Author Topic: How you make those columns?  (Read 1053 times)

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halfapint

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How you make those columns?
« on: August 15, 2000, 06:30:00 AM »
Another activated silica column, for halogenation of phenylpropenes. An inquiry whether phenyl-iso-propenes might conceivably yield the 2-brominated derivative, with vapor-phase H2O2, in an identical column. Also, a proposed amination column for 2-halogenated phenylpropylamines.

Silica gel beads are baked in dry Sodium Carbonate for 2 hours at 380 degrees in a reducing atmosphere. This dries them, before they are baked with the halogen acid fumes, or NBS, or ethylenediamine hydriodide or hydrobromide as my guess, in a reducing atmosphere.

The beads are weighed, and packed loosely in a tared borosilicate column, terminated in a wad of stainless millings, or stainless pot scrubber. The column is held at 60 degrees in a stream of dry hydrogen for 1 hour, then the temperature is raised to 300 degrees and the acid gas of the halogen is introduced. The temperature is held at 300 degrees for 6 hours, in a stream of the acid gas with dry hydrogen. The column is cooled for 10 hours, then flushed with dry nitrogen for 12 hours at 60 degrees. The absorption of halide radicals is determined by weight. The ends of the column are sealed until use.

The vapor of the propenyl benzene are drawn through this column, held at 280 degrees, by pressure reduction from a condensor circulated with water at 50 degrees. The allyl benzene must have hydrogen peroxide vapor diluted with nitrogen introduced in its traverse of the halogenation column. The partially halogenated oil is held at room temperature for 10 hours, with aliquats removed for analysis. The oil is weighed, and the analysis to determine halogenation is performed. The desirable species is partially separated by fractional distillation, and the most desireable fraction is then drawn through a column which provides amination.

Silica beads are washed in an acetone in methanol suspension of 800 mg palladium chloride. Then the suspension is precipitated by rapidly raising the temperature to 300 degrees, and holding it at 300 degrees for 3 hours in a stream of hydrogen. The silica gel beads are packed in a column terminated with a 1 micron fiberglass filter fitted over a wad of stainless turnings or scouring pad. It is filled with formamide, which is boiled off, as the temperature is brought to 80 degrees. Then after being held at room temperature for 10 hours, the column is weighed, flushed with nitrogen and sealed.

This column is wrapped in aluminum foil for half its length, to give a temperature gradient. The lower end of the leads to a condensor. The product is fractionated by preparative column chromatography, in a solvent mixture of xylenol or DCM with increasing fractions of DMF or DMSO.

Example of asarone to 2-DMMDA. Example of anethole to PMA. Example p=methoxy allyl benzene to PMA ( I don't recall the Shulgin designation of the 4-methoxy amphetamine.) Example of safrole to MDA. Example of isosafrole to MDA.

OK, we are getting closer to the fabled continuous process, with the intent to make our pastime an industry. These columns are exhausted of their reagent by the reaction, but in some kind of futuristic science fiction dream they might be refreshed by the beads themselves being pumped through SS preparative columns. Pumping beads through the reaction zone in a cyclic process in which their reagents are renewed, who ever heard of such a silly thing? If people quote patent numbers at me, my heart will be broken, and I will give up chemistry and retire into a life of sin and misery at Lake Tahoe.

Half-a-Pint




Half a pint's a half a pound, a half the world around, around.