1. Functional Group Reactions Organic Chemistry Lesson # 4

2. 1. Combustion of Alcohols Alcohols can react like hydrocarbons with oxygen to create carbon dioxide and water. Example: propanol + oxygen → carbon dioxide + water C 3 H 7 OH (l) + O 2 (g) → CO 2 (g) + H 2 O (g)

3. 2. Elimination of Alcohols Alcohols can be converted to alkenes through elimination – specifically dehydration. In a dehydration, the hydroxyl group and an adjacent hydrogen are removed and a double bond is formed. This reaction requires a sulfuric acid catalyst.

4. Elimination Example Butan-2-ol →

5. 3a. Substitution with Alcohols Alcohols can be converted to alkyl halides only in the presence of a strong acid that contains a halogen, like HCl (aq). This reaction can happen with any alcohol, but is very slow with both primary and secondary alcohols, as pulling off the nucleophile hydroxide to exchange it with a halide is not desirable. This reaction happens more quickly with tertiary alcohols.

6. Alcohol Substitution Example Ethanol + Hydrogen Chloride →

7. 3b. Substitution with Amines  Substitution can also occur with amines and alkyl halides to create more complex amines (secondary or tertiary).

8. Amine Substitution Example 1 Ethanamine + Bromoethane 1° Amine

9. Amine Substitution Example 2 N-ethylethanamine+ Bromoethane 2° Amine

10. 4a. Oxidation of Alcohols Oxidation is defined as a reaction in which a carbon atom forms more bonds to oxygen, or fewer bonds to hydrogen. Alcohols can be converted to aldehydes and ketones through controlled oxidation, which is actually a type of elimination reaction. In this type of reaction, an oxidizing agent, such as hydrogen peroxide (H 2 O 2 ), potassium permanganate (KMnO 4 ) or potassium dichromate (K 2 Cr 2 O 7 ) is added to the alcohol and allowed to slowly react – the oxidizing agent is not present in excess. If it was, combustion would occur instead. Primary alcohols will create aldehydes, and secondary alcohols will create ketones. These reactions do not happen with tertiary alcohols.

11. Oxidation of Primary Alcohols Ethanol + [O] →

12. Oxidation of Secondary Alcohols Propan-2-ol + [O] →

13. 4b. Oxidation of Aldehydes  An aldehyde can further be converted to a carboxylic acid through an oxidation reaction.  Ketones cannot be converted to acids. Butanal + [O] →

14. 5a. Reduction of Carbonyls Reduction is defined as a reaction in which a carbon atom forms fewer bonds to oxygen, or more bonds to hydrogen. Aldehydes and ketones can be converted back to alcohols through a hydrogenation reaction when a reducing agent, such as lithium aluminum hydride, LiAlH 4, or hydrogen over a platinum catalyst, is present.

15. Reduction of Aldehydes Example Propanal + [H] →

16. Reduction of Ketones Example Propanone + [H] →

17. 5b. Reduction of Carboxyls  Carboxylic acids can be converted back to aldehydes through a hydrogenation reaction when a reducing agent and a platinum catalyst are present. Butanoic Acid + [H] →

18. 6a. Condensation to Ethers A condensation reaction is one in which two large molecules combine and form one larger molecule and one very small molecule, usually water. In simple terms, water is removed to form one molecule. Condensation is important in all living systems – these type of reactions form most of the large biomolecules, such as proteins, carbohydrates, fats, and DNA. Two alcohols can undergo condensation to form an ether and water. A sulfuric acid catalyst is necessary.

19. Condensation to Ethers Example 1 Propan-1-ol + Ethanol →

20. Condensation to Ethers Example 2 Butan-1-ol + Pentan-3-ol →

21. 6b. Condensation to Esters  Carboxylic acids can react with alcohols to form esters. A sulfuric acid catalyst is necessary. Propanoic acid + Pentan-1-ol →

22. Condensation to Esters Example Ethanoic Acid + Butan-2-ol →

23. 6c. Condensation to Amides  Carboxylic acids can react with amines to form amides. Butanoic Acid + propan-1-amine →

24. 7a. Hydrolysis of Esters A hydrolysis reaction is essentially the reverse of a condensation reaction. It means “breaking apart using water”. The compounds that are formed in condensation can be broken down by hydrolysis. The hydroxyl in a water molecule is added to one side of a bond such as an ester or amide, and the hydrogen is added to the other side, which breaks the bond. Esters react with water to form alcohols and carboxylic acids.

25. Hydrolysis of Esters Example Ethyl propanoate +Water →

26. 7b. Hydrolysis of Amides  Amides react with water to form amines and carboxylic acids. N-propyl-2-methylpropanamide + Water →

27. Functional Group ReactionsTypeConditions AlcoholsAlcohol + Oxygen → Carbon Dioxide + Water Alcohol → Alkene + Water Alcohol + Acid Halide → Alkyl Halide + Water Alcohol + Alcohol → Ether + Water Primary Alcohol + [O] → Aldehyde + Water Secondary Alcohol + [O] → Ketone + Water Alcohol + Carboxylic Acid → Ester + Water Combustion Elimination Substitution Condensation Oxidation Condensation H 2 SO 4 Oxidizing Agent H 2 SO 4, heat EthersNONE AldehydesAldehydes + [O] → Carboxylic Acid Aldehydes + [H] → Primary Alcohol Oxidation Reduction Oxidizing Agent Pt, heat, pressure KetonesKetone + [H] → Secondary AlcoholReductionPt, heat, pressure Carboxylic Acids Carboxylic Acid + [H] → Aldehyde + Water Carboxylic Acid + Alcohol → Ester + Water Carboxylic Acid + Amine → Amide + Water Reduction Condensation Pt, heat, pressure H 2 SO 4, heat EstersEster + Water → Carboxylic Acid + AlcoholHydrolysis AminesAmine + Alkyl Halide → Amine (of higher bonds) Amine + Carboxylic Acid → Amide + Water Substitution Condensation AmidesAmide + Water → Amine + Carboxylic AcidHydrolysis