Acids + Bases Flashcards
The Lewis definition concerns itself with the
Transfer of electrons
The Brønsted–Lowry definition focuses on
Proton transfer
An acid–base reaction will only proceed if the products that will be formed are
Weaker than the original reactants
Lewis acids tend to be
Electrophiles
Lewis acids have
Vacant p-orbitals
A Lewis base is defined as an
Electron donor
Ka is given by
Ka = [H][A-] / [HA]
How is the pKa of strongly acidic molecules?
Super small / negative
How is the pKA for basic molecules?
Large
Which pKa values are considered as strong?
Acids with a pK below –2
Weak organic acids often have pKa values between
-2 and -20
The more electronegative an atom, the
Higher the acidity
Which are the main functional groups that act as bases?
Amines and amides
Nucleophiles are defined as
“nucleus-loving” species with either lone pairs or π
bonds that can form new bonds to electrophiles
Good nucleophiles tend to be
Good bases
Nucleophilicity is determined by:
- Charge
- Electronegativity
- Steric Hinderance
- Solvent
Nucleophilicity increases with
Increasing electron / negative charge
Nucleophilicity decreases as
Electronegativity increases
In polar protic solvents, nucleophilicity increases
Down the periodic table
In polar aprotic solvents, nucleophilicity increases
Up the periodic table
What are leaving groups?
The molecular fragments that retain the electrons after
heterolysis
What make good leaving groups?
Weak bases, like conjugate bases of strong acids
Why don’t alkanes and hydrogen ions serve as good leaving groups?
They form very reactive, strongly basic anions
What is necessary in order for the nucleophile to attack?
It must be more reactive than the leaving group
What happens in both S 1 and S 2 reactions?
A nucleophile forms a bond with a substrate carbon and a leaving group leaves
What happens in SN1?
- LG leaves, forming carbocation
- Nucleophile attacks carbocation
In SN1, the rate of the reaction depends on the
Substrate
SN2 only has one step, resulting in
A backside attack
SN2 reactions prefer
Less-substituted reactions
For a reaction involving nucleophiles and electrophiles,
reactions also tend to occur at
The highest-priority functional group because it
contains the most oxidized carbon.
SN2 reactions won’t occur with
3º
Good electrophiles are
Positively charged or polarized
Good leaving groups are
Weak bases
SN1 reactions show first-order kinetics because
The rate-limiting step involves only one molecule
Which alcohols can undergo oxidation?
1º and 2º
Ketones are less reactive compared to aldehydes due to
Steric hinderance
