Nomenclature

Introduction to Organic Chemistry

Define nomenclature.

A system of rules used for naming chemical compounds.

What does IUPAC stand for?

International Union of Pure and Applied Chemistry.

Why is IUPAC nomenclature used?

To provide systematic and unambiguous names for chemical compounds.

Define a prefix.

A set of letters written at the beginning of a name.

Define a suffix.

A set of letters written at the end of a name.

Define a locant.

A number used to indicate which carbon atom in a chain an atom or group is attached to.

What are multiplying prefixes used for?

To show that two or more identical groups are present.

Which multiplying prefix means two?

di-.

Which multiplying prefix means three?

tri-.

How are locants separated when there is more than one?

By commas, e.g. 2,3-dimethylbutane.

How are numbers and words separated in an IUPAC name?

By hyphens.

What code represents a chain containing 1 carbon atom?

meth-.

What code represents a chain containing 2 carbon atoms?

eth-.

What code represents a chain containing 3 carbon atoms?

prop-.

What code represents a chain containing 4 carbon atoms?

but-.

What code represents a chain containing 5 carbon atoms?

pent-.

What code represents a chain containing 6 carbon atoms?

hex-.

What code represents a chain containing 7 carbon atoms?

hept-.

What code represents a chain containing 8 carbon atoms?

oct-.

What code represents a chain containing 9 carbon atoms?

non-.

What code represents a chain containing 10 carbon atoms?

dec-.

What is the alkyl group containing 1 carbon atom called?

methyl.

What is the alkyl group containing 2 carbon atoms called?

ethyl.

What is the alkyl group containing 3 carbon atoms called?

propyl.

What is the alkyl group containing 4 carbon atoms called?

butyl.

What is the alkyl group containing 5 carbon atoms called?

pentyl.

What is the alkyl group containing 6 carbon atoms called?

hexyl.

What is the alkyl group containing 7 carbon atoms called?

heptyl.

What is the alkyl group containing 8 carbon atoms called?

octyl.

What is the alkyl group containing 9 carbon atoms called?

nonyl.

What is the alkyl group containing 10 carbon atoms called?

decyl.

What suffix is used for alkanes?

-ane.

What suffix is used for alcohols?

-ol.

What prefix indicates a bromine atom?

bromo-.

What does the prefix methyl- represent?

A CH₃ group.

What does the prefix ethyl- represent?

A C₂H₅ group.

What is the first step when naming a branched alkane?

Identify the longest continuous carbon chain.

How does the longest carbon chain determine the parent name?

The number of carbon atoms determines the stem, such as prop-, but- or pent-.

How should the carbon chain be numbered?

From the end that gives the substituents the lowest possible locant numbers.

What should you do if two or more identical substituents are present?

Use a multiplying prefix such as di- or tri- and give the locant of each substituent.

In what order are different substituent prefixes written?

Alphabetical order.

When arranging substituents alphabetically, are multiplying prefixes such as di- considered?

No; alphabetise using the substituent name itself.

Why is CH₃CH(CH₃)CH₃ called methylpropane rather than 2-methylpropane?

The methyl group can only be on carbon 2; putting it on an end carbon would make the longest chain four carbons and the compound would be butane.

Name CH₃CH₂CH(CH₃)CH₂CH₃.

3-methylpentane.

Name CH₃CH(CH₃)CH₂CH₂CH₃.

2-methylpentane.

Why is 2-methylpentane used instead of 4-methylpentane?

The chain is numbered from the end that gives the substituent the lowest possible locant.

Name CH₃CH(CH₃)CH(CH₃)CH₃.

2,3-dimethylbutane.

Why is a comma used in 2,3-dimethylbutane?

To separate the two locant numbers.

Why is 3-ethyl-2-methylpentane written with ethyl before methyl?

Different substituents are written in alphabetical order.

What is the main difference when naming alcohols rather than alkanes?

The hydroxyl group is represented by the suffix -ol.

Which group has priority when numbering an alcohol chain?

The hydroxyl, –OH, group.

How should an alcohol chain be numbered?

From the end that gives the –OH group the lowest possible locant.

Name CH₃CH₂OH.

ethanol.

Name CH₃CH₂CH₂OH.

propan-1-ol.

What does the 1 in propan-1-ol indicate?

The –OH group is attached to carbon 1.

Name CH₃CH(OH)CH(CH₃)CH₃.

3-methylbutan-2-ol.

Why is 3-methylbutan-2-ol not called 2-methylbutan-3-ol?

The –OH functional group must receive the lowest possible locant.

What does the name 3,3-dimethylbutan-1-ol tell you?

The longest chain has four carbons, the –OH is on carbon 1, and two methyl groups are attached to carbon 3.

When converting an IUPAC name into a structural formula, what should you identify first?

The parent carbon chain indicated by meth-, eth-, prop-, but-, pent-, etc.

When drawing a structural formula from an IUPAC name, what do the locants tell you?

The carbon atoms where substituents or functional groups are attached.

What should you check after drawing a structural formula?

That each carbon atom forms four bonds.

What common error should be avoided when drawing structural formulae?

Drawing a carbon atom with three or five bonds instead of four.

What does dimethylpropane indicate?

A three-carbon parent chain with two methyl groups attached.

What is the structural formula of dimethylpropane?

CH₃C(CH₃)₂CH₃.

What information does 3-methylbutan-1-ol give?

A four-carbon chain with an –OH group on carbon 1 and a methyl group on carbon 3.

What is the structural formula of 3-methylbutan-1-ol?

HOCH₂CH₂CH(CH₃)CH₃.

What are the key steps for naming a branched organic compound?

Find the longest carbon chain, identify the substituents or functional group, number the chain to give the lowest locants, use multiplying prefixes where necessary, arrange different prefixes alphabetically, and add the correct suffix.