SOAP FROM NUTMEG: AN INTEGRATED INTRODUCTORY ORGANIC CHEMISTRY LABORATORY EXPERIMENT
Marcio C.S. de Mattos and David E. Nicodem
Departamento de Química Orgânica, Instituto de Química,
Universidade Federal do Rio de Janeiro, Caixa Postal 68545
21945-970, Rio de Janeiro, Brazil
1) Written material used by students
2) Instructor notes
3) Chemical abstract registry number of chemicals
1) Written material used by students
Soaps are fatty acid alkali metal salts using linear aliphatic carboxylic acids of from ten to eighteen carbon atoms, the hydrocarbon chain being oil soluble and the carboxylate ion end water-soluble (1). The number of carbon atoms in the chain is very important for the utilization of a soap in cleaning: if it is less than ten carbon atoms, it will not cause emulsification of oil and if more than eighteen carbon atoms are present, the salt is not sufficiently soluble in water to form an adequate colloidal solution (1). Soaps are usually obtained by saponification (basic hydrolysis) of commercially available triglycerides (fats and oils) and their preparation dates back more than five thousand years (2). [pic]
Trimyristin (glyceryl trimyristate) is a triglyceride easily obtained from nutmeg by extraction with boiling ether (3).
Saponification of trimyristin produces the salt of myristic acid (CH3-(CH2)12-CO2Na) (3), which is a soap (4).
Tests with sodium myristate:
1. produces a clean solution when added to a suspension of vegetable oil in water; 2. reacts with calcium salts to produce insolube calcium myristate; 3. reacts with iron(III) salts to produce insolube iron myristate; acidification produces myristic acid, a fatty-acid.
Caution! Appropriate safety precautions must be observed (5). Solid NaOH and its strong solutions cause severe burns of the eyes and skin. HCl severely irritates the eyes and respiratory system; it also irritates the skin and may cause severe burns to both eyes and skin. Inhalation of diethyl ether vapor may cause drowsiness, dizziness, mental confusion, faintness and, in high concentration, unconsciousness. Ethanol and diethyl ether are highly flammable, keep flames away. Do not allow iodine to come in contact with skin and do not inhale its vapor, as it is corrosive and toxic.
Ground nutmeg (20.00 g) was heated under reflux (30 min) with diethyl ether (50 ml). After cooling to room temperature, the solid was decanted and washed with diethyl ether (20 ml). The combined liquid was distilled (simple distillation) to recover the solvent. The yellow solid residue (4.20 g, smell of nutmeg) was recrystallized from ethanol to produce 1.02 g (5% based on the mass of nutmeg) of trimyristin (white solid without smell), mp 56-58 oC, lit. 56.5 oC (6), Rf 0.50 (silica gel, hexane as eluent and detection by vapor of iodine).
Trimyristin (1.02 g), NaOH (0.20 g) and 95% ethanol (20 ml) were heated under reflux for 15 min, during which, a white volumous solid formed. After cooling to room temperature, water (20 ml) was added to the solid followed by a solution of 35% NaCl (40 ml). The solid (soap) was filtered in a Buchner funnel and washed with cold water (30 ml) to produce 0.85 g (80%) of sodium myristate.
Tests on sodium myristate
Sodium myristate (0.50 g) was dissolved in water (50 ml) and 5 ml of the solution added to each of 3 different test tubes. To one test tube was added a few drops of vegetable oil and a homogeneous solution was obtained after vigorous shaking. A solution of 1% FeCl3 was added to a second test tube and a dark precipitate of ferric myristate immediately appeared. A solution of 1% CaCl2 was added to the third test tube and a white precipitate of calcium myristate appeared.
A cooled solution (ice-bath) of sodium myristate (0.20 g)...
Cited: 1. Ikan, R. Natural Products. A Laboratory Guide, 2nd ed.; Academic Press: New York, 1991. pp 26-29.
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