Concept Summary

Acids and Bases

Nucleophiles, Electrophiles, and Leaving Groups

Lewis   acids   are electron    acceptors;  they    have    vacant  orbitals    or  positively  polarized   atoms.

Lewis   bases   are electron    donors; they    have    a   lone    pair    of  electrons   and are often   anions.

Brønsted–Lowry  acids   are proton  donors; Brønsted–Lowry  bases   are proton  acceptors.

Amphoteric  molecules   can act as  either  acids   or  bases,  depending   on  reaction    conditions. Water

is  a   common  example of  an  amphoteric  molecule.

The acid    dissociation    constant,   Ka, is  a   measure of  acidity.    It  is  the equilibrium constant

corresponding   to  the dissociation    of  an  acid,   HA, into    a   proton  (H+)    and its conjugate   base    (A–).

pKa is  the negative    logarithm   of  Ka. A   lower   (or even    negative)   pKa indicates   a   stronger    acid.

pKa decreases   down    the periodic    table   and increases   with    electronegativity.

Alcohols,   aldehydes,  ketones,    carboxylic  acids,  and carboxylic  acid    derivatives are common  acidic

functional  groups. α-hydrogens (hydrogens  connected   to  an  α-carbon,   a   carbon  adjacent    to  a

carbonyl)   are acidic.

Amines  and amides  are common  basic   functional  groups.

Nucleophiles    are “nucleus-loving”    and contain lone    pairs   or  π   bonds.  They    have    increased

electron    density and often   carry   a   negative    charge.

Nucleophilicity is  similar to  basicity;   however,    nucleophilicity is  a   kinetic property,   while

basicity    is  thermodynamic.

Charge, electronegativity,  steric  hindrance,  and the solvent can all affect  nucleophilicity.

Amino   groups  are common  organic nucleophiles.

Electrophiles   are “electron-loving”   and contain a   positive    charge  or  are positively  polarized.