Larry Emme Chemeketa Community College

1. Alcohols, Ethers, Phenols, and Thiols Chapter 22 Larry Emme Chemeketa Community College

2. Functional Groups

3. The various classes of compounds are identified by the presence of certain characteristic groups called functional groups. • Through the chemical reactions of functional groups, it is possible to create or synthesize new substances.

5. Classification of Alcohols

6. Alcohols are classified by the number of R groups (i.e. carbon atoms) attached to the hydroxyl carbon as shown here. 6

7. Tests for Alcohols

8. Lucas Test • Addition of ZnCl2 in concentrated HCl forms a “turbid” solution. Order of reactivity is 3o > 2o >> 1o.

9. 9

10. Polyhydroxy alcohols and polyols are general terms for alcohols that have more than one –OH group per molecule. • Polyhydroxy compounds are very important molecules in living cells, as they include the carbohydrate class of biochemicals.

11. Structural Representations of Alcohols • An alcohol such as 2-butanol can be written in a single-line formula by enclosing the –OH group in parentheses and placing it after the carbon to which it is bonded. =

12. Application to Biochemistry Blood sugar (glucose) contains five alcohol groups. Using the structure of glucose shown here, label each group as 1°, 2°, or 3°. O=CHCH(OH)CH(OH)CH(OH)CH(OH)CH2OH

13. Application to Biochemistry

14. Naming Alcohols

15. IUPAC Rules for Naming Alcohols • Select the longest continuous chain of carbon atoms containing the –OH group. • Number the carbon atoms in this chain so that the one bearing the -OH group has the lowest possible number.

16. IUPAC Rules for Naming Alcohols 3. Form the parent alcohol name by replacing the final –e of the corresponding alkane by –ol. When isomers are possible, locate the position of the –OH group by placing the number (hyphenated) of the carbon atom to which the –OH is bonded immediately before the parent alcohol name. 4. Name each alkyl side chain (or other group), and designate its position by number.

17. Name CH3CH2CH2CH2OH 1-butanol

18. Nomenclature of Alcohols

19. Physical Properties of Alcohols

20. Physical Properties of Alcohols • The physical properties of alcohols are related to those of both water and alkane hydrocarbons. • An alcohol molecule is made up of a waterlike hydroxyl group joined to a hydrocarbonlike alkyl group.

21. Boiling Points of Alcohols • Alcohols have relatively high boiling points. • The boiling points of the normal alcohols increase in a regular fashion with increasing number of carbon atoms. • Branched-chain alcohols have lower boiling points than corresponding straight-chain alcohols.

23. Alcohols containing up to three carbon atoms are infinitely soluble in water. • The –OH group on the alcohol molecule is responsible for both the water solubility and relatively high boiling points of the low-molar-mass alcohols.

24. Hydrogen Bonding in Alcohols

26. Glucose is one of the most important carbohydrates in biochemistry. It has six carbons and five alcohol groups (molar mass = 180.2 g). How would you predict the water solubility of glucose to differ from that of 1-hexanol?

27. Effect of Hydroxyl Groups on Solubility Note the difference in solubility of hexanol (only one –OH group) and glucose ( five –OH groups). CH3CH2CH2CH2CH2CH2OH 1-hexanol (solubility = 0.6g/100g H2O) D-glucose (solubility = 95g/100g H2O) 28

28. A branched-chain alcohol will have a lower boiling point than the corresponding straight-chain alcohol. For example 2-butanol is branched and has a b.p. of 91.5 C versus 118 C for 1-butanol. Effect of Branching on Boiling Point CH3CH2CH2CH2OH 1-butanol 29

29. Chemical Properties of Alcohols

30. Chemical Properties of Alcohols • Acidic and Basic Properties • Oxidation • Dehydration • Esterification (Chapter 24)

31. Basic Properties • If an alcohol is mixed with a strong acid, it will accept a proton (act as a Brønsted-Lowry base) to form a protonated alcohol or oxonium ion.

32. Acidic Properties • Alcohols can also act as Brønsted-Lowry acids. • The resulting anion in the alcohol reaction is known as an alkoxide ion (RO-).

33. Oxidation • Oxidation is the loss of hydrogen or the gain of bonds to oxygen by the organic reactant. • Carbon atoms exist in progressively higher stages of oxidation in different functional groups.

34. The –OH group gives an organic compound the capability of forming an aldehyde, ketone, or carboxylic acid.

35. Common Oxidizing Agents • KMnO4 • K2Cr2O7 • O2

36. Dehydration • Alcohols can be dehydrated with sulfuric acid to form alkenes.

37. Dehydration • For many alcohols, there is more than one way to remove water. Therefore the double bond can be located in different positions. • The major product in such cases is the alkene in which the C=C bond has the greatest number of alkyl substituents on it (or the least number of hydrogens).

38. Utility of the Hydroxyl Functional Group

39. Common Alcohols

40. Preparation of Methanol • Methanol is a common industrial solvent prepared • by the high-pressure catalytic hydrogenation of carbon monoxide. • The most economical nonpetroleum source of carbon monoxide for making methanol is coal. 49

41. Uses of Methanol • Conversion to formaldehyde (use in manufacture of polymers). • Manufacture of other chemicals, especially various kinds of esters • Denaturing ethyl alcohol • Industrial solvent

42. Ethanol • Large quantities of ethanol are prepared by fermentation. • The conversion of simple sugars to ethanol is accomplished by yeast. • Industrially, ethanol is made by acid-catalyzed addition of water to ethylene.

43. Uses of Ethanol • An intermediate in the manufacture of other chemicals such as acetaldehyde, acetic acid, ethyl acetate, and diethyl ether. • A solvent for many organic substances. • A compounding ingredient for pharmaceuticals, perfumes, flavorings, etc. • An essential ingredient in alcoholic beverages.

44. 2-Propanol (Isopropyl Alcohol) • 2-Propanol is made from propene.

45. Uses of 2-Propanol (Isopropyl Alcohol) • To manufacture other chemicals (especially acetone). • As an industrial solvent. • As the principal ingredient in rubbing alcohol formulations.

46. Ethylene Glycol (1,2-Ethanediol) • Industrial synthesis

47. Uses of Ethylene Glycol (1,2-Ethanediol) • In the preparation of the synthetic polyester fiber Dacron and film Mylar • As a major ingredient in “permanent-type” antifreeze cooling systems • As a solvent in the paint and plastic industries • In the formulations of printing ink and ink for ballpoint pens.

48. Glycerol (1,2,3-Propanetriol) • Glycerol (also known as glycerine) is an important trihydroxyalcohol. • It is obtained as a by-product of the processing of animal and vegetable fats to make soap and other products. • It is synthesized commercially from propene.

49. Uses of Glycerol • Each directly related to the three –OH groups. • As a raw material in the manufacture of polymers and explosives (nitroglycerin). • As an emollient in cosmetics. • As a humectant in tobacco products. • As a sweetener.

50. Phenols