Alcohols and Phenols

• Alcohols


  Compounds that contain a hydroxyl group (OH) bonded directly to a sp3 hybrid carbon atom
• Aliphatic hydroxyl compounds


  Alcohols that contain straight or branched chain hydrocarbons
• Common examples of alcohols

  • Ethanol
  • Methanol
• Ethanol production


  1. Natural fermentation of sugars and starch

  2. Enzymes of yeast decompose aqueous solutions of sugars and starches to produce ethanol and carbon dioxide
• Methanol production


  1. Originally obtained by heating wood in the absence of air

  2. Modern method is catalytic reduction of carbon monoxide by hydrogen gas
• Industrial uses of methanol


  • Raw material in production of methanal
  • Antifreeze in washer solutions
  • Additive to jet fuels
• Primary alcohol (1° alcohol)

  Alcohol with only one alkyl group (R) directly bonded to the sp3 hybrid carbon atom
• Examples of 1° alcohols

  • Ethanol
  • 1-propanol
  • 1-butanol
  • 2,2-Dimethyl-1-propanol
• Secondary alcohol (2° alcohol)

  Alcohol with two alkyl groups (RR) directly bonded to the sp3 hybrid carbon atom
• Examples of 2° alcohols

  • 2-propanol
  • 2-butanol
  • Cyclopentylalcohol
• Tertiary alcohol (3° alcohol)


  Alcohol with three alkyl groups (RR'R") directly bonded to the sp3 hybrid carbon atom
• Examples of 3° alcohols

  • 2-Methyl-2-propanol
  • 2-Methyl-2-butanol
• Naming alcohols using IUPAC rules

  1. Select longest continuous carbon chain with OH group

  2. Obtain parent alkane name

  3. Replace terminal -e with -ol

  4. For multiple OH groups, use -diol, -triol etc.

  5. Name substituents alphabetically before alcohol name

  6. If other functional groups, name them alphabetically and change parent name
• Alcohols as organic derivatives of water

  • Alkyl group is non-polar and hydrophobic
  • Hydroxyl group is polar and hydrophilic
• Solubility of alcohols in water

  • Decreases as number of carbon atoms increases
  • Alcohols with 9+ carbon atoms are insoluble in water
• Boiling point of alcohols

  • Increases as number of carbon atoms increases due to differences in intermolecular forces
• Polarity of alcohols


  • Decreases as number of carbon atoms increases
• Reaction of alcohols with strong base

  Forms alkoxide ion (RO-) which can act as nucleophile
• Reaction of alcohols with alkali metals

  1. Forms alkoxide ion and hydrogen gas

  2. Reactivity decreases as alkyl portion increases: K > Na > Li
• Esterification reaction


  Alcohols react with carboxylic acids in presence of acid catalyst to form esters and water
• Reaction of alcohols with hydrogen halides

  Forms haloalkanes, replacing OH with halogen
• Reaction of alcohols with phosphorus tribromide

  Replaces OH with bromine to form bromoalkane
• Reaction of alcohols with thionyl chloride

  Replaces OH with chlorine to form chloroalkane
• Oxidation of primary and secondary alcohols

  Oxidised to aldehydes and ketones respectively
• ethyl-2-propanol


  Organic compound
• 1. Chloro-2-methylpropane


  Organic compound
• wooupA()


  Organic compound
• Reaction to prepare 1,2° and 3° haloalkanes

  1. Hydroxyl group of alcohol replaced by halogen atom

  2. Depends on type of alcohol used
• Reaction with Phosphorus tribromide (PBr3)

  Hydroxyl group replaced by bromine atom to form bromoalkane
• Reaction with Thionyl Chloride (SOCl2)

  Hydroxyl group replaced by chlorine atom to form chloroalkane
• Oxidation of Primary Alcohols

  1. Oxidized to aldehydes

  2. Aldehydes easily oxidized further to carboxylic acids
• Oxidation of Secondary Alcohols

  Oxidized to ketones
• Oxidation of Tertiary Alcohols not possible
• Phenols


  Compounds containing hydroxyl group bonded directly to benzene ring
• Phenol acidity (pKa)


  10, much more acidic than alcohols (pKa around 18)
• Effect of substituents on phenol acidity

  Nitro groups greatly increase acidity, other substituents have small effect
• Phenols less acidic than carboxylic acids
• Naming of Phenols


  Follows same pattern as alcohols, but other functional groups take precedence over hydroxyl
• Bromination of Phenols


  1. In acidic/non-polar solvents, bromination occurs at para-position

  2. In polar solvents, phenoxide ion forms and 2,4,6-tribromophenol is produced
• Nitration of Phenols


  Forms both ortho- and para-isomers, temperature must be kept below 20°C to avoid quinone formation