1. PPT 102 ORGANIC CHEMISTRY 1 SEM 1 (2012/2013) 1

2. © 2011 Pearson Education, Inc. Outline Nomenclature Physical Properties General Mechanism for Nucleophile Addition-Elimination Reaction Acid Catalyzed Esterification Reaction of Carboxylic acids Reaction of Amides 2

3. © 2011 Pearson Education, Inc. Compound that containing carbonyl groups –called carbonyl compound. An acyl group consists of a carbonyl group attached to an alkyl group ( R) or an aryl group (Ar)

4. © 2011 Pearson Education, Inc. 4 Carbonyl compound can be divide into 2 classes: Class 1: carbonyl compounds are those in which the acyl group is attach to a group (or atom) that can be replace by another group. Which compound belong to this class? Carboxylic acid Acyl halides Acid anhydride Ester Amides

5. © 2011 Pearson Education, Inc. 5 Class I Carbonyl Compounds Carboxylic Acid Deritives

6. © 2011 Pearson Education, Inc. 6 Why it called as carboxylic acid derivatives ? Because they differ from carboxylic acid only the nature of the group or atom that has replace the OH group of the carboxylic acid. Because they differ from carboxylic acid only the nature of the group or atom that has replace the OH group of the carboxylic acid.

7. © 2011 Pearson Education, Inc. 7 Class II : Carbonyl compounds are those in which the acyl is attached to a group that cannot be readily replaced by another group.

8. © 2011 Pearson Education, Inc. 8 The functional group of a carboxylic acid is called a carboxyl group Carboxylic Acid Nomenclature

9. © 2011 Pearson Education, Inc. 9 In IUPAC nomenclature, a carboxylic acid is named by replacing the terminal “e” of the alkane with “oic acid” Carboxylic Acid Nomenclature

10. © 2011 Pearson Education, Inc. 10 In systematic nomenclature, the carbonyl carbon is always C-1 In common nomenclature, the carbon next to the carbonyl is the  -carbon

11. © 2011 Pearson Education, Inc. 11 Carboxylic Acid Nomenclature Carboxylic acid in which a carboxyl group is attached to a ring are named by adding “carboxylic acid” to the name of the cyclic compound.

12. © 2011 Pearson Education, Inc. 12 Salts of Carboxylic Acids

13. © 2011 Pearson Education, Inc. 13 Acyl Halides Acyl halides have a Cl or Br in place of OH. Acyl halides are named by replacing “ic acid” with the “yl chloride”

14. © 2011 Pearson Education, Inc. 14 Acid Anhydrides Loss of water from 2 molecules of a carboxylic results of acid anhydride.

15. © 2011 Pearson Education, Inc. 15 Symmetrical anhydride when R 1 the same as R 2 Mixed (unsymmetrical anhydride) when R 1 the not the same as R 2 There are 2 types of acid anhydride: Ethanoic Anhydride Acetic Anhydride Ethanoic Methanoic Anhydride Acetic Formic Anhydride

16. © 2011 Pearson Education, Inc. 16 Esters

17. © 2011 Pearson Education, Inc. 17 Amides An amide has an NH 2, NHR, or NHR 2 group in place of OH group. Amides are named by replacing “oic acid”, “ic acid” or “ylic acid” of the acid name with “amide”

18. © 2011 Pearson Education, Inc. 18 Nitriles Nitriles are compound that contain C≡N functional group, called a cyno group. In common nomenclature, nitriles are named by replacing “ ic acid” with the “onitrile”

19. © 2011 Pearson Education, Inc. Physical Properties The carboxyl group contains three polar covalent bonds; C=O, C-O, and O-H –the polarity of these bonds determines the major physical properties of carboxylic acids δ- O – H δ+ δ- O – H δ+ δ+ C=O δ- R

20. © 2011 Pearson Education, Inc. Physical Properties –The carbonyl group has a large dipole –The hydroxy group is capable of hydrogen bonding. –The molecules can H-bond to each other

21. © 2011 Pearson Education, Inc. H 3 CC OH O O H OHH H Solubility in Water Carboxylic acids are similar to alcohols in respect to their solubility in water Form hydrogen bonds to water

22. © 2011 Pearson Education, Inc. Physical Properties –Carboxylic acids are more soluble in water than are alcohols, ethers, aldehydes, and ketones of comparable molecular weight –Sharp and or sour odor/taste Vinegar, rancid butter, sweat, sauerkraut.

23. © 2011 Pearson Education, Inc. 23 Carboxylic acids have relatively high boiling points because… Amides have the highest boiling points:

24. © 2011 Pearson Education, Inc. 24 How the carbonyl compound react?

25. © 2011 Pearson Education, Inc. The reactivity of the carbonyl compound is due to the polarity of the carbonyl group that result from oxygen being more electronegative than carbon. So the carbonyl carbon is therefore electron deficient (electrophile) 25

26. © 2011 Pearson Education, Inc. 26 The tetrahedral intermediate is a transient species that eliminates the leaving group Y – or the nucleophile Z – : This is a nucleophilic acyl substitution reaction When nucleophile adds to the carbonyl carbon, the weakest bond in the molecule- the carbon-oxygen π bond- breaks =tetrahedral intermediate

27. © 2011 Pearson Education, Inc. 27 Z – will be expelled if it is a much weaker base than Y – ; that is, Z – is a better leaving group than Y – (k –1 >> k 2 ):

28. © 2011 Pearson Education, Inc. 28 Y – will be expelled if it is a weaker base than Z – ; that is, Y – is a better leaving group than Z – (k 2 >> k –1 ):

29. © 2011 Pearson Education, Inc. 29 The reactivity of a carboxylic acid derivative depends on the basicity of the substituent attached to the acyl group:

30. © 2011 Pearson Education, Inc. General Mechanism for Nucleophile Addition-Elimination Reaction All carboxylic acids derivatives undergo nucleophilic addition-elimination reaction by the same mechanism. 30

31. © 2011 Pearson Education, Inc. 31 Mechanism: Negatively charge nucleophile 1. The nucleophile adds to the carbonyl carbon, forming a tetrahedral intermediates. 2. The tetrahedral intermediates collapse, eliminating the weaker base

32. © 2011 Pearson Education, Inc. 32 If the nucleophile is neutral… Where :B represent any spesies in the solution that is capable of removing a proton, and HB+ Represent any spesies in solution that is capable of donation a proton. 1.The nucleophile adds to the carbonyl carbon, forming a tetrahedral intermediate. 2.A proton is loss from the tetrahedral intermediate, resulting in a tetrahedral intermediate equivalent to the one formed by a negatively charge nucleophile. 3.The π bond re-form and the weaker of the two base is eliminated.

33. © 2011 Pearson Education, Inc. 33 Reaction of Carboxylic Acid

34. © 2011 Pearson Education, Inc. Nucleophililic Acyl Substitutution Reactions 34 1. Preparation of Acyl Chloride 2. Preparation of Acid Anhydride 3. Preparation of ester

35. © 2011 Pearson Education, Inc. 35 4. Preparation of Amide 5.Reduction Of Carboxylic Acid

36. © 2011 Pearson Education, Inc. Reactions of Carboxylic Acids Carboxylic acid can undergo nucleophilic acyl substitution reactions only when they are in their acidic form. The basic form of a carboxylic acid cannot undergo nucleophilic acyl substitution reactions because the negatively charge carboxylate ion is resistant to nucleophilic reaction 36

37. © 2011 Pearson Education, Inc. 37 Reactions of Carboxylic Acids

38. © 2011 Pearson Education, Inc. 38 Carboxylic acid react with alcohol to form esters. The reaction must carried out in an acidic solution, not only to catalyze the reaction but also to keep the carboxylic acid in its acidic form so that the nucleophilic will react with it. Since the tetrahedral intermediate formed in this reaction has two potential leaving groups of aproximately the same basicity, the reaction must carried out with excess alcohol to drive it towards product.

39. © 2011 Pearson Education, Inc. Emil Fischer was the first to discover that an ester could be prepared by treating a carboxylic acids with excess alcohol in the presence of an acid catalyst. The reaction is called, FISCHER ESTERIFICATION. Its mechanism is the exact reverse of the mechanism for the acid catalyzed hydrolysis of an ester. 39

40. © 2011 Pearson Education, Inc. 40 Carboxylic acids do not undergo nucleophilic acyl substitution reactions with amines at room temperature Because a carboxylic acid is an acid and an amine is base, the carboxylic acid immediately donates a proton to the amine.

41. © 2011 Pearson Education, Inc. 41 Reactions of Amides Amides are very unreactive carboxylative derivatives. Amides do not react with halide ions, carboxylate ions, alcohols, or water because in each case, the incoming nucleophile is a weaker base than the leaving group of the amide ( Table 17.1)

42. © 2011 Pearson Education, Inc. 42 Amides can react with water and alcohols if an acid catalyst is present:

43. © 2011 Pearson Education, Inc. 43 Dehydration of an Amide Dehydration reagents commonly used are SOCl 2, P 2 O 5, or POCl 3

44. © 2011 Pearson Education, Inc. Acid catalyzed Esterification Ester hydrolyzed slowly because water is a poor nucleophile and ester have very basic leaving groups. However the rate of hydrolysis can be increased by either acid or hydroxide ion. 44

45. © 2011 Pearson Education, Inc. When you examine the mechanisms for these reactions, notice the two following features that hold for all organic reactions: 1. All organic intermediates and products in acidic solution are positively charge or neutral 2. All organic intermediates and products in basic solutions are negatively charge. 45

46. © 2011 Pearson Education, Inc. 46 Hydrolysis of an ester with primary or secondary alkyl groups can be catalyzed by an acid The carbonyl oxygen is first protonated, MECHANISM FOR ACID CATALYZED ESTER HYDROLYSIS

47. © 2011 Pearson Education, Inc. 47 There are no negatively charged species in the reaction:

48. © 2011 Pearson Education, Inc. 48 Excess water will force the equilibrium to the right Excess alcohol will force the equilibrium to the left Because tetrahedral intermediate I and III are equally likely to collapse, both ester and carboxylic acid will present in approximately equal amounts when the reaction reach equilibrium

49. © 2011 Pearson Education, Inc. 49 Esters with tertiary alkyl groups undergo hydrolysis much more rapidly than do others: 1.An acid protonates the carbonyl oxygen 2.The leaving group departs, forming the tertiary carbocation 3.A nucleophile react with the carbocation 4.A base removes a proton fronm the strongly acidic protonated alcohol

50. © 2011 Pearson Education, Inc. 50 Transesterification is also catalyzed by acid: TRANSESTERIFICATION The reaction of an ester with an alcohol. The mechanism is identical to the mechanism for acid catalyzed ester hydrolysis (for ester with primary or secondary alkyl groups), except that the nucleophile is ROH rather than H 2 0

51. © 2011 Pearson Education, Inc. Biodiesel Production- Transesterification.

52. © 2011 Pearson Education, Inc. 52

53. © 2011 Pearson Education, Inc. Rudolf Diesel (1893) “The use of vegetable oils for engine fuels may seem insignificant today,” he argued, “but such oils may become, in the course of time, as important as petroleum and the coal-tar products of the present time."

54. © 2011 Pearson Education, Inc. Biodiesel Biodiesel is not the same thing as raw vegetable oil. It is produced by a chemical process which removes the glycerol from the oil. Biodiesel –Domestic –Renewable –For diesel engines –Derived from oils and fats

55. © 2011 Pearson Education, Inc. Biodiesel production Biodiesel is typically produced by a reaction of a vegetable oil or animal fat with an alcohol such as methanol or ethanol in the presence of a catalyst to yield mono-alkyl esters and glycerol, which is removed.

56. © 2011 Pearson Education, Inc. How? Tranesterification: alcohol + ester → different alcohol + different ester –Base of acid as a catalyst –The oil is mixed with an alcohol, usually methanol or ethanol, and separated into methyl esters (biodiesel) and glycerol.

57. © 2011 Pearson Education, Inc. Transesterification Methyl esters

58. © 2011 Pearson Education, Inc.

59. Biodiesel technology

60. © 2011 Pearson Education, Inc.

61. Possible sources Vegetable oil (soy, canola, palm, rapeseed, coconut etc.) Non food plants (jatropha) Recycled oil (McDonald’s fryer) Animal fats (fish oil) Algae