Problem with fluorination during the salt decomposition of aniline-based fluoroboric acid diazotization; filtration was performed, but no toluene could be detected?
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6. Add fluorine-boron-acid, then perform back filtration; the filtrate is clear, but no toluene can be detected? Where has toluene gone? Is it all contained in the filter cake? Wash with cold water – does cold water remove the salts and acids, as well as fluorine and boron acids, thereby preventing the formation of chlorinated compounds during cracking? Can this portion of the wash water be used as the diluent water in the salt-acid dilution for the next batch? If it’s used, are there any downsides? Washed with ethanol, washed with methyl-tert-butyl ether. The filtrate after washing with methyl-tert-butyl ether is very dark in color; was this due to the removal of the conjugates from it?
It is best not to wash it with water, as this affects the yield. Moreover, this washing water should not be reused, as it contains fluoroborates; when salt formation occurs at high temperatures in the presence of water, these fluoroborates decompose to produce tar. MTBE washing may have removed the azo compounds.