It is said that the concept of "sustainable chemistry" is a relatively new philosophy linked to the ecological movement of the 1990s, yet for clandestine chemists the ever-increasing control measures imposed upon the availability of precursors and common reagents over the last two decades have consequentially led to a raising of awareness with regards to a reduction in waste, use of energy and resources. The main focus of "sustainable clandestine chemistry" isn't so much the prevention of pollution an sich, although this is certainly not unimportant given the stigma the fine art and science of clandestine chemistry carries in the eyes of the general public, but rather the recycling of key intermediates which are often obtained in a riskful manner legally speaking..
It is in this light that I'm happily able to share with you the following anecdotal report, to illustrate this concept of sustainable clandestine chemistry:
A little over three years ago the Henry reaction was performed on a mixture of piperonal and 1-nitropropane (1.5 mol equiv) using 1 mol% methylamine acetate as catalyst in 3-phenylpropan-1-ol as the solvent, slightly acidified with glacial acetic acid. To be more precise a commercially available solution of 15% piperonal in 3-phenylpropan-1-ol was used as is. 3,4-Methylenedioxyphenyl-2-nitrobutene was isolated as a yellow precipitate in moderate yield.. The reddish-orange filtrate was saved and stored for more than 3 years at room temperature, this was about ~100ml.
After this period an equal volume of water was added, the mixture shaken and it was left for 24 hours, during which an additional crop of dirty-looking nitrobutene precipitated. This was filtered and washed with methanol to leave 5.7 grams. The organic phase was washed 3x with equal volumes of water. A saturated solution of bisulfite in 50% methanol (from potassium metabisulfite) was added to the organic phase with stirring and the mixture was stirred for 24 hours and filtered. The orange precipitate was washed with copious amounts of water, several times with methanol and twice with ether. A yellowish crystalline solid was obtained which proved to be the bisulfite addition compound of piperonal, it was dried for several days over CaCl2 and weighed around 10 grams.
The filtrate was again washed 4 times with equal volumes of water and dried over MgSO4, 5 ml of silicon oil was added, and it was distilled in vacuo at the fridge compressor (15mmHg, ~120°C). No forerun was observed and a single fraction consisting of 25 grams of a slightly yellowish-brown tinged oil was obtained, subsequently identified as 3-phenylpropan-1-ol. In the distilling flask was left a black tarry residu which instantly solidified after removing the heat source.
It is in this light that I'm happily able to share with you the following anecdotal report, to illustrate this concept of sustainable clandestine chemistry:
A little over three years ago the Henry reaction was performed on a mixture of piperonal and 1-nitropropane (1.5 mol equiv) using 1 mol% methylamine acetate as catalyst in 3-phenylpropan-1-ol as the solvent, slightly acidified with glacial acetic acid. To be more precise a commercially available solution of 15% piperonal in 3-phenylpropan-1-ol was used as is. 3,4-Methylenedioxyphenyl-2-nitrobutene was isolated as a yellow precipitate in moderate yield.. The reddish-orange filtrate was saved and stored for more than 3 years at room temperature, this was about ~100ml.
After this period an equal volume of water was added, the mixture shaken and it was left for 24 hours, during which an additional crop of dirty-looking nitrobutene precipitated. This was filtered and washed with methanol to leave 5.7 grams. The organic phase was washed 3x with equal volumes of water. A saturated solution of bisulfite in 50% methanol (from potassium metabisulfite) was added to the organic phase with stirring and the mixture was stirred for 24 hours and filtered. The orange precipitate was washed with copious amounts of water, several times with methanol and twice with ether. A yellowish crystalline solid was obtained which proved to be the bisulfite addition compound of piperonal, it was dried for several days over CaCl2 and weighed around 10 grams.
The filtrate was again washed 4 times with equal volumes of water and dried over MgSO4, 5 ml of silicon oil was added, and it was distilled in vacuo at the fridge compressor (15mmHg, ~120°C). No forerun was observed and a single fraction consisting of 25 grams of a slightly yellowish-brown tinged oil was obtained, subsequently identified as 3-phenylpropan-1-ol. In the distilling flask was left a black tarry residu which instantly solidified after removing the heat source.
GB1421052A.pdf
Normally I get an average of 30mmHg from a fridge compressor, but this one was salvaged from these large flat types you see in stores. The compressor is also continuously cooled with a strong fan when in operation.