Nomenclature
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Nomenclature

 

Types of Names

As was the case with alcohols, amines can be named in two ways.

First, they can be viewed as having an amino group, an -NH2 group, attached to an alkane. This approach is used for the IUPAC names.
Second, they can be seen as having an alkyl group attached to the nitrogen in the amine. This approach is used in creating common names.

Which type of name is used is a matter of personal preference combined with the complexity of the compound. Primary amines can usually be named easily either way. Secondary and tertiary amines are a different story.

IUPAC Names for Primary Amines

If you consider a primary amine to be an amino group attached to an alkane, you would simply name it as you would an alkane derivative. This is the IUPAC method for naming these compounds.

(The structural formulas of the amines below are also given in Example 1 in your workbook.)

This is an amine in which the nitrogen is bonded to one alkyl group and to two hydrogen atoms. Therefore it is a primary amine. The IUPAC name is aminomethane because the amino group is attached to a methane chain. (The common names are also given here, we will get to those soon.)
CH3-NH2

H   
|   
H - C - N - H
  |   | 
H   H

aminomethane
(or methylamine)
This compound contains a chain of four carbon atoms with an amino group bonded to the second one. Thus, it is called 2-aminobutane.
H   H   H   H
|   |   |   |
H - C - C - C - C - H
|   |   |   |
H   N   H   H
/ \   
H  H   
2-aminobutane
(or sec-butylamine)
For similar reasons this compound is named 1-aminopropane,
     H    H   H    H
     |   |   |    /
H - C - C - C - N
     |   |   |    \
      H   H   H     H
1-aminopropane
(or propylamine)
and this one is named 2-aminopropane.

Take a look at these names and formulas and make sure that the IUPAC names make sense to you. If not, stop now and check with an instructor to get that clarified.

H   H   H
|   |   |
H - C - C - C - H
|   |   |
H   N   H
/ \
H  H
2-aminopropane
(or isopropylamine)

 

Common Names for Primary Amines

You can also name primary amines by naming the alkyl group, followed by the word "amine". This should be written all as one word, even though you may sometimes see the parts written separately.

With this method the compound shown here would be named methylamine. (The IUPAC names are also shown.)
CH3-NH2

H   
|   
H - C - N - H
|   |
H   H

methylamine
(or aminomethane)
This compound is called sec-butylamine, because it consists of a sec-butyl group (do you remember that one?) attached to the nitrogen atom.
H   H   H   H
|   |   |   |
H - C - C - C - C - H
|   |   |   |
H   N   H   H
/ \   
H  H   
sec-butylamine
(or 2-aminobutane)
This one would be called propylamine. A more complete name would be n-propylamine so as to distinguish it from the next compound.
      H    H   H     H
     |   |   |    /
H - C - C - C - N
     |   |   |    \
      H   H   H     H
propylamine
(or 1-aminopropane)
This compound is called isopropylamine.

As long as you are working with simple alkyl groups, this is a very straightforward way of naming amines.

H   H   H
|   |   |
H - C - C - C - H
|   |   |
H   N   H
/ \
H  H
isopropylamine
(or 2-aminopropane)

 

Common Names for Secondary Amines

Amines which have two alkyl groups attached to the nitrogen are called secondary amines. Secondary amines are usually named by listing both of the alkyl groups that are attached to the nitrogen, followed by the name "amine."

In this example there is an ethyl group and a propyl group attached to the nitrogen. Consequently, this amine is called ethylpropylamine. We'll come back to the IUPAC name soon.
H   H        H   H   H
|   |       |   |   |
H - C - C - N - C - C - C - H
|   |   |   |   |   |
H   H   H   H   H   H
ethylpropylamine

 

 

Common Names for Tertiary Amines

Amines which have three alkyl groups attached to the nitrogen atom are called tertiary amines. These also are named by naming each of the alkyl groups attached to the nitrogen, followed by the word "amine."

An example of a tertiary amine is shown here. This amine has two methyl groups and one ethyl group attached to the nitrogen. Consequently, it would be called dimethylethylamine.
H      H     H
|       |   |
H - C - N - C - C - H
|   |   |   |
H   |   H   H
|   
H-C-H   
|   
H   
dimethylethylamine

 

 

IUPAC Names for Secondary and Teriary Amines

It is also possible to name secondary and tertiary amines (like those shown above) using the IUPAC method. To do that, you need to know one additional aspect of the IUPAC methodology. That is using the letter N to show the location of an alkyl group that is attached to the nitrogen atom.

First, you find and name the longest continuous carbon chain that has the nitrogen attached to it. With ethylpropylamine that would be propane for the three-carbon chain.
H   H       H   H   H
|   |       |   |   |
H - C - C - N - C - C - C - H
|   |   |   |   |   |
H   H   H   H   H   H
propane
The nitrogen atom of the amino group is attached to the first carbon atom of the chain, so the name becomes 1-aminopropane.
H   H       H   H   H
|   |       |   |   |
H - C - C - N - C - C - C - H
|   |   |   |   |   |
H   H   H   H   H   H
1-aminopropane
Then there is the ethyl group. You have to add that to the name and show where it is attached. Since it is attached to the nitrogen atom, you put N- rather than a number in front of ethyl.
H    H       H   H   H
|   |       |   |   |
H - C - C - N - C - C - C - H
|   |   |   |   |   |
H   H   H   H   H   H
N-ethyl-1-aminopropane
Thus the name for this compound becomes N-ethyl-1-aminopropane. Again, this is all written as one word.
H   H       H   H   H
|   |       |   |   |
H - C - C - N - C - C - C - H
|   |   |   |   |   |
H   H   H   H   H   H
N-ethyl-1-aminopropane

 

In this example, the longest continuous chain is an ethane chain with two carbon atoms.
H       H   H
|       |   |
H - C - N - C - C - H
|   |   |   |
H   |   H   H
|   
H-C-H   
|   
H   
ethane
Again, the nitrogen atom is attached to the number one carbon, so part of the name is 1-aminoethane.
H        H   H
|       |   |
H - C - N - C - C - H
|   |   |   |
H   |   H   H
|   
H-C-H   
|   
H   
1-aminoethane
Since there are two methyl groups attached to the nitrogen, we add N,N-dimethyl- to the front of the name. Note each methyl group gets its own locator, thus there are two Ns in the name.
H        H   H
|       |   |
H - C - N - C - C - H
|   |   |   |
H   |   H   H
|   
H-C-H   
|   
H   
N,N-dimethyl-1-aminoethane
The IUPAC name for this compound is N,N-dimethyl-1-aminoethane.
H        H   H
|       |   |
H - C - N - C - C - H
|   |   |   |
H   |   H   H
|   
H-C-H   
|   
H   
N,N-dimethyl-1-aminoethane

 

Choice of Methods

Let's review the two methods for naming amines based on their structural formulas.

The IUPAC method requires that you first select the longest carbon chain and name the amino groups and other groups attached to that carbon chain. Show the location of each group attached to the chain by using numbers. Then locate and name any additional groups attached to the nitrogen atom. Show their location by the symbol N.
The common method requires that you first locate and name the amine group. Then identify and name each of the attached alkyl groups, putting those names in front of the amine.

 

Structure from Name

Coming up with the structure for an amine, given the name, is, of course, just the reverse of the procedure for naming amines. For that reason I will give you general guidelines rather than specific examples here. First look at what kind of name you have.

If it is an IUPAC name,
write down the carbon chain as indicated,
then attach the amino and other groups to it as indicated,
then attach any additional groups to the nitrogen if indicated.
If it is a common name,
write down the nitrogen,
then attach the alkyl groups as indicated.

Then, in both cases, fill in the hydrogen atoms, remembering that each carbon atom has four bonds and each nitrogen atom has three. If you do have any problems with this, be sure to check with an instructor.

 

Practice

I would like you now to take the time to name the amines for which the formulas are given below (and shown in Exercise 2 in your workbook). Also draw the structural formulas for the amines which are listed below (and in Exercise 3 in your workbook). Check your answers below before you continue with the lesson.

CH3 - CH2 - N - CH2 - CH3
|
  CH3
CH3 - CH2 - N - H
        |
          CH3
H - N - CH2 - CH3
|        
H        
E - N - H
|
D
isopropylamine
diethylamine
2-aminopropane
N,N-dimethyl-3-aminopentane
methylisopropylbutylamine

 

 

Answers

 

CH3 - CH2 - N - CH2 - CH3
|
  CH3
diethylmethylamine
methyldiethylamine
N-ethyl-N-methyl-1-aminoethane
CH3 - CH2 - N - H
        |
          CH3
ethylmethylamine
methylethylamine
N-methyl-1-aminoethane
H - N - CH2 - CH3
|        
H        
ethylamine
aminoethane
E - N - H
|
D
Idi Amin
(sorry)
isopropylamine   CH3 - CH - CH3 
|
  NH2
diethylamine CH3 - CH2 - N - CH2 - CH3
|
H
2-aminopropane   CH3 - CH - CH3 
|
  NH2
N,N-dimethyl-3-aminopentane CH3 - CH2 - CH - CH2 - CH3

CH3 - N - CH3
 
methylisopropylbutylamine CH3 - N - CH2 - CH2 - CH2 - CH3
|                 
CH3 - CH - CH3                 

 

 

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