Basic Organic Nomenclature

An Introduction

Dave Woodcock,
Associate Professor Emeritus UBC (Okanagan)
©1996,2000, 2008

3. Functional Groups with Prefix Only (ii)
Alkoxyalkanes
(Ethers)

Index


Examination of the following line diagram for a representative ether:
shows that there are two chains of carbon atoms present, separated by the oxygen atom. The basis of the IUPAC system is to name the shortest carbon chain, including the oxygen, as a substituent on the other carbon chain. In the above molecule, the shortest carbon chain is two carbons, so this chain, with the oxygen becomes the substituent whilst the remaining three carbon chain forms the root. The substituent chain is named as a prefix using the generic alkoxy (alk + oxy), in this example it is ethoxy (2 carbons = eth + oxy) and it is substituted on the first carbon of the remaining three carbon chain. The root takes on the ane ending and the full name of this example is 1-ethoxypropane.

In summary:

    the IUPAC systematic name for this family of compounds is alkoxyalkane where
      the shorter of the two carbon chains with the oxygen forms the alkoxy prefix.
      the longer of the two chains forms the root name, alkane.

Examine the following :

methoxymethane,

methoxyethane,

1-methoxypropane,

2-methoxypropane,

3-isopropoxypentane,

propoxycyclohexane,

When more substituents are present, the alkoxy substituent takes up its alphabetical position in the list of prefixes:

3-ethoxy-2-methylpentane,

2-bromo-3-isopropoxy-4-methylpentane,


A note on common names for ethers.

An older but still acceptable naming system for the smaller ethers was to use the generic name: alkyl alkyl ether (note the spaces between the words!) , where the alkyls represent the two carbon chains, and the ether the disubstituted-oxygen family.

Examples of this method for compounds previously named are:

dimethyl ether,

methyl ethyl ether,

methyl n-propyl ether,

methyl isopropyl ether,

Notes:
  1. when the two alkyl groups are the same, they can be abbreviated dialkyl.
  2. common names must be used for the alkyl chains, thus n-propyl and isopropyl ( not 1-propyl or 2-propyl)
  3. diethyl ether or ethoxyethane,
    is also known simply as ether.
Self-Assessment Problems.
Review Fuctional Groups with Prefix Only (i)

Next page : Functional Groups with Suffixes Only (i)

Index


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