Chapter 21
Nomenclature:
Highest precedence at the top
Functional Group
Carboxylic acid
Aldehyde
Ketone
-COOH
-CHO
Alcohol
thiol
Amine
-OH
-SH
-NH2
O
Suffix if Higher
in Precedence
-oic acid
-al
-one
Prefix if lower in
Precedence
oxooxo-
-ol
-thiol
-amine
hydroxy-sulfanyl
-amino
Naming Aldehydes:
Remove the –e add an al ending. Common names: formaldehyde, acetaldehyde, benzaldehyde.
O
O
H
O
H
Acetaldehyde (ethanal)
H
O
H
5-hexenal
2-phenylpropanedial
Carboxyllic acids take precedence over aldehydes. You can also name aldehydes off rings.
O
O
OH
H
O
H
O
O
OH
H
4-Formyl-hexanoic acid
5-Oxo-pentanoic acid
Cyclopentanecarbaldehyde
Naming ketones:
Remove the –e add an one ending. Common names: acetone, acetophenone, benzophenone.
Alternate common system: Name one side, then the other and then add “ketone”
O
O
O
O
2-butanone
4-Ethyl cyclohexanone
Methyl ethyl ketone (MEK)
2, 4-hexanedione
Carboxyllic acids and aldehydes take precedence over ketones.
O
O
O
O
O
OH
H
3-Oxo-hexanoic acid
3-Oxo-hexanal
1-Cyclopentyl-ethanone (?)
Preparation
p742
The Wittig reagent, converts ketones to alkenes.
Preparation of the reagent:
Ph
PPh3
H3C Br
Ph
H
+
Ph
BuLi
P C H BrPh H
+
Ph
+ butane
P C H
Ph H
+ LiBr
The Wittig reaction
O
H2C PPh3
+
Ph3P C
HH
Ph Ph
Ph P+
O
Ph Ph
Ph P
Ph3PO
O
The Wittig can produce both cis and trans isomers although there are some conditions where
mostly the cis is obtained and other conditions where trans is the predominant product.
CH3CH PPh3
O
+
H
H
H
Acetal and Hemiacetal formation, Nucleophillic addition, Acidic conditions.
MeO OH
O
MeO OMe
CH3OH
H
CH3OH
H
+
H3C O OMe
H
H
+
+
H3C O OH H3C O
O
H3C
+
O H
O
HOCH3
+
CH3OH
Sugars react to form acetals.
OH
O
H
OH
H+
O
Acetals can be used as protecting groups for ketones and aldehydes.
H+, H2O
O
H+
OH
OH
O
O
Water can react with ketones in a similar way.
H+, H2O
HO OH
O
Reactions with amines. (Nucleophillic addition under buffered conditions)
Primary amines form imines or Schiff bases.
O
CH3NH2
NCH3
mild acid
CH3NH2
+
H OH2
H H+
H3C N O
H
H
+
H3C N
H
H3C N OH
H3C N
H
+
O H
Secondary amines for enamines.
O
(CH3)2NH
H3C
N
CH3
mild acid
H2O
+
H OH2
(CH3)2NH
H3C H+
H3C N O
CH3
H3C N OH
Addition of Cyanide
OH
NaCN, H2O
O
then H2SO4
H3C C CH3
CN
-:CN
H C N
O
H3C C CH3
CN
CH3
+
H3C N
CH3 H
H3C N
+
O H
H