Chapter 3- Acids and Bases

a Bronsted-Lowry acid is what and a base is?

acid- proton donor
base- proton acceptor

the mechanism of proton transfer always involves how many curved arrows?

2

a strong acid has a _____ pKa and a weak acid has a ______ pKa?

strong- low pKa
weak- high pKa

a Bronsted-Lowry acid-base reaction always produces which 2 things?

1. conjugate acid
2. conjugate base

equilibrium always favors formation of what in an acid-base reaction?

formation of the weaker acid (higher pKa)

how can relative acidity be determined?

by analyzing conjugate base
(stable A?= strong acid; unstable A?= weak acid)

what are the 5 factors when comparing conjugate bases?

1. Charge
2. Atom holding proton
3. Resonance
4. Induction
5. Orbitals

when comparing conjugate bases, elements in the same row are determined how and in the same column?

row- electronegativity
column- size

what is induction?

electron-withdrawing groups stabilize nearby negative charges (ie. halogens)

in orbitals, a negative charge is more stable where?

in a sp-orbital (closer to the nucleus)

the equilibrium of an acid-base reaction always favors the more _________ _______ charge?

stabilized negative charge

negatively charged bases are always accompanied by what?

positive cations

a Lewis acid is what and a Lewis base is?

acid- electron acceptor
base- electron donor

what are the 3 steps to drawing a proton transfer?

1. id acid and base
2. draw 1st curved arrow (tail on lone pair of base and head on proton from acid)
3. draw 2nd curved arrow (tail on bond and head on atom- creates lone pairs)

what 3 steps can be used for pKa to compare basicity?

1. draw conjugate acid
2. compare pKa values
3. identify stronger base (weaker acid generates stronger base)

what are the 2 steps for using pKa to predict the position of equilibrium?

1. identify acid on each side of reaction
2. compare pKa values
(equilibrium favors weaker acid)

what 3 steps are used for assessing relative stability? (atom factor)

1. draw conjugate base
2. compare location of charge by 2 trends (electronegativity and size)
3. determine more stable conjugate base (the more acidic proton)

what 3 steps are used for assessing relative stability?
(resonance factor)

1. draw conjugate base
2. look for resonance stabilization
3. determine the more stabilize conjugate base (the one with more resonance)

what 3 steps are used for assessing relative stability?
(induction factor)

1. draw conjugate base
2. look at inductive effects
3. determine more stabilize conjugate base (the one closer to the electron-withdrawing groups like halogens)

what 3 steps are used for assessing relative stability?
(orbital factor)

1. draw conjugate base
2. analyze orbitals
3. determine more stabilize conjugate base (the one closer to the nucleus sp>sp�>sp�)

what 3 steps are used for predicting position of equilibrium without using pKa?

1. id base on both sides of reactions
2. compare stability of conjugate base using all 5 factors (CARIO)
3. equilibrium will favor more stable base

what 3 steps are used to chose the appropriate reagent for a proton transfer reaction?

1. draw equilibrium and id base on both side of reaction
2. compare stability of conjugate bases using all 5 factors (CARIO)
3. equilibrium will favor more stable base
(products favored= useful reaction; reactants favored= reaction is not useful)

what 2 steps are involved in determining Lewis acid-bases?

1. id direction of flow of electrons
2. electron acceptor= Lewis acid
electron donor= Lewis base

when dealing with cario, the comparision between resonance and induction will produce what?

resonance beats induction so that proton will always be more stable