Revision Notes for Class 12 CBSE Chemistry, Aldehydes, Ketones and Carboxylic Acids - Topperlearning
Alcohol aldehydes cetones and carboxylic acidsjulivan/medical-chemistry/...Physical properties of...
Transcript of Alcohol aldehydes cetones and carboxylic acidsjulivan/medical-chemistry/...Physical properties of...
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Alcohol aldehydes
cetones and
carboxylic acids
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Classes of organic compounds
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Alcohols
Alcohols are organic compounds containing
hydroxyl (-OH) group attached to C atom.
In an alcohol, -OH group replaces a
hydrogen atom in an alkane.
In a phenol, -OH group is attached to a
benzene ring.
Methane
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Classification of alcohols (1)
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Classification of alcohols (2)
According to the number of -OH groups, there are
monohydroxylic, dihydroxylic and trihydroxylic alcohols.
According to the saturation of C atom chain, alcohols fall into
saturated and unsaturated aliphatic, cyclic and aromatic.
CH3
CH2
CH2
OH
OH CH2
OH
1-propanol(aliphatic alcohol)
cyclohexanol(cyclic alcohol)
phenylmethanol(aromatic alcohol)
CH3
CH2
OH CH2
CH2
OH OH
CH2
CH CH2
OH OH OHethanol(monohydroxylicalcohol)
1,2-ethanediol(dihydroxylicalcohol)
1,2,3-propanetriol(trihydroxylic alcohol)glycerol
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Naming alcohols (1)
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Naming alcohols (2)
Dihydroxylic alcohols are called glycols, or
according to IUPAC: -diols;
trihydroxylic alcohols: -triols.
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Chemical properties of alcohols (1)
Acidic-basic properties: although OH group is polar, alcohols are very weak acids.
The acidic properties of di- and trihydroxylic alcohols are stronger than those of monohydroxylic alcohols. They react with bases producing salts: diols form glycolates, triols - glycerates.
The reaction for identification of -CHOH-CHOH- fragment in various compounds:
CH2
CH2
OH
OH
+ Cu(OH)2 + CuO
O
O
O
CH2
CH2
CH2
CH2
2K+ + 4H2O
blue colourprecipitate
water solubleblue complex compound
KOH2
2-
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Chemical properties of alcohols (2)
Oxidation of primary alcohols results in formation
of aldehydes, and then aldehydes undergo
further oxidation to carboxylic acids.
Under oxidation of secondary alcohols, ketones
are produced. Ketones are more resistant to
oxidation.
R CH2
OH[O]
-H2OR C
O
H
[O]R C
O
OH
R CH R1
OH
[O]
-H2OR C R1
O
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Chemical properties of alcohols (3)
Formation of ethers:
Formation of esters with both mineral and
organic acids.
Esters of glycerol and organic acids are
triacylglycerols (fats).
R1 CH2
OH +R2 CH2
OH R1 CH2
O CH2
R2
-+R1 CH2
OH H2SO4 R1 CH2
O SO3
R1 CH2
OH + R COOH R C O CH2
R1
O
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Ethers
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Physical properties of alcohols
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Aromatic alcohols
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Oxidation of aromatic alcohols
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Phenols(1)
Phenol is soluble in water
because the hydroxyl group
ionizes slightly as a weak
acid.
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Phenols(2)
Phenol
1,2,5-benzenetriol
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Chemical properties of phenols (1)
Phenols are are stronger acids than aliphatic and
aromatic alcohols .
Form salts:
Form ethers:
Form esters:
OH
NaOH
-H2O
ONa
phenol sodium phenolateO
CH3
methyl phenyl ether (anisol)
OCOCH3
phenylethanoate17
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Chemical properties of phenols (2)
• Phenols are characterized with one specific
reaction. They can form coloured
compounds reacting with ferric trichloride. In
such reaction phenols form coloured
coordination compounds - ferric phenolates:
FeCl3 + 6C6H5OH = [Fe(OC6H5)6]3- + 6H+ + 3Cl-
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Phenols: examples
OH
OH
CH
OH
CH2
NH CH3
adrenaline
OH
OH
CH
OH
CH2
NH2
noradrenaline
Physiologically active aromatic alcohols:
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Alcohol in the body
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Carbonyl compounds: Aldehydes
and ketones
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The polar carbonyl group
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Groups of carbonyl compounds
propanone (acetone) Benzophenone
Aldehydes
Ketones
ethanal benzaldehyde
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Naming aldehydes
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Naming ketones
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Physical properties of carbonyl
compounds (1)
Aldehydes and ketones with up to 4 C atoms in
molecules are volatile liquids of specific odour.
They are soluble in water and in organic
solvents.
Solubility in water decreases with an increase of
a number of C atoms in a chain.
Aldehydes containing 8-10 C atoms in a chain
have odour of flowers and are used in
perfumery.
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Physical properties of carbonyl
compounds (2)
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Chemical properties of carbonyl
compounds
Reduction producing alcohols (both aldehydes
and ketones).
Oxidation producing acids (only aldehydes).
CH3
C CH3
O
C CH3
H
OH
CH3
propanone(acetone)
CH3
C H
O[O]
CH3
C OH
O
Acetaldehyde Acetic acid
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Tollens’ test
Ag+ + 1e- Ag (s)
CH3
C H
O
+ 2Ag+ [O]
2Ag(s) +Acetaldehyde
CH3
C OH
O
Acetic acidTollensreagent
Silvermirror
Example:
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Benedict’s test
Example: CH3
C C
OH
H
O
+ Cu2+ Cu2O(s) + CH3
C C
OH
OH
O
2-Hydroxypropanal Benedict'sreagent
Brick-redsolid
2-Hydroxypropanoic acid
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Carboxylic acids
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Preparation of carboxylic acids
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Naturally occurring carboxylic acids
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Naming carboxylic acids
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Some common names of
carboxylic acids
Common IUPAC Formula
Formic methanoic HCOOH
Acetic ethanoic CH3COOH
Propionic propanoic CH3CH2COOH
Butyric butanoic CH3(CH2)2COOH
Capric decanoic CH3(CH2)8COOH
Lauric dodecanoic CH3(CH2)10COOH
Stearic octadecanoic CH3(CH2)16COOH
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Aromatic carboxylic acids
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Polar functional groups in
carboxylic acids
Carboxylic acids are among the most polar organic compounds because the functional carboxyl group consists of two polar groups: a hydroxyl (-OH) group and a carbonyl (C=O) group.
HC
OH
O
-
+
-
+
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Physical properties of carboxylic
acids
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The acidity of carboxylic acids
The equilibrium concentrations of the carboxylic acid
R-COOH and the carboxylate ion R-COO- depend upon pH:
At low pH the acid form predominates, at pH 7.4 the
carboxylate ion predominates.
Carboxylic acids react with bases to produce carboxylate
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Salts of carboxylic acids
The carboxylic acid salts are solids at room temperature.
Because they are ionic compounds, carboxylic acid salts
of the alkali metals (Li+, Na+, and K+) and NH4+ are
usually soluble in water.
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Soap formation
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Cleaning action of soap
One of the problems of using soaps is that the carboxylate end reacts
with ions in water such as Ca2+ and Mg2+ and forms insoluble
substances.
2CH3(CH2)16COO- + Mg2+ [CH3(CH2)16COO-]2Mg2+
Stearate ion Magnesium stearate (insoluble) 42
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Esterification
Carboxylic acids, acid chlorides and acid anhydrides
react with alcohols to produce esters.
Esters can also be formed when inorganic acids
(e.g., phosphoric acid) react with alcohols.
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Esters
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Examples of esters
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Reactions of esters - hydrolysis
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Esters in medicine
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Acid anhydrides
They form from the combination of two carboxylic
acids and the loss of water.
Examples:
CH2
C O C CH2
O O
CH3
CH3
propanoic anhydride
C O C
O O
benzoic anhydride
CH3
C OH
O
2H+, heat
CH3
C O C CH3
O O
+ H2O
ethanoic acid ethanoic anhydride
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Reactions of acid anhydrides
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