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Chapter 34 Carbonyl Compounds
1 34.1
34.2
34.3
34.4
34.5
34.6
Introduction Nomenclature of Carbonyl Compounds Physical Properties of Carbonyl Compounds Preparation of Carbonyl Compounds Reactions of Carbonyl Compounds Uses of Carbonyl Compounds
New Way Chemistry for Hong Kong A-Level Book 3B
34.1
Introduction (SB p.2)
Aldehydes and ketones :
carbonyl compounds, contain
General formula of aldehydes
:
Examples:
group 2 New Way Chemistry for Hong Kong A-Level Book 3B
34.1
Introduction (SB p.2)
General formula of ketones
:
Examples:
3 New Way Chemistry for Hong Kong A-Level Book 3B
34.1
Introduction (SB p.3) • Carbonyl carbon is
sp
2 -hybridized
• The
bond
is formed by the
head-on overlap of an
sp
2 hybrid orbital of C and one p prbital of O
• The
bond
is formed by the
side-way overlap of p orbitals of C and O
4 New Way Chemistry for Hong Kong A-Level Book 3B
34.1
Introduction (SB p.3) • • The three atoms that are bonded to the carbonyl carbon forms a
trigonal planar structure
The bond angles between three attached atoms are
120
5 New Way Chemistry for Hong Kong A-Level Book 3B
34.1
Introduction (SB p.3) • Oxygen is
more electronegative
• The
carbonyl oxygen bears a partial negative charge
and the
carbonyl carbon bears partial positive charge
6 New Way Chemistry for Hong Kong A-Level Book 3B
34.2
Nomenclature of Carbonyl Compounds (SB p.3)
Aldehydes
Aldehydes are named by
replacing the final “-e” of the name of the corresponding alkane with “-al”
Examples:
7 New Way Chemistry for Hong Kong A-Level Book 3B
34.2
Nomenclature of Carbonyl Compounds (SB p.4)
Ketones
• Ketones are named by
replacing the final “-e” of the name of the corresponding alkane with “-one”.
• The parent chain is then numbered in the way that
gives the carbonyl carbon atom the lowest possible number
, and this number is used to indicate its position.
Examples: 8 New Way Chemistry for Hong Kong A-Level Book 3B
34.2
Nomenclature of Carbonyl Compounds (SB p.4)
Check Point 34-1
(a) Draw the structural formulae of all carbonyl compounds having the molecular formula C 4 H 8 O. Give their IUPAC names.
Answer 9 New Way Chemistry for Hong Kong A-Level Book 3B
34.2
Nomenclature of Carbonyl Compounds (SB p.4)
Check Point 34-1
(b) Draw the structural formulae of all straight-chain carbonyl compounds having the molecular formula C 5 H 10 O.
Answer 10 New Way Chemistry for Hong Kong A-Level Book 3B
11
34.2
Nomenclature of Carbonyl Compounds (SB p.4)
Check Point 34-1
(c) Explain why there is no such a compound called “ethanone”.
Answer (c) Ketones are compounds with the group situated between two carbon chains. 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.
New Way Chemistry for Hong Kong A-Level Book 3B
34.3
Physical Properties of Carbonyl Compounds (SB p.5) • Simple aldehydes and ketones are gases or liquids at room temperature •
Aliphatic aldehydes have unpleasant and pungent smell
•
Ketones and benzaldehyde have a pleasant and sweet odour
12
Carbonyl compound Aldehydes:
Methanal Ethanal Propanal Butanal Methylpropanal Benzaldehyde
Formula
HCHO CH 3 CHO CH 3 CH 2 CHO CH 3 (CH 2 ) 2 CHO (CH 3 ) 2 CHCHO C 6 H 5 CHO
Boiling point (
°
C) Melting point (
°
C) Density at 20
°
C (g cm –3 )
–21 20.8
48.8
75.7
64.2
179 –92 –124 –81 –99 –65.9
–26 — 0.783
0.807
0.817
0.790
1.046
New Way Chemistry for Hong Kong A-Level Book 3B
34.3
Physical Properties of Carbonyl Compounds (SB p.5)
Carbonyl compound Ketones:
Propanone Butanone Pentan-3-one Pentan-2-one 3-Methylbutan-2-one Hexan-2-one Phenylethanone
Formula
CH 3 COCH 3 CH 3 COCH 2 CH 3 CH 3 CH 2 COCH 2 CH 3 CH 3 CO(CH 2 ) 2 CH 3 CH 3 COCH(CH 3 ) 2 CH 3 CO(CH 2 ) 3 CH 3 C 6 H 5 COCH 3
Boiling point (
°
C) Melting point (
°
C) Density at 20
°
C (g cm –3 )
56.2
79.6
102 102 95 127 202 –95.4
–86.9
–39.9
–77.8
–92 –56.9
19.6
0.791
0.806
0.814
0.811
0.803
0.812
1.028
13 New Way Chemistry for Hong Kong A-Level Book 3B
34.3
Physical Properties of Carbonyl Compounds (SB p.5)
Boiling Point and Melting Point
• •
Carbonyl compounds have higher b.p. and m.p. than hydrocarbons of similar relative molecular masses
∵ the presence of
dipole-dipole interactions Carbonyl compounds have lower b.p. and m.p. than the corresponding alcohols
∵
dipole-dipole interactions are weaker than intermolecular hydrogen bonds
14 New Way Chemistry for Hong Kong A-Level Book 3B
34.3
Physical Properties of Carbonyl Compounds (SB p.6)
Density
• The densities of aliphatic carbonyl compounds are
lower
than that of water at 20 ° C •
Aromatic carbonyl compounds are slightly denser than water 20
°
C
•
Densities increase with increasing relative molecular masses
15 New Way Chemistry for Hong Kong A-Level Book 3B
34.3
Physical Properties of Carbonyl Compounds (SB p.6) •
Solubility
Aldehydes and ketones of low molecular masses
show
appreciable solubilities in water
∵
carbonyl oxygen can form strong hydrogen bonds with water molecules
16 • e.g. propanone and ethanal are soluble in water in all proportions New Way Chemistry for Hong Kong A-Level Book 3B
17
34.3
Physical Properties of Carbonyl Compounds (SB p.7)
Example 34-1
(a) In each pair of compounds below, select the one you would expect to have a higher boiling point.
(i) A: CH 3 CH 2 CHO (ii) C: B: CH 3 CH 2 CH 2 OH D: (iii)E: CH 3 CH 2 CH 2 CHO (iv) G:
Solution:
F: CH H: 3 CH 2 CH 2 CH 3 (a) (i) (ii) (iii) (iv)
B D E H Answer New Way Chemistry for Hong Kong A-Level Book 3B
18
34.3
Physical Properties of Carbonyl Compounds (SB p.7)
Example 34-1
(b) Propanone, CH 3 COCH 3 , is completely soluble in water, but octan-4-one, CH 3 CH 2 CH 2 COCH 2 CH 2 CH 2 CH 3 , is almost insoluble in soluble in water. Explain their difference in solubility.
Answer
Solution:
(b)
This is because the solubility in water decreases as the hydrophobic hydrocarbon portion lengthens New Way Chemistry for Hong Kong A-Level Book 3B
34.4
Preparation of Carbonyl Compounds (SB p.7)
Dehydrogenation of Alcohols
Industrially,
lower members of aldehydes and ketones
are prepared by passing alcohol vapour over hot silver catalyst 19 New Way Chemistry for Hong Kong A-Level Book 3B
34.4
Preparation of Carbonyl Compounds (SB p.8)
Oxidation of Alcohols
• Example of oxidizing agents:
acidified K 2 Cr 2 O 7 Aldehydes
are prepared by
oxidation of 1
°
alcohols
20 •
Ketones
are prepared by
oxidation of 2
°
alcohols
New Way Chemistry for Hong Kong A-Level Book 3B
34.4
Preparation of Carbonyl Compounds (SB p.8)
Oxidative Cleavage of Alkenes (Ozonolysis)
• Ozone reacts with alkenes vigorously to from
ozonides
• Ozonides are reduced by Zn and H 2 O to give
aldehydes and/or ketones
21 New Way Chemistry for Hong Kong A-Level Book 3B
34.4
Preparation of Carbonyl Compounds (SB p.8)
Decarboxylation of Acid Salts
Aldehydes
can be prepared by
heating a mixture of calcium methanoate and calcium carboxylate
e.g.
22 New Way Chemistry for Hong Kong A-Level Book 3B
34.4
Preparation of Carbonyl Compounds (SB p.9)
Ketones
can be prepared by
heating calcium carboxylate
e.g.
23 New Way Chemistry for Hong Kong A-Level Book 3B
34.4
Preparation of Carbonyl Compounds (SB p.9)
Reduction of Acyl Chlorides
•
Aldehydes
can be prepared by reducing acyl chlorides by treatment with H 2 catalyst and S in the presence of Pd / BaSO 4 • The purpose of adding sulphur is to
poison the catalyst
, so that
the reduction does not proceed to produce alcohols
24 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.9)
Nucleophilic Addition Reactions
• Carbonyl group is susceptible to
nucleophilic attack
∵
carbonyl carbon bears a partial positive charge
• Nucleophiles use its
lone pair electrons to form a bond with carbonyl carbon
•
One pair of bonding electrons of the carbon-oxygen bond shift out to the carbonyl oxygen
25 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.10) •
The electron-rich oxygen transfers its electron pair to a proton
addition of Nu – H to the carbonyl group 26 • The carbonyl carbon changes
from a trigonal planar geometry (i.e. sp 2 -hybridized) to a tetrahedral geometry (i.e. sp 3 -hybridized)
New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.10) •
Aldehydes are more reactive than ketones
∵
inductive effect
and
steric effect 1. The inductive effect
The
carbonyl carbon in ketones is less electron deficient
because
two alkyl groups release electrons
whereas
only one present in aldehydes
27 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.10) •
2. The steric effect
Aldehyde molecules are relatively open
to the attack of nucleophiles ∵ one group being attached to the carbonyl carbon is a
small hydrogen atom
• In ketones, the two alkyl or aryl substituents cause a
greater steric hindrance
to the nucleophiles 28 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.11) • Due to the above 2 factors, the general order of reactivity of carbonyl compounds: 29 • The
delocalization of
electrons from the benzene ring reduce the electron deficiency of the carbonyl carbon atom
and makes
aromatic carbonyl compounds even less reactive than aliphatic ketones
New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.11)
Addition of Hydrogen Cyanide
Addition of hydrogen cyanide to the carbonyl group to form
2-hydroxyalkanenitriles
(also known as
cyanohydrins
) 30 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.11)
Examples:
31 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.11)
Mechanism for the nucleophilic addition of hydrogen cyanide to the carbonyl group:
32 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.11) •
HCN is a poor nucleophile
while
CN – is much stronger
the reaction can be
catalyzed by a base stronger than CN –
, as the base can increase the concentration of CN – HCN + OH – CN – + H 2 O • As
HCN is very toxic and volatile
, it is safer to generate it in the reaction mixture 33 • Mixing KCN or NaCN with dilute H 2 SO 4 at 10 – 20 ° C gives HCN: 2KCN + H 2 SO 4 2NaCN + H 2 SO 4 2HCN + K 2 SO 4 2HCN + Na 2 SO 4 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.12) •
2-Hydroxyalkanenitriles
organic synthesis are useful intermediates in • On acid hydrolysis, 2-hydroxyalkanenitriles are converted to
2-hydroxycarboxylic acids
or
2-alkenoic acids
e.g.
34 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.12) • With the use of reducing agents (e.g. LiAlH 4 ), 2-hydroxyalkanenitriles are reduced to
amines
e.g.
35 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.13)
Addition of Sodium Hydrogensulphate(IV)
Carbonyl compounds react reversibly with excess 40% aqueous hydrogensulphate(IV) solutions at room temperature 36 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.13)
Examples:
37 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.13) The reaction mechanism: 38 • The reaction is initiated by the
attack of nucleophile, HSO 3 –
New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.13) • This reaction is
very sensitive to steric hindrance
and is
limited to aliphatic aldehydes and sterically unhindered ketones
• This reaction can be used for the
separation and purification of the aldehydes and ketones
, as they can be regenerated by treating the bisulphite addition product with aqueous alkalis or dilute acids.
39 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.14)
Example 34-2
Outline how you are going to separate a mixture of butanone (b.p. 79.6
°
C) and 1-chlorobutane (b.p. 78.5
°
C) in diethyl ether.
Answer 40 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.14)
Solution:
The mixture of butanone and 1-chlorobutane cannot be separated by distillation as their boiling points are too close. However, they can be separated through the nucleophilic addition reaction of sodium hydrogensulphate(IV). With the addition of sodium hydrogensulphate(IV) to the mixture, only butanone reacts to give the bisulphite addition product which is soluble in water. Then the organic later (containing 1 chlorobutane) and the aqueous layer (containing the bisulphite addition product of butanone) are separated using a separating funnel. 1 Chlorobutane can be obtained by distilling off the ether. On the other hand, with the addition of a dilute acid, the bisulphite addition product is converted to the carbonyl compound (i.e. butanone) which dissolves in diethyl ether. The organic layer (containing butanone) is separated from the aqueous layer by means of a separating funnel. Butanone is obtained after distilling off the ether.
41 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.14)
Addition – Elimination (Condensation) Reactions
• Addition – elimination reactions involve the
first addition of two molecules
to form an unstable intermediate followed by the
spontaneous elimination of the elements of water
• e.g. reaction of aldehydes or ketones with the derivatives of ammonia 42 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.14)
Reaction with Hydroxylamine
• Carbonyl compounds react with
hydroxylamine (NH 2 OH)
to form
oximes
43 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.15)
Examples:
44 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.15)
Reaction with 2,4-dinitrophenylhydrazine
• Carbonyl compounds react with 2,4-dinitrophenylhydrazine to form
2,4-dinitrophenylhydrazones
45 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.15)
Examples:
46 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.16) • The oximes and 2,4-dinitrophenylhydrazones are used to
identify unknown aldehydes and ketones
47 • They are
insoluble solids
and have
sharp characteristic melting points
• The products are purified by recrystallization from ethanol and then filtered and washed under suction • Their melting points are determined and compared with that in data book to identify the original aldehyde or ketone New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.16) 48
Carbonyl compound Aldehydes:
Methanal Ethanal Propanal Butanal Benzaldehyde
Ketones:
Propanone Butanone Pentan-2-one Pentan-3-one Hexan-2-one Phenylethanone
Formula
HCHO CH 3 CHO CH 3 CH 2 CHO CH 3 CH 2 CH 2 CHO C 6 H 5 CHO CH 3 COCH 3 CH 3 CH 2 COCH 3 CH 3 CH 2 CH 2 COCH 3 CH 3 CH 2 COCH 2 CH 3 CH 3 CH 2 CH 2 CH 2 COCH 3 C 6 H 5 COCH 3
Melting point of 2,4-dinitrophenylhydrazone (
°
C)
167 146, 164 (2 forms) 156 123 237 128 115 141 156 107 250 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.17)
Check Point 34-2
49 attack.
In the case of alkenes, they always undergo electrophilic addition reactions. As the bonding electrons of the carbon-carbon double bond are only loosely held by the carbon atoms and are exposed, the carbon carbon double bond is susceptible to electron-loving reagents (i.e. electrophiles) New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.17)
Check Point 34-2
(b) Describe briefly how you can distinguish between two carbonyl compounds having similar boiling points.
Answer (b) The two compounds can be distinguished by determining the melting points of their 2,4-dinitrophenylhydrazone derivatives.
50 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.17)
Oxidations
• Aldehydes can be oxidized to carboxylic acids by
strong oxidizing agents such as KMnO 4 and K 2 Cr 2 O 7
, and also by
mild oxidizing agents such as Tollen’s reagent and Fehling’s reagent
51 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.18)
Reaction with Potassium Manganate(VII) and Potassium Dichromate(VI)
• Aldehydes are oxidized readily by common oxidizing agents such as
KMnO 4 /H +
and
K 2 Cr 2 O 7 /H +
52 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.18) • Generally,
ketones do not undergo oxidation
as their oxidation involves the
cleavage of the strong carbon carbon bond
•
More severe conditions
are required to bring about the oxidation 53 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.18)
Reaction with Tollens’ Reagent (Silver Mirror Test)
• Tollens’ reagent contains
Ag(NH 3 ) 2 +
• Ag(NH 3 ) 2 + oxidizes aldehydes to carboxylic acids while it is reduced to metallic silver which deposits on the wall of the reaction vessel as
silver mirror
54 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.19) • Aldehydes are mixed with Tollens’ reagent in a clean test tube and placed in water bath kept at 60 ° C •
If the wall of the reaction vessel is not clean enough, a silver mirror cannot be formed
and a black precipitate is deposited instead •
All ketones give a negative result of the silver mirror test
• This reaction can be used
to distinguish aldehydes from ketones
55 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.18)
Reaction with Fehling’s Solution (Fehling’s Test)
• Fehling’s solution is an alkaline solution of copper(II) tartrate. It is a blue solution •
Aliphatic aldehydes reduce the Cu 2+ ion in Fehling’s solution to form a brick-red precipitate of Cu 2 O
56 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.18) Addition of an aliphatic aldehyde Fehling’s solution 57 •
Ketones and aromatic aldehydes give a negative result of Fehling’s test
• This reaction can be used to
distinguish aliphatic aldehydes from ketones and aromatic aldehydes
New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.20)
Reductions
• Aldehydes and ketones undergo
reduction reactions
forming 1 ° and 2 ° alcohols respectively 58 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.20)
Reaction with Lithium Tetrahydridoaluminate
•
Lithium tetrahydridoaluminate
(also called lithium aluminium hydride, LiAlH 4 ) is a powerful reducing agent • It reduces
aldehydes to 1
°
alcohols
and
ketones to 2
°
alcohols
59 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.20) 60 • LiAlH 4 is able to reduce
give alcohols carboxylic acid and esters to
•
LiAlH 4 reacts violently with water
, therefore the reaction must be carried out
in anhydrous solutions
, usually
in dry ether
New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.21)
Reaction with Sodium Tetrahydridoborate
In practice, the reduction of aldehydes and ketones to alcohols is carried out by
sodium tetrahydridoborate
(also called sodium borohydride, NaBH 4 ) 61 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.21) •
NaBH 4 is a less powerful reducing agent than LiAlH 4
• NaBH 4 reduces only
aldehydes and ketones
• The reduction by NaBH 4 can be carried out
in water or alcohol solutions
62 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.21)
Triiodomethane Formation (Iodoform Reaction)
Aldehydes or ketones having the group react with
iodine in aqueous sodium hydroxide solution
to give a
bright yellow precipitate of iodoform (CHI 3 )
63 New Way Chemistry for Hong Kong A-Level Book 3B
34.5
Reactions of Carbonyl Compounds (SB p.21) •
Ethanol and secondary alcohols
with the also give a
positive result of iodoform test
group ∵ the group is first oxidized to group and further oxidized to give the carboxylate and the iodoform 64 •
Iodoform test is test for the presence of
New Way Chemistry for Hong Kong A-Level Book 3B
or
65
34.5
Reactions of Carbonyl Compounds (SB p.22)
Check Point 34-3
Draw the structural formulae of the major organic products A to H in the following reactions:
(a) A:
(a) CH 3 CH 2 CHO
20
°
C
B:
A
B (b) CH 3 CH 2 CHO
(b) C:
C (c) CH 3 CH 2 CHO
2. H 3 O + D (d) CH 3
(c) D: CH 3 CH 2 CH 2 OH
NaBH 4 CH = CHCH
(d) E: CH 3
2 CHO
CH = CHCH 2 CH 2 OH
E
Answer New Way Chemistry for Hong Kong A-Level Book 3B
66
34.5
Reactions of Carbonyl Compounds (SB p.22)
Check Point 34-3
Draw the structural formulae of the major organic products A to H in the following reactions: (e)
(e) F:
(f)
(f) G: Answer H: CHI 3 New Way Chemistry for Hong Kong A-Level Book 3B
34.6
Uses of Carbonyl Compounds (SB p.22)
As Raw Materials for Making Plastics
Urea-methanal
Urea-methanal is produced by
condensation polymerization of urea and methanal
under heat and pressure with the
elimination of a water molecule
67 New Way Chemistry for Hong Kong A-Level Book 3B
34.6
Uses of Carbonyl Compounds (SB p.23) In the presence of excess methanal, cross linkages will be formed 68 New Way Chemistry for Hong Kong A-Level Book 3B
34.6
Uses of Carbonyl Compounds (SB p.24)
Urea-methanal
•
thermosetting polymer
(cannot be softened and insoluble in any solvents) •
excellent electrical insulator
•
resistant to chemical attack
• used for moulding
electrical sockets
69 New Way Chemistry for Hong Kong A-Level Book 3B
34.6
Uses of Carbonyl Compounds (SB p.24)
Perspex
Propanone is converted to methyl 2-methylpropenoate, which is the monomer for the production of perspex 70 • Perspex is a dense, transparent solid • Used to make safety goggles, advertising signs and carside light protectors New Way Chemistry for Hong Kong A-Level Book 3B
34.6
Uses of Carbonyl Compounds (SB p.24)
As Solvents Propanone
• Liquid with a boiling point of 56.2
° C • Can
dissolve a variety of organic compounds
• Important solvent used in industry and in the laboratory 71 New Way Chemistry for Hong Kong A-Level Book 3B
The END
72 New Way Chemistry for Hong Kong A-Level Book 3B