# Does anything like this covalent concerted bond exchange reaction exist?

I'm wondering if any reaction pathway exists (not involving enzymes) to do the following in aqueous solvent at temperatures < ~100°C:

To clarify, it's important however that the reaction is concerted, and that the W - X and Y - Z bonds are not broken until both the W-Y and X-Z bonds are formed. Bonds here must be covalent, but otherwise can be of any type. Any kind of catalyst can be used. Of course, it would be nice to know of an efficient reaction with minimally exotic conditions or reagents (i.e. it would be nice to avoid heavy metals for oxidative-addition type reactions), but I won't push my luck.

Does something like this exist?

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(Let's get unnecessarily technical) What exactly defines a 'covalent bond'? –  LordStryker May 12 '14 at 14:45
@LordStryker I hardly see why getting technical in this manner is unnecessary. I'm alright here with any bond that will be stable @ 50 C in aqueous solvent for, on order, a few days. By "covalent" perhaps I should have said "not hydrogen or Van der Waals bonded". –  user5475 May 12 '14 at 14:57
'Covalent' is a widely used term to generally describe a bond. I describe my question as being 'unnecessary' because, while it serves as a good reminder that nobody really knows what a covalent bond truly is (not a line drawn between two atoms, not an 'equal' sharing of a pair of electrons, etc.), it is rather silly to launch into a debate/discussion about it anytime someone wants to use 'covalent bonding' as a general description of something (whether here on SE or in the literature). That is all. –  LordStryker May 12 '14 at 15:18
@LordStryker Oh ok I see. Just saying though, I wouldn't want to rule out pseudo-ionic bonds between, for example, carbon and heavy metals (which are sort of a mix between covalent and ionic bonds). –  user5475 May 12 '14 at 15:23

$$\ce{W=X + Y=Z ->[\mathrm{cat}] W=Y + X=Z}$$ is known as olefin metathesis, achieved using Grubbs/Hoyveda/Fürstner catalysts.

Water-soluble Ru catalysts have been prepared in the Grubbs group (DOI).

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And we can learn a lot about that for free from Nobelprize.org. –  Martin - マーチン May 12 '14 at 14:19
@Klaus Warzecha Yup, there it is. Can this work in water at near pH ~ 7 and temperatures below ~100 C? I've looked the reaction up, but its not clear what the answer is since these are probably not optimal reaction conditions. –  user5475 May 12 '14 at 15:01
@Klaus Warzecha Actually, I just found a bunch of water-soluble catalysts for the reaction. –  user5475 May 12 '14 at 15:09
@Klaus Warzecha Thanks for the additional link! So, I keep seeing the reaction: CH3=C-R1 + R2-C=CH3 --> R1-C=C-R2 (releasing H2C=CH2 gas). Can those terminal methane groups be anything? –  user5475 May 12 '14 at 15:14
@Klaus Warzecha I should specify that by "anything" I mean, can those CH3 groups be CH2 - CH3 / etc. groups. –  user5475 May 12 '14 at 15:20

And the Wittig reaction works in a quite similar fashion:

Note that the Phosphorous Oxygen Ylide Bond may has mesomeric forms: $$\ce{-{}^{+}P-C^{-}-<->-P=C{}-}$$