QO323

Química Orgânica I(Engenharia Química)

MARCOS N. EBERLIN

Acidez e BasicidadeAcidez e Basicidade

AcidezOH

< R OH

O

< HClR-OH <R-H <

pKa ~ 50

R-NH2

pKa ~ 37

<

pKa ~ 16pKa ~ 50

pKa ~ 10pKa ~ 4

pKa ~ -7pKa ~ 37

48p =

+

aK

δ-δ

3 H

CH

38p =

+

aK

δ-δ

2 H

NH

15,7p =

+

aK

δ-δ

H

OH

3,2p =

+

aK

δ-δ

H

F

Aumento da Acidez

Differences in acid strengths between carboxylic acids,

phenols and alcohols The factors to consider

Two of the factors which influence the ionisation of an acid

are:

1. the strength of the bond being broken,

2. the stability of the ions being formed.

pKa = -1,9

pKa

HCOOH 3.75

CH3COOH 4.76

CH3CH2COOH 4.87

CH CH CH COOH 4.82CH3CH2CH2COOH 4.82

pKa

CH2FCOOH 2.66

CH2ClCOOH 2.86

CH2BrCOOH 2.90

CH2ICOOH 3.17

Basicidade