文档介绍：D. A. Evans Acid-Base Properties anic Molecules Chem 206
Articles on the Acidities anic Molecules
/~chem206/
Lowry & Richardson: 3rd Edition, Chapter 3
Chemistry 206 Acids and Bases
anic Chemistry "Equilibrium acidities in DMSO Solution", F. G. Bordwell.
Acc. Chem. Res. 1988, 21, 456-463.
Here is a web site containing Brodwell pKa data
Lecture Number 17
Acid-Base Properties anic Molecules ■ Problems of the Day:
Explain why 1 and 3 are ~4 pKa units more acidic than their acyclic
■ Bronsted Acidity Concepts in the Activation anic Structures counterparts 2 and 4. (J. Org. Chem. 1994, 59, 6456)
■ Medium Effects on Bronsted Acidity
O
O
■ Substituent & Hybridization Effects on Bronsted Acidity O O
■ O
ic & Thermodynamic Acidity of Ketones 1 2 Me Et 3 HN O 4 Me Et
O N O
■ ic Acidity: Carbon vs. Oxygen Acids
H
■ Tabulation of Acid Dissociation Constants in DMSO
The thermodynamic acidities of phenol and nitromethane are both
■ Reading Assignment for this Lecture:
~10; however, using mon base, phenol is deprotonated 10+6
Carey & Sundberg: Part A; Chapter 7 times as fast. Rationalize
Carbanions & Other Nucleophilic Carbon Species
Base
pKa(H2O) O O
"Equilibrium acidities in DMSO Solution", F. G. Bordwell. ~10 +6
Acc. Chem. Res. 1988, 21, 456-463. H rel rate: 10
Monday,
Matthew D. Shair O O
October 28, 2002 pKa(H2O) Base
~10 H3C N H2C N
O rel rate: 1 O
D. A. Evans Acidity Concepts-1 Chem 206
■ Definition of Ka
Activation anic Molecules
Let H–X be any Bronsted acid. In water ionization takes place:
+
■ Base Activation H–X + HOH H3O + X–
R1 R1
base + –
[H O ] [X ] -1
C H C Nucleophile where Keq = 3 where [HOH] = mol L (A)
[H–X] [HOH]
R2 - H-base R2
R3 R3
Since [HOH] is, for all practical purposes, a constant value, the acid
dissociation constant Ka is defined wilthout regard to this entity. .
pK , describes quantitatively