Which of the following indicators is commonly used to visualize bands of amino acids?

A) ninhydrin
B) bromocresol green
C) potassium permanganate
D) vanillin dip

Esters and amides are most easily made by nucleophilic acyl substitution reactions on ________.

A) alcohols.
B) acid anhydrides.
C) carboxylates.
D) carboxylic acids.
E) acid chlorides.