Oxidation of 1,3,5-Triphenylverdazyl

Demonstration Experiment on Video

Oxidation of 1,3,5-Triphenylverdazyl

Peter Keusch

German version

Chemicals:
1,3,5-triphenylverdazyl
bromine water 0.1 %
ethanol 96 %
tin chloride

1,3,5-triphenylverdazyl solution: 12.4 mg of triphenylverdazyl are dissolved in 1200 mL of ethanol 96 % .

Apparatus and glass wares:

3 conical measures, graduated, 500 mL

2 beakers 20 mL

beaker 1500 mL

10 mL measuring pipette (fully graduated 0.1 mL divisions)

pipette bulb

3 glass stirring rods

watch glass

spatula

Hazards and safety precautions:

Bromine is highly toxic if inhaled, ingested or comes in contact with the skin.

Bromine water is harmful if ingested or inhaled. Prolonged skin contact can cause burns. Eye irritant - lengthy contact will lead to eye damage. Sn(II) chloride is harmful if swallowed. Eye, skin and respiratory irritant.

Ethanol is highly flammable.

Safety glasses and protective gloves should be worn. Effective ventilation! Bromine water should be prepared in a fume hood!

Experimental procedure:

Three conical measures are each filled with 500 mL of 1,3,5-triphenylverdazyl solution. 8 mL of 0.1% bromine water are added to the solution in the conical measures 2 and 3. Afterwards the solution in the third glass is mixed with a small "spatula-tip" full of SnCl₂.

Results:

When bromine water is added to the conical measures 2 and 3, the green solutions turn red violet. After the addition of SnCl₂ to the solution in conical measure 3 immediately a decolorization occurs.

Video clip (Download RealPlayer .rm file)

Discussion:

· The green triphenylverdazyl (radical) is oxidized by bromine to the violet verdazylium ion (1).

· SnCl₂ reduces verdazylium ion to the colorless "Leucoverdazyl" (2).

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