Comparison of Chemical Oxidation of Alkanes, Alkenes, and Alcohols on the Overhead Projector This overhead projector demonstration utilizes two classical chemical oxidants, permanganate and dichromste, to distinguish between alkanes, alkenes, and primary, secondary, and tertiary alcohols.
Oxldallon with Permanganate Comparison of a n Alkane, a n Alkene, and anAlcoho1. Four 30-mL beakerseontaining 2-3 mL of aqueous basic KMnO, (3 mL 6 M NaOH per 100 mL 0.001 M KMnOn) are placed on the stage of an overhead projector, preferably on write-on film with the names or formulasof the organiccompounds t o beexamined and the oxidant being used. A singlesquirt (about0.5 mL) of cyclohexane is added to the first beaker and alikeamount of eyclohexane and eyelohexanol to the second and third beakers, with the fourth beaker serving as a standard. Thebeakers are swirled t o aid in mixing these immiscible systems. In less than 20 s the cyclohexene-permanganate begins to discolor. Next the cyclohexanol-permanganate starts t o discolor. Within a minute both of these mixtures exhibit a pattern of color changes. After the initial darkening they become brownish in color and then a clear ereen as the ourole (MnO-) . . nermaneanate . . . is reduced to the ereen maneanate ion (hln0,--1 W ~ t hh a w prrmangnnatP the ryrlohermc renets maFkedly fastrr than the cyclohexanol~ I f the suiutions are nllourd tostand fur several minutes, a tme prer~pitate, t i hlnQ forms and thr mixture brcomrs tan in color.)
Oxldallon with Dlchromate ( ' I m p n r i v m b / o n Albanr,, on Alkene, a n d a n .ilcohol. Thesame procedure used above is repeated with 2-3 mL ufacid dichwnlotr wldtion I?'; K.Cr:O, with 20mLuf conr. H?SO,nddrd per IOOml.,. With thedichromatr only thecyclohexanol is c,ridiml, as is wiaent by i t 9 quickly discoloring and then turnmg hlue in about a niinutr. Standing for several more minutes produces no further change in any of the solutions
Comparison of Primary, Secondary, a n d Tertiary Alcohols. In each of three beakers is placed -2 mL of the orange dichromate solution used above. One squirt ( 4 . 5 mL) of ethanol is added to the diehromate in one beaker and a like amount of 2-orooanal and 2-methvl-2-nrooanol to the second and third beakers. In about 10-20 s a darkenine in color is . . . srrn in the lreakers rontninmg the rthanol and 2-prdpanol. In about :tU iboth solutions hecmne greeni~hm color, and after aluut a minute they chanze to hlur. INo color chnngr is obsrrved with the 2-methyl-2-propanul.(Thrs demonsrratim ran :ilrt, he dune in a Petri d ~ r h divided into quarters, using thr fourth quadrant as a reference standard.)
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Work done a t the Institute For Chemical Education a t University of Wisconsin, Madison. Kenneth E. Kolbl Bradley University Peoria, IL 61625
Volume 63
Number 11 November 1966
977
