ASAM
KARBOKSILAT
PENDAHULUAN





ASAM KARBOKSILAT ADALAH SENYAWA YANG
MEMILIKI GUGUS FUNGSI C=O DAN -OH YANG
TERIKAT PADA SATU ATOM KARBON
GUGUS KARBOKSIL DITULISKAN SBB :
-COOH.
ASAM KARBOKSILAT ALIFATIK MEMILIKI GUGUS
ALKIL YANG TERIKAT PADA -COOH.
ASAM KARBOKSILAT AROMATIK MEMILIKI GUGUS
ARIL.
ASAM LEMAK ADALAH ASAM KARBOKSILAT ASAM
KARBOKSILAT ALIFATIK YANG BERANTAI PANJANG.
=>
2
ASAM KARBOKSILAT
Karbonil
O
R
Apa
istimewanya?
C
Hidroksil
OH
Contoh-contoh senyawa asam karboksilat
O
OCCH
O
CH C
Aspirin
(CH ) CO H
H
OH
OH
CO H
O
Asam asetat (asam cuka)
C
H
C
H
(CH ) CH
C
H
OH
Prostalandin E (PGE )
Suatu moderator aktivitas hormon
Cari contoh lain sebanyak-banyaknya!!!
Carboxylic Acids
Nomenclature
Properties
 Preparation reactions
 Typical reactions

Nomenclature

Carboxylic acids
»IUPAC
»Common
Tatanama asam Karboksilat
a.Nama IUPAC
Untuk asam Karboksilat “alifatik”
alkana induk huruf akhir “a” menjadi “oat”. (Inggris: -e menjadi –oic acid)
Jangan lupa! Depannya diberi “asam”
Contoh :
CH4 : Metana
HCO2H : asam metanoat
Penomoran
Cl
CH CHCO H
HO CCH CO H
Contoh Soal: tulis nama IUPAC-nya
CH
CH =CHCO H
BrCHCO H
HO CCH CH CH CO H
b. Nama trivial
CH
BrCHCO H
Penomoran

CH CH CH CO H Seperti aldehid
dan keton


Berilah nama senyawa senyawa
a)
CH CH CHCO H
b) CH CH CH-CHCO H
CH CH
CH
d) CH CH CHCO H
OH
Br
CH
COOH
NO
CO H
e) CH CHCO H
CH CH CO H
CH
Cl
CH CH CH CO H
Cl
COONa
CCH CO H
CH -CH-COOK
NO
(CH COO) Ca
Br
Br
HCOONH
20.2 Structure and Physical Properties
of Carboxylic Acids


Carboxylic acids form hydrogen bonds, existing as cyclic
dimers held together by two hydrogen bonds
Strong hydrogen bonding causes much higher boiling
points than the corresponding alcohols
20.3 Dissociation of Carboxylic
Acids


Carboxylic acids are proton donors toward weak and
strong bases, producing metal carboxylate salts, RCO2 +M
Carboxylic acids with more than six carbons are only
slightly soluble in water, but their conjugate base salts are
water-soluble
Acidity Compared to Alcohols


Carboxylic acids are better proton donors than are alcohols
(The pKa of ethanol is ~16, compared to ~5 for acetic acid)
In an alkoxide ion, the negative charge is localized on
oxygen while in a carboxylate ion the negative charge is
delocalized over two equivalent oxygen atoms, giving
resonance stabilization
20.4 Substituent Effects on
Acidity

Electronegative substituents promote formation of the
carboxylate ion
Substituent Effects


An electronegative group will drive the ionization
equilibrium toward dissociation, increasing acidity
An electron-donating group destabilizes the carboxylate
anion and decreases acidity
Examples of Inductive Effects on
Acidity


Fluoroacetic, chloroacetic, bromoacetic, and iodoacetic
acids are stronger acids than acetic acid
Multiple electronegative substituents have synergistic
effects on acidity
20.5 Substituent Effects in
Substituted Benzoic Acids
RCOOH Preparation Reactions
Oxidation of Primary Alcohols
 Oxidation of Aldehydes
 Oxidation of Substituted Aromatics
 Carbonation of Grignard reagents
 Hydrolysis of Acid derivatives and Nitriles
 Haloform reaction
 Periodic acid Cleavage of Vicinal
Dials/Diketones
 Oxidative Cleavage of Alkenes/Alkynes

Carboxylic Acids via Oxidation
 From
Primary Alcohols
 From Aldehydes
 From Substituted Aromatics
KMnO 4
or
K 2Cr 2O 7
²
KMnO 4
R C H
or
K 2Cr 2O 7
O
²
KMnO 4
R
or
K 2Cr 2O 7
²
RCH 2OH
RCOOH
RCOOH
COOH
Carbonation of
Grignard Reagents

O
R
C
Mg
O
X
+
O
+
O
H
R C OMgX
R C OH
H 2O
Hydrolysis of Acid Derivatives and Nitriles
+
H
R C G
R C OH + HG
H 2O
O
O
OH R C O - + GR C G
H 2O
O
O
where G = -X,- OR, -NH 2 , - NHR, NR
2
, &- O C R
O
H + or OH RC N
R C NH
H 2O
O
2
R C OH ( R C O )
O
O
Haloform Reaction
Cleavage of methyl carbinols
Cleavage of methyl carbonyls
H
CH 3
C R
OH
CH 3 C R
O
X2
-
OH /H 2O
X2
-
OH /H 2O
-
RCOO + HCX 3
-
RCOO + HCX 3
Periodic Acid Cleavage of
Vicinal Dials/Diketones
H C C H
O O
R C C H
O O
R C C R'
O O
HIO 4
HIO 4
HIO 4
2 HCOOH + HIO 3
RCOOH + HCOOH + HIO 3
RCOOH + R'COOH + HIO 3
Oxidative Cleavage Reactions
Alkene
Cleavage
Hot Potassium Permanganate
Alkyne
Cleavage
Hot Potassium Permanganate
Ozonolysis
HO
O
R
HC
CH
R'
KMnO 4
R
+
C
OH
HC
CH
R'
ozonolysis or
KMnO 4
R
OH
C
R'
HO
+
C
R'
O
O
R
C
O
Typical RCOOH reactions







Conversion to carboxylate salts
Conversion to acid halides
Conversion to esters
Conversion to amides
Conversion to anhydrides
Reduction to alcohols
Decarboxylation
Carboxylates from Carboxylic Acids
 Reaction
with Active Metals
 Reaction with Strong Base
 Reaction with Weak Base
RCOOH
RCOOH
RCOOH
Na
o
Na OH
RCOO - Na + +
RCOO - Na + + H 2O
-
Na HCO
RCOO Na
3
1
2H2
+
+ H 2O + CO 2
Reduction of Carboxylic Acids
 Lithium
Aluminum Hydride reduction
 Diborane reduction
RCOOH
RCOOH
LiAlH
ether
4
B 2H 6
diglyme
H+
H 2O
RCH 2OH
RCH 2OH
(selective reduction of
carboxyl group in
preference to carbony l
of aldehydes/ketones)
Decarboxylation of RCOOH
 Thermolysis
of beta-diacids
 Thermolysis of beta-keto acids
COOH
C
COOH
H
²
COOH
COOH
C
C
O
+ CO 2
C
H
²
+ CO 2
C
C
O