Transcript Amines: The Basic Group

Power Point to Accompany
Principles and Applications of
Inorganic, Organic, and Biological
Chemistry
Denniston, Topping, and Caret
4th ed
Chapter 16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
16-1
16.1 Amines
Amines have these structures:
RNH2, R2NH, R3N (R is aliphatic or
aromatic)
Amines, like alcohols, can be put into
classes. Class depends on the
number of carbons directly bonded to
the nitrogen atom: a primary amine
has one bond, a secondary two, etc.
RNH2, R2NH, R3N
1o
2o
3o
16-2
Amines: Physical properties
Most amines up
to 5 or 6 carbons
H
are water soluble
CH
N
due to hydrogen
3
bonding with the
H
water molecule.
O
H
H O
H
H
16-3
Amines: Physical properties-2
Amines have boiling points between
alkanes and alcohols. They hydrogen
bond but not as strongly as alcohols.
Tertiary amines cannot hydrogen bond
to each other and boil lower then 1o or
2o of similar molecular weight.
C4H8 (58), bp 0 oC
C3H7NH2 (59), bp 48 oC
o
C3H7OH (60), bp 97 C
16-4
Amine names: Chem Abstracts
Primary aliphatic amines are named by
dropping the final –e of the parent
name and adding the suffix -amine.
Name: CH3CH2NH2
ethanamine
16-5
Amine names: Chem Abstracts-2
The prefix N-alkyl is added to the
name of the parent for 2o and 3o
amines. Name:
H
CH3CH2N CH2CH3
N-ethylethanamine
16-6
Amine names: IUPAC
For primary amines, the prefix amino
and a number designates the position
of the amino group on an alkane
parent chain. A substituent on the N
uses the –N prefix as with the Chem
Abstracts system.
CH3CH CH3 2-aminopropane
NH2
CH3CH CH3 N-methyl-2-aminopropane
NH CH3
16-7
Amine names: Common Names
Name the alkyl groups attached to the N
in alphabetical order and add –amine.
The name is continuous, no spaces
between groups. Name:
CH3CH2CH CH3
CH3 NH
Methylsec-butylamine
16-8
Amine names
Aromatic amines are named as
N-substituted derivatives of
aniline. (See aromatics) Name
a) and b):
a) m-nitroaniline
NH2
b) N-methylaniline
a)
HN CH3
NO2
b)
16-9
Reactions of Amines: Preparation
Aliphatic amines are prepared via
reduction of amides. E. g.
O
[H]
CH3CH2C NH CH3
CH3CH2CH2 NH CH3
Aromatic amines are prepared via
reduction of nitro compounds. E. g.
NO2
[H]
NH2
16-10
Reactions of Amines: Basicity
Amines are weak bases. They accept
protons from water making solutions
basic.
CH3CH2NH2 + H2O
+
CH3CH2NH3
+ OH
16-11
Reactions of Amines: Neutralization
Amines form salts by accepting a proton
from strong mineral acids.
Converting amines to salts often makes
insoluble amines soluble!!!!!
CH3 CH2CH2 NH2
+ HCl
+
CH3CH2 CH2NH3
Cl
Name amine salts by replacing the suffix
–amine with ammonium and the name of
the anion.
E. g. propylammonium chloride
16-12
Reactions of Amine Salts: Neutralization
Amine salts revert to the amine
(donate a proton) in strong base.
+
H3N
Cl
H2N
+ NaOH
NO2
+ NaCl + H2O
NO2
16-13
Amine Reactions: “Quats”
3o amines react with alkyl chlorides
to give quaternary ammonium salts
which are very important in
biochemistry.
CH3
CH3 N
+ CH3Cl
CH3
CH3
+
CH3 N CH3 Cl
CH3
16-14
“Quats” cont.
CH3 Cl+
C18H37 N CH2
CH3
CH3 Cl+
CH3N CH2CH2OH
CH3
Benzalkonium chloride (ZephiranTM) and
choline are important examples.
16-15
16.2 Heterocyclic Amines
Heterocyclic amines have at least one
nitrogen in the ring. MANY are
physiologically active and many are critical
in biochemistry.
HN
N
pyrrole
N
N
N
pyrimidine
N
N
N
H
purine
16-16
Examples of Heterocyclic Amines
CH3
N
N nicotine
H2N CH2CH2 N
histamine
N
H
CH2 CH2 NH2
HO
N
H
serotonin,
a neurotransmitter
16-17
Examples of Heterocyclic Amines-2
H3C O
HO
CH2 NH2
CH2 OH
O
H
C
N
3
NCH3
pyridoxamine
HO
a
B
vitamin
Codine
HO
HO
CH2 CH2 NH2
dopamine
neurotransmitter 16-18
16.3 Amides
Most amides are solids at room
temperature due to internal hydrogen
bonding.
They are not bases. A resonance
structure shows why the N lone pair is
unavailable to accept a proton.
O
CH3C NH2
O
+
CH3C NH2
16-19
Amide Names
Names are derived from the acid.
Remove –ic acid (common) or –oic acid
(IUPAC) and replace with –amide.
Nitrogen substituents are prefixed to the
name and indicated by N.
O
CH3C NH2
ethanamide
or
acetamide
O
CH3CH2C NH CH3
N-methylpropanamide
16-20
Preparation of Amides
1o and 2o amines react with acid
chlorides to give amides.
O
CH3C Cl +
NH2
O H
CH3 C N
+ HCl
The acid chloride transfers its acyl
group to the N of the amine.
16-21
Preparation of Amides-2
1o and 2o amines react with acid
anhydrides to give amides. E. g.
with acetic anhydride.
O O
CH3COC CH3+ H2 NCH3
OH
O
CH3C NCH3+CH3COH
16-22
Amino Acids and Proteins
An alpha amino acid is a carboxylic acid
with an amino group on the carbon
alpha to the carboxylic acid .
The alpha carbon also has an R group
side chain except for glycine which
has two Hs.
Generic amino
acid at physiological
pH.
H O
+
H3 N C C O
aC
R1
16-23
Peptides
A peptide is a polymer of about 2-100
amino acids linked by the peptide(amide)
bond. As the amino group and the
carboxyl group link, water is lost.
H O
H O
H O
+
+
+
H3 N C C O H3 N C C O H3 N C C O
R1
-H2O
R1
-H2O
R1
H O
H O
H O
+
H3 N C C N C C N C C O
H
H
R1
R1
R1
Peptide bonds
16-24
Hydrolysis of Amides
a) Amides hydrolyze with acid to give the
carboxylic acid and the amine salt.
b) Amides hydrolyze with base to give the
carboxylic acid salt and the amine.
C
CH3CH2C NH CH3+ H3O+
C
CH3CH2C OH
+
+ NH3 CH3
C
CH3CH2C NH CH3+ NaOH
C
CH3CH2C ONa
+
H2N CH3
16-25
16.4 Amino Acids and Protein Synthesis
a-amino acids are attached to transfer
RNA molecules (t-RNA). The acyl
group ( and the amino acid) are
transferred to the nitrogen of another
amino acid to form a peptide (amide)
bond.
HC
H2N C C transfer RNA
R
Aminoacyl group
from amino acid
16-26
16.5 Neurotransmitters
Neurotransmitters carry signals from a nerve
cell to a target They can be excitatory or
inhibitory. All contain nitrogen.
catecholamines
A deficiency in dopamine results in
Parkinson’s disease. Too much is
associated with schizophrenia. It is also
associated with the “high” of drugs.
HO
HO
CH2CH2 NH2
16-27
Neurotransmitters-cont.
Catecholamines-cont.
Epinephrine (adrenaline) and norepinephrine
are involved in the fight or flight response.
CH3
OH
CH CH2 NH
HO
HO
epinephrine
(nor=no CH3)
HO
+
CH2CH2 NH3
serotonin
N
Serotonin
H
A deficiency is associated with depression,
bulemia and anorexia nervosa. It also affects
pain perception, thermoregulation, and sleep.
16-28
Neurotransmitters-cont.
Histamine is released
+
during an allergic response.
CH2CH2 NH3
Benadryl is a typical
+
antihistamine used for HN NH
colds and other allergic histamine
responses.
Acetylcholine
functions at the
O
+
neuromuscular
CH3C O CH2CH2 N CH3
junction to cause
acetyl choline
muscles to contract.
3
16-29
The End
Amines and
Amides
16-30