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16-1
Principles and Applications ofInorganic, Organic, and Biological
ChemistryDenniston, Topping, and Caret
4th ed
Chapter 16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Power Point to Accompany
16-2
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
16.1 Amines
16-3
Amines: Physical properties
Most amines up to 5 or 6 carbons are water soluble due to hydrogen bonding with the water molecule.
CH3NH
HH
OH
HO
H
16-4
Amines: Physical properties-2Amines 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
C3H7OH (60), bp 97 oC
16-5
Amine names: Chem AbstractsPrimary aliphatic amines are named by
dropping the final –e of the parent name and adding the suffix -amine.
Name: CH3CH2NH2
ethanamine
16-6
Amine names: Chem Abstracts-2
The prefix N-alkyl is added to the name of the parent for 2o and 3o amines. Name:
CH3CH2N
H
CH2CH3
N-ethylethanamine
16-7
Amine names: IUPACFor 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 CH3NH2
CH3CH CH3NH CH3
2-aminopropane
N-methyl-2-aminopropane
16-8
Amine names: Common NamesName the alkyl groups attached to the N
in alphabetical order and add –amine. The name is continuous, no spaces between groups. Name:
CH3CH2CH CH3
NHCH3
Methylsec-butylamine
16-9
Amine names
Aromatic amines are named as N-substituted derivatives of aniline. (See aromatics) Name a) and b):
NH CH3NH2
NO2a) b)
a) m-nitroaniline
b) N-methylaniline
16-10
Reactions of Amines: PreparationAliphatic amines are prepared via reduction of amides. E. g.
CH3CH2CO
CH3NH[H]
CH3CH2CH2 CH3NH
Aromatic amines are prepared via reduction of nitro compounds. E. g.
NO2
[H]NH2
16-11
Reactions of Amines: BasicityAmines are weak bases. They accept protons from water making solutions basic.
CH3CH2NH2+ H2O CH3CH2NH3
+
+ OH-
16-12
Reactions of Amines: Neutralization
Amines form salts by accepting a proton from strong mineral acids.
Converting amines to salts often makes insoluble amines soluble!!!!!
CH3CH2CH2NH2
+ HClCH3CH2CH2NH3
+Cl-
Name amine salts by replacing the suffix –amine with ammonium and the name of the anion.
E. g. propylammonium chloride
16-13
Reactions of Amine Salts: Neutralization
Amine salts revert to the amine (donate a proton) in strong base.
NH3
+
NO2
NH2
NO2
Cl-
+ NaOH + NaCl + H2O
16-14
Amine Reactions: “Quats”3o amines react with alkyl chlorides to give quaternary ammonium salts which are very important in biochemistry.
CH3 N
CH3
CH3
CH3Cl+ CH3 N
CH3
CH3
CH3+
Cl -
16-15
“Quats” cont.
Benzalkonium chloride (ZephiranTM) and choline are important examples.
CH3N+
CH3
CH3
CH2CH2OHCl-
Cl-
C18H37 N+
CH3
CH3
CH2
16-16
16.2 Heterocyclic AminesHeterocyclic amines have at least one
nitrogen in the ring. MANY are physiologically active and many are critical in biochemistry.
NH N
pyrrole
pyrimidinepurine
N
N
NH
NN
N
16-17
Examples of Heterocyclic Amines
N
N
CH3
nicotineN
N
H
CH2CH2NH2
histamine
NH
OH CH2 CH2 NH2
serotonin,a neurotransmitter
16-18
Examples of Heterocyclic Amines-2
O
OCH3
OHNCH3
Codine
pyridoxaminea B vitamin
NCH3
OHCH2 NH2
CH2OH
OH
OH CH2 CH2NH2dopamineneurotransmitter
16-19
16.3 AmidesMost 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.
CH3C
O
NH2 CH3C
O
NH2
+
16-20
Amide NamesNames 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.
CH3C
O
NH2
CH2C
O
NHCH3 CH3
ethanamideoracetamide
N-methylpropanamide
16-21
Preparation of Amides1o and 2o amines react with acid chlorides to give amides.
CH3C
O
Cl
NH2
+ NCH3C
O H
+ HClThe acid chloride transfers its acyl group to the N of the amine.
16-22
Preparation of Amides-21o and 2o amines react with acid anhydrides to give amides. E. g. with acetic anhydride.
CH3CO
OCO
CH3 NH2 CH3+
NCH3CH3COH
+CH3CO
OH
16-23
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.
C C
R1
H
NH3
+O
OGeneric aminoacid at physiologicalpH. C
16-24
PeptidesA 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.
C C
R1
H
NH3
+O
O
Peptide bonds
C C
R1
H
NH3
+O
OC C
R1
H
NH3
+O
O
C C
R1
H
NH3
+O
C C
R1
H
NH
OC C
R1
H
NH
OO
-H2O -H2O
C C
R1
H
NH3
+O
O
Peptide bonds
C C
R1
H
NH3
+O
OC C
R1
H
NH3
+O
O
C C
R1
H
NH3
+O
C C
R1
H
NH
OC C
R1
H
NH
OO
-H2O -H2O
16-25
Hydrolysis of Amidesa) 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.
CH3CH2CC
NHCH3 CH3CH2CC
OH
NH3
+CH3
+H3O+
+
CH3CH2CC
NHCH3 CH3CH2CC
ONa
NH2 CH3
+NaOH
+
16-26
16.4 Amino Acids and Protein Synthesis
-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.
RC C
Ctransfer RNANH2
H
Aminoacyl groupfrom amino acid
16-27
16.5 NeurotransmittersNeurotransmitters carry signals from a nerve
cell to a target They can be excitatory or inhibitory. All contain nitrogen.
catecholaminesA deficiency in dopamine results in
Parkinson’s disease. Too much is associated with schizophrenia. It is also associated with the “high” of drugs.
OH
OH
CH2CH2NH2
16-28
Neurotransmitters-cont.Catecholamines-cont.
Epinephrine (adrenaline) and norepinephrine are involved in the fight or flight response.
Serotonin
A deficiency is associated with depression, bulemia and anorexia nervosa. It also affects pain perception, thermoregulation, and sleep.
OH
OH
CH CH2NH
OH CH3
epinephrine(nor=no CH3)
serotoninNH
OH CH2CH2NH3
+
16-29
Neurotransmitters-cont.Histamine is released during an allergic response.
Benadryl is a typical antihistamine used for colds and other allergic responses.
Acetylcholine functions at the neuromuscular junction to cause muscles to contract.
histamineNH NH
+
CH2CH2NH3
+
acetyl cholineCO
CH3 O CH2CH2N+
CH3 3
16-30
Amines and Amides
The End