[minimal]

I have a question after checking out the wikipedia page about synthons(http://en.wikipedia.org/wiki/Synthon).  How do they determine that CN- is a synthetic equivalent for COOH-?  Just because there is a similar carbanion? I understand that they get there in two steps (first the NaCN and then adding H20), but that really doesn't make CN- a synthetic equivalent unless you add the part about adding H20 correct? Unless I'm missing something.  Wouldn't a synthetic equivalent be more like NaCOOH? instead of CN- and then H20?
Is there a good source on being able to identify synthetic equivalents anywhere?

[agrobert]

Synthetic equivalents have similar chemistry.  Which is why CN^- and COOH^- are considered equivalent.  It has to do with the environment of the carbon, the overall charge and the number/types of bonds made to heteroatoms.  Think about carbonyls, semiacetals and hemiacetals.  How are they considered equivalent. (reversibility???)

[Dan]

Wouldn't a synthetic equivalent be more like NaCOOH? instead of CN- and then H20?

No because NaCOOH cannot exist as it would react with itsself to form HCOONa (sodium formate) and thus will not be a carbon nucleophile.

[minimal]

Great, thanks for the info, do you guys know of some resources (online preferably, but all will do), where I can check out some more information on synthetic equivalents?

[agrobert]

http://www.amazon.com/Logic-Chemical-Synthesis-E-Corey/dp/0471115940