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Before you can learn about aldehydes and ketones, you
must first know something about the nomenclature of
carboxylic acids since many of the names of aldehydes
and ketones are derived from the names of the
corresponding carboxylic acids.

R-COOH, R-CO2H,
 Common names:
 HCO2H
 CH3CO2H
 CH3CH2CO2H
formic acid L. formica ant
acetic acid L. acetum vinegar
propionic acid
G.
“first salt”
 CH3CH2CH2CO2H
butter
 CH3CH2CH2CH2CO2H
butyric acid L. butyrum
valeric acid L. valerans
Carboxylic
acids,
common
names
 CH3(CH2)4CO2H
caproic acid L. caper






goat
CH3(CH2)5CO2H
CH3(CH2)6CO2H
CH3(CH2)7CO2H
CH3(CH2)8CO2H
CH3(CH2)9CO2H
CH3(CH2)10CO2H
--caprylic acid
--capric acid
--lauric acid oil of lauryl
5 4 3 2 1
C—C—C—C—C=O
δ γ β α used in common names
IUPAC nomenclature for carboxylic acids:
 parent chain = longest, continuous carbon chain that contains
the carboxyl group
 HCOOH
 CH3CO2H
 CH3CH2CO2H

CH3
 CH3CHCOOH
alkane, drop –e, add –oic acid
methanoic acid
ethanoic acid
propanoic acid
2-methylpropanoic acid

Br
 CH3CH2CHCO2H 2-bromobutanoic acid
dicarboxylic acids
:
 HOOC-COOH
 HO2C-CH2-CO2H
 HO2C-CH2CH2-CO2H
 HO2C-CH2CH2CH2-CO2H
 HOOC-(CH2)4-COOH
 HOOC-(CH2)5-COOH
oxalic acid
malonic acid
succinic acid
glutaric acid
adipic acid
pimelic acid
salts of carboxylic acids:
 name of cation + name of acid: drop –ic acid, add –ate
 CH3CO2Na sodium acetate
or sodium ethanoate
 CH3CH2CH2CO2NH4

 (CH3CH2COO)2Mg

ammonium butyrate
ammonium butanoate
magnesium propionate
magnesium propanoate
physical properties:





polar + hydrogen bond relatively high mp/bp
water insoluble
exceptions: four carbons or less
acidic turn blue litmus red
soluble in 5% NaOH
RCO2H + NaOH → RCO2-Na+ + H2O

stronger
stronger
weaker
weaker

acid
base
base

acid



RCO2H
covalent
water insoluble
RCO2ionic
water soluble
 Carboxylic acids are insoluble in water, but soluble in 5%
NaOH.
 Identification.
 Separation of carboxylic acids from basic/neutral organic
compounds.

The carboxylic acid can be extracted with aq. NaOH
and then regenerated by the addition of strong acid.
Carboxylic acids, syntheses:
1. oxidation of primary alcohols

 2.

RCH2OH + K2Cr2O7  RCOOH
oxidation of arenes
ArR + KMnO4, heat  ArCOOH
 3.
carbonation of Grignard reagents

RMgX + CO2  RCO2MgX + H+  RCOOH
 4.
hydrolysis of nitriles

RCN + H2O, H+, heat  RCOOH
oxidation of 1o alcohols:
 CH3CH2CH2CH2-OH

n-butyl alcohol

1-butanol
+
CrO3

CH3
 CH3CHCH2-OH + KMnO4
 isobutyl alcohol
 2-methyl-1-propanol`
methylpropanoic acid
CH3CH2CH2CO2H
butyric acid
butanoic acid
CH3
CH3CHCOOH
isobutyric acid
2-
oxidation of arenes:
note: aromatic
acids only!
carbonation of Grignard reagent:
 R-X
RMgX
RCO2MgX
RCOOH
 Increases the carbon chain by one carbon.

Mg
 CH3CH2CH2-Br
CH3CH2CH2COOH
 n-propyl bromide
acid
CO2 H+
CH3CH2CH2MgBr
butyric
Hydrolysis of a nitrile:






H2O, H+
R-C N
R-CO2H
heat
H2O, OHR-C N
R-CO2- + H+
R-CO2H
heat
 R-X + NaCN → R-CN + H+, H2O, heat → RCOOH
 1o alkyl halide
 Adds one more carbon to the chain.
 R-X must be 1o or CH3!
carboxylic acids, reactions:
 as acids
 conversion into functional derivatives






a) acid chlorides
b) esters
c) amides
reduction
alpha-halogenation
EAS







as acids:
with active metals
RCO2H + Na
RCO2-Na+ + H2(g)
with bases
RCO2H + NaOH
RCO2-Na+ + H2O
relative acid strength?
CH4 < NH3 < HC CH < ROH < HOH < H2CO3 < RCO2H <
HF
 quantitative

HA + H2O
H3O+ + Aionization in
water

Ka = [H3O+] [A-] / [HA]






Ka for carboxylic acids ~ 10-5
Why are carboxylic acids more acidic than alcohols?
ROH + H2O ↔ H3O+ + RORCOOH + H2O ↔ H3O+ + RCOOΔGo = -2.303 R T log Keq
The position of the equilibrium is determined by the free
energy change, ΔGo.
 ΔGo = ΔH - TΔS
 ΔGo ~ ΔH
Ka is inversely related to ΔH, the
potential energy difference between the acid and its
conjugate base. The smaller the ΔH, the larger the Ka and
the stronger the acid.
The smaller the ΔH, the more the
equilibrium lies to the right, giving a larger
Ka ( a stronger acid ).
Resonance stabilization of the carboxylate ion
decreases the ΔH, shifts the ionization in water to
the right, increases the Ka, and results in
carboxylic acids being stronger acids.
 Effect of substituent groups on acid strength?




CH3COOH
ClCH2COOH
Cl2CHCOOH
Cl3CCOOH
1.75 x 10-5
136 x 10-5
5,530 x 10-5
23,200 x 10-5
 -Cl is electron withdrawing and delocalizes the negative
charge on the carboxylate ion, lowering the PE, decreasing
the ΔH, shifting the ionization to the right and increasing
acid strength.
acids?
 Electron withdrawing groups will stabilize the anion,
decrease the ΔH, shift the ionization to the right,
increasing the Ka, increasing acid strength.
 Electron donating groups will destabilize the anion,
increase the ΔH, shift the ionization in water to the
left, decreasing the Ka, decreasing acid strength.














-NH2, -NHR, -NR2
-OH
-OR
-NHCOCH3
-C6H5
-R
-H
-X
-CHO, -COR
-SO3H
-COOH, -COOR
-CN
-NR3+
-NO2
electron donating
electron withdrawing
 Relative acid strength?








Ka
p-aminobenzoic acid
p-hydroxybenzoic acid
p-methoxybenzoic acid
p-toluic acid
benzoic acid
p-chlorobenzoic acid
p-nitrobenzoic acid
1.4 x 10-5
2.6 x 10-5
3.3 x 10-5
4.2 x 10-5
6.3 x 10-5
10.3 x 10-5
36 x 10-5
Conversion into functional derivatives:
acid chlorides

esters

“direct”




esterification:
H+
RCOOH + R´OH ↔ RCO2R´ + H2O
-reversible and often does not favor the ester
-use an excess of the alcohol or acid to shift equilibrium
-or remove the products to shift equilibrium to completion
 “indirect” esterification:

RCOOH + PCl3 →RCOCl + R´OH
RCO2R´

-convert the acid into the acid chloride first; not reversible
 amides
 “indirect” only!
 RCOOH + SOCl2

RCOCl + NH3
RCONH2
amide
 Directly reacting ammonia with a carboxylic acid results in
an ammonium salt:

RCOOH + NH3 → RCOO-NH4+

acid
base
Reduction
 :


RCO2H + LiAlH4; then H+ → RCH2OH
1o alcohol
 Carboxylic acids resist catalytic reduction under normal conditions.

RCOOH + H2, Ni →NR
Alpha-halogenation
 Alpha-halogenation: (Hell-Volhard-Zelinsky reaction)




RCH2COOH + X2, P → RCHCOOH + HX
X
α-haloacid
X2 = Cl2, Br2
directing)
spectroscopy:
 spectroscopy:
 IR:
-COOH
3000 cm-1 (b)

O—H stretch
C=O stretch

 nmr: -COOH
10.5 – 12 ppm
2500 –
1680 – 1725 (s)







Carboxylic acids, syntheses:
oxidation of primary alcohols
RCH2OH + K2Cr2O7 → RCOOH
2. oxidation of arenes
ArR + KMnO4, heat → ArCOOH
3. carbonation of Grignard reagents
RMgX + CO2 → RCO2MgX + H+ →
RCOOH
 4. hydrolysis of nitriles

RCN + H2O, H+, heat → RCOOH
 carboxylic acids, reactions:
 as acids
 conversion into functional derivatives






a) acid chlorides
b) esters
c) amides
reduction
alpha-halogenation
EAS