An important class of substitution reactions that you will study in Chapter 21 is called nucleophilic acyl substitution. Substitution reactions of this type occur at the carbon of a carbonyl (C = O) group. An important laboratory example is the reaction of nucleophiles (ammonia in the example below) with acyl chlorides (also called acid chlorides).

The corresponding derivatives found in biology are acyl phosphates. Draw the general structure of an acyl phosphate. Be sure to show its ionization state at physiological pH. Show how Mg²⁺ ions or hydrogen-bond-donating groups in an enzyme active site might enhance the reactivity of acyl phosphates.

Transcribed Image Text:

R-C-Cl + NH3 an acyl chloride R-C-NH₂ + H-Cl