Amines and Amides

1
Amines and Amides
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2
Amines

• Nitrogen containing compound
• Nitrogen is a group 5A element with 5 valence
  electrons
• Nitrogen has 3 bonds and 1 lone pair
• Ammonia derivatives where at least one H is
  replaced by an alkyl, cycloalkyl, or aryl group

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3
Amines

Classified as primary, secondary, tertiary
CH
CH
3
3
½
½
CH

N
H
CH

N
H
CH

N

CH
3
2
3
3
3
1
2
3
3
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Structure of Amines

• Aliphatic amines
• N bonded to alkyl groups

• Aromatic Amines
• N bonded to one or more aryl groups

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5
Heterocyclic Amines

• Heterocyclic aliphatic amines
• Ring is saturated and N is part of a ring

• Heterocyclic aromatic amines
• When nitrogen is part of an aromatic ring

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Naming Amines

• Amines may be named using either common or IUPAC
  rules
• For common names, list the alkyl groups attached
  to the N in ABC order and use the suffix amine,
  which is written as one word
• Prefixes di- and tri- are used if identical
  groups are present

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IUPAC Naming of 1o Amines

• 1. Select the longest carbon chain that contains
  the N as the parent
• 2. Name parent as an alkan-amine by removing the
  e of the alkane and replacing it with the suffix
  amine
• 3. the parent from the end nearest the N
• 4. The location of the amino group comes before
  the parent
• 5. If the parent is substituted, its name and
  comes before the parent

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Examples
CH3CH2NH2
ethanamine
(ethylamine)
CH3CHCH2NH2 CH3 3-Methyl-1-propanamine (Is
obutylamine)
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IUPAC Naming 1o Amines

• Compounds with 2 amino groups are named by adding
  suffix -diamine. The final e of the parent
  hydrocarbon is retained

H2NCH2CH2CH2CH2CH2CH2NH2
N
H
2

1,6-hexanediamine
CH
CHCH2NH2
3
1,2- propanediamine
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IUPAC Naming 2o and 3o Amines

• 2o and 3o amines are named as N-substituted
  primary amines
• The largest alkyl chain is considered the parent
• The other alkyl chains are placed in front of the
  parent using the prefix N- to denoted that it is
  attached to the N

N,N-dimethylcyclohexanamine
CH3NHCH2CH3 N- methylethanamine
N(CH3)2

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Examples
N
-
methylaniline
Aniline
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Nomenclature Priority

• If other functional groups are present on an
  amine, the NH2 group is a substituent and is
  called amino
• Priority List from highest to lowest
• carboxylic acid, aldehyde, ketone, alcohol,
  amine

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Learning Check
Give the name and classify
A.
CH
NHCH
CH
3
2
3
B.
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Solution
A.
3
, 2
N-methylethanamine
CH
3

B.
CH
CH
NCH
3
2
3
N,N- dimethylethanamine
, 3
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Learning Check
Write a structural formula for
A.
1
-
pentanamine
B. 1,3
-
cyclohexanediamine
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Solution
A.
1
-
pentanamine
CH
CH
CH
CH
CH
-
NH
3
2
2
2
2
2
B.
1,3
-
cyclohexanediamine
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Physical Properties

• Amines are polar compounds
• Both 1 and 2 amines form intermolecular
  hydrogen bonds
• Boiling points are higher than corresponding
  alkanes but lower than the corresponding alcohols
• Are soluble if 6 or less carbons are present

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Physical Properties

• Amines are polar compounds
• 3 amines have no N-H bond and cannot form
  hydrogen bonds with one another

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Boiling Points

• N-H less polar than O-H.
• Weaker hydrogen bonding.
• Tertiary amines cannot hydrogen bond.

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Physical Properties of Amines
Boiling points of amines are higher than those of
alkanes but lower than those of alcohols
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Basicity of Amines

• Lone pair of electrons on nitrogen can accept a
  proton from an acid
• All amines are weak bases and aqueous solutions
  of amines are basic

-





H
H
Hydroxide ion
Methylamine
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Ammonium Salts

• When 4 atoms or groups of atoms are bonded to a
  nitrogen atom, N has a positive charge (NH4)
• The positively charged nitrogen is associated
  with anion to produce a salt

CH
NH
HCl
CH
NH
Cl


3
2
3
3
methylammonium
chloride
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Synthesis of Amines

• Alkylation

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Neurotransmitters

• Neurotransmitter chemical substance that is
  released at the end of a nerve, travels across
  the synaptic gap, and then bonds to a receptor
  site on another nerve, causing a nerve impulse

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Alkaloids
Physiologically active nitrogen
-
containing

compounds
Extracted from bark, leaves, berries fruits

Used as anesthetics, antidepressants, and

stimulants
Many are addictive

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Nicotine
Derived from tobacco leaves Small doses
stimulant effect Large doses poison Nicotine
salts - insecticides
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Caffeine
Found in coffee beans and tea
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Amides

• Amides derivatives of carboxylic acids where
  the OH is replaced with an amino (-NH2) or
  substituted amino group
• Are either un-, mono-, di-substituted
• Also called 1o, 2o, or 3o
• May be aromatic or cyclic (called lactams)

O

O

C

NH
R


2
R

C

OH
amide
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Amide Nomenclature

• Are named as derivatives of carboxylic acids so
  the name is based on the name of a parent acid
• The ending of the acid is changed from oic acid
  to amide
• Names of groups attached to N precede the parent
  with the N- prefix as the locator

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Examples
A.
Pentanamide
O

CH
CH
CH
CH
C

NH
3
2
2
2
2
B.
N
-
methylbutylamide
O

CH
CH
CH
C

NHCH
3
2
2
3
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-
Naming Amides with N
Groups
O

CH
C

NHCH
N
-
methyl
ethanamide
3
3
O

CH
CH
C

N(CH
)
3
2
3
2
N,N
-
dimethyl
propanamide
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Aromatic Amides
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Learning Check
Name the following amides
O

A.
CH
CH
CH
C

NH
3
2
2
2
O

B.
CH
C

N(CH
CH
)
3
2
3
2
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Solution
O

A.
CH
CH
CH
C

NH
3
2
2
2
butanamide
O

B.
CH
C

N(CH
CH
)
3
2
3
2
N,N
-
diethylethanamide

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Learning Check
Draw the structures of
A.
Hexanamide
-
methylheptamide
B.
N

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Cyclic Amides

• Biologically significant lactams include
  penicillin and penicillin derivatives
• such as ampicillin and amoxicillin

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Physical Properties of Amides

• Are not basic like amines
• If they have 6 or less carbons, they are soluble
  in water
• Have the ability to H-bond

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Synthesis of Amides
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Reactions of Amides
Amides undergo
acid hydrolysis
base hydrolysis
carboxylic acid
salt of carboxylic acid
ammonium salt
amine
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Reactions of Amides
acid hydrolysis
O

HCl H
O
NH
Cl


RCOH
2
4
O

Heat
RCNH
2
O

RC
O

Na


NH
3
NaOH
base hydrolysis
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Learning Check
Hydrolysis of
N
-
ethylpropanamide
with NaOH
gives what products.
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Solution
Hydrolysis of
N
-
ethylpropanamide
with NaOH
gives the following products.
O

CH
CH
CO
Na
CH
CH
NH


3
2
3
2
2
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Polyamides