Analysis of Alcohols and Phenols

• Alcohols are aliphatic compounds that contain the hydroxyl (-OH) group.

  Aromatic compounds with an -OH group attached to the ring are called phenols.

  Reactions of alcohols may be grouped into oxidation reactions, replacement of the -OH group or removal of an acidic hydrogen.
• Chromic Acid test

  Primary alcohols are readily oxidized to aldehydes which are oxidized further to carboxylic acids. Secondary alcohols are oxidized to ketones while tertiary alcohols do not undergo oxidation. When the oxidizing agent used is the yellow-orange colored K2Cr2O7, in the presence of sulfuric acid, the dichromate ion is reduced to the blue-green colored chromic ion.
• Lucas test

  This test involves the formation of water immiscible organic halide.

  The reaction is substitution by the SN1 mechanism so that the rate of formation of the alkyl halide varies with the stability of the potential carbonium ion intermediate.
• Sodium Metal test

  This is a test for the presence of easily replaceable hydrogens in alcohols. Although alcohols are weakly acidic to react appreciably with NaOH, they do react with active metals like sodium to liberate hydrogen gas.
• Reactions of phenols are those that involve the acidic hydrogen, the enol group and electrophilic substitution reactions at the ortho and para positions relative to the -OH group.
• Ferric Chloride test for enols

  Phenols form a colored complex with neutral ferric chloride. The color ranges from red to blue and purple. This is the characteristic reaction of compounds which contain the enol group, -C=C-ОН, а group in which the -OH is attached to a doubly bonded carbon atom.
• Test/Reactions of Alcohols

  Chromic Acid Test

  Lucas Test

  Sodium Metal Test
• Test/Reactions of Phenols

  Ferric Chloride Test

  Bromine Water Test

  Sodium Hydroxide Test
• Bromine Water test

  Phenols and other aromatic compounds with ring activating groups react with bromine to produce a bromo substituted product. The addition of red colored bromine to a solution of phenol produces a precipitate of tribromophenol which in turn is converted to a yellow tetrabromocyclohexadiene upon adding an excess of bromine water.
• Sodium Hydroxide test

  Phenols react with NaOH to form phenolate anions. These anions are sometimes colored and are easily oxidized to a brown colored product.
• APPARATUS

  Test tubes, droppers, cork/rubber stopper
• SAFETY PRECAUTION

  
  

  1. Sodium metal reacts violently with water, with the production, and possible explosive combustion, of hydrogen gas. Do not handle sodium metal with your bare fingers.

  2. Bromine is a hazardous chemical even in solution. Perform all operations involving bromine in a hood and wear rubber gloves. In case of skin contact, wash the affected area with warm water and soak in 0.6M NaS203 solution.

  
  

  3. Phenol, resorcinol and a-naphthol are harmful if ingested, inhaled or absorbed through the skin. In case of contact, flush with large amounts of water.
• Chromic acid test


  1. Place 10 drops of n-butyl alcohol, s-butyl alcohol, t-butyl alcohol in three separate test tubes

  2. Add 5 drops of 10% aqueous K2Cr207 and 5 drops of 6M H2SO4

  3. Observe any color change
• Lucas test


  1. Place 5 drops of n-butyl alcohol, s-butyl alcohol, t-butyl alcohol in three separate test tubes

  2. Add 20 drops of Lucas reagent to each test tube

  3. Stopper the tube and shake vigorously

  4. Let stand and note the time required for the appearance of immiscible layers
• Sodium Metal test

  1. Place 20 drops each of n-butyl alcohol, s-butyl alcohol and t-butyl alcohol in separate test tubes

  2. Add a small piece of sodium metal to each tube

  3. Take note of the time it takes for a gas to be evolved
• Ferric Chloride test for enol

  a.Add 10 drops each (or dissolve a crystal of the following test compounds to 1 mL of water in separate test tubes: phenol, resorcinol and a-naphthol.

  b. Add to each tube 5 drops of 1% FeCl solution. Take note of the color change.
• Bromine Water test

  a.Place 5 drops each of the following test compounds in separate test tubes: phenol, resorcinol and a-naphthol. (Caution: phenol is caustic.)

  b. Add bromine water dropwise with shaking until the red color is retained. Record your observation.