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Chapter 8 Alcohols, Phenols, and Ethers

Chapter 8 Alcohols, Phenols, and Ethers. 薄荷腦. 8.1 Naming Alcohols, Phenols, and Ethers. Alcohols. Simple alcohols are named in the IUPAC system as derivatives of the parent alkane, using the suffix – ol. 2-Methyl pentan- 2-ol. cis - Cyclohexane- 1,4-diol. 3-Phenyl butan- 2-ol.

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Chapter 8 Alcohols, Phenols, and Ethers

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  1. Chapter 8 Alcohols, Phenols, and Ethers

  2. 薄荷腦

  3. 8.1 Naming Alcohols, Phenols, and Ethers Alcohols Simple alcohols are named in the IUPAC system as derivatives of the parent alkane, using the suffix –ol.

  4. 2-Methylpentan-2-ol cis-Cyclohexane-1,4-diol 3-Phenylbutan-2-ol

  5. (2-Methylpropan-2-ol) (Propane-1,2,3-triol) (Ethane-1,2-diol)

  6. Phenols

  7. Ethers

  8. If more than one ether linkage is present, or of other functional groups are present, the ether part is named as an alkoxy substituent on the parent compound. 4-tert-Butoxycyclohex-1-ene

  9. 5-Methylhexane-2,4-diol • 2-Methyl-4-phenolbutan-2-ol • 4,4-Dimethylcyclohexanol • cis-2-Bromocyclopentanol

  10. 2-Methylhexan-2-ol (b) Hexane-1,5-diol • (c) 2-Ethylbut-2-en-1-ol (d) Cyclohex-3-en-1-ol • (e) o-Bromophenol (f) 2,4,6-Trinitrophenol

  11. Diisopropyl ether • Cyclopentyl propyl ether • 1-Bromo-4-methoxybenzene (p-Bromoanisole) • Ethyl isobutyl ether

  12. 8.2 Properties of Alcohols, Phenols, and Ethers: Hydrogen Bonding Alcohols, phenol, and ethers can be though of as organic derivatives of water in which one or both of the hydrogens have been replaced by organic parts

  13. Alcohols and phenols have unusually high boiling points because, like water, they form hydrogen bonds in the liquid state.

  14. 8.3 Properties of Alcohols and Phenols: Acidity Alcohols and phenols, like water, are both weakly basic and weakly acidic. As weak Lewis bases, alcohols and phenols are reversibly protonated by strong acids to yield oxonium ions, ROH2+

  15. As weak acids, alcohols and phenols dissociate to a slight extent in dilute aqueous solution by donating a proton to water, generating H3O+ and an alkoxide ion (RO-) or a phenoxide ion (ArO-).

  16. Alcohols are about as acidic as water. Thus, they react with alkali metals to yield metal alkoxides that are themselves strong bases.

  17. Phenols are about a million times more acidic than alcohols. Phenols are soluble in dilute aqueous NaOH, but alcohols are not. Phenols are more acidic than alcohols because the phenoxide anion is resonance-stabilized by the aromatic ring.

  18. 8.4 Synthesis of Alcohols Alcohols can be prepared by hydration of alkenes. The most general method for preparing alcohols is by reduction of carbonyl compounds.

  19. Reduction of Aldehydes and Ketones

  20. Reducing reagent : NaBH4 sodium borohydride (sodium borohydride) Butan-1-ol

  21. Reduction of esters and carboxylic acids Esters and carboxylic acids are reduced to give primary alcohols:

  22. These reactions proceed more slowly than the corresponding reductions of aldehydes and ketones, so the more powerful reducing agent LiAlH4 is used rather than NaBH4. Octadec-9-enoic acid Octadec-9-en-1-ol Methyl pent-2-enoate Pent-2-en-1-ol

  23. Hexan-3-one Hexan-3-ol

  24. 8.5 Reactions of Alcohols Dehydration of alcohols

  25. Acid-catalyzed dehydrations usually follow Zaitsev’s rule and yield the more highly substituted alkene as major product. 2-Methylbut-2-ene 2-Methylbutan-2-ol 2-Methylbut-1-ene

  26. Mechanism of the acid-catalyzed dehydration of a tertiary alcohol by an E1 reaction.

  27. 3-Methylpent-2-ene 3-Methylpent-1-ene 3-Methylpentan-2-ol

  28. Oxidation of alcohols Tertiary alcohols don’t normally react with oxidizing agents.

  29. Decan-1-ol Primary alcohols are oxidized either to aldehydes or to carboxylic acids, depending on the reagents chosen. Heptan-1-ol PCC, C5H6NCrO3Cl(pyridinium chlorochromate) CrO3(chromium trioxide)

  30. Secondary alcohols are oxidized easily to produce ketones. Na2Cr2O7 (sodium dichromate)

  31. Conversion into ethers Williamson ether synthesis Primary alkyl halides work best because competitive E2 elimination of HX can occur with more hindered substrates.

  32. Best prepared by reaction of the more hindered alkoxide partner with the less hindered alkyl halide partner.

  33. 8.6 Synthesis and Reaction of Phenols

  34. Alcohol-like reactions of phenols Phenols can be converted into ethers by SN2 reaction with alkyl halides in the presence of base. Williamson ether synthesis with phenols occurs easily because phenols are more acidic than alcohols and are therefore more readily converted into their anions.

  35. Electrophilic aromatic substitution reactions of phenols

  36. Oxidation of phenols: quinones cyclohexadienedinone Quinones can be easily reduced to hydroquinones by NaBH4 or SnCl2. and hydroquinones can be easily oxidize back to quinones by Na2Cr2O7.

  37. 8.7 Synthesis and Reactions of Ethers Synthesis of ethers Ethers are easily prepared from alcohols by conversion to the alkoxide ion followed by SN2 reaction with a primary alkyl halide.

  38. Reactions of ethers Ethers are unreactive to most common regents. Ethers undergo only one general reaction  they are cleaved by strong acids such as aqueous HI or HBr. They take place by either an SN1 or SN2 pathway, depending on the structure of the ether. SN2

  39. Ethers with a tertiary alkyl group cleave by an SN1 mechanism because they can produce stable intermediate carbocations. SN1

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