Quiz 2

• 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 Test


  • Primary Alcohols - oxidized to aldehydes
  • Secondary Alcohols - oxidized to ketones
  • Change in color of the solution from orange to green
  • Chromic Acid - oxidizes primary alcohols to carboxylic acids, oxidizes secondary alcohols to ketones, oxidizes aldehydes to ketones

  
• Tertiary Alcohols


  • Not readily oxidized by the Chromic acid due to the absence of alpha hydrogen

  
• Lucas Test


  To further distinguish different classes of alcohols

  
• Lucas Test


  • Tertiary Alcohols - react immediately with Lucas reagent to form an immiscible upper layer of alkyl chloride
  • Lucas Reagent - HCl in the presence of ZnCl2
  • Positive Result - indicated by a change from clear and colorless to turbid, formation of an insoluble layer of alkyl chloride
  • Secondary Alcohols - cloudiness appears after 5 minutes
  • Primary Alcohols - do not react 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) which has a pungent odor

  
• Lucas Test


  1. Put n-butanol, 2-butanol, 2-methyl-2-propanol, and alcohol X in test tubes

  2. Add 2 ml of lucas reagent to each

  3. Observe for changes and record time

  4. Tertiary Alcohol - immediately reacts with lucas reagent

  5. Secondary Alcohol - cloudiness appears after 5 minutes

  6. Primary Alcohol - do not react

  
• Oxidation Test


  1. Dispense 5 ml of sodium dichromate into 4 test tubes

  2. Add 1 drop of concentrated H2SO4 to each

  3. Put 1 ml of n-butanol, 2-butanol, 2-methyl-2-propanol, and alcohol X in each test tube

  4. Put test tubes in 80°C water bath for 10 mins

  5. Observe color changes

  6. Primary and Secondary Alcohols - changed from orange to green

  7. Tertiary Alcohol - no color change
• Esterification


  Reaction of alcohol with carboxylic acid to form ester and water, used in pharmaceutical, adhesive, bioplastic, cosmetic, pesticide, food, and biodiesel industries

  
• Esterification Test


  1. Dispense 2 ml of Ethanol in a test tube

  2. Add 1 ml of Anhydride Glacial Acetic Acid

  3. Put 3 drops of concentrated H2SO4, make homogeneous

  4. Warm in 60°C water bath for 1 min

  5. Add 3 ml of distilled water and note the fruity smell of the vapor release

  
• 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


  1. Add 2M sodium hydroxide and 10% iodine solution to ethanol, propan-1-ol, propan-2-ol, and butan-1-ol

  2. Observe color changes and conclusions

  3. Positive test - yellow and cloudy color, indicates presence of methyl ketone or secondary alcohol with methyl group in alpha position

  4. Negative test - colorless, no iodoform formation

  
• Iodine test

  1. Using a small syringe

  2. Keep adding NaOH until the brown color of the iodine disappears and shake it

  3. Check the color of the solution after multiple input of NaOH and shaking
• Second test


  1. Begin by propan-1-ol in a test tube

  2. Add 1.5 times as much of 10% iodine solution

  3. Keep adding a drop of NaOH until the brown color just disappears
• Third test


  1. Put the propan-2-ol in a test tube

  2. Put the 10% iodine solution

  3. Begin to add slowly with shaking the NaOH solution

  4. Continue slowly adding NaOH while shaking until the color changes

  5. Put it in the warm water bath and wait for the outcome

  
• Fourth test


  1. Put the butan-1-ol in a test tube

  2. Do the same procedure that was done to the previous test and wait for the result

  3. Butan-1-ol is more viscous so it needs more shaking
• Iodine doesn't actually dissolve in water, but it is dissolved in a dilute aqueous solution of potassium iodide
• Negative test


  If the color of the solution disappears
• Positive test


  Color - lighter and brown, yellow or yellow and cloudy

  Produces a solid yellow precipitate triiodomethane

  Has an antiseptic smell

  
• Using a Buchner funnel and Buchner flask attached to a siphon pump (draws the air)

  1. Do a vacuum filtration or filtering under reduced pressure

  2. Into the Buchner funnel, put a filter paper of an appropriate size to cover the holes

  3. Wet the filter paper a little bit for it to stick down over the holes, otherwise the precipitate will go underneath

  4. Pour the positive solvents in

  5. The triiodomethane will be left behind on the filter paper and the liquids will go down the flask
• Ethanol + 10% Iodine + 2M NaOH


  • fine yellow precipitate with antiseptic smell (Triiodomethane)

  
• Propan-1-ol + 10% Iodine + 2M NaOH

  • Colorless
• Propan-2-ol + 10% Iodine + 2M NaOH

  • pale yellow precipitate with an antiseptic smell

  
• Butan-1-ol + 10% Iodine + 2M NaOH

  • Colorless
• Alcohols


  may be classified based on the number of OH groups

  Monohydroxy alcohols

  Polyhydroxy alcohols

  Ethylene glycol

  Glycerol/1,2,3-propanetriol

  
• 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) which has a pungent odor