Transcript 無投影片標題 - SALEM-Immanuel Lutheran College
Alkanes and Free Radical Substitution
1 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Preparation of Alkanes
2 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Crude Oil as a Source of Alkanes
Petroleum Refining
• The first step is fractional distillation separate petroleum into fractions based on the volatility of its components performed in a petroleum refinery a fractionating tower is used 3 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Petroleum Refining
4 A petroleum refinery New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
A simplified diagram of a fractionating tower Contains H 2 S Removed by treatment with a weak base 5 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
6 Typical fractions obtained by fractional distillation of petroleum
Fraction
Fuel gas (e.g. LPG) Petrol Naphtha Gas oil (Diesel oil)
Boiling point range
40
( o C)
< 40 220 – 150 – 350
Number of carbon atoms that the molecules contain
1 – 4
Major uses
Gaseous fuel, raw materials for manufacture of chemicals 5 – 10 Fuel for motor vehicles 10 – 14 For making town gas 14 – 25 Fuel for trucks, lorries and locomotives New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
7 Typical fractions obtained by fractional distillation of petroleum
Fraction
Fuel oil Lubricating oil Bitumen
Boiling point range ( o C) Number of carbon atoms that the molecules contain
> 350 > 25
Major uses
Fuel for cargo ships and generating electricity in power stations > 350 > 350 > 25 > 25 Lubricating oil for moving parts of machinery For surfacing roads and roofs New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Cracking of Petroleum
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9
Cracking of Petroleum
• Convert hydrocarbons from heavier fractions into lighter fractions • Performed in the absence of air • Providing lighter fractions of petroleum , alkenes and sometimes H 2 and C C 14 H 30 C 11 H 24 C 8 H 18 C + 9 H 20 2CH 2 + CH =CH 2 2 =CH + 2 2C + 2H 2 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
10
Thermal Cracking
• The process is done at high temperature in the absence of catalysts
Hydrocracking
• The process is done at very high pressure of H 2 in the absence of catalysts
Alkanes obtained are mainly unbranched
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11
Catalytic Cracking
• When a mixture of alkanes from the heavier fractions is heated at relatively low T & P in the presence of catalysts • The molecules break down and
rearrange
into smaller,
highly branched
hydrocarbons New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Unbranched petrol is not a good motor fuel It burns before it is ignited by the spark plug of the petrol engine (
pre-ignition
).
The shock wave creates the characteristic metallic pinging sound (
engine knocking
) A waste of energy Branched (anti-knocking) petrol can be produced by
reforming
.
12 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Reforming
• Straight-chain alkanes under pressure in the presence of a platinum catalyst are heated
reforming
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Laboratory Preparation of Alkanes
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1.
Hydrogenation of alkenes + H 2 Ni, 200 ° C high P + H 2 Pt, 25 ° C H H H H 15 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Methods 2 and 3 below are specific to the preparation of
methane
and
benzene
.
16 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
2.
Decarboxylation sodium benzoate by heating with soda lime (NaOH + CaO) of sodium ethanoate or CH 3 COO Na O H(s) from soda lime fusion CH 4 + Na 2 CO 3 COO Na (s) Na O H(s) from soda lime fusion + Na 2 CO 3 17 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
RCH 2 COO Na + Na O H More difficult Na 2 CO 3 + RCH 3 + other C x H y Not easy to separate mixture into individual alkanes.
Not suitable for preparing alkanes other than methane.
18 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
3. Heating aluminium carbide with HCl (Optional) Al 4 C 3 + 12H Cl 3CH 4 + 4AlCl 3 19 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
4.
Reduction of halogenoalkanes (optional) 20 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Reactions of Alkanes
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22
Reactivity of Alkanes
• Inertness to chemical reactions strong C C and C H bonds • C and H have nearly the same electronegativity C H bonds are only slightly polarized not easily attacked by charged particles
Alkanes
paraffin
little affinity
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Two Ways of Breaking Covalent Bonds : 1. Homolytic fission 2. Heterolytic fission 23 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Homolytic fission (homolysis) A B Symmetrical breaking 24 A + B Free radicals each containing an unpaired electron New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Homolytic fission (homolysis) 25 A B The movement of single electron is represented by a half-curly arrow A + B Free radicals are very reactive(unstable). They tend to look for an additional electron to complete the octet.
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Homolytic fission is favoured 1. when the bonding atoms have equal or similar electronegativities; 2. at high temperature; 3. when the reaction mixture is exposed to UV light; 4. in the presence of peroxides ( - O – O - ) (All favour the formation of free radicals) 26 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Heterolytic fission (heterolysis) A B Unsymmetrical breaking A + + B when B is more electronegative A B A + B + when A is more electronegative 27 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Heterolytic fission (heterolysis) A B A + + B A B A + B + The movement of an electron pair is represented by a curly arrow.
28 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Hetrolytic fission is favoured 1. when the bonding atoms have significantly different electronegativities; 2. in the presence of a polar solvent which can stabilize the ions formed by ion-dipole interaction.
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Q.23
Homolytic fission H H C H H C H H 30 H H C + H H C H H H H C H H C H + H New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Q.23
31 H carb H C H
anion
H C H H H H H + + H H C H C H C H H H C H H H C + C H H New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A H
Q.23
32 H H C H
carbo
H C H H
cation or carbonium ion
H H H + + H H C H C H C H H H C H H H C + C H H New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A H
1. Pyrolysis (Cracking) Homolytic fission of C – C and/or C – H bonds e.g. C 6 H 14 heat catalyst C 3 H 8 + C 3 H 6 33 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Q.24
C 6 H 14 C 6 H 14 C 6 H 14 C 6 H 14 C 6 H 14 34 C 2 H 6 C 4 H 10 CH C 2 4 C 2 H 4 H 6 + C + C + C 5 + C New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A 4 3 2 H H H 8 10 + C 4 H 8 H 8 4 + H 2 + C
Q.25
35 CH 2 H CH 2 + New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
36
2. Combustion
• When alkanes react with sufficient oxygen carbon dioxide and water are formed release a large amount of heat known as complete combustion New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Combustion
• General equation for the complete combustion of an alkane: C n H 2n+2 3 n 2 1 + ( )O 2 nCO 2 + (n + 1) H 2 O 37 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
38
Combustion
• Alkanes are a common fuel • Methane gas is the main component of natural • Butane is a component of bottle gas Butane is used as the fuel for a portable gas burner New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Q.26
• In limited supply of oxygen, • Large alkanes with high carbon contents 39 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
3. Halogenation (free radical substitution) Alkanes react with halogens to give haloalkanes and hydrogen halide RH + X 2 UV light or heat or peroxide RX + HX X 2 = F 2 , Cl 2 , Br 2 or I 2 40 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Halogenation
• One or more hydrogen atoms in methane are substituted by chlorine atoms depend on the relative amounts of methane and chlorine 41 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
42
Halogenation
CH 4 (g) + Cl 2 (g) CH 3 Cl (g) + HCl(g) CH 3 Cl (g) + Cl 2 (g) CH 2 Cl 2 (g) + HCl(g) CH 2 Cl 2 (g) + Cl 2 (g) CHCl 3 (g) + HCl(g) CHCl 3 (g) + Cl 2 (g) CCl 4 (g) (g) + HCl(g) New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
43
Halogenation
• When methane is in excess chloromethane predominates in the products • When chlorine is in excess tetrachloromethane predominates in the products New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
44
Halogenation
• The reactivity of halogens decreases in the order: F 2 > Cl 2 > Br 2 > I 2 • Not a good method to prepare haloalkanes since it is difficult to separate the resulting mixture into individual haloalkanes.
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Q.27(a) C n H 2n+2 = 72 12n + 2n + 2 = 72 n = 5 H 3 C CH 3 C CH 3 CH 3 All 12 H atoms are identical and only ONE kind of monochlorinated product can be obtained.
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Q.27(b) 3C 1C H * 2C 46 * * H H New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Q.27(b) 47 H * * H New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
1.
Which piece of evidence suggests that the reaction is a chain reaction ?
C For each photon of light absorbed, many thousands of molecules of chloromethane are formed.
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2.
Which of the following is the first step of the mechanism?
CH 4 Cl 2 CH 2Cl 3 CH 4 CH 4 Cl 2 CH CH Cl + 3 3 + + H + H + H + Cl + homolytic heterolytic 49 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
For
elementary
transition state resembles that of the final products.
steps, the structure of the 50 the stability of the transition state is determined by the stability of the final products.
the activation energy can be estimated by the enthalpy change of the elementary step The more endothermic reaction proceeds more slowly.
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CH 4 CH 3 + H H = +435 kJ mol 1 Cl 2 2Cl H = +242 kJ mol 1 51 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
CH 4 H CH 3 + + H +435 +949 78 CH 3 + H H = +435 + 949 -78 = +1306 kJ mol 1 52 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
CH 4 H CH 3 + H + +435 -7.7
+1310 CH 3 + H H = +435 -7.7 +1310 = +1737.3 kJ mol 1 53 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Cl 2 H Cl + + Cl +242 +1260 355 Cl + Cl H = +242 + 1260 -355 = +1147 kJ mol 1 54 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Cl 2 2Cl H = +242 kJ mol 1
First step of the mechanism
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3.
Second step of the mechanism Cl + CH 4 CH 3 Cl + H Cl + CH 4 CH 3 + HCl 56 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Cl + CH 4 CH 3 Cl + H +435 Cl 350 + CH 3 + H H = +435 -350 = +85 kJ mol 1 57 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
58 Cl + CH 4 CH 3 + HCl +435 431 Cl + H + CH 3 H = +435 -431 = +4 kJ mol 1 does not lead to formation of H 2 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
4.
The 3rd step of the mechanism It gives the other product CH 3 Cl It gives another Cl cycle.
to complete the chain CH 3 + Cl 2 CH 3 Cl + Cl 59 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
5.
Termination steps CH 3 Cl + CH 3 + Cl CH 3 + Cl CH 3 CH 3 Cl Cl CH 3 Cl 60 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Reaction Mechanism: Free Radical Substitution Reaction 1. Chain initiation • Homolytic fission of a chlorine molecule • Two chlorine radicals are formed 61 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Reaction Mechanism: Free Radical Substitution Reaction 2. Chain propagation 62 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Reaction Mechanism: Free Radical Substitution Reaction 3. Chain termination 63 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
7.
Which step is rate-determining ?
64 The propagation stage is the most time consuming.
Cl + CH 4 CH 3 + HCl H = +4 kJ mol 1 CH 3 + Cl 2 CH 3 Cl + Cl +242 CH 3 + 350 Cl + Cl H = +242 -350 = 108 kJ mol 1 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
7.
Which step is rate-determining ?
The propagation stage is the most time consuming.
1. Cl + CH 4 2. CH 3 + Cl 2 CH 3 + HCl CH 3 Cl + Cl 65 Or, E(C – H) > E(Cl – Cl) 435 kJ mol 1 Step 1 has higher E a 242 kJ mol 1 rate-determining New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
66 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Stability of Alkyl Radicals • According to the number of alkyl groups directly attached to the carbon that bears the unpaired electron alkyl radicals are classified as primary , secondary or tertiary 67 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Stability of Alkyl Radicals
Methyl radical
( no alkyl group attached to the carbon that bears the unpaired electron) 68
Primary radical Secondary radical
( one alkyl group attached to the carbon that bears the unpaired ( two alkyl groups attached to the carbon that bears the unpaired electron) electron) New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Tertiary radical
( three alkyl groups attached to the carbon that bears the unpaired electron)
69 Stability of Alkyl Radicals • The stability of the alkyl radicals decreases in the order: R 3 C Tertiary alkyl radical > R 2 CH Secondary alkyl radical > RCH 2 Primary > alkyl radical CH 3 Methyl radical New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
70 Stability of Alkyl Radicals • Alkyl radical has an unpaired electron • Electron-deficient • Stabilized by substituents (e.g. alkyl groups ) release electrons to the carbon atom bearing the unpaired electron New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Electron-donating property of alkyl groups arises from the polarization of C – H bonds + H + H C C + H 71 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Electron-donating groups(e.g. alkyl groups) cause
positive inductive effect
on adjacent groups.
Electron-withdrawing groups(e.g. -F) cause
negative inductive effect
on adjacent groups.
Inductive effect arises
from polarization of
bonds.
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Q.28(a) Cl 73 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A Cl
Cl No. of reaction sites Cl 74 2 reaction sites 6 reaction sites Stability of free radical intermediates is more important than the no. of reaction sites available New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Q.28(a) Cl Cl 75 Stability : H 3 C H > H 2 C 2 ° CH 3 H 3 C 1 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A ° 2
Q.28(b) Cl Cl 76 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Cl No. of reaction sites 77 Cl 9 reaction sites 1 reaction site Stability of free radical intermediates is more important than the no. of reaction sites available New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
Q.28(b) 78 Cl Cl Stability : H 3 C CH 2 CH 1 ° CH 3 < H 3 C CH 3 C 3 ° CH 3 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
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The END
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27.2
Nomenclature of Alkanes (SB p.148)
Draw the structures of the following compounds. Are the names provided correct or incorrect? If they are incorrect, give the correct name.
(a) 2,4-Dimethylpentane
Answer
(a) The name is correct. 81 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.2
Nomenclature of Alkanes (SB p.148)
Draw the structures of the following compounds. Are the names provided correct or incorrect? If they are incorrect, give the correct name.
(b) 1,3-Dimethylpentane
Answer
(b) The name is incorrect. The correct name is 3-methylhexane. 82 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.2
Nomenclature of Alkanes (SB p.148)
Draw the structures of the following compounds. Are the names provided correct or incorrect? If they are incorrect, give the correct name.
(c) 4-Ethyl-1-methylheptane
Answer
(c) The name is incorrect. The correct name is 4-ethyloctane.
83 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.2
Nomenclature of Alkanes (SB p.149)
Draw the structures of all the isomers of C 6 H 14 , and give the IUPAC names for all the structures drawn.
Answer
84 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.4
Preparation of Alkanes (SB p.155)
Define each of the following terms and give an example of each: (a) Catalytic cracking
Answer
85 (a) Catalytic cracking is the process in which a mixture of alkanes from the heavier fractions is heated at very high temperatures, in the presence of catalysts and the absence of air. Smaller and highly branched hydrocarbons are formed.
For example, C 8 H 18 C 5 H 12 + C 3 H 6 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.4
Preparation of Alkanes (SB p.155) 86
Define each of the following terms and give an example of each: (b) Thermal cracking
Answer
(b) Thermal cracking is the breakdown of large alkane molecules in the heavier fractions into lighter fractions of smaller molecules in the absence of catalysts and air. Straight-chain alkanes are usually formed in this process. For example, C 14 H 30 C 8 H 18 + 2CH 2 = CH 2 + 2C + 2H 2 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.4
Preparation of Alkanes (SB p.155)
Define each of the following terms and give an example of each: (c) Reforming
Answer
(c) Reforming is a process in which straight-chain alkanes are heated under pressure in the presence of a platinum catalyst. The chains break up and reform to give branched-chain molecules. For example, 87 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.5
Reactions of Alkanes (SB p.161)
(a) Explain why cracking has to be carried out in the absence of air.
Answer
(a) Cracking must be carried out in the absence of air because combustion occurs instead of cracking in the presence of air.
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27.5
Reactions of Alkanes (SB p.161)
(b) An alkane has a relative molecular mass of 72 and produces one product only on monochlorination. Deduce its structure.
Answer
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27.5
Reactions of Alkanes (SB p.161)
(b) Let the molecular formula of the alkane be C n H 2n+2 .
Relative molecular mass of the alkane = 72 12.0 × n + 1.0 × (2n + 2) = 72 n = 5 ∴ The alkane has the molecular formula of C 5 H 12 .
As the alkane produces one product only on monochlorination, all hydrogen atoms of the alkane molecule must be equivalent.
∴ It must be 90 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.5
Reactions of Alkanes (SB p.161) Two isomeric compounds A and B have the molecular formula C 3 H 7 Cl. Chlorination of A gave a mixture of two dichlorides of formula C 3 H 6 Cl 2 . Chlorination of B gave three different compounds of formula C and the dichlorides obtained from each?
3 H 6 Cl 2 (they may not all be different from the dichlorides from A). What are the structural formulae of A and B
Answer
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27.5
Reactions of Alkanes (SB p.161) A: B: Dichlorides formed from A: 92 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.5
Reactions of Alkanes (SB p.161) Dichlorides formed from B:
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27.5
Reactions of Alkanes (SB p.162)
The chlorination of butane gives a mixture of products as shown below:
94
Explain their formation and also their relative abundances.
Answer
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27.5
Reactions of Alkanes (SB p.162) The two products arise because in one of the propagation steps of the reaction, a chlorine atom may abstract a hydrogen atom from either C1 or C2 of butane to give two different radicals.
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27.5
Reactions of Alkanes (SB p.162) 96 The resulting free radicals react with chlorine in a succeeding propagation step to give the corresponding haloalkane. Butyl radical gives only 1-chlorobutane while secondary butyl radical gives only 2 chlorobutane.
Since the more stable secondary radical is formed at a higher rate, 2-chlorobutane is formed as the major product of the reaction.
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27.5
Reactions of Alkanes (SB p.162)
Give the structure of the major product formed by free radical bromination of each of the following: (a) Methylcyclopentane
Answer
(a) Bromomethylcyclopentane 97 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A
27.5
Reactions of Alkanes (SB p.162)
Back Give the structure of the major product formed by free radical bromination of each of the following: (b) 2,2,4-Trimethylpentane
Answer
(b) 4-Bromo-2,2,4-trimethylpentane 98 New Way Chemistry for Hong Kong A-Level 3A New Way Chemistry for Hong Kong A-Level Book 3A