C25 09/17/2013 14:16:12 Page 367 CHAPTER 25 AMIDES AND AMINES: ORGANIC NITROGEN COMPOUNDS SOLUTIONS TO REVIEW QUESTIONS 1. The lowest boiling point amide in the table is methanamide (formamide), b.p. ¼ 210 C. NH 2 HC O The highest boiling point amide is N-phenylethanamide (acetanilide), b.p. ¼ 304 C. CH 3 C N H O The larger size of N-phenylethanamide contributes significantly to its higher boiling point. 2. Procaine contains an amine. When the amine reacts with HC1 it forms a salt that is much more soluble in water. 3. (a) With reference to Section 25.6, acetylcholine contains a quaternary (4 ) amine. (b) With reference to Section 25.8, cocaine contains a tertiary (3 ) amine. (c) With reference to Section 25.7, serotonin contains a primary (1 ) and a secondary (2 ) amine. (d) With reference to Section 25.8, methamphetamine contains a secondary (2 ) amine. 4. Amides: Unsubstituted amides (except formamide) are solids at room temperature. Many are odorless and colorless. Low molar-mass amides are water soluble. Solubility in water decreases as the molar mass increases. Amides are neutral compounds. The NH 2 group is capable of hydrogen bonding. Amines: Low molar-mass amines are flammable gases with an ammonia-like odor. Aliphatic amines up to six carbon atoms are water soluble. Many amines have a “fishy” odor and many have very foul odors. Aromatic amines occur as liquids and solids. Soluble aliphatic amines give basic solutions. Aromatic amines are less soluble in water and less basic than aliphatic amines. The NH 2 group is capable of hydrogen bonding. 5. Unlike esters, unsubstituted amides can hydrogen bond to each other. Thus, they have a higher melting point than esters of similar molar mass. 6. (a) Heterocyclic compounds are those in which all the atoms in the ring are not alike. (b) The number of heterocyclic rings in each of the compounds is: (i) purine, 2 (ii) histamine, 1 (iii) methadone, 0 (iv) nicotine, 2 7. Ammonia is a toxic, basic, water-soluble compound which can increase the pH of the blood and the urine and would be painful to pass through bodily tissues. However, ammonia is converted in the liver to the neutral diamide, urea, which is water soluble and is excreted in the urine. - 367 -
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C25 09/17/2013 14:16:12 Page 367
C H A P T E R 2 5
AMIDES AND AMINES: ORGANIC NITROGEN COMPOUNDS
SOLUTIONS TO REVIEW QUESTIONS
1. The lowest boiling point amide in the table is methanamide (formamide), b.p. ¼ 210�C.
NH2HC
O
The highest boiling point amide is N-phenylethanamide (acetanilide), b.p. ¼ 304�C.
CH3C NH
O
The larger size of N-phenylethanamide contributes significantly to its higher boiling point.
2. Procaine contains an amine. When the amine reacts with HC1 it forms a salt that is much more soluble
in water.
3. (a) With reference to Section 25.6, acetylcholine contains a quaternary (4�) amine.
(b) With reference to Section 25.8, cocaine contains a tertiary (3�) amine.
(c) With reference to Section 25.7, serotonin contains a primary (1�) and a secondary (2�) amine.
(d) With reference to Section 25.8, methamphetamine contains a secondary (2�) amine.
4. Amides: Unsubstituted amides (except formamide) are solids at room temperature. Many are odorless
and colorless. Low molar-mass amides are water soluble. Solubility in water decreases as the molar
mass increases. Amides are neutral compounds. The NH2 group is capable of hydrogen bonding.
Amines: Low molar-mass amines are flammable gases with an ammonia-like odor. Aliphatic amines up
to six carbon atoms are water soluble. Many amines have a “fishy” odor and many have very foul odors.
Aromatic amines occur as liquids and solids. Soluble aliphatic amines give basic solutions. Aromatic
amines are less soluble in water and less basic than aliphatic amines. The NH2 group is capable of
hydrogen bonding.
5. Unlike esters, unsubstituted amides can hydrogen bond to each other. Thus, they have a higher melting
point than esters of similar molar mass.
6. (a) Heterocyclic compounds are those in which all the atoms in the ring are not alike.
(b) The number of heterocyclic rings in each of the compounds is: