3.6.4

Nomenclature contd.

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IUPAC rules

Molecules are named following the internationally-recognised IUPAC rules. The rules for naming compounds is known as 'nomenclature'.

Name stem

Name stem

  • The stem of a name is the first part of the name. It is decided by the number of carbon atoms:
    • 1 carbon → meth-
    • 2 carbons → eth-
    • 3 carbons → prop-
    • 4 carbons → but-
    • 5 carbons → pent-
Name ending

Name ending

  • The functional group gives the ending to the name.
    • Carboxylic acid: → Propanoic acid.
    • Alcohol: → ethanol.
    • Ketone: → propanone.
    • Aldehyde: → ethanal.
Complex molecules

Complex molecules

  • Most molecules are more complex. This means they have multiple functional groups or side chains.
Naming conventions

Naming conventions

  • The molecule is always named after the longest possible carbon chain that includes the functional group.
  • The carbons are numbered to give the functional group the lowest number possible.
  • Side chains are written as prefixes to the name.
An example

An example

  • The molecule shown above is 4-methyl-hexan-1-ol, NOT 2-methyl-hexan-6-ol or 4-ethyl-pentan-1-ol.
  • First, count the longest chain.
    • This gives a hexanol.
    • Put the alcohol at the lowest number.
    • Now name the position of the side chain.
Rings

Rings

  • For molecules that contain rings, add 'cyclo-' at the start of the name:
    • E.g. Cyclohexane.
    • E.g. Cyclohexanol.
    • E.g. Cyclohexanone.
Jump to other topics
1

Structure - Models of the Particulate of Matter

2

Structure - Models of Bonding & Structure

3

Structure - Classification of Matter

3.1

The Periodic Table: Classification of Elements

3.2

Periodic Trends

3.3

Group 1 Alkali Metals

3.4

Halogens

3.5

Noble gases, group 18

3.6

Functional Groups: Classification of Organic

3.7

Functional Group Chemistry

3.8

Alkanes

3.9

Alcohols

3.10

Halogenoalkanes

4

Reactivity - What Drives Chemical Reaction?

5

Reactivity - How Much, How Fast & How Far?

6

Reactivity - The Mechanisms of Chemical Change

7

Measurement, Data Processing & Analysis

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