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CHE 242 Unit V Structure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR Spectroscopy CHAPTER TEN Terrence P. Sherlock Burlington.

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Presentation on theme: "CHE 242 Unit V Structure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR Spectroscopy CHAPTER TEN Terrence P. Sherlock Burlington."— Presentation transcript:

1 CHE 242 Unit V Structure and Reactions of Alcohols, Ethers and Epoxides; Basic Principles of NMR Spectroscopy CHAPTER TEN Terrence P. Sherlock Burlington County College 2004

2 Chapter 102 Classify these: =>

3 Chapter 103 Name these: 2-methyl-1-propanol 2-methyl-2-propanol 2-butanol 3-bromo-3-methylcyclohexanol =>

4 Chapter 104 Naming Priority Acids Esters Aldehydes Ketones Alcohols Amines Alkenes Alkynes Alkanes Ethers Halides =>

5 Chapter 105 Hydroxy Substituent When -OH is part of a higher priority class of compound, it is named as hydroxy. Example: 4-hydroxybutanoic acid also known as GHB =>

6 Chapter 106 Glycols 1, 2 diols (vicinal diols) are called glycols. Common names for glycols use the name of the alkene from which they were made. 1,2-ethanediol ethylene glycol 1,2-propanediol propylene glycol =>

7 Chapter 107 Naming Phenols -OH group is assumed to be on carbon 1. For common names of disubstituted phenols, use ortho- for 1,2; meta- for 1,3; and para- for 1,4. Methyl phenols are cresols. 3-chlorophenol meta-chlorophenol 4-methylphenol para-cresol =>

8 Chapter 108 Physical Properties Unusually high boiling points due to hydrogen bonding between molecules. Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases. =>

9 Chapter 109 Boiling Points =>

10 Chapter 1010 Solubility in Water Solubility decreases as the size of the alkyl group increases. =>

11 Chapter 1011 Acidity of Alcohols pK a range: 15.5-18.0 (water: 15.7) Acidity decreases as alkyl group increases. Halogens increase the acidity. Phenol is 100 million times more acidic than cyclohexanol! =>

12 Chapter 1012 Table of K a Values =>

13 Chapter 1013 Formation of Alkoxide Ions React methanol and ethanol with sodium metal (redox reaction). React less acidic alcohols with more reactive potassium. =>

14 Chapter 1014 Formation of Phenoxide Ion Phenol reacts with hydroxide ions to form phenoxide ions - no redox is necessary. OH + OH O + HOH pK a = 10 pK a = 15.7 =>

15 Chapter 1015 Synthesis (Review) Nucleophilic substitution of OH - on alkyl halide Hydration of alkenes  water in acid solution (not very effective)  oxymercuration - demercuration  hydroboration - oxidation =>

16 Chapter 1016 Glycols (Review) Syn hydroxylation of alkenes  osmium tetroxide, hydrogen peroxide  cold, dilute, basic potassium permanganate Anti hydroxylation of alkenes  peroxyacids, hydrolysis =>

17 Chapter 1017 Organometallic Reagents Carbon is bonded to a metal (Mg or Li). Carbon is nucleophilic (partially negative). It will attack a partially positive carbon.  C - X  C = O A new carbon-carbon bond forms. =>

18 Chapter 1018 Grignard Reagents Formula R-Mg-X (reacts like R: - + MgX) Stabilized by anhydrous ether Iodides most reactive May be formed from any halide  primary  secondary  tertiary  vinyl  aryl =>

19 Chapter 1019 Some Grignard Reagents =>

20 Chapter 1020 Organolithium Reagents Formula R-Li (reacts like R: - + Li) Can be produced from alkyl, vinyl, or aryl halides, just like Grignard reagents. Ether not necessary, wide variety of solvents can be used. =>

21 Chapter 1021 Reaction with Carbonyl R: - attacks the partially positive carbon in the carbonyl. The intermediate is an alkoxide ion. Addition of water or dilute acid protonates the alkoxide to produce an alcohol. =>

22 Chapter 1022 Synthesis of 1° Alcohols Grignard + formaldehyde yields a primary alcohol with one additional carbon. =>

23 Chapter 1023 Synthesis of 2º Alcohols Grignard + aldehyde yields a secondary alcohol. =>

24 Chapter 1024 Synthesis of 3º Alcohols Grignard + ketone yields a tertiary alcohol. =>

25 Chapter 1025 How would you synthesize… =>

26 Chapter 1026 Grignard Reactions with Acid Chlorides and Esters Use two moles of Grignard reagent. The product is a tertiary alcohol with two identical alkyl groups. Reaction with one mole of Grignard reagent produces a ketone intermediate, which reacts with the second mole of Grignard reagent. =>

27 Chapter 1027 Grignard + Acid Chloride (1) Ketone intermediate => Grignard attacks the carbonyl. Chloride ion leaves.

28 Chapter 1028 Grignard and Ester (1) Grignard attacks the carbonyl. Alkoxide ion leaves! ? ! Ketone intermediate =>

29 Chapter 1029 Second step of reaction Second mole of Grignard reacts with the ketone intermediate to form an alkoxide ion. Alkoxide ion is protonated with dilute acid. =>

30 Chapter 1030 How would you synthesize... Using an acid chloride or ester. =>

31 Chapter 1031 Grignard Reagent + Ethylene Oxide Epoxides are unusually reactive ethers. Product is a 1º alcohol with 2 additional carbons. =>

32 Chapter 1032 Limitations of Grignard No water or other acidic protons like O-H, N-H, S-H, or -C—C-H. Grignard reagent is destroyed, becomes an alkane. No other electrophilic multiple bonds, like C=N, C—N, S=O, or N=O. =>

33 Chapter 1033 Reduction of Carbonyl Reduction of aldehyde yields 1º alcohol. Reduction of ketone yields 2º alcohol. Reagents:  Sodium borohydride, NaBH 4  Lithium aluminum hydride, LiAlH 4  Raney nickel =>

34 Chapter 1034 Sodium Borohydride Hydride ion, H -, attacks the carbonyl carbon, forming an alkoxide ion. Then the alkoxide ion is protonated by dilute acid. Only reacts with carbonyl of aldehyde or ketone, not with carbonyls of esters or carboxylic acids. =>

35 Chapter 1035 Lithium Aluminum Hydride Stronger reducing agent than sodium borohydride, but dangerous to work with. Converts esters and acids to 1º alcohols. =>

36 Chapter 1036 Comparison of Reducing Agents LiAlH 4 is stronger. LiAlH 4 reduces more stable compounds which are resistant to reduction. =>

37 Chapter 1037 Catalytic Hydrogenation Add H 2 with Raney nickel catalyst. Also reduces any C=C bonds. =>


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