"It seems that GlycerOx it works as a strong acid when water appear."

Fernando,

I looked up the first ionization constant for oxalic acid and found it to be 1.25 versus 3.75 for formic acid.  So a pH reading of about 0.7 for either a solution of oxalic acid in water or a solution of the glycerol ester of oxalic acid in water is reasonable.  Making the glycerol mono ester is not going to change that pKa very much.  I would think that mostly you would make the ester on the center carbon with minor traces of ester on the terminal carbon.  From the standpoint of pKa it really should not make much difference, both are going to be reasonably strong acids with close to the same pKa.  If you really want to know the ratio between the two esters a simple proton NMR spectra would likely give you an answer close enough for government work.  Do you even know for sure you are making the ester in significant amounts?  Or are you just making mainly a solution of oxalic acid in glycerol?  Your temperature of only 55 deg C seems a bit low to rapidly
 make the ester, but more than enough to get the oxalic acid to dissolve.  Glycerin with acids such as sulfuric plus temps of more like 100 deg C will pull off that secondary hydroxyl and the cation will rapidly go to acrolein.  But, I do not think this happens to any significant extent at 55 deg C.

If free oxalic acid kills mites due to its acidity then I would think the ester would exhibit the same mode of action.  Both have enough acidity to damage tissues on any extended exposure.  It is just a real puzzle to me how that acidity would kill mites but not kill honey bees.  From what I know it seems oxalic acid is safer to bees than formic acid even thou oxalic acid is a considerably stronger acid than formic acid.  If the effect was simply due to acidity why does oxalic seem safer to bees?  Not that the mechanism of kill really matters.  What matters is the product kills mites and not bees.

Dick



" Any discovery made by the human mind can be explained in its essentials to the curious learner."  Professor Benjamin Schumacher talking about teaching quantum mechanics to non scientists.   "For every complex problem there is a solution which is simple, neat and wrong."  H. L. Mencken

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