diethyl bromomalonate

Meaning: Diethyl bromomalonate is diethyl malonate with one α-hydrogen replaced by bromine: BrCH(CO₂CH₂CH₃)₂. The central carbon sits between two ester carbonyls, which gives it two features. The C–Br carbon is an electrophile, and a halide on a carbon next to a carbonyl is displaced readily by SN2 nucleophiles. The one remaining α-H is still acidic (diethyl malonate has a pKa near 13), so a base can form a resonance-stabilized enolate.

On the MCAT: You are not expected to memorize this as a named reagent. It appears in passages built on malonic ester chemistry. Expect to identify it as the electrophile, predict the SN2 product with a nucleophile such as an amine or an enolate, or note that ethoxide is the matching base for ethyl esters because it avoids transesterification. If the product diester is hydrolyzed to the diacid and heated, it loses CO₂ (decarboxylation), as in the standard malonic ester synthesis.

Common confusion: Students carry over the pattern from diethyl malonate, where the central carbon is the nucleophile after deprotonation. The bromine reverses the polarity of that carbon. The fact that settles it: the C–Br carbon carries a partial positive charge and Br⁻ is a good leaving group, so it behaves as an alkyl halide.