Transcript CH 3 CH 2 CH 2 CH 3

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Carbonyl Compounds
and Nucleophilic
Addition
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New Way Chemistry for Hong Kong A-Level Book 3A
Carbonyl compounds
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Contain at least one carbonyl group.
Aldehyde
R
R
C
O
H
C
O
'R
R : H, alkyl or aryl group
2
2
Ketone
R, R' : alkyl or aryl group
R = R’ or R  R’
New Way Chemistry for Hong Kong A-Level Book 3A
Aldehydes  terminal carbonyl groups
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O
O
O
C
C
C
H
H
propanal
butanal
H
pentanal
No need to specify the position of the
carbonyl group
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O
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O
pentan-2-one
4
4
pentan-3-one
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cyclohexanone
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O
O
cyclohexanecarbaldehyde
cyclohexylmethanal
C
H
O
C
H2
cyclohexylethanal
C
H
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O
O
C
C
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CH3
H
benzaldehyde
1-phenylethanone
O
C
diphenylmethanone
benzophenone
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O
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4-oxopentanoic acid
COOH
H
C
COOH
5-oxopentanoic acid
O
O
4-oxopentanal
CHO
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Physical Properties
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1. Most simple aliphatic ketones and
aldehydes are liquids at room temperature
except methanal (b.p. = 21C) and ethanal
(b.p. = 20.8C)
Aliphatic aldehydes have an unpleasant
and pungent smell
Ketones and aromatic aldehydes have a
pleasant and sweet odour
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Physical properties of some aldehydes and ketones
Molecular
Boiling Melting Density
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formula
point
point at 20 C
Name
o
(oC)
(oC)
(g cm-3)
Aldehydes:
Methanal
HCHO
-21
-92

Ethanal
CH3CHO
20.8
-124
0.783
Propanal
CH3CH2CHO
48.8
-81
0.807
Butanal
CH3(CH2)2CHO
75.7
-99
0.817
Methylpropanal (CH3)2CHCHO
64.2
-65.9
0.790
Benzaldehyde
179
-26
1.046
9
9
C6H5CHO
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2. Less dense than water except aromatic members
Molecular formula Boiling Melting Density
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Name
point
(oC)
point
(oC)
at 20oC
(g cm-3)
Ketones:
Propanone
CH3COCH3
56.2
-95.4
0.791
Butanone
CH3COCH2CH3
79.6
-86.9
0.806
Pentan-2-one
CH3CO(CH2)2CH3
102
-77.8
0.811
Pentan-3-one
CH3CH2COCH2CH3
102
-39.9
0.814
3-Methylbutan-2-one CH3COCH(CH3)2
95
-92
0.803
Hexan-2-one
Phenylethanone
127
202
-56.9
19.6
0.812
1.028
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10
CH3CO(CH2)3CH3
C6H5COCH3
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Boiling point : - (similar molecular masses)
carboxylic acid > alcohol > aldehyde, ketone > CxHy
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Presence
of polar group
Absence of –OH group
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Solubility
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Small
aldehydes and ketones show appreciable
solubilities in water due to the formation of
intermolecular hydrogen bonds with water
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Solubility
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Ethanal
and propanone are miscible with water
in all proportions.
Propanone(acetone) is volatile and miscible
with water
 Once used to clean quick-fit apparatus
potentially carcinogenic
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Solubility
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Methanal
gas dissolves readily in water
Aqueous solutions of methanal (Formalin) are
used to preserve biological specimens
Methanal(formaldehyde) is highly toxic
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Industrial preparation
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By dehydrogenation
(oxidation) of alcohols
H
H
Ag
2 H
C
O
H
+
O2
2
C
O
+
2H2O
heat
H
H
Further oxidation is prohibited
H
O
Cu
H3C
C
H3C
C
CH3
O
+
heat
H3C
H
Out-dated
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H2
Laboratory preparation
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1. Oxidation
of alcohols
1 alcohol  aldehyde  carboxylic acid
2 alcohol  ketone
Further oxidation of aldehyde to carboxylic
acid is prohibited by
(i) using a milder O.A., e.g. H+/ Cr2O72
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New Way Chemistry for Hong Kong A-Level Book 3A
Laboratory preparation
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1. Oxidation
of alcohols
1 alcohol  aldehyde  carboxylic acid
2 alcohol  ketone
Further oxidation of aldehyde to carboxylic
acid is prohibited by
(i) using a milder O.A., e.g. H+/ Cr2O72
(ii) distilling off the product as it is formed
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70C > T > 21C
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Heating under reflux
Ethanol  ethanoic acid
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carboxylic acid
2 alcohol  ketone
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Further oxidation of ketone to carboxylic acid
has not synthetic application since
1. it requires more drastic reaction conditions
2. it results in a mixture of organic products
H3C
[o]
C
H3C
21
21
O
H3C
C
High T
O
HO
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+ ot her product s
2. Reduction of acid chlorides
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The catalyst Pd or BaSO4 is poisoned
with S to prevent further reduction to
alcohol
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oxidation
Carboxylic
acid
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Aldehyde
Alcohol
or acyl chloride
reduction
Aldehydes
 Intermediate oxidation state
 Preparation must be well controlled.
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3. Friedel-Crafts acylation
(Preparation of aromatic ketones)
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O
C
O
CH3
AlCl3
+
H3C
C
Cl
O
O
C
C
Cl
AlCl3
+
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New Way Chemistry for Hong Kong A-Level Book 3A
4. Decarboxylation of calcium salts
Symmetrical
ketones can be obtained by
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heating a single calcium carboxylate
H3C
dry dist il
(CH3COO)2Ca
+
O
o
3
CaCO
400 C
H3C
O
C
dry dist il
Ca
COO
400oC
2
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New Way Chemistry for Hong Kong A-Level Book 3A
+ CaCO 3
4. Decarboxylation of calcium salts
Aldehydes
can be obtained by heating a
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mixture of two calcium carboxylates
Cross decarboxylation is preferred
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New Way Chemistry for Hong Kong A-Level Book 3A
Decarboxylation of sodium salts gives methane
or benzene.(p.30 and p.49)
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CH3COONa(s)
COONa (s)
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27
NaOH(s) from
soda lime
fusion
CH4 + Na2CO3
NaOH(s) from
soda lime
fusion
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+ Na2CO3
5. Catalytic hydration of alkynes
enol
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C
C
H
HC
C
dilute H2SO 4
H3C
CH2
3
HgSO4, 60oC
OH
Keto-enol
tautomerism
H3C
CH3
C
O
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New Way Chemistry for Hong Kong A-Level Book 3A
ketone
5. Catalytic hydration of alkynes
enol
dilute H2SO 4
H
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C
C
H
C
H C
2
HgSO4, 60oC
H
OH
Keto-enol
tautomerism
H3C
aldehyde
H
C
O
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New Way Chemistry for Hong Kong A-Level Book 3A
6. Ozonolysis of symmetrical alkenes
H3C
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1. O
H3C
H
3
H
CH3
H3C
CH3
2. Zn / H2O
30
30
CH3
C
O
C
O
H
H3C
1. O3
H3C
2
2. Zn / H2O
New Way Chemistry for Hong Kong A-Level Book 3A
2
H3C
Unsymmetrical alkenes give a mixture of two
carbonyl compounds making subsequent
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purification more difficult.
H3C
CH3
C
H
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31
C
CH3
1. O3
2. Zn dust / H2O
CH3
H3C
C
H
New Way Chemistry for Hong Kong A-Level Book 3A
O
+
O
C
CH3
Reactions of Aldehydes and Ketones
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A. Nucleophilic Addition Reactions (Ad )
N
B. Condensation Reactions
(Addition-Elimination)
C. Iodoform Reactions (Oxidation)
D. Oxidation Reactions
E. Reduction Reactions
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New Way Chemistry for Hong Kong A-Level Book 3A
Bonding in the Carbonyl Group
The 按一下以編輯母片標題樣式
carbonyl carbon atom is sp2-hybridized
sp2 – 2p head-on overlap   bond
2p – 2p side-way overlap   bond
The  and  bonds in the C = O bond
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New Way Chemistry for Hong Kong A-Level Book 3A
The carbonyl group is planar(sp2-hybridized)
and highly polarized due to
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(i) Polarization of  bond (inductive effect)
(ii) Polarization of  bond (mesomeric effect)
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34
+

C
O
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Susceptible to nucleophilic attack
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50%
+
C

O
Nu
50%
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New Way Chemistry for Hong Kong A-Level Book 3A
Bond Enthalpy (kJ/mol) :
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C=C (611) < 2 C–C (346) ( bond <  bond)
C=O (749) > 2 C–O (358) ( bond >  bond)
Due to polarization of the C-O  bond
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A. Nucleophilic Addition Reactions (AdN)
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Acid-catalyzed
C
O
+ H+
C
OH
More susceptible to
nucleophilic attack
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New Way Chemistry for Hong Kong A-Level Book 3A
A. Nucleophilic Addition Reactions (AdN)
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Base-catalyzed
H
O
H2O
H
38
38
Nu
+
Nu
Stronger
nucleophile
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C
O
AdN vs AdE
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(Non-polar)
(Non-polar)
(Polar)
+
C

O
Nu
39
39
E
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Reaction mechanism
R
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R
C
O
C
'R
'R
Nu
Slow (r.d.s.)
O
Nu
H+ and Nu added across
the C=O bond
R
C
'R
40
40
R
+
O
Nu
H
C
'R
New Way Chemistry for Hong Kong A-Level Book 3A
OH
Nu
Fast
Q.52
50%
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R
Nu
O
C
R
R'
C
O
Nu
'R
50%
+
50%
O
Nu
H+
R
C
'R
R
C
R'
50%
R
OH
Nu
+
HO
Nu
C
A racemic mixture
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R'
Reactivity depends on two factors : (i)
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Electronic effect
(ii) Steric effect
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New Way Chemistry for Hong Kong A-Level Book 3A
(i) Electronic effect
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Electron-deficiency of carbonyl C 
 Ease of nucleophilic attack 
 Reactivity 
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New Way Chemistry for Hong Kong A-Level Book 3A
Decreasing reactivity
H
H
R
R
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C
O
C
O
C
O
>
>
H
'R
Decreasing positive charge
on carbonyl carbon
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New Way Chemistry for Hong Kong A-Level Book 3A
H
O
C
H
O
H
C
O
C
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Carbonyl C is less positive due
to delocalization of positive
charge to the benzene ring. Or,
H
The C-O bond has less  character
 less mesomeric effect
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New Way Chemistry for Hong Kong A-Level Book 3A
O
C
Reactivity : -
H
O
C
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R
O
C
>
R'
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New Way Chemistry for Hong Kong A-Level Book 3A
(ii) Steric effect
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No. /bulkiness of R groups at carbonyl C 
 Steric hindrance 
 Reactivity 
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New Way Chemistry for Hong Kong A-Level Book 3A
Decreasing reactivity
H
H
R
R
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C
O
C
O
C
O
>
>
H
Increasing
steric hindrance
48
48
New Way Chemistry for Hong Kong A-Level Book 3A
'R
pentan-3-one
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49
49
New Way Chemistry for Hong Kong A-Level Book 3A
Reactivity of AdN : -
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1. Aldehydes > ketones
2. Aliphatic > aromatic
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New Way Chemistry for Hong Kong A-Level Book 3A
Q.53
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H
Reactivity
:C
H
51
51
O
C
>
H
H3C
H3C
H
Cl3C
O
>
C
H
O
C
>
H3C
New Way Chemistry for Hong Kong A-Level Book 3A
O
>
O
C
Examples of AdN
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1. Addition
of Hydrogen Cyanide
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1. Addition of Hydrogen Cyanide
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New Way Chemistry for Hong Kong A-Level Book 3A
Mechanism : -
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HCN is very toxic  in situ preparation
NaCN + H2SO4  NaHSO4 + HCN
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New Way Chemistry for Hong Kong A-Level Book 3A
Mechanism : -
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HCN is a weaker nucleophile than CN
NaCN + H2SO4  NaHSO4 + HCN
excess
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New Way Chemistry for Hong Kong A-Level Book 3A
Mechanism : -
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A mixture of CN/HCN is a buffer of pH  9
NaCN + H2SO4  NaHSO4 + HCN
excess
pKa of HCN = 9.4
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New Way Chemistry for Hong Kong A-Level Book 3A
The reaction mixture is buffered at pH 9 to
ensure highest yield at greatest rate.
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If pH < 9,
H+ + CN
HCN
The equilibrium position shifts to the right
 [CN] 
 Reactivity 
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New Way Chemistry for Hong Kong A-Level Book 3A
The reaction mixture is buffered at pH 9 to
ensure highest yield at greatest rate.
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If pH > 9,
R
R
C
'R
O
CN
+
H+
C
'R
OH
CN
[H+] 
 The equilibrium position shifts to the left
 Yield 
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New Way Chemistry for Hong Kong A-Level Book 3A
Used for lengthening the carbon chain
R
R
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70% H2SO 4
NaCN
C
C
O
dilute H2SO 4
'R
'R
R
OH
CN
reflux
'R
C
OH
COOH
1. LiAlH4/dry ether
2. H2O
R
C
'R
OH
CH2NH2
Dry ether is used as LiAlH4 reacts violently with
water H2O(l) + H(aq)  H2(g) + OH(aq)
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59
from AlH4
New Way Chemistry for Hong Kong A-Level Book 3A
HCN adds preferentially to C=O leaving C=C
and benzene ring unaffected.
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OH
O
HCN
H2C
C
H
C
room temperature
H2C
H
O
C
H
C
H
60
60
C
CN
H+
H2C
C
H
At pH 9, H+ is not
concentrated enough to
trigger electrophilic
attack
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H
HCN adds preferentially to C=O leaving C=C
and benzene ring unaffected.
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OH
O
HCN
H2C
C
H
C
room temperature
H2C
C
H
H
H
CN
CN
O
H2C
C
H
No reaction
C
H
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61
C
Or, H in HCN is not positive enough to
trigger electrophilic attack
New Way Chemistry for Hong Kong A-Level Book 3A
H
HCN adds preferentially to C=O leaving C=C
and benzene ring unaffected.
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OH
O
HCN
H2C
C
H
C
room temperature
H2C
H
C
H
C
H
CN
+
H
Cl
O
H2C
C
H
O
H3C
C
C
H
H
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New Way Chemistry for Hong Kong A-Level Book 3A
C
H
Q.57
Cl
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and HSO  are much weaker bases and
4
nucleophiles than CN to trigger nucleophilic
attacks.
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New Way Chemistry for Hong Kong A-Level Book 3A
Q.54
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CH

CH3CH2CH2COOH
3CH2CHO
H2SO4
H
excess
NaCN
Ni
H
H2
H
H
C
C
70% H2SO4
H3C
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64
C
C
H
OH
CN
reflux
H3C
New Way Chemistry for Hong Kong A-Level Book 3A
COOH
2. Addition of Sodium Hydrogensulphate(IV)
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R
R
C
O
Na SO3H
excess
excess &
saturated
'R
C
'R
O Na
SO3H
'R
R
C
OH
SO3 Na
bisulphit e adduct
Excess NaHSO3 should be used to shift the
equilibrium position to the right (yield )
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New Way Chemistry for Hong Kong A-Level Book 3A
2. Addition of Sodium Hydrogensulphate(IV)
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R
R
C
Na SO3H
O
C
'R
excess
excess &
saturated
'R
O Na
SO3H
'R
R
C
OH
SO3 Na
bisulphit e adduct
Q.55
Since the equilibrium position lies on the right
Acidity : -OH < -SO3H
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New Way Chemistry for Hong Kong A-Level Book 3A
OH
HO
C
O
S
O
S
C
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O
O
O
O
More stable
O
HO
S
O
O
C
O
S
O
C
OH
Less stable
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New Way Chemistry for Hong Kong A-Level Book 3A
O
Very sensitive to steric hindrance
 limited
to aliphatic aldehyde and
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sterically unhindered ketones
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New Way Chemistry for Hong Kong A-Level Book 3A
The aldehydes and ketones can be
regenerated by treating the bisulphite
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addition product with H+(aq) or OH(aq)
R
+
-
R
H or OH
C
'R
OH
SO3 Na
C
O
'R
Used for the purification of carbonyl compounds
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New Way Chemistry for Hong Kong A-Level Book 3A
Q.56
Outline how you can separate a mixture of
butanone (b.p. = 79.6°C) and 1-chlorobutane (b.p. = 78.5°C)
in ether.
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The mixture of butanone and 1-chlorobutane
cannot be separated by distillation as
(1) their boiling points are too close
(2) butanone tends to decompose below its b.p.
(p.91, 1st paragraph)
70
70
New Way Chemistry for Hong Kong A-Level Book 3A
按一下以編輯母片標題樣式
CH3
C
C2H5
OH
SO3 Na
Ionic
 water soluble
71
71
New Way Chemistry for Hong Kong A-Level Book 3A
按一下以編輯母片標題樣式
organic layer (with 1-chlorobutane)
aqueous layer (with adduct)
72
72
New Way Chemistry for Hong Kong A-Level Book 3A
按一下以編輯母片標題樣式
CH3
C
C2H5
OH
SO3 Na
CH3COC2H5
+ NaCl + H2O
+ SO2
73
73
New Way Chemistry for Hong Kong A-Level Book 3A
按一下以編輯母片標題樣式
organic layer (with butanone)
aqueous layer (with NaCl)
74
74
New Way Chemistry for Hong Kong A-Level Book 3A
按一下以編輯母片標題樣式
Diethyl ether has a much lower
b.p. (34.6C)
 can be removed easily without
decomposition of butanone
75
75
New Way Chemistry for Hong Kong A-Level Book 3A
R
HCN
C
'R
toxic
按一下以編輯母片標題樣式
'R
Not recommended
O
C
R
C
'R
76
76
R
OH
SO3 Na
New Way Chemistry for Hong Kong A-Level Book 3A
CN
OH
B. Condensation (Addition-Elimination)
Reactions
按一下以編輯母片標題樣式
H
G
R
N
H
C
O
G
'R
Addition
H
O
N
C
H
R'
OH
R
R
H2O +
N
G
77
77
C
R'
New Way Chemistry for Hong Kong A-Level Book 3A
G
N
C
H
R'
R
Overall reaction : R
G
R
按一下以編輯母片標題樣式
NH
O
C
G
2
N
hydrazine
78
78
N
H
O2N
H2O
NH2
phenylhydrazine
NO2
NH2–NH2
+
R'
R'
HO–NH2
hydroxylamine
C
Brady’s reagent
N
H
NH2
2,4-DNP
2,4-dinitrophenylhydrazine
New Way Chemistry for Hong Kong A-Level Book 3A
Reaction with hydroxylamine
按一下以編輯母片標題樣式
R
R
C
'R
O
H2N
OH
OH
C
R
C
N
'R
'R
cis or trans
oxime
79
79
New Way Chemistry for Hong Kong A-Level Book 3A
N
OH
Reaction with hydrazine
按一下以編輯母片標題樣式
80
80
New Way Chemistry for Hong Kong A-Level Book 3A
Reaction with hydrazine
按一下以編輯母片標題樣式
Examples
:-
81
81
New Way Chemistry for Hong Kong A-Level Book 3A
Reaction with phenylhydrazine
按一下以編輯母片標題樣式
R
R
C
'R
O
H2N
C
N
H
N
N
H
'R
phenylhydrazone
82
82
New Way Chemistry for Hong Kong A-Level Book 3A
Reaction with 2,4-dinitrophenylhydrazine
按一下以編輯母片標題樣式
coloured ppt
83
83
New Way Chemistry for Hong Kong A-Level Book 3A
Examples : -
按一下以編輯母片標題樣式
84
84
New Way Chemistry for Hong Kong A-Level Book 3A
Identification of carbonyl compounds
Derivatives (e.g. oximes) of carbonyl compounds
按一下以編輯母片標題樣式
are insoluble solids with have sharp m.p.
The carbonyl compounds can be identified by
• preparing their solid derivatives followed by
• recrystallization and
• metling point determination (checked against
data books)
85
85
New Way Chemistry for Hong Kong A-Level Book 3A
2. Reaction with 2,4-Dinitrophenylhydrazine
按一下以編輯母片標題樣式
Brady’s reagent is especially important in
this respect since the products
(2,4-dinitrophenylhydrazones) are
coloured ppt with sharp melting points.
86
86
New Way Chemistry for Hong Kong A-Level Book 3A
M.p. of 2,4-DNP derivatives of some aldehydes and ketones
Molecular formula
Melting point of
按一下以編輯母片標題樣式
Name
2,4-dinitrophenylhydrazine (oC)
Aldehydes:
Methanal
HCHO
167
Ethanal
CH3CHO
168
Propanal
CH3CH2CHO
156
Butanal
CH3CH2CH2CHO
123
Benzaldehyde
C6H5CHO
237
87
87
New Way Chemistry for Hong Kong A-Level Book 3A
M.p. of 2,4-DNP derivatives of some aldehydes and ketones
Molecular formula
Melting point of
按一下以編輯母片標題樣式
2,4-dinitrophenyl-
Name
hydrazine (oC)
Ketones:
Propanone
CH3COCH3
128
Butanone
CH3CH2COCH3
115
Pentan-2-one
CH3CH2CH2COCH3
141
Pentan-3-one
CH3CH2COCH2CH3
156
Hexan-2-one
CH3CH2CH2CH2COCH3
107
Phenylethanone
C6H5COCH3
250
88
88
New Way Chemistry for Hong Kong A-Level Book 3A
Q.58
(a)
1.
For cyclopentanone,
按一下以編輯母片標題樣式
Prepare BOTH oxime and 2,4-DNP derivatives.
Oxime
2,4-DNP
Methyl propyl ketone
58C
144C
cyclopentanone
50C
142C
2. Purify the products by recrystallization.
3. Determine the melting points of the
derivatives and compare the results with
those in the above table.
89
89
New Way Chemistry for Hong Kong A-Level Book 3A
Q.58
(a)
1.
For 4-methylcyclohexanone,
按一下以編輯母片標題樣式
Prepare BOTH oxime and 2,4-DNP derivatives.
Oxime
2,4-DNP
propanone
59C
126C
4-methylcyclohexanone
37C
130C
2. Purify the products by recrystallization.
3. Determine the melting points of the
derivatives and compare the results with
those in the above table.
90
90
New Way Chemistry for Hong Kong A-Level Book 3A
C. Iodoform Reactions
按一下以編輯母片標題樣式
H3C
NaOH/I2
C
O
warm
O
C
O
+ CHI3(s)
CHI3(iodoform) : a yellow crystal with a characteristic smell
91
91
New Way Chemistry for Hong Kong A-Level Book 3A
C. Iodoform Reactions
按一下以編輯母片標題樣式
H3C
NaOH/I2
C
O
warm
O
C
O
+ CHI3(s)
Used as a test for carbonyl compounds with
at least one methyl group attached to the
carbonyl C.
92
92
New Way Chemistry for Hong Kong A-Level Book 3A
C. Iodoform Reactions
按一下以編輯母片標題樣式
H3C
NaOH/I2
C
O
warm
O
C
O
+ CHI3(s)
The only aldehyde that gives +ve result is
H3C
C
93
93
O
ethanal
H
New Way Chemistry for Hong Kong A-Level Book 3A
C. Iodoform Reactions
按一下以編輯母片標題樣式
H3C
NaOH/I2
C
O
warm
O
C
O
+ CHI3(s)
Give two ketones that give +ve results
H3C
H3C
C
94
94
H3C
O
C
C2H5
New Way Chemistry for Hong Kong A-Level Book 3A
O
O.A.
H3C
NaOH/I2
O
按一下以編輯母片標題樣式
C
O
C
O + CHI (s)
warm
warm
NaOH/I2
CH3
C
O
H
H
95
95
New Way Chemistry for Hong Kong A-Level Book 3A
3
Iodoform test
CH3
C
O
H
按一下以編輯母片標題樣式
H
96
96
CH3OH
-ve
1 alcohol
CH3CH(H)OH only
2 alcohol
CH3CH(CH3)OH,
CH3CH(C2H5)OH, ……
3 alcohol
All give –ve results
New Way Chemistry for Hong Kong A-Level Book 3A
Lucas test : ZnCl2/conc.HCl
按一下以編輯母片標題樣式
97
97
CH3OH
-ve
1 alcohol
-ve
2 alcohol
+ve within 5 mins
3 alcohol
+ve, turns cloudy immediately
New Way Chemistry for Hong Kong A-Level Book 3A
Reaction with Na
按一下以編輯母片標題樣式
CH3OH
1 alcohol
2 alcohol
3 alcohol
98
98
Colourless gas burns with a pop
sound
Colourless gas burns with a pop
sound
Colourless gas burns with a pop
sound
Colourless gas burns with a pop
sound
New Way Chemistry for Hong Kong A-Level Book 3A
Reaction with KMnO4/H+
CH3OH
 HCOOH  CO2(g) + H2O
按一下以編輯母片標題樣式
99
99
CH3OH
+ve, gas bubbles(of CO2)
1 alcohol
+ve
2 alcohol
+ve
3 alcohol
-ve
New Way Chemistry for Hong Kong A-Level Book 3A
H3C
NaOH/I2
O
按一下以編輯母片標題樣式
C
O
C
O + CHI (s)
3
warm
H+
Preparation of carboxylic
acid with one less C atom
than the starting compound
100
100
HO
New Way Chemistry for Hong Kong A-Level Book 3A
C
O
H3C
Na O
H
NaOH / I2
C
HO
+
O
C
+
O
CHI3
C
Solid removed
按一下以編輯母片標題樣式
warm
R
R
R
by filtration
-
hot KMnO
4 / OH
Q.59
not recommended
H3C
KMnO4/OH
C
R
O
H3C
HO
C
heat
O
R
+
C
O
HO
Purification is difficult
101
101
New Way Chemistry for Hong Kong A-Level Book 3A
O
Oxidation reactions of ketones have no
synthetic
use except
按一下以編輯母片標題樣式
[O]
C
O
COOH
HOOC
Only ONE organic
product is formed
(refer to p.93)
102
102
New Way Chemistry for Hong Kong A-Level Book 3A
D. Oxidation
按一下以編輯母片標題樣式
1. Oxidized to carboxylic acids by strong O.A.
O.A. : -
KMnO4/H+ or OH
K2Cr2O7/H+
conc. HNO3
103
103
New Way Chemistry for Hong Kong A-Level Book 3A
D. Oxidation
按一下以編輯母片標題樣式
1. Oxidized to carboxylic acids by strong O.A.
Ease of oxidation : Aldehyde > ketone
Aliphatic > aromatic
104
104
New Way Chemistry for Hong Kong A-Level Book 3A
2. Oxidized to salts of carboxylic acids by
mild O.A.
按一下以編輯母片標題樣式
O.A. : -
Tollen’s reagent
Fehling’s reagent
Benedict’s solution
105
105
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Tollen’s reagent (silver mirror test)
+
Preparation
of
Tollen’s
reagent,
[Ag(NH
)
]
3
2
按一下以編輯母片標題樣式
•Adding aqueous ammonia solution to silver nitrate
solution until the precipitate of silver(I) oxide
just redissolves.
2Ag+(aq) + 2OH(aq)  Ag2O(s) + H2O(l)
Ag2O(s) + 4NH3(aq) + H2O(l)
 2[Ag(NH3)2]+(aq) + 2OH(aq)
106
106
Unstable  freshly prepared
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Tollen’s reagent (silver mirror test)
+1
+1
按一下以編輯母片標題樣式
2[Ag(NH
3)2]OH + RCHO
+3
0
 RCOONH4+ + 2Ag(s) + H2O + 3NH3
Forming a silver coating (mirror) on the
surface of glassware.
107
107
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Tollen’s reagent (silver mirror test)
+1
+1
按一下以編輯母片標題樣式
2[Ag(NH
3)2]OH + RCHO
+3
0
 RCOONH4+ + 2Ag(s) + H2O + 3NH3
Black solid deposit is formed instead of
the silver mirror if the surface of the
glassware (e.g. test tube) is not clean.
108
108
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Tollen’s reagent (silver mirror test)
+1
+1
按一下以編輯母片標題樣式
2[Ag(NH
3)2]OH + RCHO
+3
0
 RCOONH4+ + 2Ag(s) + H2O + 3NH3
No reaction with ketones
Aliphatic aldehyde > aromatic aldehyde
109
109
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Tollen’s reagent (silver mirror test)
+1
+1
按一下以編輯母片標題樣式
2[Ag(NH
3)2]OH + RCHO
+3
0
 RCOONH4+ + 2Ag(s) + H2O + 3NH3
Forming highly explosive silver nitride
when the resulting mixture is heated to
dryness
2Ag3N(s)  6Ag(s) + N2(g) + energy
110
110
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Fehling’s reagent/Benedict’s solution
按一下以編輯母片標題樣式
Preparation
of Fehling’s
reagent
Mixing solution A (CuSO4(aq)) with solution B
(tartrate / excess NaOH)
Deep blue solution due to complex formation
of Cu2+ with tartrate
111
111
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Fehling’s reagent/Benedict’s solution
按一下以編輯母片標題樣式
Preparation
of Benedict’s solution
Mixing solution A (CuSO4(aq)) with solution B
(citrate / excess NaOH)
Deep blue solution due to complex formation
of Cu2+ with citrate
112
112
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Fehling’s reagent/Benedict’s solution
from Cu(II) complex
+1
按一下以編輯母片標題樣式
+2
RCHO + 2Cu2+ + NaOH + H2O
+3
+1
 RCOONa+ + Cu2O(s) + 4H+
Forming a reddish brown ppt of Cu2O
113
113
New Way Chemistry for Hong Kong A-Level Book 3A
Reactions with Fehling’s reagent/Benedict’s solution
+1
按一下以編輯母片標題樣式
+2
RCHO + 2Cu2+ + NaOH + H2O
+3
+1
 RCOONa+ + Cu2O(s) + 4H+
Only aliphatic aldehydes give +ve results
No reaction with aromatic aldehydes and
ketones.
114
114
New Way Chemistry for Hong Kong A-Level Book 3A
Tollen’s /Fehling’s reagents are used to
distinguish
between aldehydes and other
按一下以編輯母片標題樣式
organic compounds
115
115
New Way Chemistry for Hong Kong A-Level Book 3A
Reagents commonly used to distinguish
between aldehydes and ketones
按一下以編輯母片標題樣式
Result
116
116
Reagent
Aldehyde
Ketone
KMnO4/H+
Give acids with
the same number
of C atoms
readily (Purple to
colourless or
brwon)
More difficult,
gives acids of
fewer C atoms
(Purple to
colourless or
brown)
New Way Chemistry for Hong Kong A-Level Book 3A
Reagents commonly used to distinguish
between aldehydes and ketones
按一下以編輯母片標題樣式
Result
Reagent
Aldehyde
Ketone
K2Cr2O7/H+
Give acids with
the same number
of C atoms
readily (Orange
to green)
No observable
change
117
117
New Way Chemistry for Hong Kong A-Level Book 3A
Reagents commonly used to distinguish
between aldehydes and ketones
按一下以編輯母片標題樣式
Result
118
118
Reagent
Aldehyde
Ketone
Tollen’s
reagent
Silver mirror is
formed
No observable
change
New Way Chemistry for Hong Kong A-Level Book 3A
Reagents commonly used to distinguish
between aldehydes and ketones
按一下以編輯母片標題樣式
Result
119
119
Reagent
Aldehyde
Ketone
Fehling’s
reagent
Reddish brown
ppt is formed
with aliphatic
aldehydes only
No observable
change
New Way Chemistry for Hong Kong A-Level Book 3A
Reagents commonly used to distinguish
between aldehydes and ketones
按一下以編輯母片標題樣式
Result
Reagent
I2/NaOH
(Iodoform
test)
120
120
Aldehyde
Ketone
Yellow ppt is
formed for
ethanal only
Yellow ppt is
formed for
ketones with
-CH3 attached
to carbonyl
group
New Way Chemistry for Hong Kong A-Level Book 3A
Reagents commonly used to distinguish
between aldehydes and ketones
按一下以編輯母片標題樣式
Result
Reagent
Schiff’s
reagent
121
121
Aldehyde
Ketone
Pink colour
appears
No observable
except with
propanone
New Way Chemistry for Hong Kong A-Level Book 3A
Schiff’s reagent
Preparation
: - Passing SO2 to magenta (a red
按一下以編輯母片標題樣式
dye) solution until it becomes colourless
122
122
New Way Chemistry for Hong Kong A-Level Book 3A
Schiff’s reagent
Principle
: - SO2 bleaches the dye leaving a
按一下以編輯母片標題樣式
colourless solution
SO2 + H2O
H2SO3
H2SO3 + H2O
HSO3 + H3O+
HSO3 + H2O
SO32 + H3O+
SO32 + magenta
123
123
SO42 + colourless
solution
New Way Chemistry for Hong Kong A-Level Book 3A
SO2 + H2O
H2SO3
(1)
H2SO3 + H2O
HSO3 + H3O+
(2)
HSO3 + H2O
SO32 + H3O+
(3)
按一下以編輯母片標題樣式
SO32 + magenta
SO42 + colourless
solution (4)
Sterically unhindered aldehydes or propanone
react with HSO3 to give bisulphite adduct
124
124
New Way Chemistry for Hong Kong A-Level Book 3A
SO2 + H2O
H2SO3
(1)
H2SO3 + H2O
HSO3 + H3O+
(2)
HSO3 + H2O
SO32 + H3O+
(3)
按一下以編輯母片標題樣式
SO32 + magenta
[HSO3] 
SO42 + colourless
solution (4)
 Shifting (1) & (2) to the right (3) & (4) to
the left
 SO32/SO2 is removed
 The red colour of magenta is restored
125
125
New Way Chemistry for Hong Kong A-Level Book 3A
Q.60
Step按一下以編輯母片標題樣式
1 : Qualitative tests
Iodoform test  +ve result
Schiff’s reagent  +ve result
The liquid is either ethanal or propanone
126
126
New Way Chemistry for Hong Kong A-Level Book 3A
Q.60
Step按一下以編輯母片標題樣式
2 : Confirmatory tests
•
Preparation of 2,4-DNP derivatives
•
Purification of products
•
Melting point determination
•
Comparison against values in data book
127
127
New Way Chemistry for Hong Kong A-Level Book 3A
E. Reduction (to alcohols)
1.
按一下以編輯母片標題樣式
Reactions with H2/Ni, Pt or Pd
R
C
'R
128
128
O
+
H2
Ni
High T & P
R
'R
C
H
New Way Chemistry for Hong Kong A-Level Book 3A
OH
2.
Reactions with LiAlH4 or NaBH4
按一下以編輯母片標題樣式
LiAlH4
R
R
dry ether
C
O
H3O+
'R
NaBH4
'R
R
C
O
H
'R
C
H
water or CH3OH
• Both LiAlH4 and NaBH4 have no reaction
with C=C double bond.
129
129
New Way Chemistry for Hong Kong A-Level Book 3A
OH
2.
Reactions with LiAlH4 or NaBH4
按一下以編輯母片標題樣式
LiAlH4
R
R
dry ether
C
O
H3O+
'R
NaBH4
'R
R
C
O
H
'R
C
OH
H
water or CH3OH
• NaBH4 is less reactive than LiAlH4
 can be used in protic solvent
 cannot reduce carboxylic acids and their
derivatives to alcohols
130
130
New Way Chemistry for Hong Kong A-Level Book 3A
Q.61(a)
按一下以編輯母片標題樣式
CH COOH
CH CH COOH
3
3
2. H3O+
1. LiAlH4/dry ether
H3O+
reflux
CH3CH2CN
CN
CH3CH2OH
131
131
2
PBr3
heat
C2H5OH
CH3CH2Br
New Way Chemistry for Hong Kong A-Level Book 3A
Q.61(b)
按一下以編輯母片標題樣式
CH COOH
HCOOH
3
CH3CH2OH
132
132
New Way Chemistry for Hong Kong A-Level Book 3A
Q.61(c)
O
按一下以編輯母片標題樣式
CH2CH2OH
heat
C
conc. H2SO4
reflux
CH3
K2Cr2O7/H+
HO
CH=CH2
133
133
H3O+(aq)
New Way Chemistry for Hong Kong A-Level Book 3A
CH
CH3
Q.61(d)
NOH
按一下以編輯母片標題樣式
NH2OH
H3O+(aq)
OH
K2Cr2O7/H+
reflux
134
134
New Way Chemistry for Hong Kong A-Level Book 3A
O
31.2 Nomenclature of Carbonyl Compounds (SB p.4)
按一下以編輯母片標題樣式
Explain why there is no such a compound called
“ethanone”.
Ketones are compounds with the carbonyl group
situated between two carbon chains or carbon
rings. Therefore, the simplest ketone is the one
with three carbon atoms. “Ethanone”, however,
suggests that there are two carbon atoms in it
and it does not exist.
Back
135
135
New Way Chemistry for Hong Kong A-Level Book 3A
Answer
31.2 Nomenclature of Carbonyl Compounds (SB p.4)
按一下以編輯母片標題樣式
(a) Draw the structural formulae of all carbonyl
compounds having the molecular formula C4H8O. Give
their IUPAC names.
Answer
(a)
136
136
New Way Chemistry for Hong Kong A-Level Book 3A
31.2 Nomenclature of Carbonyl Compounds (SB p.4)
Back
按一下以編輯母片標題樣式
(b) Draw the structural formulae of all straight-chain
carbonyl compounds having the molecular formula
C5H10O. Give their IUPAC names.
Answer
(b)
137
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New Way Chemistry for Hong Kong A-Level Book 3A
31.3 Physical Properties of Carbonyl Compounds (SB p.7)
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(a) In each pair of compounds below, select the one you
would expect to have a higher boiling point.
(i) A: CH3CH2CHO
B: CH3CH2CH2OH
(ii) C:
D:
(iii) E: CH3CH2CH2CHO
F: CH3CH2CH2CH3
(iv) G:
H: HOCH2CH2CH2OH
(a) (i) B (ii) D (iii) E (iv) H
Answer
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31.3 Physical Properties of Carbonyl Compounds (SB p.7)
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(b) Propanone, CH3COCH3, is completely soluble in water,
but octan-4-one, CH3CH2CH2COCH2CH2CH2CH3, is
almost insoluble in water. Explain their difference in
solubility.
Answer
(b) The solubility of ketones in water decreases
as the hydrophobic hydrocarbon portion
lengthens.
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31.4 Preparation of Carbonyl Compounds (SB p.8)
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Is dehydrogenation of alcohols an oxidation or a
reduction process?
Answer
Dehydrogenation of alcohols is an oxidation process.
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31.4 Preparation of Carbonyl Compounds (SB p.9)
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What are “primary alcohols” and “secondary alcohols”?
Primary alcohols have no or only one alkyl or aryl
group directly bonded to the carbon atom bearing
the hydroxyl group.
Secondary alcohols have two alkyl or aryl groups
directly bonded to the carbon atom bearing the
hydroxyl group.
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Answer
31.5 Reactions of Carbonyl Compounds (SB p.14)
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Both alkenes and carbonyl compounds are unsaturated
compounds. Their principal reactions are addition
reactions. What is the major difference between the
addition reactions of the two groups of compounds?
Alkenes are nucleophiles. They undergo
electrophilic addition reactions readily.
Carbonyl compounds are electrophiles. They
undergo nucleophilic addition reactions readily.
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Answer
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(a) Describe briefly how you can distinguish between two
carbonyl compounds having similar boiling points.
The two compounds can be distinguished by
determining the melting points of their 2,4dinitrophenylhydrazone derivatives.
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31.5 Reactions of Carbonyl Compounds (SB p.18)
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(b) Draw the structural formulae of the major organic
products A to C in the following reactions:
KCN / H2SO4
conc. HCl
(i) CH3CH2CHO 
A  B
o
20 C
2,4-dinitrophenylhydrazine
(ii) CH3CH2CHO  C
Answer
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31.5 Reactions of Carbonyl Compounds (SB p.18)
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(b) (i) A:
B:
(ii) C:
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2. Reaction with 2,4-Dinitrophenylhydrazine
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•
Purified by recrystallization from ethanol
•
After recrystallization,
 the products are filtered under suction
 washed with a few drops of ethanol
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2. Reaction with 2,4-Dinitrophenylhydrazine
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The set-up of suction filtration
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2. Reaction with 2,4-Dinitrophenylhydrazine
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• Their m.p. can be determined
• Compare the values with those from data
books
 identify the original aldehyde or ketone
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