Carbonyl Group- The functional unit
is called carbonyl group.
C=O present in the organic compound
ALDEHYDE- They have the functional group ---CHO.
KETONES- Have the functional group R---CO----R’.
ACYL HALIDES- They are derived by replacing the hydroxyl groupof a carboxylic
acid by a halogen atom.-R—CO—Cl.
ACID ANHYDRIDES- They are obtained by the loss of water from two molecules
of an acid. (RCO)2O.
ESTERS- contains RCOOR group having pleasant smell.
Preparation of aldehydes and ketones----1- From Alcohols- K2Cr2O7/H2SO4
RCH2OH
R’
K2Cr2O7/H2SO4
RCHOH
RCHO
R’
R-C=O
2- From AlkynesHgSO4/H2SO4
CHΞCH
H2O
CH3-CH=O
Chemical ReactionsAldehydes and ketones undergo NUCLEOPHILIC ADDITION reactions
with complete transfer of electron to the oxygen atom.
Nu
OH+
OH
Nu
C=O
C
C
CLEMMENSEN REDUCTION---- Amalgated Zinc and conc. HCL reduces
aldehydes and ketones to hydrocarbons.
Zn/HCl
CH3CHO
CH3-CH3 + H2O
WOLFF-KISHNER REDUCTION--- In presence of Hydrazine and heating with
KOH
N2H4
KOH GLYCOL
R-CHO
R-CH=N-NH2
R-CH3 + N2
ALDOL CONDENSATION----- Aldehydes and ketones having atleast one alpha
hydrogen undergo a reaction in presence of dil alkali to form β-hydroxy
ketone.
Dil NaOH
CH3-CHO
OH
heat
CH3-CH-CH2-CHO
CH3-CH=CH-CHO
3-hydroxy butanal
But-2-enal
CANNIZARO REACTION-----If no alpha hydrogen is present in aldehyde
undergo disproportionation.
Conc. KOH
2 HCHO
CH3OH + HCOONa
TEST TO DISTINGUISH ALDEHYDES AND KETONES
1. Tollens reagent test----Tollens reagent ( ammonical siver nitrate)
reduces aldehyde to form silver mirror.
RCHO + 2[Ag(NH3)2]+ +3 OH-
RCOO- + 2 Ag + 2 H2O +4 NH3
2. Fehlings Test--- When aldehydes are warmed with Fehlings solution a
red ppt is formed.
CH3CHO + 2 Cu(OH)2 + 2 NaOH
CH3COONa + Cu2O + 3 H2O
CARBOXYLIC ACIDS--- “e” of the alkane is replaced by “ oic acid”
CH3CH2COOH -- Propanoic acid.
COOH
------- Benzoic acid
PREPARATION--1. From primary alcohols and aldehydes—
Alk KMnO4/ H2O
RCH2OH
RCOOH
2. From Grignard reagent--Dry ether/H3O+
R-Mg-X + O=C=O
RCOOH
Chemical properties—Carboxylic acid is stronger acid than the phenol because
the COO- ion has two equivalent resonating structures than the phenoxide ion
which has five non equivalent structure.
O
R-C-O-
Oand
R-C=O
Presence of electron withdrawing group increases the acidic strength and
presence of electron donating group decreases the strength.
CCl3COOH >CHCl2COOH >ClCH2COOH
REACTIONS--1. Esterification –
RCOOH + R’OH
H+
RCOOR’ + H2O
2.Reaction with Ammonia----With ammonia they give ammonium salts which
on further heating give amides.
CH3COOH + NH3
CH3COONH4
heat
CH3COONH2
Acetamide
3.HALOGENATION---Carboxylic acids having an alpha hydrogen are
halogenated at the alpha position on treating with halogen in presence of red
phosphorus.
X2/ red phosphorus
R-CH2-COOH
R-CH-COOH
H2O
acid)
X
(α-halocarboxylic