THF -> GBL patents etc.

[moo]

Its funny how these refs just keep on turning up. When is it going to end?

Patent SU523093

is essentially the method described in Elektrokhimiya (1978), 14(4), 627 (

Post 243610

(foxy2: "Re: Easy Oxidation of THF to GBL", Novel Discourse)), but the actual article gives no procedure, it's almost as good as the abstract   . I have translated the best (most volume-efficient, high-yielding) procedure for the electrochemical, or should I say electrocatalytic, oxidation of THF from the patent with my minimal russian language skills. There might be mistakes but it seems unlikely as it's not that complicated a procedure.

Example 4
In the cathode compartment of a thermostatically temperature-controller electrolytic cell with a ceramic divider is placed 50 mL of 1M aqueous KBr. In the anode compartment is placed 150 mL of 1M aqueous KBr and 5M THF (54 g). Platinum plates are used as electrodes. Current is passed for 26,8 hours with a current density of 0,15 A/cm² at the temperature of 52 °C. Analysis of the anolyte shows that during the eletrolysis 58 g (89% yield) of gamma-butyrolactone is formed with current efficiency of 90%.

Na₂SO₄ can also be used as a catholyte. From the other examples it is possible to calculate that the oxidation takes 4 equivalents of electrons, and that in the example 4 they used a current of 3 amperes with a 20 cm² cathode. They would've got higher yield had they passed current longer (90% current yield, 89% chemical yield see?). Also, the current density can be higher, but as any sane person would use platinum-plated metal electrodes the surface area isn't big deal. What do you think?

THF can also be oxidised electrochemically directly at the platinum anode, but the yields of GBL don't get much higher than 50%. Refs: Electrochimica Acta (1999), 44(19), 3295-3301; Elektrokhimiya (1979), 15(6), 819-22.

Patent US3074964

is more of a curiosity. It describes the oxidation with elemental chlorine or bromine in large scale. Using chlorine seems, not surprisingly, to cause more unwanted side-reactions than bromine and as the yields are similar to the hypochlorite oxidation one could theoretize that the methods also share the high amounts chlorinated byproducts, which could end up in the GHB .


Funnily enough tetrahydrofuran hydroperoxide (the bad stuff everyone is afraid of) decomposes to 2-tedrahydrofuranol, 4-hydroxybutanal and gamma-butyrolactone as an effect of ultraviolet light or heat (Journal of Organic Chemistry, 34, 1345-1348, (1969)). The hydroperoxide can also be decomposed to these compounds by metal ions, FeSO₄ for example (Bull. Chem. Soc. Japan, 36(5), 527-30 (1963)). Too bad this has very little preparative value, but if synthesizing GBL was considered a crime, there would be a lot of criminals!

[Osmium]

> Patent US3074964 is more of a curiosity. It describes the
> oxidation with elemental chlorine or bromine in large scale.

That's exactly the same that happens in the other patent too.
I'm not fat just horizontally disproportionate.

[moo]

But would you prefer elemental, as in from the bottle to the addition funnel, bromine over a small amount of bromine generated in situ? Yes, these reactions revolve around the same idea as the sodium bromate method, it's just the different variations I'm interested in. This isn't quite the Novel Discourse.