1. A guide for A level students KNOCKHARDY PUBLISHING
AN INTRODUCTION TO ORGANIC CHEMISTRY
A guide for A level students
KNOCKHARDY PUBLISHING

2. KNOCKHARDY PUBLISHING
ORGANIC CHEMISTRY
INTRODUCTION
This Powerpoint show is one of several produced to help students understand selected topics at AS and A2 level Chemistry. It is based on the requirements of the AQA and OCR specifications but is suitable for other examination boards.
Individual students may use the material at home for revision purposes or it may be used for classroom teaching if an interactive white board is available.
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CONTENTS

3. ORGANIC CHEMISTRY CONTENTS Scope of organic chemistry
Special nature of carbon
Types of formulae
Homologous series
Functional groups
Nomenclature
Investigating molecules
Revision check list
CONTENTS

4. Before you start it would be helpful to…
ORGANIC CHEMISTRY
Before you start it would be helpful to…
Recall how covalent bonding arises
Recall simple electron pair repulsion theory
CONTENTS

5. ORGANIC CHEMISTRY
Organic chemistry is the study of carbon compounds. It is such a complex branch of chemistry because...
• CARBON ATOMS FORM STRONG COVALENT BONDS TO EACH OTHER
• THE CARBON-CARBON BONDS CAN BE SINGLE, DOUBLE OR TRIPLE
• CARBON ATOMS CAN BE ARRANGED IN STRAIGHT CHAINS
BRANCHED CHAINS
and RINGS
• OTHER ATOMS/GROUPS OF ATOMS CAN BE PLACED ON THE CARBON ATOMS
• GROUPS CAN BE PLACED IN DIFFERENT POSITIONS ON A CARBON SKELETON
CONTENTS

6. SPECIAL NATURE OF CARBON - CATENATION
CATENATION is the ability to form bonds between atoms of the same element.
Carbon forms chains and rings, with single, double and triple covalent bonds, because it is able to FORM STRONG COVALENT BONDS WITH OTHER CARBON ATOMS
Carbon forms a vast number of carbon compounds because of the strength of the C-C covalent bond. Other Group IV elements can do it but their chemistry is limited due to the weaker bond strength.
BOND ATOMIC RADIUS BOND ENTHALPY
C-C nm kJmol-1
Si-Si nm kJmol-1
The larger the atoms, the weaker the bond. Shielding due to filled inner orbitals and greater distance from the nucleus means that the shared electron pair is held less strongly.
CONTENTS

7. CHAINS AND RINGS THE SPECIAL NATURE OF CARBON
CARBON ATOMS CAN BE ARRANGED IN
STRAIGHT CHAINS
BRANCHED CHAINS
and RINGS
You can also get a combination of rings and chains
CONTENTS

8. THE SPECIAL NATURE OF CARBON MULTIPLE BONDING AND SUBSTITUENTS
CARBON-CARBON COVALENT BONDS CAN BE SINGLE, DOUBLE OR TRIPLE
CONTENTS

9. THE SPECIAL NATURE OF CARBON MULTIPLE BONDING AND SUBSTITUENTS
CARBON-CARBON COVALENT BONDS CAN BE SINGLE, DOUBLE OR TRIPLE
DIFFERENT ATOMS / GROUPS OF ATOMS CAN BE PLACED ON THE CARBONS
The basic atom is HYDROGEN but groups containing OXYGEN, NITROGEN, HALOGENS and SULPHUR are very common.
CARBON SKELETON FUNCTIONAL CARBON SKELETON FUNCTIONAL
GROUP GROUP
The chemistry of an organic compound is determined by its FUNCTIONAL GROUP
CONTENTS

10. MULTIPLE BONDING AND SUBSTITUENTS
THE SPECIAL NATURE OF CARBON
MULTIPLE BONDING AND SUBSTITUENTS
ATOMS/GROUPS CAN BE PLACED IN DIFFERENT POSITIONS ON A CARBON SKELETON
THE C=C DOUBLE BOND IS IN A DIFFERENT POSITION
PENT-1-ENE PENT-2-ENE
THE CHLORINE ATOM IS IN A DIFFERENT POSITION
1-CHLOROBUTANE CHLOROBUTANE
CONTENTS

11. TYPES OF FORMULAE - 1 MOLECULAR FORMULA C4H10
The exact number of atoms of each
element present in the molecule
EMPIRICAL FORMULA C2H5
The simplest whole number ratio
of atoms in the molecule
STRUCTURAL FORMULA CH3CH2CH2CH CH3CH(CH3)CH3
The minimal detail using conventional
groups, for an unambiguous structure there are two possible structures
DISPLAYED FORMULA
Shows both the relative placing of atoms
and the number of bonds between them
THE EXAMPLE BEING USED IS... BUTANE
CONTENTS

12. TYPES OF FORMULAE - 2 SKELETAL FORMULA
A skeletal formula is used to show a simplified organic formula by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups
for
CYCLOHEXANE
THALIDOMIDE
CONTENTS

13. TYPES OF FORMULAE - 2 SKELETAL FORMULA
A skeletal formula is used to show a simplified organic formula by removing hydrogen atoms from alkyl chains, leaving just a carbon skeleton and associated functional groups
GENERAL FORMULA
Represents any member of for alkanes it is CnH2n+2
a homologous series possible formulae CH4, C2H C99H200
The formula does not apply to cyclic compounds such as cyclohexane is C6H12
- by joining the atoms in a ring you need fewer H’s
for
CYCLOHEXANE
THALIDOMIDE
CONTENTS

14. ALCOHOLS - FIRST THREE MEMBERS OF THE SERIES
HOMOLOGOUS SERIES
A series of compounds of similar structure in which each member differs from the next by a common repeating unit, CH2. Series members are called homologues and...
all share the same general formula.
formula of a homologue differs from its neighbour by CH2. (e.g. CH4, C2H6, ... etc )
contain the same functional group
have similar chemical properties.
show a gradual change in physical properties as molar mass increases.
can usually be prepared by similar methods.
ALCOHOLS - FIRST THREE MEMBERS OF THE SERIES
CH3OH C2H5OH C3H7OH
METHANOL ETHANOL PROPAN-1-OL
CONTENTS

15. FUNCTIONAL GROUPS H H H H H H C C C C C NH2 H H H H H H C C C C C OH
Organic chemistry is a vast subject so it is easier to split it into small sections for study. This is done by studying compounds which behave in a similar way because they have a particular atom, or group of atoms, FUNCTIONAL GROUP, in their structure.
Functional groups can consist of one atom, a group of atoms or multiple bonds between carbon atoms.
Each functional group has its own distinctive properties which means that the properties of a compound are governed by the functional group(s) in it.
H H H H H
H C C C C C NH2
H H H H H
H C C C C C OH
Carbon Functional Carbon Functional
skeleton Group = AMINE skeleton Group = ALCOHOL
CONTENTS

16. COMMON FUNCTIONAL GROUPS
GROUP ENDING GENERAL FORMULA EXAMPLE
ALKANE ane RH C2H ethane
ALKENE ene C2H ethene
ALKYNE yne C2H ethyne
HALOALKANE halo - RX C2H5Cl chloroethane
ALCOHOL ol ROH C2H5OH ethanol
ALDEHYDE al RCHO CH3CHO ethanal
KETONE one RCOR CH3COCH propanone
CARBOXYLIC ACID - oic acid RCOOH CH3COOH ethanoic acid
ACYL CHLORIDE - oyl chloride RCOCl CH3COCl ethanoyl chloride
AMIDE - amide RCONH2 CH3CONH ethanamide
ESTER - yl - oate RCOOR CH3COOCH3 methyl ethanoate
NITRILE - nitrile RCN CH3CN ethanenitrile
AMINE - amine RNH2 CH3NH methylamine
NITRO nitro- RNO2 CH3NO nitromethane
SULPHONIC ACID - sulphonic acid RSO3H C6H5SO3H benzene sulphonic acid
ETHER - oxy - ane ROR C2H5OC2H ethoxyethane
CONTENTS

17. COMMON FUNCTIONAL GROUPS
ALKANE
ALKENE
ALKYNE
HALOALKANE
AMINE
NITRILE
ALCOHOL
ETHER
ALDEHYDE
KETONE
CARBOXYLIC ACID
ESTER
ACYL CHLORIDE
AMIDE
NITRO
SULPHONIC ACID
CONTENTS

18. HOW MANY STRUCTURES? C2H6 ONE C3H9Br TWO
Draw legitimate structures for each molecular formula and classify each one according to the functional group present. Not all the structures represent stable compounds.
carbon atoms have 4 covalent bonds surrounding them
oxygen atoms 2
nitrogen atoms 3
hydrogen 1
halogen atoms 1
C2H6 ONE
C3H9Br TWO
C4H8 FIVE - 3 with C=C and 2 ring compounds with all C-C’s
C2H6O TWO - 1 with C-O-C and 1 with C-O-H
C3H6O SIX - 2 with C=O, 2 with C=C and 2 with rings
C2H7N TWO
C2H4O2 SEVERAL - Only 2 are stable
C2H3N TWO
CONTENTS

19. HOW MANY STRUCTURES? C2H6 ONE C3H9Br TWO
Draw legitimate structures for each molecular formula and classify each one according to the functional group present. Not all the structures represent stable compounds.
carbon atoms have 4 covalent bonds surrounding them
oxygen atoms 2
nitrogen atoms 3
hydrogen 1
halogen atoms 1
C2H6 ONE
C3H9Br TWO
C4H8 FIVE - 3 with C=C and 2 ring compounds with all C-C’s
C2H6O TWO - 1 with C-O-C and 1 with C-O-H
C3H6O SIX - 2 with C=O, 2 with C=C and 2 with rings
C2H7N TWO
C2H4O2 SEVERAL - Only 2 are stable
C2H3N TWO
CONTENTS

20. NOMENCLATURE
Ideally a naming system should tell you everything about a structure without ambiguity. There are two types of naming system commonly found in organic chemistry;
Trivial : based on some property or historical aspect;
the name tells you little about the structure
Systematic : based on an agreed set of rules (I.U.P.A.C);
exact structure can be found from the name (and vice-versa).
HOMOLOGOUS SERIES
trivial name systematic name example(s)
paraffin alkane methane, butane
olefin alkene ethene, butene
fatty acid alkanoic (carboxylic) acid ethanoic acid
INDIVIDUAL COMPOUNDS
trivial name derivation systematic name
methane methu = wine (Gk.) methane (CH4)
butane butyrum = butter (Lat.) butane (C4H10)
acetic acid acetum = vinegar (Lat.) ethanoic acid (CH3COOH)
CONTENTS

21. A systematic name has two main parts.
I.U.P.A.C. NOMENCLATURE
A systematic name has two main parts.
STEM number of carbon atoms in longest chain bearing the functional group +
a prefix showing the position and identity of any side-chain substituents.
Apart from the first four, which have trivial names, the number of carbons atoms is indicated by a prefix derived from the Greek numbering system.
The list of alkanes demonstrate the use of prefixes.
The ending -ane is the same as they are all alkanes.
Prefix C atoms Alkane
meth- 1 methane
eth- 2 ethane
prop- 3 propane
but- 4 butane
pent- 5 pentane
hex- 6 hexane
hept- 7 heptane
oct- 8 octane
non- 9 nonane
dec decane
Working out which is the longest chain can pose a problem with larger molecules.
CONTENTS

22. I.U.P.A.C. NOMENCLATURE CH3 CH3 CH2 CH2 CH2 CH3 CH2 CH3
How long is a chain?
Because organic molecules are three dimensional and paper is two dimensional it can confusing when comparing molecules. This is because...
1. It is too complicated to draw molecules with the correct bond angles
2. Single covalent bonds are free to rotate
All the following written structures are of the same molecule - PENTANE C5H12
CH2
CH3
CH2
CH3
CH3
CH2
CH2
CH3
A simple way to check is to run a finger along the chain and see how many carbon atoms can be covered without reversing direction or taking the finger off the page. In all the above there are... FIVE CARBON ATOMS IN A LINE.
CONTENTS

23. How long is the longest chain?
I.U.P.A.C. NOMENCLATURE
How long is the longest chain?
Look at the structures and work out how many carbon atoms are in the longest chain.
CH2
CH3 CH
THE ANSWERS ARE
ON THE NEXT SLIDE
CH2
CH3 CH
CH3 CH
CH2
CONTENTS

24. How long is the longest chain?
I.U.P.A.C. NOMENCLATURE
How long is the longest chain?
Look at the structures and work out how many carbon atoms are in the longest chain.
CH2
CH3 CH
LONGEST CHAIN = 5
CH2
CH3 CH
LONGEST CHAIN = 6
CH3 CH
CH2
LONGEST CHAIN = 6
CONTENTS

25. A systematic name has two main parts. 1-CHLOROBUTANE 2-CHLOROBUTANE
I.U.P.A.C. NOMENCLATURE
A systematic name has two main parts.
SUFFIX An ending that tells you which functional group is present
See if any functional groups are present.
Add relevant ending to the basic stem.
In many cases the position of the functional group must be given to avoid any ambiguity
Functional group Suffix
ALKANE - ANE
ALKENE - ENE
ALKYNE - YNE
ALCOHOL - OL
ALDEHYDE - AL
KETONE - ONE
ACID - OIC ACID
1-CHLOROBUTANE CHLOROBUTANE
SUBSTITUENTS Many compounds have substituents (additional atoms, or groups)
attached to the chain. Their position is numbered.
CONTENTS

26. I.U.P.A.C. NOMENCLATURE
SIDE-CHAIN carbon based substituents are named before the chain name.
they have the prefix -yl added to the basic stem (e.g. CH3 is methyl).
Number the principal chain from one end to give the lowest numbers.
Side-chain names appear in alphabetical order butyl, ethyl, methyl, propyl
Each side-chain is given its own number.
If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa
Numbers are separated from names by a HYPHEN e.g methylheptane
Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane
Alkyl radicals methyl CH CH3
ethyl CH3- CH C2H5
propyl CH3- CH2- CH C3H7
CONTENTS

27. I.U.P.A.C. NOMENCLATURE CH3 CH2 CH
SIDE-CHAIN carbon based substituents are named before the chain name.
they have the prefix -yl added to the basic stem (e.g. CH3 is methyl).
Number the principal chain from one end to give the lowest numbers.
Side-chain names appear in alphabetical order butyl, ethyl, methyl, propyl
Each side-chain is given its own number.
If identical side-chains appear more than once, prefix with di, tri, tetra, penta, hexa
Numbers are separated from names by a HYPHEN e.g methylheptane
Numbers are separated from numbers by a COMMA e.g. 2,3-dimethylbutane
Example longest chain 8 (it is an octane)
3,4,6 are the numbers NOT 3,5,6
order is ethyl, methyl, propyl
3-ethyl-5-methyl-4-propyloctane
Alkyl radicals methyl CH CH3
ethyl CH3- CH C2H5
propyl CH3- CH2- CH C3H7
CH3
CH2 CH
CONTENTS

28. I.U.P.A.C. NOMENCLATURE CH2 CH3 CH CH2 CH3 CH CH3 CH CH2
Apply the rules and name these alkanes
THE ANSWERS ARE ON THE NEXT SLIDE
CH2
CH3 CH
CH2
CH3 CH
CH3 CH
CH2
CONTENTS

29. Apply the rules and name these alkanes
I.U.P.A.C. NOMENCLATURE
I.U.P.A.C. NOMENCLATURE
Apply the rules and name these alkanes
CH2
CH3 CH
CH2
CH3 CH
CH3 CH
CH2
CONTENTS

30. Apply the rules and name these alkanes
I.U.P.A.C. NOMENCLATURE
I.U.P.A.C. NOMENCLATURE
Apply the rules and name these alkanes
Longest chain = 5 so it is a pentane
A CH3, methyl, group is attached to the third carbon from one end...
3-methylpentane
CH2
CH3 CH
CH2
CH3 CH
CH3 CH
CH2
CONTENTS

31. Apply the rules and name these alkanes
I.U.P.A.C. NOMENCLATURE
I.U.P.A.C. NOMENCLATURE
Apply the rules and name these alkanes
Longest chain = 5 so it is a pentane
A CH3, methyl, group is attached to the third carbon from one end...
3-methylpentane
CH2
CH3 CH
Longest chain = 6 so it is a hexane
A CH3, methyl, group is attached to the second carbon from one end...
2-methylhexane
CH2
CH3 CH
CH3 CH
CH2
CONTENTS

32. Apply the rules and name these alkanes
I.U.P.A.C. NOMENCLATURE
I.U.P.A.C. NOMENCLATURE
Apply the rules and name these alkanes
Longest chain = 5 so it is a pentane
A CH3, methyl, group is attached to the third carbon from one end...
3-methylpentane
CH2
CH3 CH
Longest chain = 6 so it is a hexane
A CH3, methyl, group is attached to the second carbon from one end...
2-methylhexane
CH2
CH3 CH
Longest chain = 6 so it is a hexane
CH3, methyl, groups are attached to the third and fourth carbon atoms (whichever end you count from).
3,4-dimethylhexane
CH3 CH
CH2
CONTENTS

33. NAMING ALKENES
Length In alkenes the principal chain is not always the longest chain
It must contain the double bond
the name ends in -ENE
Position Count from one end as with alkanes.
Indicated by the lower numbered carbon atom on one end of the C=C bond
CH3CH2CH=CHCH3 is pent-2-ene (NOT pent-3-ene)
Side-chain Similar to alkanes
position is based on the number allocated to the double bond
CH2 = CH(CH3)CH2CH CH2 = CHCH(CH3)CH3
2-methylbut-1-ene 3-methylbut-1-ene
CONTENTS

34. Elucidation of the structures of organic compounds - a brief summary
WHICH COMPOUND IS IT?
Elucidation of the structures of organic compounds - a brief summary
Organic chemistry is so vast that the identification of a compound can be involved. The characterisation takes place in a series of stages (see below). Relatively large amounts of substance were required to elucidate the structure but, with modern technology and the use of electronic instrumentation, very small amounts are now required.
Elemental composition
One assumes that organic compounds contain carbon and hydrogen but it can be proved by letting the compound undergo combustion. Carbon is converted to carbon dioxide and hydrogen is converted to water.
Percentage composition by mass
Found by dividing the mass of an element present by the mass of the compound present, then multiplying by Elemental mass of C and H can be found by allowing the substance to undergo complete combustion. From this one can find...
mass of carbon = 12/44 of the mass of CO2 produced
mass of hydrogen = 2/18 of the mass of H2O produced
CONTENTS

35. INVESTIGATING MOLECULES
Empirical formula
The simplest ratio of elements present in the substance. It is calculated by dividing the mass or percentage mass of each element by its molar mass and finding the simplest ratio between the answers. Empirical formula is converted to the molecular formula using molecular mass.
CONTENTS

36. INVESTIGATING MOLECULES
Empirical formula
The simplest ratio of elements present in the substance. It is calculated by dividing the mass or percentage mass of each element by its molar mass and finding the simplest ratio between the answers. Empirical formula is converted to the molecular formula using molecular mass.
Molecular mass
Traditionally found out using a variety of techniques such as ... volumetric analysis or molar volume methods (Dumas, Victor-Meyer or gas syringe experiments). Mass spectrometry is now used. The m/z value of the molecular ion and gives the molecular mass. The fragmentation pattern gives information about the compound.
CONTENTS

37. INVESTIGATING MOLECULES
Empirical formula
The simplest ratio of elements present in the substance. It is calculated by dividing the mass or percentage mass of each element by its molar mass and finding the simplest ratio between the answers. Empirical formula is converted to the molecular formula using molecular mass.
Molecular mass
Traditionally found out using a variety of techniques such as ... volumetric analysis or molar volume methods (Dumas, Victor-Meyer or gas syringe experiments). Mass spectrometry is now used. The m/z value of the molecular ion and gives the molecular mass. The fragmentation pattern gives information about the compound.
Molecular formula
The molecular formula is an exact multiple of the empirical formula. Comparing the molecular mass with the empirical mass allows one to find the true formula. e.g.
if the empirical formula is CH (relative mass = 13) and the molecular mass is 78
the molecular formula will be 78/13 or 6 times the empirical formula i.e. C6H6 .
CONTENTS

38. INVESTIGATING MOLECULES
Empirical formula
The simplest ratio of elements present in the substance. It is calculated by dividing the mass or percentage mass of each element by its molar mass and finding the simplest ratio between the answers. Empirical formula is converted to the molecular formula using molecular mass.
Molecular mass
Traditionally found out using a variety of techniques such as ... volumetric analysis or molar volume methods (Dumas, Victor-Meyer or gas syringe experiments). Mass spectrometry is now used. The m/z value of the molecular ion and gives the molecular mass. The fragmentation pattern gives information about the compound.
Molecular formula
The molecular formula is an exact multiple of the empirical formula. Comparing the molecular mass with the empirical mass allows one to find the true formula. e.g.
if the empirical formula is CH (relative mass = 13) and the molecular mass is 78
the molecular formula will be 78/13 or 6 times the empirical formula i.e. C6H6 .
Structural formula
Because of the complexity of organic molecules, there can be more than one structure for a given molecular formula. To work out the structure, different tests are carried out.
CONTENTS

39. INVESTIGATING MOLECULES
Empirical formula
The simplest ratio of elements present in the substance. It is calculated by dividing the mass or percentage mass of each element by its molar mass and finding the simplest ratio between the answers. Empirical formula is converted to the molecular formula using molecular mass.
Molecular mass
Traditionally found out using a variety of techniques such as ... volumetric analysis or molar volume methods (Dumas, Victor-Meyer or gas syringe experiments). Mass spectrometry is now used. The m/z value of the molecular ion and gives the molecular mass. The fragmentation pattern gives information about the compound.
Molecular formula
The molecular formula is an exact multiple of the empirical formula. Comparing the molecular mass with the empirical mass allows one to find the true formula. e.g.
if the empirical formula is CH (relative mass = 13) and the molecular mass is 78
the molecular formula will be 78/13 or 6 times the empirical formula i.e. C6H6 .
Structural formula
Because of the complexity of organic molecules, there can be more than one structure for a given molecular formula. To work out the structure, different tests are carried out.
CONTENTS

40. INVESTIGATING MOLECULES
Chemical Chemical reactions can identify the functional group(s) present.
Spectroscopy IR detects bond types due to absorbance of i.r. radiation
NMR gives information about the position and relative
numbers of hydrogen atoms present in a molecule
Confirmation By comparison of IR or NMR spectra and
mass spectrometry
CONTENTS

41. What should you be able to do?
REVISION CHECK
What should you be able to do?
Recall and explain the reasons for the large number of carbon based compounds
Be able to write out possible structures for a given molecular formula
Recognize the presence of a particular functional group in a structure
Know the IUPAC rules for naming alkanes and alkenes
Be able to name given alkanes and alkenes when given the structure
Be able to write out the structure of an alkane or alkene when given its name
Recall the methods used to characterise organic molecules
CAN YOU DO ALL OF THESE? YES NO
CONTENTS

42. You need to go over the relevant topic(s) again
Click on the button to
return to the menu
CONTENTS

43. Try some past paper questions
WELL DONE!
Try some past paper questions
CONTENTS

44. © 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING
AN INTRODUCTION TO ORGANIC CHEMISTRY
THE END
© 2003 JONATHAN HOPTON & KNOCKHARDY PUBLISHING