Alcohols, Phenols, Thiols, and Ethers

1. Alcohols, Phenols, Thiols, and Ethers Chapter 13

2. Introduction • Alcohol – organic compound that contains a hydroxyl (-OH) group attached to an alkyl group • Phenol – organic compound that contains a hydroxyl (-OH) group attached to an aryl group • Ether – organic compound that has two alkyl or aryl groups attached to the oxygen atom; can be thought of as a substituted alcohol.

3. Examples Alcohols -OH hydroxyl CH3-OH CH3CH2-OH Phenols Ethers -O- CH3-O-CH3

4. Practice Problem 1 Classify each as an alcohol (1), phenol (2), or an ether (3): A. _____ CH3CH2-O-CH3C. _____ CH3CH2OH B. _____

5. Solution 1 Classify each as an alcohol (1), phenol (2), or an ether (3): A. ____ CH3CH2-O-CH3C. ____ CH3CH2OH B. ___

6. Structure and Properties • R-O-H portion of alcohol is similar to the structure of water. • The oxygen and two atoms bonded to it lie in the same plane. • The bond angle is 104° • Hydroxyl groups are very polar because of significantly different electronegativities. • Hydrogen bonding can form between alcohol molecules.

7. Hydrogen Bonding

8. Results of Hydrogen Bonding • Alcohols boil at much higher temperatures than hydrocarbons of similar molecular weight. • Alcohols with fewer than five carbons are very soluble in water. • Alcohols with five to eight carbons are moderately soluble in water. • As the nonpolar (R) portion of the alcohol gets larger, the water solubility decreases.

9. Solubility of Alcohols • Very large alcohols are not soluble in water. • Hydrophobic – “water fearing”; used to describe nonpolar region of molecule • Hydrophilic – “water loving”; used to describe polar region of molecule CH3CH2CH2CH2CH2CH2CH2CH2CH2OH Hydrophobic Hydrophilic

10. Solubility of Alcohols • An increase in the number of hydroxyl groups will increase the influence of the polar hydroxyl group. • Diols and triols are more water soluble than alcohols with only a single hydroxyl group.

11. Practice Problem 2 • Circle the more soluble alcohol in each pair.

12. Solution 2 • Circle the more soluble alcohol in each pair.

13. Nomenclature of Alcohols • A carbon compound that contain -OH (hydroxyl) group • In IUPAC name, the -e in alkane name is replaced with -ol. CH4 methane CH3OH methanol (methyl alcohol) CH3CH3 ethane CH3CH2OH ethanol (ethyl alcohol)

14. More Names of Alcohols • IUPAC names for longer chains number the chain from the end nearest the -OH group. CH3CH2CH2OH OH CH3CHCH3 CH3 OH CH3CHCH2CH2CHCH3

15. Alcohols that contain more than one hydroxyl group • Alcohols containing two hydroxyl groups are named –diols. • Alcohols containing three hydroxyl groups are named –triols. • A number giving the position of each of the hydroxyl groups is needed in these cases.

16. Practice Problem 3 Name the following alcohols: A. OH CH3CHCHCH2CH3 CH3 OH B.

17. Solution 3 Name the following alcohols: A. OH CH3CHCHCH2CH3 CH3 OH B.

18. Homework Pages 379-380 13.11-13.14 Page 360 13.1 – 13.2 Due Tomorrow!!!!

19. Section 13.3 • It is your responsibility to read over section 13.3 – Medically Important Alcohols (pgs. 360-361) and take notes on the material covered! • It will be on the weekly quiz and the test!

20. Classification of Alcohols • Alcohols can be classified as primary (1°), secondary (2°), or tertiary (3°) depending on the number of alkyl groups attached to the carbon bearing the –OH group. Methanol 1° alcohol 2° alcohol 3° alcohol ethanol 2-propanol 2-methyl-2-propanol

21. Practice Problem 4 Classify each of the following alcohols as primary, secondary, tertiary, or aromatic. • 1-butanol • 3-pentanol • 1-methylcyclopentanol • 2-methyl-2-pentanol

22. Solution 4 • 1-butanol • 3-pentanol • 1-methylcyclopentanol • 2-methyl-2-pentanol

23. Homework • Pages 380-381: 13.15, 13.16, 13.18, 13.19, 13.20, 13.21, 13.22, 13.27, and 13.28 Due Tomorrow!

24. Preparation of Alcohols • REVIEW: Hydration – an addition reaction in which a water molecule is added to an alkene; requires acid as catalyst Alkene Water Alcohol • Markovnikov’s rule applies!!

25. Hydration Examples • Ethene • 1-butene

26. Preparation of Alcohols • Hydrogenation of aldehydes and ketones In an aldehyde, R1 and R2 may be either alkyl groups or H. In a ketone, R1 and R2 are both alkyl groups. We will discuss this in more detail in section 14.4.

27. Hydrogenation Examples • Ethanal • 2-propanone

28. Preparation of Alcohols YOU TRY THESE! +

29. Dehydration of Alcohols • Alcohols undergo dehydration (lose water) when heating with concentrated sulfuric or phosphoric acid. • Dehydration is an example of an elimination reaction. • Elimination reaction – a reaction in which a molecule loses atoms or ions from its structure. • Dehydration is opposite of hydration!

30. Dehydration of Alcohols • General Reaction • Ethanol • 2-butanol Heat Heat

31. Dehydration of Alcohols • Zaitsev’s rule – in an elimination reaction, the alkene with the greatest number of alkyl groups on the double bonded carbon (more highly substituted alkene) is the major product of the reaction • Another example:

32. Oxidation Reactions • Oxidation – loss of electrons; add O and/or lose H • Reduction – gain of electrons; add H and/or lose O • Common oxidizing agents: • Basic potassium permanganate (KMnO4/OH-) • Chromic Acid (H2CrO4) • [O] Any general oxidizing agent

33. Oxidation of Primary Alcohols • General equation: • Primary alcohol aldehyde RCH2CH=O EXAMPLE: 1-propanol

34. Oxidation of Secondary Alcohols • General equation: • Secondary alcohol ketone O R-C-R EXAMPLE: 2-propanol

35. Oxidation of Tertiary Alcohols • General equation: • Tertiary alcohol NO REACTION!!!

36. YOU TRY THESE!

37. Phenols • Phenols – compounds in which the hydroxyl group is attached to a benzene ring • They are polar compounds because of the polar hydroxyl group. • Smaller phenols are somewhat soluble in water. • They are found in fragrances and flavorings and are also used as preservatives and germicides.

38. (CH3)2HC CH3 OH Common Phenols and their Uses Thymol (mint) (CH3)2HC CH3 Carvacrol (savory) OH

39. C(CH3)3 CH3 OH (CH3)3C OH Common Phenols and their Uses Butylated hydroxytoluene, BHT(Food preservative) Phenol (Carbolic acid when dissolved in water) Antiseptic and disinfectant used by Joseph Lister to bathe wounds and sterlize instruments

40. Ethers

41. Ethers • What are they? • How are they used? • What do you know about them?

42. Structure of Ethers • Similar structure to alcohols Alcohols: R-OH –OH is “hydroxy” group Ethers: R-OR –OR is “alkoxy” group

43. “R” groups can be the same: CH3-O-CH3 Both “R” groups have one carbon “R” groups can be different: CH3CH2CH2-O-CH3 One “R” group has three carbons while the other has one Alkoxy group

44. Alkoxy group • The root names are used with –oxy to name that portion of the ether: • meth- + -oxy • eth- + -oxy • prop- + -oxy = methoxy = ethoxy = propoxy

45. Naming ethers – IUPAC Way • Find the root name of the smaller “R” group Ex: meth-, eth-, prop- • Add –oxy Ex: methoxy, ethoxy, propoxy • Add the full name of the larger “R” group EXAMPLE: methoxypropane

46. Name that ether

48. Draw the structure of: 1. methoxypropane 2. methoxyoctane 3. propoxypropane 4. ethoxypentane

49. Naming Ethers – Common Name • Name by placing the names of the two alkyl groups attached to the ether oxygen as words in front of the word “ether.” Typically this is done in alphabetical order. Diethyl Ether Ethyl methyl ether Butyl propyl ether

50. Properties of ethers • The C-O bond in ethers is polar, making the molecule polar • Ethers have very low boiling points • Ethers are relatively inert, but flammable in air