Chemistry 2 For Ocr (Cambridge Ocr Advanced Sciences)

247 Pages·18.659 MB·English

by  David Acaster, Lawrie Ryan, Brian Ratcliff, Helen Eccles, Anne McCarthy

Introduction
Chapter 1: Atomic structure
Cambridge OCR Advanced Sciences
The new Cambridge OCR Advanced Sciences course in Unit F325. The content of the chapters is generally
provides complete coverage of the revised OCR arranged in the same sequence as in the specification.
AS and A2 Level science specifications (Biology, The book builds on the material covered in
Chemistry A and Physics A) for teaching from Chemistry 1 for OCR. The language is kept simple,
September 2008. There are two books for each to improve accessibility for all students, while still
subject – one covering AS and one covering A2. maintaining scientific rigour throughout. Care is
Some material has been drawn from the existing taken to introduce and use all the specialist terms that
Cambridge Advanced Sciences books; however the students need to gain a complete understanding of the
majority is new. chemical concepts introduced. In the text, key terms
The course has been developed in an innovative are highlighted in bold.
format, featuring Cambridge’s new interactive PDFs The depth and breadth of treatment of each topic
on CD-ROM in the back of the books, and free access is pitched at the appropriate level for OCR A2
to a dedicated website. The CD-ROM provides students. The accompanying CD-ROM also contains
additional material, including detailed objectives, some extension material that goes a little beyond
hints on answering questions, and extension material. the requirements of the specification, which should
It also provides access to web-based e-learning interest and stretch more able students.
activities to help students visualise abstract concepts, Some of the text and illustrations are based on
understand calculations and simulate scientific material from the endorsed text Chemistry 2, which
processes. covered the earlier OCR specification, while some
The books contain all the material required for is completely new. All of it has been reviewed and
teaching the specifications, and can be used either on revised, ensuring that the new specification is fully
their own or in conjunction with the interactive PDFs covered. In addition to the main content in each
and the website. chapter, there are also How Science Works boxes,
In addition, Teacher Resource CD-ROMs with describing issues, applications or events, which put
book PDFs plus extra material such as worksheets, the chemical content introduced into a social context.
practical activities and tests, are available for each Self-assessment questions (SAQs) in each chapter
book. These CD-ROMs also provide access to the provide opportunities to check understanding. They
new Cambridge OCR Advanced Sciences Planner often address misunderstandings that commonly
website with a week-by-week adaptable teaching appear in examination answers, and will help students
schedule. to avoid such errors. Some SAQs are marked, with a
vertical red bar, as ‘stretch and challenge’ questions.
Introduction to Chemistry 2 for OCR – These ask students to draw together their ideas about
the chemistry A2 text a topic, and to organise and discuss these in a well-
This book covers the entire OCR A2 Chemistry A structured and broad-ranging answer. These questions
specification for first examination in 2010. Chapter give students the opportunity to demonstrate their
1 revisits AS Level organic chemistry. Chapters 2 to potential, and may help them to recognise areas
10 correspond to Unit F324, Rings, Polymers and of weakness in which further work is needed. Past
Analysis. Chapters 11 to 17 correspond to Unit F325, examination questions at the end of each chapter
Equilibria, Energetics and Elements. Each chapter allow students to practise answering exam-style
covers one of the numbered sections within the three questions. The answers to these, along with exam-
Modules in Unit F324, and within the three Modules style mark schemes and hints on answering questions,
are found on the accompanying CD-ROM.
v
Contents
Chapter 1: Atomic structure
Introduction v 6 Amino acids and chirality 46
Amino acids 46
Proteins and polypeptides 47
Acknowledgements vi
Stereoisomerism 48
Unit F324: Rings, Polymers and 7 Polyesters and polyamides 53
Analysis The formation of polymers 53
Degradable plastics 58
1 AS level organic chemistry revisited 1
Some revision 1 8 Synthesis 63
Naming organic compounds 3 How do we design molecules? 63
Isomerism 5 Routes to new molecules 64
Summaries of reactions from AS Chemistry 5 Chirality in pharmaceutical synthesis 66
2 Arenes 9 9 Chromatography 71
Benzene 9 Mechanisms of chromatographic separation 72
Energetic stability of benzene 12 Paper chromatography 73
Substitution reactions 12 Thin-layer chromatography 74
Addition of halogens to benzene 14 Gas chromatography (GC) 75
Phenols and their properties 15 Gas chromatography–mass spectrometry
(GC-MS) 78
3 Carbonyl compounds 20
Aldehydes and ketones 20 10 Spectroscopy 82
Physical properties of the carbonyl group 21 Nuclear magnetic resonance spectroscopy 82
Preparation: oxidation of alcohols 21 Combined techniques 90
Reduction 22
Characteristic tests 23
Unit F325: Equilibria, energetics
and elements
4 Carboxylic acids and esters 27
Carboxylic acids 28
Esters 29 11 How fast? 96
The rate equation 97
Order of reaction 100
5 Amines 39
Concentration against time graphs 101
Primary amines 39
Half-life and reaction rates 102
The preparation of amines 40
Finding the order of reaction using raw data 103
Amines as bases 41
Rate constants and temperature changes 106
Making salts with amines 41
Rate equations and mechanisms 107
Reactions specific to phenylamine 42
iii
Contents
12 How far? 118 Using cell voltage to predict whether or
Equilibria in organic reactions 118 not a reaction will occur 184
The amounts of substances present at Limitations of the standard electrode
equilibrium 119 potential approach 186
K and Le Chatelier’s principle 123 Reaction rate has a role to play too 187
c
Storage cells 187
Fuel cells 188
13 Acids, bases and buffers 130
The hydrogen economy 191
Definitions of acids and bases 130
The role of water 133
Base behaviour and neutralisation 133 17 Transition elements 196
Introducing K , the ionic product of water 135 Electronic structures 197
w
Introducing pH 137 Properties of transition elements and their
Ionic equilibria: the definition of K compounds 198
a
and pK 138 Complexes 199
a
Calculating the pH of a weak acid 139 Redox behaviour 208
Calculating [H+] from a pH value 140
Calculating the K of a weak acid 141
a Appendix A 214
Measuring pH 141
Acids with alkalis: monitoring change 143
Appendix B 215
Buffer solutions 146
Calculating the pH of a buffer solution 148
Answers to self-assessment questions 216
14 Lattice enthalpy 154
The Born–Haber cycle 154 Glossary 232
Trends in the lattice enthalpy 157
Enthalpy change of solution 158
Index 236
Enthalpy change of hydration 159
Using enthalpies of solution and hydration 159
15 Entropy 165
Entropy changes 166
Free energy 167
16 Electrode potentials and fuel cells 171
Oxidation and reduction 171
Electrode potentials 173
Standard electrode potentials 174
Measuring a standard electrode potential 176
The meaning of E values 179
Using E values to predict cell
voltages 180
Using E values to predict whether
or not a reaction will occur 181
iv
Chapter 1
AS level organic chemistry
revisited
Some revision • A general formula may be written for each
Unit F324, Rings, Polymers and Analysis continues homologous series. For example, the general
the study of organic chemistry that you began in AS formula of the aliphatic alcohols is C H OH
n 2n+1
Unit F322 Chains, Energy and Resources (covered (where n is the number of carbon atoms present).
•
in Chapters 10–14 of Chemistry 1). You should have Empirical formulae (simplest formulae) are
a sound knowledge and understanding of the organic determined by experiments. They give the
chemistry from Chemistry 1 before you study the simplest whole-number ratio of elements present
new A2 material introduced in this unit. This chapter in a compound. However, they give no indication
provides an opportunity for you to review and extend of structure. For example, the empirical formula
appropriate material from Chemistry 1. of ethene, whose molecules contain two carbon
We can study organic chemistry in a particularly atoms and four hydrogen atoms, is CH .
2
•
structured and systematic manner. That is because The molecular formula of a compound tells us
each different atom or group of atoms attached to the actual numbers of atoms of each element in
a carbon atom in an organic compound has its own one molecule of a compound. So the molecular
characteristic set of reactions. Chemists call these formula of ethene is C H . The molecular formula
2 4
different groups of atoms functional groups. In is used when you need to calculate the molecular
Chemistry 1, you studied the reactions of the alkene mass of a compound.
•
functional group (>C=C<). Structural formulae are particularly useful
The functional groups that you will study in this when writing equations involving aliphatic
unit are shown in Table 1.1. compounds. For example, the structural formula
Table 1.1 provides you with the classes and of 3-methylpentane is CH CH CH(CH )CH CH .
3 2 3 2 3
•
structures of these functional groups. An example Skeletal formulae are the clearest and easiest way
is also provided of a simple molecule containing to represent cyclic compounds in equations. For
each functional group. Each functional group example, cyclohexane is represented by a simple
gives rise to a homologous series. For example, hexagon.
•
the alcohol functional group gives rise to the Displayed formulae (sometimes called full
homologous series of alcohols. The first four of structural formulae) show all the atoms and bonds
these are methanol (CH OH), ethanol (CH CH OH), in a molecule in a 2D drawing. They are useful in
3 3 2
propan-1-ol (CH CH CH OH) and butan-1-ol checking that you have included the correct number
3 2 2
(CH CH CH CH OH). The members of a homologous of atoms and bonds. Examination questions often
3 2 2 2
series all have similar chemical properties. ask you to provide displayed formulae. However,
Organic compounds are also classified as either remember that they do not give a true indication
aliphatic or aromatic. Aromatic compounds contain of the shape of a molecule. Shapes are best
one or more arene rings; all other organic compounds represented using three-dimensional formulae
are aliphatic compounds. which attempt to show the actual arrangement of
Chemists use different types of formulae to atoms in space by using some bonds that appear to
represent organic molecules. stick out from or retreat into the plane of the page.
1
FIGURE NUMBER: 0521798825c01awf009-17
JOB No: 8369
CLIENT: C.U.P
JOB TITLE: A2 Core Chemistry
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C C C
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CLIENT: C.U.P CLIENT: C.U.P
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CLIENT: C.U.P
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destination
FIGURE NUMBgErRo:u 0p521798825c01awf009-17 example
FIGURE NUMBER: 0521798825c01awf009-17 JOB No: 8369 O
JOB No: 8369 CLIENT: C.U.Palkenes ethene CH2=CH2
C C C
CLIENT: C.U.P JOB TITLE: A2 Core Chemistry
c01awf017-pf1
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SAVED AS: 0521798825c01awf009-1F7IG_pUfR1E NUMBER: 0521798825c01awf009-a1r7enes FIGURE NUMBER: 0521798825c01awf009-17 benzene
JOB No: 8369 C C JOB No: 8369 C C C C
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SAVED AS: 0521798825c01awf009-17_pf1 SAVED AS: 0521798825c01awf009-17_pf1 3
ac0lc1oawhfo0l0s9 a-pnfd1 phenols c0–1OawHf010-pf1 c0c011awawf0f0110m-9p-efpt1fh1anol, phenol cc0011aCawwHff00311O20-H-ppff,11 c01awf01H1-pf1 c01awf012-pf1
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CLIENT: C.U.P aldeChydCes O ethanal CCH3CHO O
C C C C
JOB TITLE: A2 CCore CChemistry C C
SAVED AS: 0521798825c01awf009-17_pf1 O OC O OHO O HCO O
H O NH O
C C C CC C O C C 2O
C C
C C kc0e1taownfe0s09C-pf1 cc0011aawwff00C11O03H--ppCOff11 cc0011aawOwff00114CC1p-O-rpCpoff11panone cc0011aaCwwfHOf001315CO2--HOppff1C1H3 c01awOf0CO16C-pf1
c01awf009-pf1 c01awf010-pf1 c01awf011-pf1 c01awCf012C-pf1 C H C NH2 C H NH2
C OH O C
c01awf013-pf1 c01awf014-pf1 c0c011awawf0f01153-p-pf1f1 cc0011aawwff001164--ppff11 c01awf0N1H5-pf1 c01awf016-pf1
2
c01awf009-pf1 c01awf010-pf1 c0c011awawf0f00191-p-pf1f1 c0c10a1wawf0f1001-2p-fp1f1 c01awf011-pf1 c01awf012-pf1
carboxylOic acids OO O ethanoic acid CH COOH
c01awf013-pf1 c01awf014-pf1 c01aOwf3015-pf1 c01awf016-pf1
O O O C N
C C C C OCC C
C
C C C C
C C OHH O C
C OH OC CN C N NH2
O esters O c01awNf0HO172-pfO1 eOtOhyl ethanoate CHO3COOC2H5 O
c01awf009-pf1 c01awCf01C0-pf1 c01c0aw1afw01f03C1-p1f-1pf1 c01ca0w1CCfaC0w1f40C-1Np2f1-pf1 c01awf01C5-pf1 c01aCwf016-pf1
c01awf013-pf1 c01awf014-pf1 c01awf015-pf1 c01awf016-pf1 C C
C OH O CC OH O C
c01awf017-pf1 c01awf01N7-Hp2f1 NH2
amines –NH methylamine CH NH
2 3 2
c01awf013-pf1 c01awf014-pf1 cc0c0101a1awawfwf00f101713-5-pp-fpf11f1 c0c10a1wawf0f1041-6p-fp1f1 c01awf015-pf1 c01awf016-pf1
O O O
amiCdesN O ethanamide CH3CONH2
CC NC C C OH
C
C OH O C
NH
2 OH OH
C N nc0it1raiwlefs017-pf1 C N ethanenitrile CH CN
c01ca0w1af0w1f70-1p3f-1pf1 c01awf014-pf1 c01awf015-pf1 c01awf016-pf1 3
OH
Table 1.1 The functional groups you will meet in this unit.
c01awf017-pf1 c01awf017-pf1
SAQ You will see various computer-generated images of
C N
OH
1 Draw the following types of formulae for molecules where appropriate throughout this book.
OH
2-methylbutan-2-ol: The colours used in these images are shown in Table 1.2.
a displayed Another type of image that will be used in this
c01awf017-pf1
b structural OH book is a sOpaHce-filling model. In space-filling models,
c skeletal. atoms are shown as including the space occupied
by their electron orbitals. As their orbitals overlap
2 What is the molecular formula of significantly, a very different image from the ball-
2-bromobutane? and-stick model results. Figure 1.1 shows these two
OH types of model for lactic acid.
2
FIGURE NUMBER: 0521798825c01awf001
JOB No: 8369
CLIENT: C.U.P
JOB TITLE: A2 Core Chemistry
SAVED AS: 0521798825c01awf002_pf2
Chapter 1: AS level organic chemistry revisited
hyperlink hyperlink
desatination dbestination
Figure 1.1 Different model types for lactic acid (2-hydroxypropanoic acid): a ball-and-stick model;
b space-filling model.
hyperlink
Colour Element atoms. They are named by adding -ane to this
destination
stem, as shown in Table 1.3.
white hydrogen
2 Branched-chain alkanes are named in the same
dark grey carbon
way. The name given to the longest continuous
red oxygen carbon chain is then prefixed by the names of the
blue nitrogen shorter side chains. The same stems are used for the
side chains, but with the suffix -yl. Hence CH– is
yellow-green fluorine 3
methyl (often called a methyl group). In general,
green chlorine
such groups are called alkyl groups. The position of
orange-brown bromine an alkyl group is indicated by a number. The carbon
atoms in the longest carbon chain are numbered
brown iodine
from one end of the chain. Numbering starts from
violet phosphorus
the end which produces the lowest possible numbers
pale yellow sulfur for the side chains. For example, the molecule
below is 2-methylpentane, not 4-methylpentane.
Table 1.2 The colours used for elements in molecular
models. CH CH CH CH CH
3 2 2 3
CH
Naming organic compounds 3
The names used in this section are known as 3 Each side chain must be included in the name.
systematic names. Such names precisely describe If there are several identical side chains, the
the structure of a molecule and enable chemists name is prefixed by di-, tri-, etc. For example,
to communicate clearly. International rules of 2,2,3-trimethyl- indicates that there are three methyl
nomenclature have been agreed for the systematic groups: two on the second carbon atom and one on
naming of organic compounds. the third carbon atom of the longest chain. Note that
The basic rules for naming hydrocarbons are as two numbers are separated by a comma, whilst a
follows. number and a letter are separated by a hyphen.
1 The number of carbon atoms in the longest chain 4 Where different alkyl groups are present, they are
provides the stem of the name. Simple alkanes placed in alphabetical order, as in 3-ethyl-
consist entirely of unbranched chains of carbon 2-methylpentane.
3
Chapter 1: AS level organic chemistry revisited
hyperlink are equivalent. When two or more groups are
Molecular Number of Stem Name
destination attached, they will require numbers. For example:
formula carbon atoms
in longest CH
3
chain
CH 1 meth- methane
4
CH
3
C H 2 eth- ethane
2 6 CH CH CH
3 3 3
C3H8 3 prop- propane methylbenzene 1,2-dimethylbenzene 1,4-dimethylbenzene
C H 4 but- butane
4 10 8 Halogeno or nitro compounds are named in the
C5H12 5 pent- pentane same way as alkyl-substituted alkanes or arenes:
C H 6 hex- hexane
6 14
NO
C H 7 hept- heptane 2
7 16
CH CH CHBrCH
3 2 3
C H 8 oct- octane
8 18
C9H20 9 non- nonane NO2
2-bromobutane 1,3-dinitrobenzene
C H 10 dec- decane
10 22
C H 20 eicos- eicosane
20 42 9 Aliphatic alcohols and ketones are named in a
similar way to alkenes:
Table 1.3 Naming simple alkanes
5 Compounds containing a ring of carbon atoms are CH CH CH OH CH CH COCH CH
3 2 2 3 2 2 3
prefixed by cyclo-. Cyclohexane is represented by: propan-1-ol pentan-3-one
H H 10 Aliphatic aldehyde and carboxylic acid groups
H H
C
can only be found at the end of a carbon chain,
C C
H H
so they do not need a number. There is only one
H H
C C
possible butanoic acid, CH CH CH COOH, or
C 3 2 2
H H
butanal, CH CH CH CHO. Note that the names of
H H 3 2 2
FIGURE NUMBER: 0521798825c01aawldf0e2h3ydes, carboxylic acids and nitriles include the
displayed formula skeletal formula
JOB No: 8369 carbon atom of the functional group in the stem of
CLIENT:C.U.P
6 Hydrocarbons containing one double bond are the name. Hence CH COOH is ethanoic acid and
JOBTITLE:A Level Chemistry 2 3
called alkenes. The same steSmAsV aErDe AuSs:e0d5 (2e1t7h9-8,8 25c01awf023_pCf2H3CN is ethanenitrile.
prop-, etc.), but they are followed by -ene. The 11 Amines are named using the alkyl- or aryl- prefix
position of an alkene double bond is indicated followed by -amine. Hence CH CH NH is
3 2 2
by the lower number of the two carbon atoms ethylamine.
involved. This number is placed between the stem
and -ene. Hence CH CH=CHCH is but-2-ene. SAQ
3 3
7 The simplest arene is benzene. When one alkyl 3 Give the systematic names of these compounds:
group is attached to a benzene ring, a number
is not needed because all the carbon atoms a b c
CH
Cl 3
BrCH CO H
2 2
NO
2
4
Chapter 1: AS level organic chemistry revisited
4 Draw structural formulae for these compounds: Isomers which contain the same atoms with the same
a aminoethanoic acid order of bonds but with different spatial arrangements
FIGURE NUMBER: 0521798825c01awf024
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CLIENT:C.U.P c 2,4,6-tribromophenol. isomerism is one type of stereoisomerism. Another
JOBTITLE:A Level Chemistry 2
type is optical isomerism. You will find out more
SAVEDAS:0521798825c01awf024_dl1
about optical isomerism and stereoisomerism in
Isomerism Chapter 6.
Structural isomers have the same molecular formula
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JOB TITLE: A2 Core Chemistry
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SAVED AS: 0521798825c01awf025_d3l1 7
Apart from combustion and substitution by halogens,
Br
alkanes are relatively unreactive. This is due to their
Br strong covalent bonds and a lack of polarity.
In general, hydrocarbons burn. Many are important
1-bromopropane 2-bromopropane
sources of energy.
SAQ combustion C H substitution
CO + H O 2 6 C H Cl + HCl
5 Draw six structural isomers 2 2 + O ethane UV light 2 5
2
+ Cl
containing a carboxyl group, 2
O Substitution by a halogen on an alkane involves a
C (free) radical mechanism. Three stages are involved,
O as follows:
•
a nd with the molecular formula Initiation to form Cl• radicals. Ultraviolet light
C H O . provides sufficient energy to break the covalent
4 8 2
bonds in chlorine, Cl (g). Homolytic fission
2
occurs and two chlorine radicals are formed.
E/Z (cis–trans) isomerism arises in alkenes because
Cl–Cl(g) → Cl•(g) + Cl•(g)
rotation about a double bond cannot occur unless a
•
π (pi) bond is broken. The molecule must have two Propagation involving a chain reaction to form
different groups attached to each carbon atom of the C H Cl:
2 5
C=C bond to exhibit E/Z isomerism. If two of the
Cl•(g) + H–CH CH (g) → Cl–H(g) + •CH CH (g)
2 3 2 3
attached groups on adjacent carbon atoms are the
Cl–Cl(g) + •CH CH (g) → Cl•(g) + Cl–CH CH (g)
2 3 2 3
same, the molecule can exhibit the special form of
•
E/Z isomerism known as cis–trans isomerism. T ermination involves radical combination
reactions. These reactions will predominate
SAQ when the reactants are running out. Examples of
6 Draw and label the cis–trans (E/Z) possible termination steps include the following:
isomers of butenedioic acid,
Cl•(g) + Cl•(g) → Cl–Cl(g)
HOOCCH=CHCOOH.
•CH CH (g) + •CH CH (g) → CH CH CH CH (g)
2 3 2 3 3 2 2 3
5