[duubs]

Does anyone know a place where I can find this value? My Reaction is

Salicylic acid + Acetic Andhydride  Acetylsalicylic Acid + Acetic Acid

[zsinger]

Well…….Measure concentrations, Do an ICE chart (Initial, Change, Equillibrium).  Boom…..theres your answer .  Being spoon fed answers will NOT help you in O-Chem.  Trust me, I had to re-LEARN (not memorize) a lot on my own!!!!!!!!!!

[TwistedConf]

How about an educated guess of what kind of number it might be?  Have you actually run the reaction?  Do you know anything about the reactions of anhydrides vs. acids and other derivatives? If you can answer these questions, an actual specific value is of little practical consequence.

[zsinger]

Yes, actually I have done this reaction.  I do not feel a need to flex my knowledge upon those who don't believe me.  I see these reactions take place in a University Lab with all reagents (When you work in a lab, naughty reagents that you can not get are available such as anhydrides).  The reason the govt. hates Acetic Anhydride, in particular, is because of its one step synthesis to heroin from Thebaine, as well as many other drugs.  Those extra "CH3" groups make drugs MUCH MUCH MUCH more fat soluble (I.E. able to pass blood brain barrier).  Look it up on google……I'm sure SOMEONE SOMEWHERE has done it.

[zsinger]

To Be Fair though……ASK SPIROCHETE…….I've never seen anybody with that amount of practical organic chemistry knowledge!!!!!  I thought I was good.

[spirochete]

I have no ideal what the exact Keq for this reaction is. I don't know where you'd find this specific information, maybe the CRC handbook of chemistry and physics?

We can use first principles to say whether the reaction will have a K>1 or less than one, however. Which side of the equation has a hotter electrophile? Does the mechanism make more sense written in the forward or reverse direction? The direction that involves booting out the best leaving group will be the direction that the equilibrium favors.

Also, common knowledge in organic chemistry shows that one side of the reaction includes an acetylating agent. That's a more specific way to think about it.