Benzoylpseudotropine, Tropacocaine HCL and solublility. Mystery.
We have acquired pseudotropine legally from a licensed chemical supplier in my country. I do not reside in Europe or North America , nor any English
speaking country so please note where we are this is legal and it is intended to be used as an anesthetic.The Benzoic Anhydride acquired from Sigma
and all that is required is a simple benzoylation using reflux for 4 hours and benzoylpseudotropine results (plus some unreacted pseudotropine).
According to Blount 1933 one then mixes in ether and hydrochloric acid to acquire the hydrochloric salt. The aqueous layer is separated out and if
necessary further HCL is added to precipitate the benzoylpseudotropine HCL salt. (a similar bezoylation is in a patent by Wolfe and Maeder 1925 in
which it is described in great detail).
The benzoylation was accomplished without difficulty and a white HCL salt was crystallized with a tested pH of 4. So far so good. Here is where the
rub comes. This benzoylpseudotropine HCL salt also is called tropacocaine HCL which is soluble in water. Subsequently, benzoylpseudotropine freebase
is not expected to be soluble in water (according the Lit.). However, on testing the benzoylpseudotropine HCL salt is NOT water soluble but the
freebase is. The benzoylpseudotropine HCL (tropacocaine HCL) is soluble in the various solvents the literature describes but with the exception of
water. We have recrystallized to increase pruity but without change. This has been repeated several times and we can find no errors in such a simple
process. A mystery. Seems the laws of chemistry and physics function different here.
Any ideas, comments or input would be appreciated.
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