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Derivatives of Carboxylic Acids and Nucleophilic Acyl Substitution

Derivatives of Carboxylic Acids and Nucleophilic Acyl Substitution. Carboxylic Acids. A class of organic compounds containing at least one carboxyl group. R = alkyl group or H  alkanoic acid(sat’d) R = aryl group  aromatic carboxylic acid. Aliphatic carboxylic acid

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Derivatives of Carboxylic Acids and Nucleophilic Acyl Substitution

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  1. Derivatives of Carboxylic Acids and NucleophilicAcyl Substitution

  2. Carboxylic Acids • A class of organic compounds containing at least one carboxyl group

  3. R = alkyl group or H  alkanoic acid(sat’d) R = aryl group  aromatic carboxylic acid

  4. Aliphatic carboxylic acid = fatty acids (sat’d or unsat’d) ∵ obtained from fat/oil E.g. stearic acid, CH3(CH2)16COOH oleic acid, CH3(CH2)7CH=CH(CH2)7COOH

  5. Carboxylic Acids • Carboxyl group •  combination of the carbonyl group and the hydroxyl group

  6. Nomenclature Suffix : carboxylic acid or oic acid Prefix : carboxy

  7. Q.62 (2Z)-but-2-enoic acid butanoic acid ethanedioic acid

  8. 3-carboxy-3-hydroxypentainedicarboxylic acid Q.62 butanedioic acid 2-hydroxypropane-1,2,3-tricarboxylic acid (citric acid)

  9. Q.62 benzoic acid Benzene-1,3-dicarboxylic acid

  10. Q.62 4-hydroxybenzoic acid phenylethanoic acid

  11. Derivatives of carboxylic acids (pp.9-10)

  12. Acyl (Acid) Chlorides Suffix : -oic acid replaced by –oyl chloride Prefix : chlorocarbonyl

  13. Acyl (Acid) Chlorides 3-chloro-3-oxopropanoic acid Priority : - -COOH > anhydride > ester > acid chloride > acid amide The carbonyl C is counted as part of the carbon skeleton

  14. Q.63 4-chloro-2-methyl-4-oxobutanoic acid hexanedioyl dichloride 3-(chlorocarbonyl)hexanedioic acid

  15. Acid anhydride Suffix : -acid replaced by –anhydride

  16. Acid anhydride * Prefix : n-(alkanoyloxy)-n-oxo(if *C is counted as part of the main chain) n indicates the position of the *C in the main chain

  17. Acid anhydride * Prefix : (alkanoyloxy)carbonyl (if *C is not counted as part of the main chain)

  18. Acid anhydride ethanoic anhydride ethanoic propanoic anhydride

  19. Acid anhydride benzoic ethanoic anhydride butanedioic anhydride

  20. Q.64 Benzene-1,2-dioic anhydride

  21. Ester Suffix : -oic acid replaced by –oate preceded by the name of R’

  22. Ester * Prefix : n-alkoxy-n-oxo(if *C is counted as part of the main chain) n indicates the position of the *C in the main chain

  23. Ester * Prefix : alkoxycarbonyl (if *C is not counted as part of the main chain)

  24. Ester methyl ethanoate ethenyl ethanoate methyl 4-bromobenzoate

  25. Q.65 2-(ethanoyloxy)benzoic acid 2-(acetyloxy)benzoic acid 2-(methoxycarbonyl)benzoic acid

  26. Acid amide Suffix : -oic acid replaced by -amide

  27. Ester * Prefix : n-amino-n-oxo(if *C is counted as part of the main chain) n indicates the position of the *C in the main chain

  28. Ester * Prefix : aminocarbonyl (if *C is not counted as part of the main chain)

  29. Ester N,N-dimethylethanamide (3) ethanamide (1) N-methylethanamide (2)

  30. Q.66 4-amino-4-oxobutanoic acid benzamide 3-(aminocarbonyl)heptanedioic acid

  31. Physical Properties of Alkanoic Acids

  32. Odour Methanoic / ethanoic acid  sharp, irritating odours • Propanoic to heptanoic acid • strong, unpleasant odours • Butanoic acid  body odour Higher members  low volatility  little odour

  33. b.p.  steadily as the number of C atoms  ∵ London dispersion forces become stronger as the size of electron cloud 

  34. HCOOH/CH3COOH have exceptionally high m.p. ∵ smaller size  1. closer packing  2. forming H-bonds more extensitively

  35. Members with EVEN no. of C atoms are more symmetrical  Higher packing efficiency  Higher m.p.

  36. Pure ethanoic acid = glacial ethanoic acid It freezes in cold weather

  37. More extensive H-bonds H-bonds Dipole-dipole interaction Dispersion forces ONLY

  38. Less dense than water except HCOOH/CH3COOH

  39.  as R.M.M.  R.M.M.   extent of H-bond formation   molecules not drawn closer  lower packing efficiency

  40. For alkanes,   as R.M.M.  ∵ no intermolecular H-bonds R.M.M.   Dispersion forces become stronger  closer packing

  41. First FOUR members are miscible with water in all proportions due to extensive H-bond formation between acid molecules and water molecules

  42. From pentanoic acid, solubility  as R.M.M.  The bulky R groups prevent formation of H-bonds between –COOH and H2O

  43. Non-polar ionic Emulsifying action of soap (salts of carboxylic acids) depends on the length of the hydrocarbon chain

  44. Preparation of Carboxylic Acids

  45. 1.Hydrolysis of Nitriles Elimination occurs for 2 and 3 RX as CN is a relatively strong base

  46. Examples

  47. 2.Oxidation of aldehydes and 1alcohols (pp.83-84, 93) 3.Oxidation of aromatic side chains(pp.54-55) 4.Iodoform reactions (p.92)

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