Matriculation Chemistry ( Carbonyl Compound )
Transcript of Matriculation Chemistry ( Carbonyl Compound )
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CARBONYLCOMPOUNDS
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Objective
Describe aldehydes and ketones. Draw the structure and name the
compound according to IUPAC nomenclature and common names.
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INTRODUCTION
Functional group: carbonyl, C=O General formula: CnH2nO Aldehyde & Ketone are isomeric Carbonyl compounds are polar In general, an aldehyde > reactive than ketone
towards nucleophilic addition reaction
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INTRODUCTION ALDEHYDE
R = alkyl, aryl @ H
KETONE
R & R’ = alkyl, aryl
C
O
R H
C
O
R R’
δ+
δ-
δ+
δ-
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Naming of Aldehyde
Aldehyde is named by substituting the letter –e of the corresponding alkane with –al
Basic name depends on the longest chain with
–CHO group The chain must be numbered by starting with
–CHO group as C-1
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Naming of Aldehyde
Structure IUPAC name General name
H-C-H
methanal formaldehyde
CH3-C-H
ethanal acetyldehyde
CH3CH2-C-H
propanal propionaldehyde
O
O
O
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Naming of AldehydeStructure IUPAC name General name
CH3CH2CH2-C-H
butanal n-butyraldehyde
CH3(CH2)3-C-H
pentanal n-valeraldehyde
Ph-C-H
benzaldehyde(phenylmethanal)
benzenecarbaldehyde
O
O
O
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Naming of Aldehyde
O
CH2C-H
Phenylethanal
(phenylacetyldehyde)
CH2=CHCH2C-H
O
3-butenal
CH3CHCHC-H
O
OH
H3C-H2C
2-ethyl-3-hydroxybutanal
4 3 2 1
4 3 2 1
2 1
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Naming of Ketone
Ketone is named by substituting the letter –e of corresponding alkane with –one
The longest chain with carbonyl group is numbered so that C in carbonyl group gets the smallest number
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Naming of KetoneStructure IUPAC name General name
CH3CCH3
propanone acetone
(dimethyl ketone)
CH3CCH2CH3 Butanone methyl ethyl ketone
CH3CCH2CH2CH3 2-pentanone methyl propyl ketone
O
O
O
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Naming of KetoneStructure IUPAC name General am
Ph-C-CH3
phenylethanone
acetophenone(phenyl methyl ketone)
Ph-C-Ph diphenylmethanone
benzophenone
(diphenyl ketone)
CH3CH2CCH2CH33-pentanone diethyl ketone
O
O
O
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O
CH2C-CH3
phenylpropanone
CH2=CHCH2CCH3
O
4-penten-2-one
CH3CCH2CH2CCH3
O
2,5-hexanadione
O
O
OH
CH2CH3
2-ethyl-2-hydroxycyclopentanone
-CH2C-CH2-
O
1,3-diphenylpropanone
5 4 3 2 1
1 2 3 4 5
1 2 3
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a. c.
b. d.
EXCERCISE
1. Write the names of the following compounds according to IUPAC nomenclature
CH3 O
CH3CHCH2CH2CH2CHC H 3CH 2C H 2C H C H
O
CH2
CH3
CH3CH2CH2C
O
CHCH3
CH3
CH3CH
2C CH2CH2CH2CH3
O
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2. Write down all structural formulae of compound with molecular formula C5H10O and name them according to IUPAC nomenclature.
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Objective
Explain the preparation of carbonyl compounds through these reactions:
a)Oxidation of alcoholsb)Ozonolysis of alkenesc) Friedel–Crafts acylation to produce aromatic
ketones
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Preparation of Carbonyl 1. Oxidation of Alcohols
[O] of 1o R-OH to form aldehyde [O] of 2o R-OH to form ketone
CH3CH2CH2CH2-OH + PCC CH3CH2CH2CH=OCH2Cl2
1-butanol butanal
-OH =OKMnO4
H+
cyclopentanol cyclopentanone
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2. Ozonolysis of alkene
(i) H3CC=CHCH3 H3CC=O + O=CCH3
CH3 CH3 H(i) O3
(ii) Zn/H2O
(ii) O=CH(CH2)4CH=O(i) O3
(ii) Zn/H2O
Preparation of Carbonyl
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4. Friedel-Crafts Acylation
-a good method for preparing of aromatic ketones
+ R-C-Cl + AlCl3 -C-R
O O
+ R-C-O-C-R + AlCl3 -C-R
O OO
Preparation of Carbonyl
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Practice Questions
(a) CH3CH(Br)CH(CH3)OH + K2Cr2O7/H2SO4
(b) CH3CH=CCH(CH3)2
CH3
(i) O3
(ii)H2O/Zn
(c) + -C=OAlCl3
Cl
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1. Oxidation
2. Reduction
3. Nucleophilic addition reaction
4. Condensation
5. Haloform reaction
CHEMICAL PROPERTIES
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To explain the chemical properties with reference to these reactions :
a) oxidation with KMnO4, K2Cr2O7,Tollens, Fehling, Benedict and Schiff reagents to differentiate between aldehydes and ketones.
b) reduction to alcohol using LiAlH4,NaBH4 and catalytic hydrogenation.
Objective
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1.0 Oxidation Aldehydes are easily oxidised to carboxylic acid by
strong oxidising reagents e.g. KMnO4/H+, K2Cr2O7/H+
Mild oxidising agents such as Tollens’, Schiff, Fehlings’ & Benedicts’ solutions can also oxidise aldehydes.
Ketones are resistant towards oxidation because they do not have hydrogen attached to the carbonyl carbon atom.
KMnO4
H+
H+
KMnO4
RCHO
RCR’
O
No reaction
RCOOH
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1.1 TOLLENS’ TEST
For identifying aldehydes and ketones. It is a mixture of aqueous silver nitrate and
ammonia. It contains Ag(NH3)2
+
In this reaction aldehyde is oxidised to carboxylate ion and argentum is deposited on the wall of the the test tube as silver mirror.
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CH
Contoh
2[Ag(NH3)2]+
+ OH-
+
RCOO-
+ NH3+Ag2 2 + NH4+
2cermin perak
CH3CH2CHO +OH-
[Ag(NH3)2]+
2+
RCH
O
O
+2[Ag(NH3)2]+
OH-
+
cermin perakNH4
+2+22Ag + NH3+CH3CH2COO
-
cermin perakNH4
+2+22Ag + NH3+
O
C O-
silver mirror
silver mirror
silver mirror
Example:
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1.2 FEHLING and BENEDICT TEST(Cu2+ tartarate complex)
Fehling reagent will oxidise aldehydes but not ketones
Used to identify aldehydes Reaction with aldehydes will produce
carboxylate ion and copper(I) oxide which is red in colour.
In this reaction copper(II) is reduced to copper(I)
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Equation;
Brick red
Brick red
blue
blue
RCHO Cu4 2+ OH-
5+ +
RCOO-
Cu2O2+
+ H2O3
CH3CH
O
3H2O+
+2Cu2O
++ OH-
5Cu4 2+ CH3CO-
Oexample
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1.3 Schiff’s reagent
Aldehyde reacts with Schiff’s reagent to give a pink colouration
Ketone give negative result
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Reduction Aldehydes are reduced to 1o R-OH & ketones to 2o
R-OH
Reagents (a) LiAlH4 @ NaBH4 in ether + H+
(b) Zn, H+, heat
(c) H2(g), Ni @ Pt, heat
2.0 Reduction
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CH3CH2CH CH3CH2CH
O OH
H
LiAlH4
H+
-C-CH3 -CH-CH3 O OH
H2 , Ni
Example:
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To explain the chemical properties with reference to these reactions :
a) nucleophilic addition with HCN, Grignard reagent, alcohol, sodium bisulphite and water.
Objective
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In C=O, the e- density is drawn more towards the O atom making the C atom deficient in e. Thus, the C atom becomes the site for Nu- attack.
When carbonyl C is attacked by Nu-, breaking the carbonyl bond & tetrahedral intermediate is formed
Hybridisation of sp2 C atom changes to sp3
3.0 Nucleophilic addition
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The HCN is prepared ‘in situ’ by the reaction of a mixture of KCN or NaCN with H2SO4
Reagents : NaCN @ KCN (aq) followed by dilute H2SO4
-C=O
HNaCN
H2SO4
-C-OH
H
CN
CH3CHCCH3
CH3
OKCN
H2SO4
CH3-CH-C-CH3
CH3
OH
CN
3.1 Addition of HCN
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yields gem-diols
H H
C=O + H2O
H+ C
H H
OH OH
H3CH2C
H3C
C=O + H2O
H+
C
OH OH
H3CH2C
H3C
3.2 Addition of Water
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Aldehyde yields hemiacetal & ketone yields hemiketal
R H
C=O + R’OH
H+ C
R H
OH OR’
hemiacetal
R R’
C=O + R’’OH
H+ C
R R’
OH OR’’
hemiketal
3.3 Addition of alcohol
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Hemiacetal & hemiketal in acidic solution react further to form acetal & ketal
H+ C
R H
OR’’ OR’
acetal
H+ C
R R’
OR’’’
OR’’
ketal
C + R’’OH
R H
OH OR’
C + R’’’OH
R R’
OH OR’’
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Examples:-
H
C=O + CH3OH
H+ C
H
OH OCH3
CH3
C=O + CH3OH
H+ C
OH OCH3
CH3
CH3 CH3
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HCHO
(i)RMgX (ii)H3O+
RCH2OH
1o Alcohol
R’CHO
(i)RMgX (ii)H3O+
R’-CH-R
2o Alcohol
OH
R’CR’’
(i)RMgX (ii)H3O+
R’-C-R’’
3o Alcohol
OHO
R
Example:
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•NaHSO3 react with aldehyde & ketone to form carbonyl bisulphite which is soluble in water
•This reaction is used for purification of aldehyde @ ketone from other non-soluble organic compounds
•Pure carbonyl compound is obtained when treated with aqueous base
3.5 Addition of sodium bisulphite
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NaHSO3 + -C-CH3 -C-CH3
O OH
OSO2-Na+
Bisulphite salt
Sodium bisulphite
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To explain the chemical properties with reference to these reactions :
a) condensation with NH3 and ammonia
derivatives eg hydrazine, phenylhydrazine, hydroxylamine and 2,4 – dinitrophenylhydrazine as identification test for carbonyl compounds.
b) iodoform test to identify compounds with these structures
Objective
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•NH3 & its derivatives react as nucleophile and react with carbonyl compounds
•Involved addition reaction followed by dehydration (elimination of H2O molecule to form C=N)R
C=O + NH3
4.0 Condensation
R
C
O-H
N-H
Carbinolamine‘Unstable intermediate’
R
R
R
C=NH R
H
+ H2Oaddition elimination
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R’ C=O NNH- -NO2
R
H
H NO2
R’ C=NNH- -NO2 + H2O
R NO2
2,4-dinitrophenylhydrazine
Brady’s reagent
yellow @ orange
precipitate
characteristic reaction of carbonyl compounds
Example:
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NH3 derivatives Name Product Name
R-NH2 @
Ar-NH2
primary amine
C=N-R @
C=N-Ar
imine
NH2NH2 hydrazine C=NNH2Hydrazone
NH2-OH hydroxyl amine
C=N-OH oxime
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NH3 derivatives Name Product Name
NH2NHC6H5
phenyl hydrazine
C=NNHC6H5 phenyl hydrazone
NH2NHCNH2
semi
carbazide C=NNHCNH2
semi
carbazone
O O
•Carbonyl react with hydrazine @ phenylhydrazine also give yellow precipitate
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Reagent : I2 in NaOH(aq), heat forms NaIO(Sodium iodate (i))
Formation of yellow precipitate, CHI3 , indicate that organic compound consist of methyl carbonyl or methyl alcohol:-
-C-CH3 @ -C-CH3
O OH
H
5. Iodoform reaction
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GENERAL REACTION:-
RCCH3 RCCI3 RCO- + CHI3
O O OI2
OH-
OH-
RCHCH3 RCCH3 RCCI3 RCO- + CHI3
OH OI2
OH- OH-
OOH-
OI2
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EXAMPLE:-
CH3CH2CCH3 CH3CH2C-O- + CHI3
O ONaIO
-C-CH3 -C-O- + CHI3
O O
I2 / NaOH
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EXAMPLE:-
H-CCH3 H-C-O- + CHI3
O OI2/NaOH
-C-CH3 -C-O- + CHI3
OH O
I2 / NaOH
H
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Practice Questions
(a) CH3CCH2CH3 + H2NNH NO2
NO2
H+
O
(b) CH3CCH2CH3 + H2NOH O
H+
(c) CH3CCH2CH3 + I2 / NaOH O
(d) CH3C-CH2-Ph + LiAlH4 O
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Practice Questions
The molecular formula of an unknown compound A is C7H14. Ozonolysis of A gave two products B and C, whereby both B and C reacted with 2,4-dinitrophenylhydrazine to give solid derivatives. B gave positive results to Tollens’ and Iodoform tests, while C gave negative result to both of the tests. Suggest the structural formula of A, B and C. Explain your answer.