Commentary on boiling point of PPA produced from above experimental.
The BP of norpseudoephedrine base : 77.5-78°
The BP of norephedrine base: 100-101
The bp of the PPA from the above experimental came over at a range of 75-85 deg C. Perhaps its possible that the product is a mixure of norpseudoephedrine and norephedrine.
This would make sence because the carbonyl of the benzaldehyde is planar therefore attack would be 50/50 from either side. d,l(R,S)-alanine is used therefore the possible isomers of PPA are (R,S) (R,R),(S,R),(S,S) and:
(R,R),(S,S): norpseudoephedrine
(R,S),(S,R): norephedrine
At around T=3hrs their is a distinctive second phase (aqueous) produced in the reaction mixture. D is not sure of the reaction mechanism of the akabori reaction but if PPA is produced by an intermediate that requires reaction with the other phase then this could account for the low yield of the reaction. Especially since the phase separation occurred around the time the reaction was stopped.
Moreover SPISSHAK
Post 356191
(SPISSHAK: "Possible 'easy' PPA", Methods Discourse) reffered to a patent that used a variation of an akabori type rxn where alanine and benzaldehyde are supposed to give a small yield of PPA with the use of a phase transfer catalyst. Is the translated version of the original patent out there?
D is contemplating a low scale run with some HTAB (hexadecyl trimethyl ammonium bromide )as a PTC, killer stirring and a long reaction time (8hrs).
Any thoughts, anyone? Wouter, where art thou?
Driven