Acid and bases Flashcards
1
Q
Theory of acid and bases
A
- Arhennius theory
- Bronsted-lowry theory
- Lewis theory
2
Q
Arhennius theory
A
- Acid produces H+/H3O+ ions
- Bases produces OH- ions
3
Q
Bronsted-lowry theory
A
- An acid is a proton (hydrogen ion) donor.
- A base is a proton (hydrogen ion) acceptor.
4
Q
Lewis theory
A
- An acid is an electron pair acceptor.
- A base is an electron pair donor.
5
Q
There isn’t an empty orbital anywhere on the HCl which can accept a pair of electrons.
Why, then, is the HCl a Lewis acid?
A
- 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
6
Q
pKa table
A
7
Q
Acid-Base reaction overview
A
- 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+
8
Q
What determines acidity?
A
- 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
9
Q
What determines basicity?
A
- Stabilizing a lone pair lowers the basicity;
- Destabilizing the lone pair increases basicity.
10
Q
Acidity trend
- the lesser the charge, the better the acidity
A
All else being equal, the lower the charge density, the more stable a species is.
11
Q
Acidity trend
Polarizability
A
12
Q
Acidity trends
- Electron withdrawing groups
A
13
Q
orbitals
A
14
Q
Acidity trend
aromacity
A
15
Q
What makes a good leaving group?
A
Good leaving groups are weak bases.
16
Q
How do we know which are weak bases?
A
- The stronger the acid, the weaker the conjugate base
- the weaker the conjugate base, the better the leaving group
19
Q
OH- is a bad leaving group
A
21
Q
OH- in SN2 example
A
conjugate acid will always be a better leaving group.
22
Q
Acids helps facillitates cleavage of ether
A
