Acid and bases

• Arhennius theory • Bronsted-lowry theory • Lewis theory

• Acid produces H+/H3O+ ions • Bases produces OH- ions

• An acid is a proton (hydrogen ion) donor. • A base is a proton (hydrogen ion) acceptor.

• An acid is an electron pair acceptor. • A base is an electron pair donor.

• HCl is polar. Chlorine is more electronegative than hydrogen, leaving the hydrogen slightly positive and the chlorine slightly negative. • Lone pair on the nitrogen of an ammonia molecule is attracted to the slightly positive hydrogen atom • e- are slowly pushed towards chlorine, HCl bond breaks and dative/coordinate bond is formed

• • The species which loses H+ is the acid • The species which gains H+ is the base • The conjugate base is what becomes of the acid after it loses H+ • The conjugate acid is what becomes of the base after it gains H+

• any factor which stabilizes the conjugate base will increase the acidity. • any factor which destabilizes the conjugate base will decrease the acidity. • a roughly equivalent word for “stability” is “basicity

• Stabilizing a lone pair lowers the basicity; • Destabilizing the lone pair increases basicity.

All else being equal, the lower the charge density, the more stable a species is.

Good leaving groups are weak bases.

• The stronger the acid, the weaker the conjugate base • the weaker the conjugate base, the better the leaving group

conjugate acid will always be a better leaving group.