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BIOCHEMISTRY SUPPLEMENT C
Amines & Amides
1. You should be able to define and/or
identify the following terms:
primary amine biological activity
secondary amine primary structure
tertiary amine secondary structure
amide alpha-helix
alpha-amino acid beta-structure
peptide bond tertiary structure
N-terminal quaternary structure
C-terminal subunit
isoelectric point conjugated
peptide denaturation
protein enzyme
2. You should be able to differentiate between the structures of
primary, secondary and tertiary amines.
3. You should be able to write formulas for amines and amides
when given the names and vice-versa.
4. You should be able to describe the general properties of amines
in terms of their structure.
5. You should be able to write equations for the preparation of
amides from amines.
6. You should be able to
a) write equations for the reactions of amines with acids and
b) describe the solubility of the product in water.
7. You should be able to determine whether an amino acid is
"neutral", "basic" or "acidic" when given the structure.
8. You should be able to explain the unusual physical properties of
amino acids in terms of their structure and "dipolar" nature.
9. You should be able to show how a peptide bond forms between amino
acids.
10. You should be able to describe the type of bonding responsible
for the primary, secondary, and tertiary structure of protein.
11. You should be able to explain how the amino acid sequence is
determined for a protein.
12. You should be able to describe the action of an enzyme.
AMINES AND AMIDES
1. Classification of Amines:
Comparison: C: primary C attached to one other C
secondary C attached to two other C's
tertiary C attached to three other C's
quaternary C attached to four other C's
But for amines look at C's attached to N:
[CH3NH2] primary amine: N attached to one C
[(CH3)2NH] secondary amine: N attached to two C's
[(CH3)3N] tertiary amine: N attached to three C's
and there is a quaternary N ion, with N attached to four C's;
example: N(CH3)4+
(These are called quaternary ammonium ions.)
2. Preparation of Amines:
a. Alkyl halides + NH3:
CH3CH2Cl + NH3 CH3CH2NH2 + HCl
primary amine
b. Alkyl halide + amines:
1) CH3CH2Cl + CH3CH2NH2 CH3CH2-N-H + HCl
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CH2CH3
secondary amine
2) CH3CH2Cl + CH3CH2-N-H CH3CH2-N-CH2CH3
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CH2CH3 CH2CH3 + HCl
tertiary amine
3. Preparation of Amides:
a. Unsubstituted: *RCOOH + NH3, : (review!)
O O
" "
CH3COH + NH3 -----> CH3CNH2 + H2O
b. Substituted: *RCOOH + R'NH2,
1) O O
" "
CH3COH + CH3NH2-----> CH3CNHCH3 + H2O
2) O O
" "
CH3COH + (CH3)2NH -----> CH3CN(CH3)2 + H2O
NOTE: only primary amines and
secondary amines form amides
O
"
*RCOOH or RCCl react the same way.
4. Reactions:
a. Amines are bases: RNH2 + HCl react.
CH3NH2 + HCl CH3NH3+ + Cl-
salt (solubility increases)
b. Formation of Amides: See #3 above.
5. Names:
a. Common names for amines:
(CH3)3N trimethylamine
b. Substituted amides:
O
"
CH3CN(CH3)2 N,N-dimethylethanamide
PRACTICE SET
Amines, Amides
1. Draw a structure for each of the following:
a. isopropylamine
b. isobutylmethylamine
c. ethylmethyl-n-propylamine
2. Classify each of the amines in 1. above as
primary, secondary or tertiary.
3. Complete the following reactions with the
organic product:
a. CH3CH2CH2NH2 + HI
b. N-CH3 + HCl
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CH3
4. Complete the following hydrolysis reactions:
a. O
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CH3CH2CH2CNH2 + H2O ----->
H+
b. O
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CH3CH2CH2C-N-CH3 + H2O ----->
H+
CH2CH3
PRACTICE SET ANSWERS
Amines, Amides
1. a. CH3CHCH3 isopropylamine
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NH2
b. CH3
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CH3-N-CH2CHCH3 isobutylmethylamine
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H
c. CH3-N-CH2CH3 ethylmethyl-n-propylamine
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CH2CH2CH3
2. a. primary amine
b. secondary amine in 1. above
c. tertiary amine
3. a. CH3CH2CH2NH2 + HI CH3CH2CH2NH3+I-
b. H+
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CH3-N-CH3 + HCl -----> CH3-N-CH3 + Cl -
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C C
/ \ / \
H-C C-H H-C C-H
|O| |O|
H-C C-H H-C C-H
\ / \ /
C C
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H H
H H
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C-C CH3
/ \ |
H-C O C-N + HCl ----->
\ / |
C-C CH3
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H H
H H
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C-C CH3
/ \ | + -
H-C O C-N-H + Cl
\ / |
C-C CH3
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H H
4. a. O O O
" H+ " "
CH3CH2CH2CNH2 + H2O ----> CH3CH2CH2COH + NH3 CH3CH2CH2CO- NH4+
b. O O
" H+ "
CH3CH2CH2C-N-CH2CH3 + H2 ------> CH3CH2CH2COH + NHCH2CH3
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CH3 CH3
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|| H+
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\/
H
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H-N-CH2CH3
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CH3
Amino Acids and Proteins
O
"
1. -Amino acids are the only ones we will focus on. -N-C-C-OH
2. Description of a protein includes
PRIMARY - amino acid sequence (amides; covalent bonds)
SECONDARY - alpha-helix or ß-pleats (H-bonding; polar forces)
TERTIARY - coiling, bending and folding into 3-D shape
and
QUATERNARY - aggregation of biologically active sub-units.
Not all proteins have a tertiary or quaternary
structure. Hemoglobin, a globular protein, does.
3. The primary structure is very important to the protein. Any change in
amino acid sequence changes the protein. Example: sickle cell
anemia
4. Denaturing proteins: irreversible destruction of all but primary
structure.
Heat; pH; solvents; agitation; heavy metals, etc.
5. Enzymes: wholly or in part proteins, that act as biological
catalysts
PRACTICE SET
Amino Acids and Proteins
12. Define the following terms:
a. tripeptide
b. isoelectric point
c. N-terminal
d. C-terminal
13. Identify the peptide (amide) linkages in the following structure:
O
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H2N-C-C-N
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CH3
O
C
O O
NH__CH__C
NH__CH__C__OH
CH2
CH2
OH
C=O
OH
14. List and describe the types of forces that determine the tertiary
structure of a protein.
15. Distinguish between the 1 , 2 , 3 and 4 structures of a
protein.
ANSWERS
12. a. tripeptide: a polymer consisting of three amino acids
linked as amides.
O R R' O R" R O
R__CH__C__N__CH__C__N__CH__C__OH
NH2
b. isoelectric point: the pH at which an amino acid exists in
its dipolar form.
O
R__CH__C
O-
NH3+
c. N-terminal end of a peptide: the end with the free amino
group.
d. C-terminal end of a peptide: the end with the free carboxyl
group.
13. O
H2N__CH__C__N
CH3
alanine O
ala C
O O
NH__CH__C
proline NH__CH__C__OH
pro CH2
CH2
OH
C=O
serine
ser OH
aspartic acid
asp
ala pro ser asp sequence
14. The tertiary structure of a protein refers to the coiling and
bending of the helix. One type of force which is responsible for
the coiling and bending is the "salt bridge" linkage, the
attraction of two oppositely charged groups such as -NH3 + and
O
-C-O -
Hydroxy side groups will align towards water because of H-bond.
S-S linkages form from S-H groups. In general, the protein will
coil with non-polar groups to the center and polar groups to the
outside.
15. Primary structure of proteins: sequence of amino acids in the
peptide.
Secondary structure of proteins: the -helix with H-bonding
between coils.
Tertiary structure of proteins: the twisting, bending and
coiling of the -helices due to ionic attractions, H-bonding.
Quaternary structure of proteins: large superstructures
resulting from the aggregation of subunits made up of the coiled,
bent alpha-helices.
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