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For the MCAT, you can treat most carbonyl analogues, such as S=O or N=O, as you would carbonyls. However, it is quite possible that the MCAT would require you to use your basic knowledge of electronegativity, bond polarity, atomic radius, etc., to predict difference in reactivity between an analogue and a carbonyl.

Properties: The carbonyl double bond is shorter and stronger than an alkene because Comparing to two carbons, a carbon and an oxygen can get closer to one another because oxygen has a smaller atomic radius. This allows for more pi overlap and therefore a stronger bond.

Key Features of Carbonyls:
1) Partial positive charge on the carbonyl carbon: This makes the carbon a good electrophile.

2) Alpha hydrogens: Hydrogens on the alpha carbon are surprisingly acidic—especially given that alkane hydrogens normally CANNOT be removed.

3) Electron donating/withdrawing groups: The reactivity of a carbonyl with a nucleophile is dramatically affected by the presence of electron donating or electron withdrawing groups on the carbonyl carbon. Donating groups decrease the reactivity of the carbonyl carbon and withdrawing groups increase its reactivity.

4) Steric hindrance: Bulky substituents attached to the carbonyl carbon decrease its reactivity.

5) Planar stereochemistry: The sp2 hybridized carbonyl carbon is planar and can therefore be attacked from either side. When the two substituents on the carbonyl carbon are NOT identical, an addition reaction could therefore create both R and S enantiomers in a racemic mixture.

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