5D: Reactivity & Functional Groups

What laboratory acyl derivative is most reactive in nucleophilic acyl substitution?

Acid chloride; it is the most reactive acyl derivative.

How does an anhydride compare with an ester in nucleophilic acyl substitution reactivity?

Anhydride is more reactive than an ester.

What is the halogen anomaly in electrophilic aromatic substitution?

Halogens deactivate the ring but still direct ortho/para.

Which substituents deactivate a benzene ring and direct electrophilic aromatic substitution meta?

$-N{O}_2$, $-CN$, $-S{O}_{3}H$, $-COOH$, and $-COR$.