Warwick University
Department of Chemistry
Basics of Organic Chemistry and Mechanism
Revision for when you are Lost and Confused
Professor Martin Wills
Unlike many other subjects, organic chemistry ‘builds upon itself’ – you must make sure that you
fully understand the earlier concepts before you move on to more challenging work.
In my experience, a lot of students struggle with organic chemistry because they ‘don’t get’
mechanisms. Anyone in this position will probably do badly in their degree course. You can’t
succeed just by memorising, you have to understand the mechanisms.
If you do feel stuck, lost and confused with organic chemistry then please read and work through
this document and it should help you. Some is very basic – but none is meant to be patronising –
so if you are 100% happy with a section then move on and work through it at your own pace.
The secret to learning this is to be absolutely sure that you know and understand what is going on
at each stage. Memorising is not good enough. Don’t move on until you are absolutely sure that
you understand.
1
, Nomenclature of Organic Compounds
IUPAC has defined systematic rules for naming organic compounds.
These will have already been covered in detail at A-level and will
only be mentioned briefly here.
The naming system (and the resulting names) can become very long with complex
molecules, therefore this section will be restricted to simple compounds.
The IUPAC naming system involves the following components:
- Identification of major chain or ring
- Side chains and functional groups are added as
appropriate, in alphabetical order.
- The sums of numbers for substituents are minimised
Professor M. Wills
2
, Nomenclature of Organic Compounds
Examples:
CH3
H2 H2
C C CH CH3
is 3-methyloctane,
H3C C C C
H2 H2 H2 not 5-methyloctane
2'
major chain 1' CH3
H3C
CH
8 H2 H2
C 6 CH 4 C 2 CH3
H3C H3C C CH C 1
CH2 7 H2 5 3
H2 CH3 CH3 CH3
H3C 6 CH 4 C 2 CH3
C CH C 1 Is 5-(1’-methylethyl)-2,2,4-trimethyloctane
7 H2 5 3
H2C CH3 CH3
CH3
Is 4,5-diethyl-2,2-dimethylheptane
H2 H2
4 C 2 CH3 4 C 2 CH3
It is NOT H3C CH 1 H3C CH 1
3,4-diethyl-6,6-dimethylheptane! 3 3
OH Cl
Butan-2-ol 2-chlorobutane
Professor M. Wills
3
, Nomenclature of Organic Compounds
Many common names persist in organic chemistry, despite IUPAC rules, e.g.
Compound ‘common’ name IUPAC name
O
C Acetone Propanone
H3C CH3
O
C Formaldehyde Methanal
H H
O
C Acetic acid Ethanoic acid
H3C OH
O Dimethylether Methoxymethane
H3C CH3
Professor M. Wills
4
Department of Chemistry
Basics of Organic Chemistry and Mechanism
Revision for when you are Lost and Confused
Professor Martin Wills
Unlike many other subjects, organic chemistry ‘builds upon itself’ – you must make sure that you
fully understand the earlier concepts before you move on to more challenging work.
In my experience, a lot of students struggle with organic chemistry because they ‘don’t get’
mechanisms. Anyone in this position will probably do badly in their degree course. You can’t
succeed just by memorising, you have to understand the mechanisms.
If you do feel stuck, lost and confused with organic chemistry then please read and work through
this document and it should help you. Some is very basic – but none is meant to be patronising –
so if you are 100% happy with a section then move on and work through it at your own pace.
The secret to learning this is to be absolutely sure that you know and understand what is going on
at each stage. Memorising is not good enough. Don’t move on until you are absolutely sure that
you understand.
1
, Nomenclature of Organic Compounds
IUPAC has defined systematic rules for naming organic compounds.
These will have already been covered in detail at A-level and will
only be mentioned briefly here.
The naming system (and the resulting names) can become very long with complex
molecules, therefore this section will be restricted to simple compounds.
The IUPAC naming system involves the following components:
- Identification of major chain or ring
- Side chains and functional groups are added as
appropriate, in alphabetical order.
- The sums of numbers for substituents are minimised
Professor M. Wills
2
, Nomenclature of Organic Compounds
Examples:
CH3
H2 H2
C C CH CH3
is 3-methyloctane,
H3C C C C
H2 H2 H2 not 5-methyloctane
2'
major chain 1' CH3
H3C
CH
8 H2 H2
C 6 CH 4 C 2 CH3
H3C H3C C CH C 1
CH2 7 H2 5 3
H2 CH3 CH3 CH3
H3C 6 CH 4 C 2 CH3
C CH C 1 Is 5-(1’-methylethyl)-2,2,4-trimethyloctane
7 H2 5 3
H2C CH3 CH3
CH3
Is 4,5-diethyl-2,2-dimethylheptane
H2 H2
4 C 2 CH3 4 C 2 CH3
It is NOT H3C CH 1 H3C CH 1
3,4-diethyl-6,6-dimethylheptane! 3 3
OH Cl
Butan-2-ol 2-chlorobutane
Professor M. Wills
3
, Nomenclature of Organic Compounds
Many common names persist in organic chemistry, despite IUPAC rules, e.g.
Compound ‘common’ name IUPAC name
O
C Acetone Propanone
H3C CH3
O
C Formaldehyde Methanal
H H
O
C Acetic acid Ethanoic acid
H3C OH
O Dimethylether Methoxymethane
H3C CH3
Professor M. Wills
4
