Expt 1

• Functional group


  A group of atoms in an organic compound that has a characteristic chemical behavior
• Common functional groups in biological compounds

  • Alkene (double bond)
  • Alkyne (triple bond)
  • Aromatic ring (benzene)
  • Alcohol
  • Ether
  • Amine
  • Thiol
  • Aldehyde
  • Ketone
  • Carboxylic acid
  • Ester
• Most biological compounds contain more than one functional group
• Knowledge of functional group properties is necessary for understanding biological compounds
• Chemical tests are used to identify functional groups
• Instruments like UV-Vis, IR, NMR, and mass spectrometry also provide information about functional groups
• Unsaturated


  Compounds containing carbon-carbon double or triple bonds, like alkenes and alkynes
• Saturated


  Compounds containing only carbon-carbon single bonds, like alkanes
• Aromatic


  Compounds with alternating carbon-carbon double bonds in a ring, like benzene
• von Baeyer's test for unsaturation

  1. Potassium permanganate (KMnO4) oxidizes carbon-carbon double/triple bonds

  2. Disappearance of violet KMnO4 color and brown MnO2 precipitate indicates unsaturation
• Bromine test for unsaturation


  1. Bromine adds to carbon-carbon double/triple bonds

  2. Disappearance of bromine color indicates unsaturation
• Alcohol


  Compound with a hydroxyl (-OH) group attached to a saturated carbon
• Phenol


  Compound with a hydroxyl (-OH) group attached to a benzene ring
• Alcohols


  • Can be classified as primary, secondary, or tertiary based on the number of carbons attached to the carbon with the -OH group
• Bordwell-Wellman test for alcohols and phenols

  1. Potassium dichromate (K2Cr2O7) in sulfuric acid oxidizes primary and secondary alcohols

  2. Oxidation produces color change from orange-yellow to green

  3. Phenol produces a brown color
• Lucas test for alcohols

  1. Converts alcohols to alkyl chlorides

  2. Primary alcohols show no reaction, secondary alcohols react more rapidly, tertiary alcohols react very rapidly
• Cr6+


  Chromic ion
• Cr3+


  Chromic ion with greenish color
• Cr6+ is reduced to Cr3+


  Produces a color change from orange yellow to green
• Color change


  Serves as an indicator for the presence of a primary or secondary alcohol
• Phenol


  Produces a brown color due to the production of benzoquinone
• Bordwell-Wellman Test Procedure


  1. Add 1 mL (20 drops) each of ethanol, isopropyl alcohol, tert-butyl alcohol, and 3% phenol solution in 4 different test tubes

  2. Add 1 mL of 0.1 M K2Cr2O7 solution to each test tube and 5 drops of concentrated sulfuric acid

  3. Shake each test tube and observe
• Lucas Test


  Used to distinguish among 1o, 2o, and 3o alcohols
• Lucas Reagent


  Mixture of concentrated hydrochloric acid and zinc chloride, which converts alcohols to the corresponding alkyl chlorides
• Lucas Test Procedure


  1. Add 1 mL (20 drops) each of ethanol, isopropyl alcohol, tert-butyl alcohol, and 3% phenol solution in 4 different test tubes

  2. Add 5 mL of Lucas reagent in each of four test tubes

  3. Shake the test tube to mix the reagents and notice whether the mixture gets cloudy

  4. For mixtures that do not get cloudy, wait for another 5-15 minutes, and observe
• Ferric Chloride Test


  A very specific test for the detection of phenols, where the -OH group of phenols forms a complex with ferric ion (Fe3+) which has a violet color
• Ferric Chloride Test Procedure

  1. Add 1 mL (20 drops) each of ethanol, isopropyl alcohol, tert-butyl alcohol, and 3% phenol solution in 4 different test tubes

  2. Add 1 drop of 2% ferric chloride solution in each of four test tubes
• Substances Tested


  • Ethanol
  • Isopropyl alcohol
  • Tert-butyl alcohol
  • Phenol
• Aldehydes


  Have at least one hydrogen bonded to the carbonyl carbon
• Ketones


  Have two carbon atoms bonded to the carbonyl carbon and no hydrogen
• 2,4-DNP Test


  Qualitative detection of carbonyl groups of aldehydes and ketones, indicated by the formation of 2,4-dinitrophenylhydrazone (yellow or orange-red precipitate)
• 2,4-DNP Test Procedure


  1. Add 0.5 mL (10 drops) each of acetaldehyde, acetone, and ethanol in 3 different test tubes

  2. Add 2 mL of 2,4-DNP reagent to the 3 solutions, shake vigorously, and observe for the formation of yellow-orange precipitate
• Tollen's Test


  Distinguishes between aldehydes and ketones, where aldehydes are oxidized to carboxylic acids and silver ion is reduced to elemental silver (silver mirror)
• Tollen's Test Procedure


  1. Add 10 drops each of acetaldehyde, acetone, and ethanol in 3 different test tubes

  2. Add 1 mL of Tollen's reagent to each of the test tubes and shake

  3. Heat the mixture in a water bath for 2 minutes and observe
• Substances Tested


  • Acetaldehyde
  • Acetone
  • Ethanol
• Carboxylic Acids


  Contain a carbonyl group and a hydroxyl (-OH) group attached to the same carbon
• Carboxyl Group (-COOH)


  Behaves as a weak acid
• Sodium Bicarbonate Test


  Carboxylic acids react with sodium bicarbonate solution producing carbon dioxide as evidence by a brisk effervescence with concomitant formation of carboxylate salt
• Sodium Bicarbonate Test Procedure


  1. Add 1 mL each of ethanol, acetaldehyde, and acetic acid on 3 different test tubes

  2. Add 1 mL of saturated sodium bicarbonate solution in each test tube and note any production of effervescence
• Substances Tested


  • Ethanol
  • Acetaldehyde
  • Acetic acid