# What is the chemical test for identification of benzophenone?

How to identify that a unknown compound is benzophenone?

My working:-

First I added 2,4- DNP(2,4-Dinitrophenyl hydrazine) to the compound. Yellow-orange crystals were formed which indicated presence of carbonyl group. Then, I added Tollen's reagent to the compound. It did not gave silver mirror which means aldehyde group is absent. So, it must be a ketone. So, I added m-Dinitrobenzene to the compound. It did not gave violet colour. Alternatively, I added Sodium nitroprusside to the compound. It did not gave a red color. Both the test is for confirmation of ketone compound.

I asked my teacher what is the unknown compound. He said that it is benzophenone. Also, in the practical book where all the chemical test were mentioned, it was mentioned as a side-note that benzophenone does not give the above mentioned test. So, what is the chemical test for identification of benzophenone?

• You can use iodoform test after Tollens test. – Aditya Dev Dec 22 '15 at 13:46
• @AdityaDev, benzophenone will not give iodoform test because it does not contain ketomethyl group ($\ce{-CH3CO}$). – Nilay Ghosh Feb 17 '16 at 7:12
• oops. i thought benzophenone was CH3-CO-ph. my mistake. – Aditya Dev Feb 17 '16 at 7:16

After identification of ketone, to identify benzophenone you need to find the range of melting point using melting point apparatus which you should get in range of $48.3\ \mathrm{^\circ C}$ to $50.6\ \mathrm{^\circ C}$.