Chemistry of thyroid hormones doesn't make sense?

[sameeralord]

Hello everyone,

This is a DIT molecule.

Now the book says there is a coupling reaction DIT + DIT ----> gives T4 molecule or tyroxine hormone

Now this is how T4 looks like

I don't understand how you can get this when there is a addition reaction between these two. Does coupling mean something else. Thank you

 

[pzona]

Coupling reactions are something entirely different from addition. Here's the basics:

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

 

[sameeralord]

Coupling reactions are something entirely different from addition. Here's the basics:

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

Thanks Somehow I totally forgot to check what coupling reaction mean, I just took it literally thinking it was an addition reaction.

 

[alxm]

This is almost certainly an enzyme-catalyzed reaction. I'm guessing that by 'coupling reaction' they just mean that it's occurring in a metalloenzyme.

Even without knowing the enzyme in question I'd expect as much, given the nature of the reaction. Substitution on a phenyl ring is not easy, and might even require forming a radical intermediate.