[Geosmitty]

I've been working on a problem and I seem to be stumped.  Here is how it is worded.  The compounds SO2 and SOCl2 undergo an exchange of radioactive labeled sulfur.  The exchange reaction is catalyzed by Cl- and by SbCl5.  Write mechanisms for both reactions.  
I think it has to do with acid/base metathesis, but have not found a solid mechanism showing exchange.  Any advice?

[AgG]

what sort of effect is Cl- going to have on SO2?

[Geosmitty]

That's where I am stuck.  I'm not sure.  The problem just says that it is catalyzed.  It seems like a simple problem, but I don't see how the radioactive S is exchanged.

[AgG]

Perhaps Cl- reacts with SO2 which then reacts w/ SOCl2?

[Geosmitty]

Thanks AgG.  I think I figured it out.  The instructor gave a better explanation of what he wanted.  I believe the reactions that cause the exchange of the marked S are:
       SCl2 + SO3 --> SO2 + SOCl2

       Then use theSO2 product to react with SbCl5 to get:

      SO2 +SbCl5 --> SOCl2 + SbCl3

It wasn't as "in depth" as I originally thought.