Question

4. How could you make benzophenone from diphenylmethanol? Name both the reaction type and name the reagent(s) you would use?

Answer 1

`C_6H_5-CH(OH)C_6H_5stackrel[O]rarrC_6H_5C(=O)C_6H_5`

Explanation:

The is an oxidation reaction......in which the alcohol is oxidized to the ketone: `C(0)rarrC(+II)`

`C_6H_5CH(OH)C_6H_5stackrel[O]rarrC_6H_5C(=O)C_6H_5+2H^+ + 2e^(-)`

And something, maybe a high valent chromium salt is reduced down to take the electrons....

`Cr_2O_7^(2-) +14H^+ + 6e^(-) rarr 2Cr^(3+) + 7H_2O`

We add the half equation in such a way as to eliminate the electrons, i.e. take three of the former, and add them to one of the latter....

`3C_6H_5CH(OH)C_6H_5+Cr_2O_7^(2-) +14H^+ + 6e^(-)rarr3C_6H_5C(=O)C_6H_5+6H^+ + 6e^(-)+2Cr^(3+) + 7H_2O`

To give finally....

`3C_6H_5CH(OH)C_6H_5+Cr_2O_7^(2-) +8H^+ rarr2Cr^(3+)+3C_6H_5C(=O)C_6H_5 + 7H_2O`

And were we to perform the reaction, we would see the orange-red colour of the dichromate dissipate to give green `Cr^(3+)`...