Question:how does these two substances going?

[skyie]

I want to know:when i mixed the solution of resorcin and the solution of Ammonium Metavanadate under the temperation 80 degree centigrade. The colour goes from orange to green .How does they going? If i want to mix them ,but make them don't reaction.which substance should i add ?
Thanks a lot for the answers and this cool forum.

[RobJim]

Originally Posted by skyie

I want to know:when i mixed the solution of resorcin and the solution of Ammonium Metavanadate under the temperation 80 degree centigrade. The colour goes from orange to green .How does they going? If i want to mix them ,but make them don't reaction.which substance should i add ?
Thanks a lot for the answers and this cool forum.

Resorcin is a phenol ring meta- substituted with two hydroxy groups (1,3 benzenediol). Ammonium metavanadate is an ionic compound made up of an ammonium ion and the metavanadate ion (NH4(+)VO3(-)). The metavanadate ion is a vanadium atom bonded to three oxygens via two double bonds and a single bond.

See http://chemfinder.cambridgesoft.com/ for the structures of these molecules.

The OH groups will encourage negative charge to exist on the ortho- and para positions. This means the VO3(-) ion will tend to attack at the meta- positions. It will probably perform an addition-elimination reaction at one of the substituted carbons, displacing the -OH group and replacing it with the -OVO2 group. That's my guess anyway.

Because the -OVO2 group will add a lot of pi- conjugation to the molecule, it makes sense that the color would change.

To be able to put both substances in the same container at reaction temperature, you'd need to modify one of them so that it would no longer react. I'm not sure how you would do that. Maybe putting them in a basic solution, deprotonating the OH groups and making them hard to displace?

That's a guess anyway.

[skyie]

Thanks for your rational explanation.
I have check the book of Organic Chemistry just now,and find that resorin is difficult to be oxidated to quinone,but when take it into worm condition,will turn to CO2 and H2O.so,i think,the Ammonium metavanadate has the preference of oxidation.therefore, Ammonium metavanadate turn to V3+(see the colour),and resorin turn to CO2 and
H2O.is this explanation feasible?

Originally Posted by RobJim

Resorcin is a phenol ring meta- substituted with two hydroxy groups (1,3 benzenediol). Ammonium metavanadate is an ionic compound made up of an ammonium ion and the metavanadate ion (NH4(+)VO3(-)). The metavanadate ion is a vanadium atom bonded to three oxygens via two double bonds and a single bond.

See http://chemfinder.cambridgesoft.com/ for the structures of these molecules.

The OH groups will encourage negative charge to exist on the ortho- and para positions. This means the VO3(-) ion will tend to attack at the meta- positions. It will probably perform an addition-elimination reaction at one of the substituted carbons, displacing the -OH group and replacing it with the -OVO2 group. That's my guess anyway.

Because the -OVO2 group will add a lot of pi- conjugation to the molecule, it makes sense that the color would change.

To be able to put both substances in the same container at reaction temperature, you'd need to modify one of them so that it would no longer react. I'm not sure how you would do that. Maybe putting them in a basic solution, deprotonating the OH groups and making them hard to displace?

That's a guess anyway.

[charco]

Vanadium in the 5 oxidation state oxidises 1,4 dihydroxybenzene to quinone fairly easily, and also the 1,2 dihydroxy isomer. The reaction for 1,3 dihydroxybenzene (resorcinol) is more difficult as the resultant molecule is not conjugated over the whole structure as is quinone.

The colour change shows that the vanadium V is being reduced to a lower oxidations state as the resorcinol is being oxidised.

The question is the identity of the oxidation product...

There cannot be conjugation with two carbonyl groups at positions 1 and 3 on the ring (which is now not aromatic) and consequently there is complete degradation to CO2 and H2O.

As to how to mix them together without a reaction.... no idea - but why would you want to?