[Nescafe]

Hi,

I recently read that in a typical click reaction you need an excess of sodium ascorbate, the reason being: "The active Cu(I) catalyst can be generated from Cu(I) salts or Cu(II) salts using sodium ascorbate as the reducing agent. Addition of a slight excess of sodium ascorbate prevents the formation of oxidative homocoupling products. Disproportionation of a Cu(II) salt in presence of a Cu wire can also be used to form active Cu(I)"

Does this mean to prevent the ascorbate from reacting with itself?

Thanks in advance,

Nescafe.

[clarkstill]

It doesn't mean dimerization of the ascorbate, it's to prevent glaser dimerization of the acetylene:

http://en.wikipedia.org/wiki/Glaser_coupling

[Nescafe]

very interesting, thanks, did not know that. But how does sodium asbcorbate do this, by maintaining a "reduced" enviroment?