Name:_______________________________________ Course:____________________ Date:________________________________________Group No:__________________ Score: Activity 11 Properties of Alcohols and Phenols The general reactions of alcohols may be summarized into (a) Replacement reaction of the OH – group which may be involve either theH atom of the entire OH – group and (b) Oxidation of the carbon atom attached to the functional group – OH. SThe typical reactions are: CH3CH2OH + Na → C6H5OH + NaOH → R – OH + R – COOH R – OH + HX → CH3CH2O – Na + H2 Sodium ethoxide C6H5O – Na + H2O Sodium phenoxide → RCOOR + H2O Carboxylic ester RX + H2O Reactions of the second type are the oxidation of the different types of alcohols. RCH2OH Primary → RCHOHR’ → Secondary RCHO + 2H+ + 3eRCOR’ + 2H+ + 2e- Primary alcohols are oxidize to aldehyde and these in return are oxidized to acids with the same number of carbon atoms that of the original alcohols. Secondary alcohols are oxidized to ketones with about the same case as primary alcohols. Further oxidation proceeds very slow since this involves rupture of the carbon to carbon bond. Tertiary alcohols are resistant to oxidation as this involves the rupture of he carbon to carbon bond in alcohol. Ths oxidizing agents may be CuO, acid dichhromate or alkaline or acid permanganate. It is well to note that permanganate ion has an oxidation value of 5 in acid solution and 3 in neutral or alkaline solution. Acid solution: 5 RCH2OH + 2 MnO4- + 6H+ → 2 Mn 2+ + 5 RCOOH + 8 H2O colorless Alkaline or neutral sollution: 3 RCH2OH + 2 MnO4- → 3 RCOOH + MnO2 + 2OH- + 2 H2O brown This change in the permanganate ion on reduction gives rise to different colors, colorless if reduced to manganous Mn2+, brown if reduced to manganese dioxide MnO2 (Mn2+), green if manganate Mn6+. The hydroxyl group in phenol is an electron donating group and is a strong ortho-para director. The addition of bromine water to solution of phenol provides a convenient means of measuring the concentration of phenol. The reaction is quantitative and the precipitate is 2,4,6 – tribromophenol. Objectives: 1. Test the chemical properties of alcohols and phenols. 2 Differentiate the rate of primary, secondary and tertiary alcohols toward oxidation. 3. Compare the solubility and acidity of alcohols and phenols. Materials and Reagents: - Ethyl alcohol N – butyl alcohol Sec – butyl alcohol Tert – butyl alcohol Glycerol Benzyl alcohol Phenol NaOH pellets Acetyl chloride - - 10% solution FeCl2 Conc. HCl Anhydrous ZnCl2 10% NaHCO3 - 0.1% KMnO4 6N H2SO4 Saturated bromine water pH paper - Hot plate Grad cylinder 10 mL Calibrated medicine droppers Pipettes - Apparatus: - Test tubes Test tube rack Test tube holder Test tube brush Procedure: Caution: Phenol is corrosive! A. Structural Effects on the Solubility of Alcohols 1. With the aid of a calibrated dropper, place about 0.5 mL of the following in the separate test tubes properly labeled; Ethyl alcohol, N- butyl alcohol, Sec – butyl alcohol, tert – butyl alcohol, glycerol, benzyl alcohol and phenol. 2. Using your calibrated dropper, add 1.0 mL of water dropwise to the tube containing the alcohols described in Procedure 1, shaking the tube after each addition. 3. If cloudiness results, continue adding water 0.5 mL at a time with vigorous shaking, until a homogenous dispersion results. Note the total volume of water added and record results in the data table. 4. If no cloudiness results on adding up to 2.0 mL of water, the alcohol is completely soluble in water. 5. Reserve the aqueous dispersions of N – butyl alcohol, sec – butyl alcohol, tert – butyl alcohol, benzyl alcohol, benzyl alcohol and phenol for procedure B. B. Solubility of benzyl alcohol and phenol in NaOH solution: 1. Determine the solubility of benzyl alcohol and phenol in a NaOH solution, using procedures 1-6. C. Structural Effects on the Acidity of alcohols 1. Determine and compare the pH of the aqueous dispersions of benzyl alcohol and phenol. Record your observation. D. Ferric chloride test for enol structure 1. Add 10% ferric chloride solution to a very dilute solution of phenol, benzyl alcohol and phenol. Record your observation. E. Rate of reaction of Primary, Secondary and Tertiary Alcohols E.1. Rate of Oxidation in alkaline permanganate 1. Place 2 mL of 0.1% potassium permanganate solution and 2 drops of 6N NaOH solution in four separate test tubes. 2. Add 5 drops of each of the following: N – butyl alcohol, sec – butyl alcohol and tert – butyl alcohol into 3 separates test tubes. Leave the fourth tube as a control. 3. Shake the tubes for a few seconds and observe any color change. E.2. Rate of Oxidation in acid permanganate 1. Place 2 mL of 0.1% potassium permanganate solution and 2 drops of 6N H2So4 solution in four separate test tubes. 2. Add 5 drops of each of the following: N – butyl alcohol, sec – butyl alcohol, tert – butyl alcohol into 3 separate test tubes. Leave the fourth tube as a control. 3. Shake the tubes for a few seconds and note any color change.
