Chapter 3: An Introduction to Organic Reactions: Acids and Bases CH 3-1: Bronsted acids & bases; Conjugate acids & bases Chapter Summary: CH 3-1: Bronsted acids & bases; Conjugate acids & bases CH 3-2: Acid/Base equilibrium; pKa’s CH 3-3: Acid/Base reactions and mechanisms CH 3-4: Predicting acid strength: Periodic Table trends, Hybridization, Resonance and Inductive effects CH 3-5: Acid/Base Structure: pH vs pKa CH 3-6: Acid-Base exchange reactions

Defining Bronsted Acids and Bases A chemical species that forms hydronium ion (H3O+) in aqueous solution; A species that gives up a proton (“H+”) to a base; An acid may be neutral or positively charged (rarely negatively charged): NH3 H2O “HX” H2SO4 HF H3O+ NH4+ H3PO4 HCl R-OH HNO3 HBr R-OH2+ HI

Conjugate Acid-Base Pairs In all Acid-Base reactions, we see the formation of Conjugate Pairs that differ only in the location of an H+: acid base conj. base conj. acid

Conjugate Acid-Base Pairs B CA B CA A CB A CB

Defining Bronsted Acids and Bases Bronsted Base: A species with a lone electron pair that can “grab” (accept) a proton (H+) from an acid; A base may be neutral or negatively charged (rarely positively charged): NH2ˉ HOˉ Xˉ HSO4ˉ Fˉ H2O NH3 H2PO4ˉ Clˉ R-Oˉ NO3ˉ Brˉ R-OH Iˉ CONJUGATE BASES of the corresponding acids!