Chem Idea 4

conjugate base

species that remains after an acid has donated a proton

ARIO

atom (type), Resonance, Induction, Orbital (type)

The type of atom that carries the charge

Draw the conjugate base of the compounds you’re looking at. Then consider the atom that is attached to the proton: 

1. the larger the atom, the more stable the negative charge (going down group) 

2. the more EN an atom, the more stable the neg charge (across the PTE)

consider size first, then EN

If there is Resonance 

it stablizes the negative charge (i.e.) by stretching it out across multiple atoms 

• conj. base having resonance = products more stable, original struct. stronger acid 

Induction

stabilizes the negative formal charge by spreading it out

• different from electronegative because it doesn’t actually give up LP’s

• more EN = more induction and lower pka

1. More electron withdrawing groups = more stable conj. base

2. Closer e- withdrawing groups to negative charge = more stable conj. base

the type of orbital affects

the stability of the formal negative charge

• the closer the e- to the nucleus, the more stable

• shorter AO = lone pairs closer to the nucleus

Predicting favored side at equilibrium

1) higher pKa of H-B or H-A will be more stable 

2) relative stability of the bases, B- and A- (ARIO)

Counter ions

also called spectator ions

always present in reaction becus they balance out the overall charge of the solution

• often not written in rxn (separate compounds and cancel out atom that doesn’t change charge in r vs p)

• often cations - metals

Acid

proton donor

anything with a H+ can be potentially act as an acid

Base

proton acceptor

anything with a lone pair that can accept H+ that act as base

Acidity

tendency of compound that has an H+ to give it up

proton transfer

acid-base reaction

shown using curved arrows that start at the base lone pair, go to the hydrogen, and show the breaking of the bond attached to the H

lower pKa

stronger acid, H+ held more tightly

pKa vs Ka

lower pKa = productors favored (high Ka), more acidic

high pKa = reactants favored, less reactive (low Ka), less acidic

the reaction always preceeds

toward the lower energy/more stable/favored species