1. Goals for the Day: Reactions of Alcohols Zaitsev’s Rule Substitution of double bonds Oxidation/Reduction

2. Reactions of Alcohols Dehydration (makes a double bond) Forming Ethers (makes an ether) Oxidation (makes a carbonyl compound) Reduction (start with a carbonyl, get an alcohol) 2

3. Substitution in Double bonds…

4. Zaitsev’s (Saytzeff’s) Rule According to Saytzeff’s rule, the dehydration of a secondary alcohol favors the product in which hydrogen is removed from the carbon atom in the chain with the smaller number of H atoms 4

5. zaitsev’s Rule… A shorter way of thinking of it is that the more substituted product is the one that is preferred, since it is more stable… so which is preferred here? 5

6. Disubstituted vs. monosubstituted… The pink structure (or 2-pentene) is preferred over 1- pentene since it is disubstituted (vs. monosubstituted) 6

7. Dehydration of Alcohols Dehydration of an alcohol occurs when heated with an acid catalyst, H + with the loss of –H and –OH from adjacent carbon atoms to form water alcohol alkene 7

8. Two main things to remember… 1) The OH and H removed have to be on carbons that are next to each other. 2) Make sure to put in the double bond in between the two carbon atoms where you took the H and OH from… alcohol alkene 8

9. Pick out the product….

10. Recall that Zaitsev’s rule indicates that the more substituted double bond will form… Minor product No reaction Missing the double bond

11. Learning Check Write the equation for the reaction when 2- propanol undergoes dehydration with H+… 11

12. First step… Draw the structure of 2-propanol… 12

13. Second step… Add in the arrows and acid catalyst symbol… (I also normally add a line on which to draw the product)… 13 Try to predict the product…

14. Hint… You know that the double bond has to involve carbon 2, because that is where the OH is attached. You can pick either H on either carbon 1 or carbon 3 to remove to form the double bond… 14

15. Product is… The product is 1-propene… 15

16. Try to draw the product of the reaction shown in your composition book (there is a hint on the next slide)

17. Hint…

18. Answer… Remember that the more substituted product is preferred! (1-butene also forms, but it is the minor product).

19. Try one more… 19

20. The more substituted product is preferred… 20

21. Formation of Ethers Ethers form when dehydration occurs at lower temperatures, (130  C) in the presence of an acid catalyst. two methanol molecules dimethyl ether 21

22. Diethyl ether prepared industrially by sulfuric acid–catalyzed dehydration of ethanol – also with other primary alcohols Synthesis of Ethers

23. Works really only if the ether that you want is symmetric….otherwise you can get mixed results.. Synthesis of Ethers

24. Problem is.....propanol reacts with itself and ethanol reacts with itself… There are other ways to make unsymmetric ethers (we don’t have to know them)…

25. FYI: Mechanism of ether formation from alcohols…

26. Predict the product... (hint on next slide)…

27. Predict the product... (remember that two alcohols together make an ether)…so just draw an oxygen in the center of the same two alkyl groups…

28. Remember this is best for symmetric ethers (meaning it only uses 1 type of alcohol to start with).…usually the number 2 is in front or there are two molecules drawn out as a hint…

29. General Definitions of Oxidation and Reduction In the oxidation of an organic compound, there is an increase in the number of C–O bonds. there is a loss of H. In the reduction of an organic compound, there is a decrease in the number of C–O bonds. there is a gain of H. 29

30. Oxidation to the right; Reduction to the left (note the change in Oxygen/Hydrgogen in each step)… An alcohol is more oxidized than an alkane; an aldehyde or ketone is more oxidized than an alcohol; a carboxylic acid is more oxidized than an aldehyde. 30

31. Oxidation to the right; Reduction to the left (note the change in Oxygen/Hydrgogen in each step)… The more bonds that a carbon atom has to an oxygen (or 2), the more oxidized it is. The highest oxidation “level” is three, with a carboxylic acid (also an ester). 31

32. You remove a hydrogen from the carbon & a hydrogen from the OH of the compound. What happens in an oxidation reaction? Keep in mind that we do not normally draw out the hydrogen on the carbon… You have to remember that it is there (see next slide). Also keep in mind that 3 o alcohols do not have a hydrogen on the carbon Atom and therefore do not oxidize!

33. A primary alcohol can actually oxidize all the way to a carboxylic acid. A secondary alcohol gives a ketone. A tertiary alcohol does not oxidize. How different alcohols react…

34. Oxidation of Primary (1  ) Alcohols Primary alcohols are oxidized to form aldehydes. Ethanol (ethyl alcohol) Ethanal (acetaldehyde) 34

35. Oxidation of Secondary (2  ) Alcohols Secondary alcohols are oxidized to form ketones. 35 2-Propanol (isopropyl alcohol)2-Propanone(dimethyl ketone, “acetone”)

36. Oxidation of Tertiary (3  ) Alcohols Tertiary alcohols do not oxidize. There is no H on the C–OH to remove! 2-Methyl-2-propanol 36

37. Reagents that Oxidize… Tollin’s reagent H2CrO4 Chromic Acid PCC [O] Benedict’s

38. “steps” for drawing oxidation products. This is a primary alcohol, so it will oxidize 38 1)Check to make sure that the alcohol is primary or secondary (i.e. not tertiary)…

39. “steps” for drawing oxidation products. 2) redraw the alcohol, but lose the hydrogen from the OH (note: you are also losing the hydrogen from the carbon atom, but you don’t have to “show” that you are losing it)… 39

40. “steps” for drawing oxidation products. 40 3) Draw in the double bond. Note: you may want to draw in the other Hydrogen on the carbonyl carbon & you can “flip” it so the oxygen is up…

41. Please try the following & draw them in your composition book…

42. Answers:

43. Learning Check Match the products with the reaction of Reaction 1: H +, heat Reaction 2: [O] Reaction 3: O 2, heat 43

44. Learning Check Match the products with the reaction of Reaction 1: H +, heat Reaction 2: [O] Reaction 3: O 2, heat 44

45. Solution This page actually moves the reactions around… Reaction 1: H +, heat (dehydration) Reaction 2: [O], (oxidation) Reaction 3: O 2, heat, (combustion) 45

46. ethanol is oxidized by enzymes in the liver aldehyde product impairs coordination. 46 Oxidation of Ethanol in the Body

47. Ethanol CH 3 ─ CH 2 ─ OH Ethanol acts as a depressant. kills or disables more people than any other drug. is metabolized at a rate of 12–15 mg/dL per hour by a social drinker… 47

48. Learning Check Select the product from the oxidation of _______.

49. Solution Select the product from the oxidation of _______. Answer is B. The secondary alcohol will oxidize to a ketone… 49