Functional Group(s): 3°alcohols, some (but not all) 2 °alcohols, 1°,2°,3° allylic alcohols Known(s): 1-butanol (1 °); 2-butanol (2 °); tert-butyl alcohol (3°)
This test is for alcohols with six or fewer carbons. The unknown must be soluble in the reagent in order for this test to be valid.
Set up 4 small (12 X 75mm) test tubes in a test tube rack in the hood. Label the test tubes #1-4. Add ~5 mg of a solid unknown/known or 0.5ml of a liquid unknown/known to each tube. Use test tube #1 for the unknown and tubes # 2-4 for each of the known alcohols to be tested. Add 1ml of the Lucas reagent to tubes #1-4. Vortex the mixture for 2 minutes, then allow the tube to sit undisturbed for 3-5 minutes. Observe each tube for formation of an insoluble layer, emulsion or color change and compare the results of the unknown with the known compounds.
An insoluble layer, cloudiness, color change (red or orange) or an emulsion will form with 1°, 2°, 3° allylic, 3° alkyl and some 2 ° alcohols and constitutes a “positive” result. Students should compare his/her results of the
unknowns with the results for known compounds when trying to decide whether a result is positive or negative. Alkenes may give a “false” positive result due to HCl reacting with the alkene through an electrophlic addition. Phenols and enols will not give a positive result.
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