THEME: Structure and chemical properties of carboxylic acids. Heterofunctional compounds.

1. LECTURE2 THEME: Structure and chemical properties of carboxylic acids. Heterofunctional compounds. Lecturer:Yevheniya. B. Dmukhalska

2. Plan • Nomenclature of carboxylic acids • Physical properties of carboxylic acids. • Classification of carboxylic acids • Methods of preparation of carboxylic acids • Chemical properties of carboxylic acids. • Heterofunctional compounds. • Hydroxy-acids, nomenclature, isomerism, chemical properties and specific reactions for hydroxy-acids. • Introduction of optical isomerous. Mirror (optical) isomerism. Asymmetric carbon atom. Properties of enantiomers.

3. Carboxylic acids Carboxylic acids are compounds whose characteristic functional group is the carboxyl group -COOH , example: • Common formula of carboxylic acid:

4. Nomenclature of carboxylic acids Nowhere in organic chemistry are common names used more often than with the carboxylicacids. Systematic names for carboxylic acids are derived by counting the number of carbonsin the longest continuous chain that includes the carboxyl group and replacing the-e ending of the corresponding alkane by -oic acid.

5. Table1. Systematic and common names of some carboxylic acids

6. Classification of carboxylic acids : 1. From the nature of hydrocarbon radical: a) saturated acid is acid, which has only simple bonds in molecule. Example: formic acid, buthanic acid; b) unsaturated acid is an acid, which has both as simple bonds and duble bonds in molecule. Example: oleic acid, linoleic acid, linolenic acid, arashdonic acid; c) aromacic acid is acid, which contain aromatic ring. Example: benzoic acid. 2.The number of carboxyl groups a) monocarboxylic acid is acid, which has one carboxylic group in molecule. Example: acetic acid, formic acid, buthanic acid; b) dicarboxylic acid is acid, which has two carboxylic group in molecule. Example: oxalic acid, malonic acid.

7. The names of some saturated monocarboxylic acids

8. The names of some unsaturated monocarboxylic acids

9. The names of some dicarboxylic acids

10. Physical properties of carboxylic acids. The melting points and boiling points of carboxylic acids are higher than those of hydrocarbons and oxygen-containing organic compounds of comparable size and shape and indicate strong intermolecular attractive forces. The hydroxyl group of one carboxylic acid molecule acts as a proton donor toward the carbonyl oxygen of a second. In a reciprocal fashion, the hydroxyl proton of the second carboxyl function interacts with the carbonyl oxygen of the first.

11. Methods of preparation of carboxylic acids. • Oxidation of alkylbenzenes.

12. 2. Oxidation of primary alcohols.Potassiumpermanganate, potassium chromate and chromic acid convert primaryalcohols to carboxylic acids by way of the correspondingaldehyde.

13. 3. Oxidation of aldehydes.Aldehydes areparticularly sensitive to oxidation and are converted tocarboxylic acids by a number of oxidizing agents,including potassium permanganate and chromic acid.

14. 4. Synthesis of carboxylic acids by the preparation and hydrolysis of nitriles. Once the cyano group has been introduced, the nitrile is subjected to hydrolysis.Usually this is carried out in aqueous acid at reflux.

15. Chemical properties of carboxylic acids. Formation of acyl chlorides. Thionyl chloride reacts with carboxylic acidsto yield acyl chlorides.

16. Formation of acyl chlorides. Reaction with halo-compounds:

17. Reduction reaction. Carboxylic acids are reduced toprimary alcohols by the powerful reducingagent lithium aluminum hydride.

18. Acidity: • Iontzation: • Reactions involving the ОН-bond

19. Reactions involving the ОН-bond • Important reaction of carboxylic acids involving the ОН bond - the reaction with bases to give salts. • Another important reaction involving this bond is the reaction of carboxylic acids with diazomethane. The products of this reaction are the methyl ester and nitrogen.

20. ESTERIFICATION • This page looks at esterification - mainly the reaction between alcohols and carboxylic acids to make esters.

21. α-halogenation of carboxylic acids The enol content of a carboxylic acid is far less than that of an aldehyde or ketone,and introduction of a halogen substituent at the -carbon atom requires a different setof reaction conditions. Bromination is the reaction that is normally carried out, and theusual procedure involves treatment of the carboxylic acid with bromine in the presenceof a small amount of phosphorus trichloride as a catalyst. • This method of α bromination of carboxylic acids is called the Hell–Volhard–Zelinsky reaction.

22. Decarboxylation of carboxylic acids. The loss of a molecule of carbon dioxide from a carboxylic acid is known as decarboxylation.

23. The formation amides.The most common reaction of this type is the reaction of carboxylic acids with ammonia or amines to give amides. When ammonia is bubbled through butyric acid at 1850, butyramide is obtained in 85% yield. The reaction involves two stages. At room temperature, or even below, butyric acid reacts with the weak base ammonia to give the salt ammonium butyrate. This salt is perfectly stable at normal temperatures. However, pyrolysis of the salt results in the elimination of water and formation of the amide.

24. Reaction formation carboxylic acid anhydrides. Acid anhydrides are the most reactive carboxylic acid derivatives.

27. 8. Carboxylic acid derivatives. These classes of compounds are classified as carboxylic acid derivatives.All may be converted to carboxylic acids by hydrolysis.

28. Functional Group is any part of an organic compound, which is not а carbon-hydrogen or carbon-carbon single bon. There are mono-, poly- and heterofunctional group in the structure of organic compounds: Monofunctional group – contains only 1 functional group. C2H5—OH Polyfunctional group – contains several similar functional group. Heterofunctional group – contains several different functional group. Sphingosine

29. Biological role: • Heterofunctional compounds are widespread in the nature. They are in fruits and vegetable leafs. Also they are formed in body. So, the lactic acid is product of transformation glucose (glycolysis) in human body. A malic and citric acid formed in a cycle of tricarboxylic acids, which is also known as citric acid cycle or Krebs' cycle. Hydroxo acids such as: pyruvic acid, acetoacetic acid, oxaloacetic acid, -ketoglutaric acid are important in metabolism of carbohydrates.

30. Hydroxyacids Hydroxyacids are the derivatives of carboxyl acids that contain –OH group (1 or more). β α 2-hydroxypropanoic acid α-hydroxypropanoic acid

31. glycolic acid, hydroxyacetic acid, hydroxyethanoic acid tartaric acid α,α’-dihydroxysuccinic acid, 2,3-dihydroxybutandioic acid, lactic acid, α- hydroxypropanoic acid, 2- hydroxypropanoic acid malic acid, hydroxysuccinic acid hydroxybutanedioic acid citric acid, 2-hydroxy-1,2,3-propantricarboxylic acid

32. In a row of hydroxyacids often found the optical isomery. D-tartaric acid L-tartaric acid mezo-tartaric acid

33. Methods of preparation of hydroxyacids: • Hydrolysis of α-halogenoacids • Oxidations of diols and hydroxyaldehydes • Hydration of α,β-unsaturated carboxylic acids lactic acid β-hydroxypropanoic acid

34. 4. Hydrolysis of hydroxynitriles (cyanohydrins)

35. Physical and chemical properties of hydroxycarboxylic acid For physical properties of hydroxycarboxylic acids are colorless liquids or crystalline substance, soluble in water. Chemical properties: in the molecule of hydroxyacids ether –OH group or carboxyl group can react. Carboxyl group can react forming: a) salts: sodium β-hydroxypropanoic acid

36. b) Ester formation: Methyl-β-hydroxypropanoate

37. c) Amides formation: II. –OH group reaction: • hydrohalogens (HCl, HBr, HI, HF) b) can oxidize amide of β-hydroxypropanoic acid β-oxopropanoic acid

38. Related to heat of: 1. α-hydroxyacids lactic acid lactide 2. β-hydroxyacids 3. γ-hydroxyacids

39. Decomposition α-hydroxyacids Ethanal formic acid

40. Representatives of hydroxyacids: lactic acid. lactic acid is a trivial name because at first it was extracted from milk. It is present in yogurt, sour milk and other milk products. It can form in muscles during hard and prolonged work. Salts of milk acid are used in medicine. Malic acid. It is present in green apples and some berries. It takes part in biological processes in human organisms and organisms of other alive creatures. It is used in medicine for synthesis of some medical preparations. Tartaric acid . It is present in grape. It is used in medicine for synthesis of some medical preparations.

41. Citric acid. It is present in orange, lemon and other citric fruits. It takes part in biological processes in human organism.

42. Phenolacids are the derivatives of aromatic carboxyl acids that contain –OH group (1 or more). Phenolacids. salicylic acid, 2-hydroxybenzoic acid o-hydroxycinnamic acid 4-hydroxybenzoic acid 3,4,5-trihydroxybenzoic acid, gallic acid

43. Chemical properties of phenolacids: Chemical properties of phenolacids due to the presence in their structure of carboxyl group, phenolic hydroxyl and the aromatic nucleus. Decarboxylation

44. The best known aryl ester is O-acetylsalicylic acid, better known as aspirin. It is prepared by acetylation of the phenolic hydroxyl group of salicylic acid: Aspirin possesses a number of properties that make it an often-recommended drug. It is an analgesic, effective in relieving headache pain. It is also an antiinflammatory agent, providing some relief from the swelling associated with arthritis and minor injuries. Aspirin is an antipyretic compound; that is, it reduces fever. Each year, more than 40 million lb of aspirin is produced in the United States, a rate equal to 300 tablets per year for every man, woman, and child.

45. Oxoacids To oxoacids include aldehydo- and ketonoacids. These compounds include in the structure of the carboxyl group, aldehyde functional group or ketone functional group. pyroracemic acid, 2-oxopropanoic acid glyoxylic acid, oxoethanoic acid acetoacetic acid, 3-oxobutanoic acid, β-ketobutyric acid γ-ketovaleric acid, 4-oxopentanoic acid, levulinic acid oxalacetic acid, oxobutanedioic acid, ketosuccinic acid

46. Chemical properties of oxoacids • Decarboxylation of α-oxoacids • Decarboxylation of β-oxoacids

47. Stereochemistry • The three-dimensional shape of an organic molecule can have а dramatic effect upon its reactivity. In fact, the study of the shapes of organic molecules is so important that it forms а separate sub-discipline within organic chemistry — stereochemistry, from the Greek word “” (stereos), meaning solid; this chapter will be devoted to the study of organic molecules in three dimensions.

48. Stereoisomers • Compounds which differ in the three-dimensional arrangement of the atoms in space but have the same connectivity are termed stereoisomers. • Stereoisomers are compounds that have the same sequence of covalent bonds and differ in the relative disposition of their atoms in space.

49. There are two major causes of stereoisomerism: • the presence of "structural rigidity" in а molecule. Structural rigidity is caused by restricted rotation about chemical bonds. It is the basis for cis - trans stereoisomerism, а phenomenon found in some substituted cycloalkanes and some alkenes; • the presence of а chiral center in а molecule.

50. COFORMATION • The methyl groups can rotate freely about the central C–C bond. Structures that differ only by rotation about one or more single bonds are defined as conformations of a compound. • For example: Ethane has two conformations: eclipsed structure, which is more higher in energy than the more stable staggered structure.