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CHAPTER 25 AMIDES AND AMINES: ORGANIC NITROGEN COMPOUNDS SOLUTIONS TO REVIEW QUESTIONS 1. Table 25.1 incorrectly reports acetaminophen’s boiling point as 169°C (this is actually the melting point for this drug). The lowest boiling point amide in the table is methanamide (formamide), b.p. = 210°C. O HC NH 2 N-phenylethanamide (acetanilide), b.p. = 304°C. The highest boiling point amide is N O CH3C H N N-phenylethanamide contributes significantly to its higher boiling The larger size of N point. 2. Procaine contains an amine. When the amine reacts with HCl it forms a salt that is much more soluble in water. 3. (a) (b) (c) (d) 4. With reference to Section 25.6, acetylcholine contains a quaternary (4°) amine. With reference to Section 25.8, cocaine contains a tertiary (3°) amine. With reference to Section 25.7, serotonin contains a primary (1°) and a secondary (2°) amine. With reference to Section 25.8, methamphetamine contains a secondary (2°) amine. 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 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 group is capable of hydrogen bonding. - 358 - - Chapter 25 - 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) (b) 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. 8. A “condensation polymer” is made when monomers connect together with the loss of a small molecule, most often, water. Heterocyclic compounds are those in which all the atoms in the ring are not alike. The number of heterocyclic rings in each of the compounds is: (i) purine, 2 (ii) ampicillin, 2 (iii) methadone, 0 (iv) nicotine, 2 HOOC ¬ (CH 2)4 ¬ COOH + H 2N ¬ (CH 2)6 ¬ NH 2 ¡ O [ 9. 10. C O (CH2)4 C NH (CH2)6 NH [ n + H2O The nitrogen in a compound that has four groups bonded to it is positively charged and is called a quaternary ammonium nitrogen. The compound is called a quaternary ammonium salt. An amine must have at least one hydrogen atom bonded to the nitrogen atom to react with an acid chloride. A tertiary amine does not meet this requirement. - 359 - - Chapter 25 - SOLUTIONS TO EXERCISES O O 1. (a) C CH3 (b) (c) NH 2 CH3CH2 C CH3 O O CH3 CH2C (d) NH2 C CH3CH C NHCH3 NH2 CH3 2. (a) CH3 CH2 CH2 CH2 O CH3 C N CH3 O (b) CH3 C NH2 CH3 CH3 O (c) CH3 CH2 CH CH C NH2 O (d) C NH CH2 CH3 3. (a) (b) (c) common, formamide; IUPAC, methanamide N N-dimethyl-3,3-dimethylbutanamide N IUPAC, N, N IUPAC, N-butylethanamide 4. (a) (b) (c) IUPAC, benzamide N N-dibutylethanamide N IUPAC, N, N-methylacetamide, IUPAC, N-methylethanamide N common, N 5. N N-diethylN The larger amides are less water soluble. Thus, the largest amide, N, 3-methylhexanamide is the least water soluble. The intermediate sized amide, 3-methylhexanamide will be of intermediate solubility and the smallest amide, acetamide, will be the most water soluble. - 360 - - Chapter 25 - 6. The larger amides are less water soluble. Thus, the largest amide, benzamide, is the least water soluble. The intermediate sized amide, propanamide, will be of intermediate solubility and the smallest amide, formamide, will be the most water soluble. H 7. O N C CH3CH2 N H O H C CH2 CH3 H O C CH3 CH2 N H H H 8. O N C CH3 N H O H C CH3 H O C CH3 N H H 9. Organic products O ‘ + (a) 3 3 3 (c) H 2NCH 2CH 2CH 2CH 2COONa (b) - 361 - O ‘ CH 3C ¬ NHCH(CH 3)2 - Chapter 25 - 10. Organic products O ‘ (a) 3 (c) CH2COOH 2 (b) 3 2 ± ± CH3NH2CH3 O ‘ C H C CH 3 2 ¬ NHCH 3 ƒ CH 3 O 11. 12. CH3CH2CH2C (b) O ‘ CH 3CH 2C ¬ OH + NH 2CH 2CH 3 (c) O ‘ HC ¬ NH ¬ (a) (b) (c) 13. OH + NH2CH3 (a) ± HCl+H2O O ‘ CH 3C ¬ NHCH 2CH 3 + NaOH O ‘ CH 3CH 2C ¬ OH + CH 3NHCH 3 O ‘ CH 3C ¬ NH 2 + HCl + H 2O Structures of amines with formula C4H 11N. CH 3CH 2CH 2CH 2NH 2 1° CH 3 ƒ CH 3CNH 2 ƒ CH 3 1° CH 3CHCH 2NH 2 ƒ CH 3 1° CH 3CH 2CHCH 3 ƒ NH 2 1° CH 3CH 2CH 2NHCH 3 (CH 3)2CHNHCH 3 2° 2° - 362 - - Chapter 25 - 13. (cont.) CH 3 ƒ CH 3CH 2NCH 3 3° CH 3CH 2NHCH 2CH 3 2° 14. Structures of amines with formula C3H 9N. CH 3CH 2CH 2NH 2 1° 15. 16. CH 3CHCH 3 ƒ NH 2 1° CH 3CH 2NHCH 3 2° CH 3NCH 3 ƒ CH 3 3° Classification of amines (a) primary (b) tertiary (c) primary (d) both primary Classification of amines (a) secondary (b) tertiary (c) secondary (d) tertiary 17. The triethylamine solution in 1.0 M NaOH would have the more objectionable odor because it would be in the form of the free amine, while in the acid solution the amine would form a salt that will have little or no odor. 18. The isopropylamine solution in 1.0 M KOH would have the more objectionable odor because it would be in the form of the free amine, while in the acid solution the amine would form a salt that will have little or no odor. 19. Names (a) dimethylamine CH2CH3 (b) o-ethylaniline NH2 (c) NH2 (d) + (e) cyclohexanamine tetraethylammonium iodide m-nitroaniline NH2 NO2 (f) (CH3CH2)2N ¬ cyclohexyldiethylamine - 363 - - Chapter 25 - 20. Names NHCH2CH3 (a) (b) 3 2 ƒ NH 2 NH (c) (f) 21. 2-butanamine diphenylamine + (d) (e) 3 N N-ethylaniline ethylammonium bromide N pyridine O ‘ CH 3C ¬ NHCH 2CH 3 N N-ethylacetamide Structural formulas (a) CH 3CH 2NHCH 3 (b) (c) (d) NH2 H 2NCH 2CH 2CH 2CH 2NH 2 CH 3CH 2NCH(CH 3)2 ƒ CH 3 (e) N (f) 22. + (CH 3CH 2)3NHCl- Structural formulas (a) CH 3CH 2CH 2CH 2NCH 2CH 2CH 2CH 3 ƒ CH 2CH 2CH 2CH 3 (b) ± ¬ NH2Cl ƒ CH3 – - 364 - - Chapter 25 - (c) (d) 23. + CH 3CH 2NH 3ClCH 3CH 2CH 2CHCH 2OH ƒ NH 2 (e) CH3 ƒ CH3CH2CH2C ¬¬ CH ¬ NH ¬ ƒ ƒ CH3 CH3 (f) H 2NCH 2CH 2NH 2 (a) Butylamine has the following structure: CH3CH2CH2CH2NH2 Its IUPAC name is 1-butanamine. tert-butylamine has the following structure: (b) CH3 CH3 C NH2 CH3 (c) Its IUPAC name is 2-methyl-2-propanamine. Formamide has the following structure: O HC NH2 Its IUPAC name is methanamide. 24. (a) Isopropylamine has the following structure: CH3 CH3C H NH2 (b) Its IUPAC name is 2-propanamine. Diethylamine has the following structure: CH3CH2NHCH2CH3 Its IUPAC name is N-ethylethanamine. - 365 - - Chapter 25 - (c) Acetamide has the following structure: O CH3C NH2 Its IUPAC name is ethanamide. 25. (a) This reaction adds methyl groups to a primary amine to form a tertiary amine. CH3 CH3 CH3 C N CH3 CH3 (b) N,N-dimethyl-2-methyl-2-propanamine N N This reaction reduces the nitro group to form a substituted aniline. NH2 CH3 (c) (d) 26. (a) (b) m-methylaniline This reaction reduces the nitrile to form an amine. CH3NH2 menthanamine (methylamine) This reaction reduces the amide to form an amine. CH3CH2NHCH2CH3 N-ethylethanamine (diethylamine) N This reaction reduces an amide to form an amine. (CH3)3N NN N, N-dimethylmethanamine (trimethylamine) This reaction reduces a nitrile to form an amine. CH3 CH3 CH2 CH CH2 NH2 2-methyl-1-butanamine - 366 - - Chapter 25 - (c) This reaction reduces a nitro group to form a substituted aniline. NH2 CH3 CH3 3,4-dimethylaniline 27. (d) This reaction adds a methyl group to a primary amine to form a secondary amine. CH3CH2NHCH3 N-methylethanamine (methylethylamine) N (a) A carboxylic acid chloride reacts with an amine to form an amide (and an amine salt). O CH3C NHCH2CH2CH3 + CH3CH2CH2NH3Cl N-propylethanamide propylammonium chloride (b) (c) An amine plus a strong acid forms an amine salt. + – CH3CH2CH2CH2NH3Cl butylammonium chloride This reaction reduces an amide to form an amine. CH3CH2NH2 ethanamine (ethylamine) 28. (a) This reaction reduces a nitrile to form an amine. CH3 CH3 CH2 CH CH2 NH2 (b) 2-methyl-1-butanamine A carboxylic acid chloride reacts with an amine to form an amide (and an amine salt). O HC NHCH3 + CH3NH3 Cl N-methylmethanamide methylammonium chloride - 367 - - Chapter 25 - (c) An aniline plus a strong acid forms an aniline salt. NH3 Br anilinium bromide 29. Amines are bases while carboxylic acids and phenols are acids. Alcohols and amides are neither acids nor bases. (a) amine, base (b) amide, neither (c) amide, neither (d) carboxylic acid, acid (e) alcohol, neither (f) alcohol, neither 30. Amines are bases while carboxylic acids and phenols are acids. Alcohols and amides are neither acids nor bases. (a) alcohol, neither (b) carboxylic acid, acid (c) amide, neither (e) amine, base (f) phenol, acid (d) amine, base 31. The main reason why trimethylamine has a lower boiling point than propylamine and ethylmethylamine is that trimethylamine cannot hydrogen bond because it has no hydrogen atoms bonded to the nitrogen atom. The other two amines do have hydrogen atom(s) bonded to the nitrogen atom and their molecules can hydrogen bond, which results in higher boiling points. 32. Biogenic amines are derived from amino acids and act as neurotransmitters and hormones in animals. In contrast, alkaloids are basic compounds derived from plants that show physiological activity. 33. This calculation requires Avogadro’s number, 6.02 × 1023 dopamine molecules/mole. (5 × 10–18 moles)(6.02 × 1023 dopamine molecules/mole) = 3 × 106 dopamine molecules About three million dopamine molecules are sent from one neuron to the next. O 34. (a) CH3 C O Cl + 2 CH3 NH2 CH3 C + NHCH3 + CH3 NH3 Cl O LiAlH4 CH3 CH2 NHCH3 (b) CH3 C (c) CH3 CH2 NHCH3 + CH3 Br (1 mole) NHCH3 - 368 - CH3 CH2 N(CH3 )2 - Chapter 25 - 35. There is one amine and two amides in ampicillin. S CH C CH3 CH3 NH N NH2 O COOH O amine amides 36. Lemon juice, being acidic, will react with the basic amines forming salts, which are soluble and can be washed away with water. NH2 37. ± NH3Cl ± HCl ¡ – 38. H 2N ¬ CH 2CH 2CH 2CH 2 ¬ NH 2 Putrescine has two primary amines. 39. Drugs are given as ammonium salts because the salts are soluble in water. 40. CH2 O ƒ ‘ H2NCHC ¬ NHCHC ¬ OCH3 ƒ ‘ O CH2COOH amine Aspartame amide 41. ¬C¬ ‘ O ¬ C ¬ NH ¬ ‘ O ¬ NH ¬ C ¬ ‘ O ¬ C ¬ NH ¬ ‘ O Kevlar polymer - 369 - ¬ NH ¬ n - Chapter 25 - 42. 43. (b) O O ‘ ‘ HO ¬ C ¬ (CH 2)8C ¬ OH O O ‘ ‘ HO ¬ C ¬ (CH 2)6C ¬ OH (a) CH 3CH 2OH (a) KCN H 2SO4 140°C and H 2N(CH 2)6NH 2 H2N ¬ and " C H “ CH 2 2 " NCCH CH CN 2 2 H2 Ni Br2 ¬ CH2 ¬ ¬ NH2 " BrCH CH Br 2 2 " H NCH CH CH CH NH 2 2 2 2 2 2 1,4-butanediamine (b) O O ‘ ‘ LiAlH 4 " CH 3C ¬ Cl + NH 3 ¡ CH 3C ¬ NH 2 CH 3CH 2NH 2 O O ‘ ‘ LiAlH 4 " CH 3C ¬ Cl + CH 3NH 2 ¡ CH 3C ¬ NHCH 3 CH 3CH 2NHCH 3 O O ‘ ‘ LiAlH 4 " CH 3C ¬ Cl + (CH 3)2NH ¡ CH 3C ¬ N(CH 3)2 CH 3CH 2N(CH 3)2 - 370 -