Amines and Amides - St. Francis Xavier University

51 Pages·2014·1.28 MB·English

Amines and Amides
Chapter 17
Bonding characteristics of nitrogen
atoms in organic compounds
• We saw already that carbon atoms (Group 4A) form four bonds to
other atoms in organic compounds.

• And oxygen atoms (Group 6A) form two bonds.

.. ..

.. ..

• Nitrogen atoms (Group 5A) require three bonds to give them
octets. Normally, nitrogen atoms are involved in three covalent
bonds to other atoms.
The important arrangement
.
for this chapter .
.. ..
Structure and classification of amines
• Amines are organic derivatives of ammonia (NH ),
..
3
in which one or more alkyl, cycloalkyl, or aromatic
groups replace hydrogen and bond to the nitrogen
atom.

Ammonia (NH ) is a weak base. Amines are also weak bases.
3
Structure and classification of amines
• Amines are classified as primary, secondary, and tertiary, as
we have seen previously for alcohols.
• For alcohols, the type of carbon atom (1o, 2o, 3o) bound to the
–OH group determined whether the alcohol was primary,
secondary, or tertiary.
• For amines, it is the number of carbon groups that are bound
to the nitrogen atom.

1o amine 2o amine 3o amine
Structure and classification of amines
• This is an important difference in the way that 1o, 2o, and 3o
classification is given.

tert-butanol tert-butylamine
a 3o alcohol a 1o amine
Nomenclature for amines
• Common and IUPAC systems are used extensively for naming
amines.
• In the common system, rules similar to what we have seen for
ethers are employed, naming the alkyl/aromatic groups
attached to the functional group, and then following these
with “amine”
Methylamine Trimethylamine Methylpropylamine
For simple amines, this
Methylphenylamine Cyclohexyldimethylamine
is a good naming system
Nomenclature for amines
• The IUPAC system for naming amines is as follows:
– Select the longest carbon chain bound to the nitrogen as
the parent chain
– Name the chain by changing the alkane name for this
chain: drop the “e” and add “amine”
– Number the chain to give the nitrogen the lowest
numbering
– The number and identity of other substituents (including
any on the main chain) are indicated at the beginning of
the amine name (some are attached to N)
For complicated amine structures, this is probably the better way of naming amines.
Structure and classification of amines
• Some examples. First, 1o amines
1-Butanamine
2-Butanamine
4-C chain (“butane”; - “e” + “amine”)
# to indicate placement of NH group
2
Structure and classification of amines
• For di- and trisubstituted amines, the non-
parent chains are indicated as N-bonded:
longest carbon
longest carbon
chain = 4 carbons
chain = 3 carbons
N,N-Dimethyl-1-propanamine
N-Ethyl-N-methyl-2-butanamine
Structure and classification of amines
• For diamines, the molecule is named as an “alkane-diamine”
with NH groups numbered.
2

1,4-Butanediamine

• …and for cases where NH -substituted alcohols or other
2
compound cases are involved, the NH -group is called an
2
“amino” substituent.
an example of an amino acid
3-Aminobutanoic acid
don’t need to name
polyfunctional carboxylic acids