2
$\begingroup$

I have read about the neutral FeCl3 test for Phenols, where a positive test is indicated by the colour of the solution which ranges from green to blue to violet. But which specific derivatives of phenol give a specific colour? Or is it random?

$\endgroup$
0

1 Answer 1

5
$\begingroup$

The color of the solution will depend on what substituent is attached to phenol. The following is an excerpt from an e-book:

Ferric Chloride Test: To 2 ml aqueous or alcoholic solution of compound, add 5-6 drops of freshly prepared neutral ferric chloride solution. Colored complexes of phenols are produced

\begin{array}{c|c} \mathbf{Compounds} & \mathbf{Color} \\\hline \text{phenol, resorcinol, o-cresol, p-cresol} & \text{Violet or blue}\\ \text{catechol} & \text{Green} \\ \text{hydroquinone} & \text{Violet or transient blue which changes to yellow on excess addition of FeCl3}\\ \text{pyrogallol} & \text{Blue rapidly changing to red}\end{array}

Aqueous solution of 1 and 2-naphthol however do not give any characteristic coloration but their alcoholic solution give violet-blue and green coloration respectively due to formation of dinaphthols.

Ref.: Systematic Lab Experiments in Organic Chemistry by Arun Sethi, New Age International, 2006

$\endgroup$
0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.