CHE 230

University of Kentucky

Identify the nucleophilic or basic atom (if there is one)

• An atom that is attached to a metal is likely to be the nucleophilic or basic atom.

• If no metal is present, a negatively charged atom that bears a lone pair is likely to be the nucleophilic or basic atom.

• If no negatively charged atom is present, a neutral atom that bears an acidic H atom may be the nucleophilic atom, especially if it is the solvent or the conditions are basic. (E.g., NH₃, HBr, HCl, H₂O, EtOH, RSH, RCO₂H such as AcOH, RC≡CH, and a C atom adjacent to a C=O group.)

• If no neutral atom bearing an acidic H atom is present, a neutral heteroatom that bears a lone pair may be the nucleophilic or basic atom. (E.g., Ph₃P, Me₂S, Et₃N.)

• A species that is present in only catalytic amounts cannot contain the nucleophilic or basic atom.

• The O atoms in H₂SO₄ and in sulfonic acids such as TsOH, MsOH, and TfOH do not act as nucleophiles.

• Solvents such as benzene, ether, THF, and CH₂Cl₂ are not usually nucleophilic.

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