogens, Cannizzaro's, absence, presence)
An alkyl group attached to the carbonyl group exerts effect and thus .............the reactivity of carbonyl group.

Explanation

To solve the question regarding the effect of an alkyl group attached to a carbonyl group on its reactivity, we can break it down into the following steps:

### Step 1: Understanding the Carbonyl Group
The carbonyl group (C=O) is a functional group found in aldehydes and ketones. The carbon atom in the carbonyl group is sp² hybridized, making it relatively electrophilic due to the presence of a partial positive charge.

**Hint:** Recall that the carbonyl carbon is more electrophilic than the carbon atom in an alkane due to the double bond with oxygen.

### Step 2: Identifying the Effect of Alkyl Groups
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