Question

Discuss/explain each classification test: what they test for and what does a negative & positive result look like:

a) Bromine Test

b) Baeyer’s Test

c) Ferric Chloride Test

Answer 1

Bromine test : It is a qualitative test for unsaturation hydrocarbon present in a compound ie this test is for alkene and alkynes

Unsaturated compounds decolorise orange brown color of bromine water while saturated compounds can't.

Reaction : CH2 = CH2 - - - - - - > BrCH2 - CH2Br

b)

Baeyer' test: It is a qualitative test for unsaturation hydrocarbon too. In this reaction test compound having double bond is reacted with cold and dilute alkaline KMno4 to form vicinal diol.

CH2 = CH2 + KMnO4 - - - - - - - - - > OHCH2-CH2OH

In this reaction purple color of KMnO4 disappears

c)

FeCl3 test: This is a qualitative test for phenols. So in this reaction test a phenol is reacted with some drops of FeCl3 to form violet colored complex.

PhOH + FeCl3 ======> {Fe-[o-Ph]6}3-

Note : In negative test either no color change or a color different from the color in positive result will appear.