Aldehydes, Ketones, and
carboxylic acids
Aldehydes
O
R
H
The term Aldehyde come for the
words alcohol dehydrogenation.
Carbonyl group
Preparation: Oxidation of primary alcohols
according to the following equation:
R
OH + [O]
R
O
 Note: Oxidation can be considered as removal of hydrogens.
 [O] can be obtained from oxidazing agents such as
KMnO4,KCr2O7,CuO.
Aldehydes
 Examples:
OH
H
Methyl alcohol
O
H
+ [O]
Formaldehyde H
H
OH
H3C
Ethyl alcohol
O
H3C
+ [O]
Acetaldehyde H
H
O
CH3
H
+ [O]
Toluene
Benzaldehyde
Aldehydes
Note:
The formation of acetaldehyde in the liver is
partailly responsible for liver cirrhosis.
The formation of formaldehyde and ist
oxidation product formic acid are responsible
for the systematic toxicity of methyl alcohol
(methanol).
The side chain in toluene is more susceptible
to oxidation than the benzne ring.
IUPAC Nomenclature of Aldehydes
 The aldehyde group is always at the end of the
chain (carbon 1)
 Aldehydes end in al
 Take the name of the longest chain cotaining the
aldehyde group
 Drop the ending e and replace it by al
Br
H3C
CH3
O
H3C H3C
6-bromo-5,7-dimethyloctanal
H3C
O
Cl
Br
3-bromo-5-chloro-4-methylhexanal
IUPAC Name
Common Name
Methanal
Formaldehyde
Ethanal
Acetaldehyde
Propanal
Propionaldehyde
2-Methylpropanal
Isobutyraldehyde
Uses of aldehydes
O
H
O
O
H
H
OH
OCH3
Formaldehyde
Vanillin
Cinnamic adehyde
 40% Formaldehyde in water (Formalin): used for
disinfection of excerta, rooms, clothing (Mechanism:
hardening of proteins), in embalming (‫ )التحنيط‬water,
and as preservative for biological specimens.
 Benzaldehyde: preparation of flavoring agents,
parfums, drugs, and dyes.
 Vanilllin (Vanilla beans) and cinnamic aldehyde
(cinnamon bark): flavoring agents.
Tests of aldehydes
 Adehydes are good reducing agents.
 Glucose contains an aldehyde group. Therefore, it can
react as an aldehyde, and can be detected in urin using
special solutions such as Benedicts, Fehlings, or Tollens
reagent.
Reactions of aldehydes
 Oxidation:  Acid
O
O
R
+
[O]
R
OH
H
 Reduction:  Alcohol
O
R
+ [H]
H
OH
R
H
Examples:
H3C
Ethanal
O + [H]
O
H3C
Ethanol OH
OH
+ [H]
Benzaldehyde
Benzylalcohol
Reactions of aldehydes
Biological oxidation-reduction reactions in
the are crried out in the body by substances
called coenzymes. One coenzyme is
NAD+(Nicotinamide Adenine Dinucleotide)
H3C
OH
+ NAD+
H3C
O + NADH
Ketones
Secondary alcohol  oxidation  ketone
CH3 + [O]
H3C
O
HO
Isopropyl alcohol
2- Propanol
O
CH3
Acetophenone
CH3
H3C
Cl
O
Acetone
Propanone
Cl
Chloracetophenone (tear gas)
Naming of Ketones
IUPAC
 Aldehydes end in -one
 Take the name of the longest chain
 Drop the ending e and replace it by -one
Common
 Each alkyl group attached to the carbonyl group is
named and the word ketone is added afterward.
O
H3C
3-Hexanone
Ethylpropylketone
CH3
H3C
CH3
Cl
Cl
O
4,4-dichloro-2-pentanone
Uses of Ketones
 Acetone is a good solvent for fats and oils
(previuosly used in finger nail polish).
 Present in small amounts in blood and urine (in
normal individuals).
 Present in large amounts in blood and urine and
expired air in case of untreated diabetes mellitus.
 Dihydroxy acetone is an intermediate in
carbohydrate metabolism.
O
O
H3 C
CH3
Acetone
HO
OH
Dihydroxy acetone
Reactions of ketones
Ketones are usually unreactive.
Ketones are not easily oxidized.
They can however be reduced to the
corresponding secondary alcohols.
Ketones give negative tests with oxidazing
agents such as Benedict‘s reagent. However
aldehyde give positive results with these
reagents.
Reactions of ketones
Hemiacetals and Hemiketals
How can an acetal or a ketal be formed?
Importance:
Hemiketal / acetal  monosaccharides
Ketal / Acetal  Di- and Polysaccharides
Carboxylic acids
Preparation
Oxidation of aldehydes
H3C
O
+
[O]
Acetaldehyde
H3C
O
Acetic acid
HO
O
+
Benzaldehyde
HO
O
[O]
Benzoic acid
Stepwise oxidation of a primary alcohol carboxylic acid
H3C OH
Methylalcohol
+
[O]
H2C O + [O]
Formaldehyde
O
HO
Formic acid
 Direct oxidation of primary alcohols  acids
HO
H3 C
OH
Ethyl alcohol
+
[O]
H3 C
O
Acetic acid
Naming of carboxylic acids
IUPAC Names
 Carboxylic acids end in –oic acid
 Take the name of the longest chain cotaining the
acid group.
 Drop the ending e and replace it by -oic
Common Names
 Derived from the names of the aldehyde forms
from which they may be prepared
HO
H3 C
O
Ethanoic acid
Acetic acid
Carboxyl group which yields
hydrogen ions
Naming of carboxylic acids
 Dicarboxylic, and tricarboxylic acids are carboxylic
acids which contain two and three carboxylic acids,
respectively.
O
O
HO
O
HO
O
HO
Ethanedioic aic
Oxalic acid
OH
O
Propanedioic acid HO
Malonic acid
OH
O
OH
Butanedioic acid
Succinic acid
O
O
OH
OH
Citric acid
O
OH
Naming of carboxylic acids
Examples:
O
H3C
H3C
OH
CH3 Cl
2-chloro-3,4-dimethylheptanoic acid
HO
O
Cl
Br
4-bromo-2-chlorobenzoic acid
Properties and Reactions of Carboxylic acids
 Weak acids
O
O
H3C
H+
+
OH
H3C
O-
Acetic acid
Hydrogen
ion
Acetate ion
 React with bases to form salts and water
O
O
H3C
+
NaOH
OH
CH3CHOOH + NaOH
H3C
-
+
O Na
+
H2O
CH3CHOONa + H2O
Properties and Reactions of Carboxylic acids
 React with bases to form salts and water
CH3CHOOH + NaHCO3
CH3CHOONa + CO2 + H2O
Sodium
bicarbonate
2 HCOOH + Na2CO3
Formic acid
Sodium
carbonate
2 HCOONa + CO2 + H2O
Sodium
formate
 Their solubility in water decreases as the length
of their carbon chains increases
 React with alcohols to form esters
Medically important acids
 Magnesium citrate  cathartic (evacuation of bowel)
 Sodium Citrate  anticoagulant (removel of Ca2+
needed for coagulation
 Lactic acid results from fermentation of milk sugar
(lactose) [lactic acidboth acid and alcohol)
 Lactic acid is formed by anarobic energy production in
the body from Pyruvate (muscle exercise)
 Pyruvic acid is formed during anarobic phase of glucose
oxidation
 Pyruvic acid  acetyl CoA  Krebs cycleEnergy
production
O
OH
O
O
H3 C
H3 C
OH
OH
Lactic acid
Pyruvic acid
Medically important acids
 Oxalic acid  removal of strains, from clothing, prevention of
blood clotting (Note: Oxalic acid is a poison if taken internally)
 Stearic acid (C18) is a fatty acid, insoluble in water, ist salt is
used as in Soap
 Bezoic acid antifungal; sodium salt  preservative
 Salicylic acid (both alcohol and acid) removal of warts and
corns
Acetylsalicylic acid (Aspirin):
OH HO
O
analgesic, antipyretic, aginst O
rheumatic
fever
( ‫الحمى‬
‫)الروماتيزمية‬, prevention of blood
OH
O CH3
clots from forming (Note:
contraindicated after Surgery)
O
helps in preventing heart
attacks, bleeding of stomach
Acetylsalicylic
(not to be taken on empty Salicylic acid
acid
stomach)