Chem 150 Unit 8 - Organic Molecules III Alcohols, Thiols, Ethers, Aldehydes and Ketones

1. Chem 150Unit 8 - Organic Molecules IIIAlcohols, Thiols, Ethers, Aldehydes and Ketones • In this unit we continue surveying some of the families of organic molecules that play important roles in biochemistry; looking both at their physical and chemical properties. The Group VIA elements, oxygen and sulfur, typically form two covalent bonds to attain a filled valence shell. The families that include oxygen and sulfur with two single bonds include alcohols C-O-H, ethers C-O-C, thiols C-S-H, sulfides C-S-C and disulfides C-S-S-C. We will also look at two more important carbonyl containing functional groups, aldehydes and ketones.

2. Introduction • The organic groups covered in this Unit all have important biological roles • Alcohols • Triglycerides • Amino acids and proteins • Ethers • Biologically active molecules • Thiols • Amino acids and proteins • Odorants • Sulfides • Amino acids and proteins • Ketones • Carbohydrates and metabolic intermediates • Aldehydes • Carbohydrates and metabolic intermediates

3. Introduction • Alcohols were first encountered back in Unit 2 • Alcohols comprise a hydroxyl group (-OH) attached to an alkane-type carbon atom.

4. Introduction • Ethers • Ethers have an oxygen attached to two alkane-type carbon atoms.

5. Introduction • Sulfur containing functional groups • Sulfur, like oxygen, is a Group VIA element • Sulfur forms functional groups which are analogous to some of the groups formed by oxygen.

6. Introduction • Thiol • Thiols look similar to alcohols and comprise a sulfhydryl (also called mercaptan) group (-SH) bonded to an alkane-type carbon.

7. Introduction • Sulfides • Sulfides look similar to ethers and contain a sulfur atom that is bonded to two alkane-type carbon atoms.

8. Introduction • Disulfides • Disulfides look similar to a sulfide, but contain two sulfur atoms that are bonded to each other and to two alkane-type carbon atoms.

9. Introduction • Ketones • Ketones are a carbonyl containing functional group in which the carbonyl carbon is bonded to two other carbon atoms.

10. Introduction • Ketones in the news; Diacetyl • http://www.usatoday.com/news/health/2007-10-27-diacetyl_N.htm

11. Introduction • Aldehydes • Aldehydes are a carbonyl containing functional group in which the carbonyl carbon is bonded to at least one hydrogen atom.

12. alkene alcohol alkene alcohol ether ether ketone amine ether Question • Circle and label the functional groups found in the following compounds.

13. alkene thiol sulfide ammonium ion carboxylate ion disulfide thiol sulfide Question • Circle and label the functional groups found in the following compounds.

14. alcohol ketone aldehyde aldehyde ketone ether phenol Question • Circle and label the functional groups found in the following compounds.

15. Alcohols, Ethers, Thiols, Sulfides and Disulfides • The IUPAC rules for naming alcohols • Find the longest carbon chain containing the carbon to which the hydroxyl group is attached. • Remove the “-e” ending and replace with “-ol” • Number the carbon chain from the end closest to the hydroxyl group. • Identify, name and locate any substituent groups • If the hydroxyl group is being treated as a substituent group, refer to it as a “hydroxyl” group.

16. Alcohols, Ethers, Thiols, Sulfides and Disulfides • Examples of alcohol names

17. Alcohols, Ethers, Thiols, Sulfides and Disulfides • The IUPAC rules for naming thiols • Find the longest carbon chain containing the carbon to which the sulfhydryl group is attached. • Add the ending“-thiol”, without removing the “-e” • Number the carbon chain from the end closest to the sulfhydryl group. • Identify, name and locate any substituent groups

18. Alcohols, Ethers, Thiols, Sulfides and Disulfides • Examples of thiol names (Common names are shown in parentheses)

19. Alcohols, Ethers, Thiols, Sulfides and Disulfides • We will not use the IUPAC rules for naming the ethers, sulfides and disulfides. • Instead of using an ending, the substituents attached to the oxygen or sulfur will be listed in front fo the family name.

20. Alcohols, Ethers, Thiols, Sulfides and Disulfides • Examples of ether, sulfide and disulfide names

21. Question • Name the following structures.

22. Alcohols, Ethers, Thiols, Sulfides and Disulfides • Alcohols are also labeled according to the number of carbons that are attached to the carbon that the hydroxyl group is attached to. • This will be important for predicting the products of oxidation reactions involving alcohols.

23. Alcohols, Ethers, Thiols, Sulfides and Disulfides • The hydroxyl groups of alcohols are good hydrogen bonding donors and acceptors

24. Alcohols, Ethers, Thiols, Sulfides and Disulfides • The other functional groups are not as good at forming hydrogen bonds. • Ethers can only accept hydrogen bonds. • Sulfur has about the same electronegativity as carbon, and therefore, is non-polar. • This is reflected in the boiling points and solubilities of these molecules.

26. Preparations of Alcohols, Ethers, Thiols and Sulfides • In this unit we will be learn many new reactions. • Pages 346 and 347 in Raymond contains a nice summary of all of the reactions that will will cover in this unit.

27. Preparations of Alcohols, Ethers, Thiols and Sulfides • Alcohols, Ethers, Thiols and Sulfides can be prepared from alkyl halides using nucleophilic substitution reactions. • A nucleophile is an electron rich atom or group or atoms. • The halogen atom make a good leaving group. • The nucleophile “attacks” that atom to which the halogen is attached and the halogen leaves. • This results in the the nucleophile substituting for the leaving group.

28. Preparations of Alcohols, Ethers, Thiols and Sulfides • Using nucleophilic substitution to prepare alcohols from alkyl halides: The OH- attacks The Cl- leaves The OH- attacks The Br- leaves The OH- attacks The I- leaves

29. Preparations of Alcohols, Ethers, Thiols and Sulfides • Using nucleophilic substitution to prepare ethers, thiols and sulfides from alkyl halides:

30. Preparations of Alcohols, Ethers, Thiols and Sulfides • Another way to produce alcohols is the hydration of alkenes • We saw this reaction back in Unit 2

31. Reactions Involving Water (Unit 4) • Hydration • In the hydration reaction water is also split, but instead of being used to split another molecule, it is added to another molecule to produce a single product. • The water it is added to either an alkene or alkyne: • The hydration of an alkene produces an alcohol.

32. Reactions Involving Water (Unit 4) • Hydration • This can also be written in shorthand as: • The H+ below the reaction arrow is used to indicate that this is an acid-catalyzed reaction. • The shorthand is used to emphasize what happens to the key reactant.

33. Reactions Involving Water (Unit 4) • Hydration example • On an earlier slide a reaction from the Citric Acid Cycle was shown, which involved the dehydrogenation of succinic acid to produce fumaric acid. • The sequent reaction in the Citric Acid Cycle is an example of a hydration reaction:

34. Preparations of Alcohols, Ethers, Thiols and Sulfides • Another way to produce alcohols is the hydration of alkenes • When we looked at hydration reactions back in Unit 2 we conveniently picked reactants that would only produce one product. • It is possible to have multiple products in hydration reactions.

35. Preparations of Alcohols, Ethers, Thiols and Sulfides • Multiple products occur whenever there are a different number of hydrogen atoms attached to the two carbons double-bonded carbons in the alkene. • Markovnikov’s Rule can be used to predict which of the two products is predicted to be the major product. • The hydrogen from the water in a hydration reaction is added to the double-bonded carbon atom that originally carried the most hydrogen atoms. • If you consider hydrogens as a source of wealth, this can be more simply stated as • “The rich get richer!”

36. Preparations of Alcohols ... • More examples of hydration reactions:

37. Reactions of Alcohols and Thiols • Back in Unit 4 we developed several definitions for Oxidation-Reduction Reactions.

38. Oxidation Reduction An atom loses electrons An atom gains electrons An atom gains a bond to oxygen An atom loses a bond to oxygen An atom loses a bond to hydrogen An atom gains a bond to hydrogen Oxidation and Reduction (Unit 4) • Ways of recognizing oxidation/reduction reactions: • Oxidation and reductions always occur together

39. Reactions of Alcohols and Thiols • Back in Unit 7 we saw how the definition “loses hydrogens” could be applied to the oxidation of hydroquinones to produce quinones

40. Carboxylic Acids & Phenols, Other Reactions (Unit 7) • The oxidation of hydroquinones is also an important biological reaction. • A chemical oxidation of hydroquinones can be carried out the oxidizing agent K2Cr2O7 (potassium dichromate) • The K2Cr2O7 is not acting as a base to remove 2 H+ ions, instead it is removing 2 H• atoms.

41. Reactions of Alcohols and Thiols • This same definition can also be applied to the oxidation of alcohols by potassium dichromate (K2Cr2O7). The oxidation requires that there are hydrogens to be removed on the carbon to which the hydroxyl is bound

42. Reactions of Alcohols and Thiols • Application: Breathalyzer(http://science.howstuffworks.com/breathalyzer3.htm 1. The sulfuric acid removes the alcohol from the air into a liquid solution. 2. The alcohol reacts with potassium dichromate to produce: * chromium sulfate * potassium sulfate * acetic acid * water The silver nitrate is a catalyst,

43. Reactions of Alcohols and Thiols • The oxidation of primary (1°) alcohols is a way for preparing aldehydes and carboxylic acids. • The oxidation of secondary (2°) alcohols is a way for preparing ketones. • The oxidation of tertiary (3°) alcohols does not occur because there are not hydrogens attached to the carbon to to which the hydroxyl is attached

44. Reactions of Alcohols and Thiols

45. Reactions of Alcohols and Thiols • In biological reactions the coenzyme NAD+ is often used as the oxidizing agent. • The NAD+ takes the electrons away from alcohols to produce aldehydes, carboxylic acids and ketones.

46. Reactions of Alcohols and Thiols • Example • The oxidation of malate to oxaloacetate that occurs in the citric acid cycle:

47. Reactions of Alcohols and Thiols • Thiols can be oxidized to form disulfides using I2 as oxidizing agent • We will see this oxidation reaction when we discuss proteins in Unit 10

48. Preparations of Alcohols, Ethers, Thiols and Sulfides • Another reaction that we saw back in Unit 2 was the dehydration of alcohols to produce alkenes. • We saw this reaction back in Unit 2

49. Preparations of Alcohols, Ethers, Thiols and Sulfides • Like the complement hydration reaction, dehydration can also produce multiple products.

50. Preparations of Alcohols, Ethers, Thiols and Sulfides • Multiple products occur whenever there are a different number of hydrogen atoms attached to the two carbons that are on either side of the carbon to which the hydroxyl is attached. • There is a rule that can be used to predict which of the two products is predicted to be the major product. • In a dehydration of an alcohol, the hydrogen will be removed from the neighboring carbon atom that carries the fewest hydrogen atoms. • If you consider hydrogens as a source of wealth, and since we are removing wealth, this can be more simply stated as • “The poor get poor!”