Left side: the nucleophile is an amine, the electrophile is the methyl carbon, and the leaving group is a sulfide.
Right side: The nucleophile is a thiolate ion, the electrophile is the carbon atom of an alkyl diphosphate, and diphosphate is the leaving group.
b) In step 1, the nucleophile is the hydroxide oxygen, and the electrophile is the carbonyl carbon of the thioester.
f) Bold dots show the two carbons that form a new bond in this reaction step.
The C to D step has the highest activation energy, and thus is the slowest, rate-determining step.
- Organic Chemistry With a Biological Emphasis, Tim Soderberg (University of Minnesota, Morris)