Acid Base Flashcards
Bronsted definition of an acid/base
Base is proton acceptor
Acid is a proton donor
(think B.A.D)
what does an acid/base reaction involve?
Every acid base reaction will involve the formation and breakage of a bond to hydrogen
How Do We Define and Measure Acidity?
Acidity is defined as the position of the equilibrium between an acid and its conjugate base. We obtain this number through experimental measurement.
what is pka?
pKa = – log Ka
does a strong acid have a high or low pka?
the lower the pka value the stronger the acid.
-10pka>1pka>10pka
What factors make an acid strong or weak?
Generally, the strength of an acid is related to the stability of the conjugate base.
what is the relationship between conjugate base stability & acid strength?
The greater the stability of the conjugate base, the stronger the acid.
The lower the stability of the conjugate base, the weaker the acid.
what is the relationship between conjugate acid/base pairs?
The stronger the acid, the weaker the conjugate base
The weaker the acid, the stronger the conjugate base.
what are the first 4 (most important) factors that stabilise negative charge?
Factor #1: The less charge, the better
Factor #2: Going across the periodic table, greater electronegativity stabilises negative charge.
Factor #3: Going down the periodic table, greater polarizability stabilizes negative charge.
Factor #4: Negative charge is stabilized by resonance, which delocalizes electron density
what are the 3 other factors which can stabilise negative charge?
Factor #5: Negative charge is stabilized by adjacent electron withdrawing groups (inductive effects)
Factor #6: Negative charge is stabilized as the hybridization includes greater s character
Factor #7: A Special case - negative charge is especially stable if the
electrons are part of an aromatic π-system
What makes an acid-base reaction favorable (or not?)
Key principle: In favorable acid-base reactions, a stronger acid adds to a
stronger base to give a weaker acid and a weaker base
How do you tell which acid is stronger or weaker?
A pKa table collates experimental measurements of acidity.
