Quiz 1

• Alcohols


  Compounds containing the hydroxyl (-OH) functional group bonded to an alkyl, R
• Classification of Alcohols


  • Primary Alcohol (1ª)
  • Secondary Alcohol (2º)
  • Tertiary Alcohol (3ª)
• Primary Alcohols


  • n-propyl alcohol
  • 1-propanol
• Secondary Alcohols


  • sec. butyl alcohol
  • 2-butanol
• Tertiary Alcohols


  • tert. butyl alcohol
  • 2-methyl-2-propanol
• Classification of Alcohols by number of OH groups

  • Monohydroxy alcohols
  • Polyhydroxy alcohols
• Polyhydroxy alcohols


  • Ethylene glycol
  • Glycerol / 1,2,3-propanetriol
• Reactivity of Alcohols


  Mainly attributed to the -OH group
• • OH Group


  Has an inherent acid character shown when the hydrogen is released from the -OH bond
• Protonation of -OH Group

  Weakens the C-O bond so that the whole group may be cleaved off as water and subsequently replaced in the molecule
• Removal of -OH Group


  Dependent upon the relative polarization of the -OH bond
• Ethyl Alcohol


  Most commonly known primary alcohol, present in alcoholic beverages, obtained from the fermentation of sugars and starches catalyzed by the enzyme zymase

  
• Fermentation of sugars and starches

  C6-CH12-O6 + Zymase

  
• Chromic Acid Test


  Used to distinguish primary and secondary alcohols from tertiary alcohols

  
• Chromic Acid


  • Oxidizes primary alcohols to aldehydes
  • Oxidizes secondary alcohols to ketones
  • Oxidizes aldehydes to ketones
  • Does not readily oxidize tertiary alcohols due to the absence of alpha hydrogen

  
• Lucas Test


  Used to further distinguish different classes of alcohols

  
• Tertiary Alcohols


  • React immediately with Lucas reagent (HCl in the presence of ZnCl2) to form an immiscible upper layer of alkyl chloride

  
• Secondary Alcohols


  • Cloudiness appears after 5 minutes with Lucas reagent

  
• Primary Alcohols


  • Do not react with Lucas reagent under these conditions
• SN1 Reaction Mechanism


  Involved with tertiary and secondary alcohols
• Glycerol


  Most important triol, obtained as a by-product from the manufacture of soap, used as a moisturizing agent in cosmetic formulations, tobacco products, and foods, detected by the acrolein test, undergoes dehydration when heated with KHSO4 to form propenal (acrolein) with a pungent odor
• Lucas Test


  Put n-butanol, 2-butanol, 2-methyl-2-propanol, and alcohol X in test tubes, add 2 ml of Lucas reagent, observe for changes and record time

  
• Tertiary Alcohol


  • Immediately reacts with Lucas reagent to form an immiscible upper layer of alkyl chloride (e.g. 2-methyl-2-propanol)

  
• Secondary Alcohol


  • Cloudiness appears after 5 minutes with Lucas reagent (e.g. 2-butanol and alcohol X)

  
• Primary Alcohol


  • Do not react with Lucas reagent even after 15 minutes (e.g. n-butanol)

  
• Oxidation Test


  Dispense 5 ml of sodium dichromate and 1 drop of concentrated H2SO4 into 4 test tubes, add 1 ml of n-butanol, 2-butanol, 2-methyl-2-propanol, and alcohol X, heat in 80°C water bath for 10 mins, observe color changes

  
• Primary and Secondary Alcohols

  • Change color from orange to green when oxidized
• Tertiary Alcohol


  • No color change, orange color remains
• Alcohol X is a secondary alcohol
• Esterification Test


  Dispense 2 ml of Ethanol in a test tube, add 1 ml of Anhydride Glacial Acetic Acid and 3 drops of concentrated H2SO4, heat in 60°C water bath for 1 min, add 3 ml of distilled water and note the smell

  
• Esterification


  Reaction of alcohol with carboxylic acid to form ester and water, used in various industries

  
• Ethanol and Ethanoic Acid


  • Reacts in the presence of acid catalyst sulfuric acid to form ethyl ethanoate (ethyl acetate) with a sweet fruity smell
• Methanol and Salicylic Acid

  Reacts to form Methyl Salicylate or Oil of Wintergreen
• Iodoform Test


  Used to identify aldehydes or ketones, forms a pale yellow precipitate of iodoform (triiodomethane) when iodine and sodium hydroxide are added to a compound that contains either a methyl ketone or a secondary alcohol with a methyl group in the alpha position

  
• Iodoform Test Procedure


  Add 2M sodium hydroxide and 10% iodine solution to ethanol, propan-1-ol, propan-2-ol, and butan-1-ol, observe color changes and precipitate formation

  
• Positive Iodoform Reaction


  • Molecule has a carbon attached to an OH and to both a methyl group and hydrogen atom
• Negative Iodoform Reaction


  • Color of the solution disappears
• Positive Iodoform Reaction


  • Lighter and brown, yellow or yellow and cloudy color, produces a solid yellow precipitate of triiodomethane with an antiseptic smell
• Vacuum Filtration of Iodoform Precipitate

  Use a Buchner funnel and flask attached to a siphon pump to filter the precipitate

  
• Ethanol + 10% Iodine + 2M NaOH - fine yellow precipitate with antiseptic smell (Triiodomethane)