Naming Organic Compounds

L. Scheffler

Lincoln High School

IB Chemistry 3-4.

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• Originally compounds were named based on their source or use

• Many organic compounds were given common names which are still in use

• However many ambiguities resulted • With the large number of organic

compounds, a method for systematically naming them is very important

Naming Organic Compounds

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• The International Union of Pure and Applied Chemists (IUPAC) developed a system for naming organic compounds.

• This system eliminated many of the ambiguities that plagued earlier naming systems

• Common names for many substances are still widely used

IUPAC Names

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A series of prefixes are used to designate the number of carbon atoms in a carbon chain

Naming Hydrocarbons using the IUPAC System

meth 1 C hex 6 C

eth 2 C hept 7 C

prop 3 C oct 8 C

but 4 C non 9 C

pent 5 C dec 10 C

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• For straight chain hydrocarbons. The prefix indicates the number of carbon atoms.

• The suffix ane is added to designate that the compound is an alkane

Naming Alkanes

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• For branched chain hydrocarbons, identify the longest consecutive (straight) chain first. Then name the side chains or branches.

• The name of the branches end in “yl” and go before the name of the straight chain

Naming Alkanes with branched chains

-methylpropane

methyl butane

dimethyl propane

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• Alkenes have one (or more) carbon to carbon double bonds

• When there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number.

• Numbering the location of the double bond(s) takes precedence over the location of side chains

Alkenes

1 butene 2-butene methylpropene 7

Naming Compounds With Functional Groups

Various functional groups have unique suffixes that designate the functional group. The functional group takes precedence in numbering the carbon chain. Branches to the carbon chain are named in the usual manner.

alcohols “ol” Amides “amide”

Aldehydes “al” Amines “amine” or amino as a prefix

Ketones “one” Ethers Ethoxy as prefix

Acids “oic” halohydrocarbons Fluoro, bromo, chloro or iodo

Esters “oate”8

Alcohols

Suffix = “ol”1- Propanol

2- Propanol

2-methyl-2-propanol

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Suffix = “al”Propanal

Note that the aldeyhde group is always on an end carbon or carbon 1

Aldehydes and Alkanals

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Suffix = “one”

Propanone(also known as acetone)

Butanone(also known as methyl ethyl ketone)

2-Pentanone(note the number is necessary Because the C=O could be on carbon 2 or carbon 3)

Ketones or Alkanones

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Suffix = “oic”

Butanoic acid

Note that the acid group (called a “carboxyl”) is always on an end carbon or carbon 1

Carboxylic Acids

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Esters

Suffix = “oate”

Ethyl butanoate

Butyl ethanoate

There are two branches. The branch with the carbonyl gets the suffix

Esters

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Suffix = “amide”

butanamide

Note that the amide group is always on an end carbon or carbon 1

Amides

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Suffix = “amine”Or prefix = “amino”

Propylamine or 1-aminopropane

2-propylamine or 2-aminopropane

2-methyl-2-propylamine or

2-methyl -2- aminopropane

Amines

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prefixes = “fluoro, chloro, bromo, iodo”

1-bromopropane

2 chlorobutane

1,2 diiodoethane

Cis 1,2difluroethene

Trans 1,2 difluoroethene

1,1,2 trifluorothene

Halohydrocarbons

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Suffix = “oxy”on first branch

Ethoxyethane(diethylether)

Ethoxybutane(ethylbutyl ether)

Ethers

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Aromatic Compounds With Functional Groups

Benzoic acid

2 hydroxybenzoic acid

3 bromobenzoic acid

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Nitriles

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Nitriles have a cyanide group. The name is based on the longest carbon chain that includes the carbon atom in the nitrile group.

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