More than Thousand Quantitative Wasteless Syntheses in 25 Reaction Types all Across Molecular Chemistry

Abstract

Gerd Kaupp

Wasteless preparative molecular and ionic solid-state reactions (gas-solid and solid-solid) proceed rapidly, with definite completion, at decreased activation energy omitting catalysis and waste-producing chromatographic workup, when properly executed. They are unbeatably specific, scalable up to industrial production, and obtain otherwise not available compounds also directly pure. The already available more than thousand 100% yield reactions in 25 reaction types (not counting subdivisions) across molecular chemistry are unfortunately mostly not cited, discussed, or compared in the inferior publications that depart from the solid-state and discredit the field by extremely long milling times, unnecessary catalysis, incomplete reactions, low selectivity, chromatographic workup, etc. Thus, the lack of temperature control and/or the retrogressive adding of “a little solvent” for synthetic milling leads to melt reactions at rapidly increasing temperature (most severe with planetary mills), losing all the benefits of the molecular solid-state. It is recapitulated how the solid-state can be retained with simple means, how Schmidt’s topochemical hypothesis (“forbidding” these unbeatable solid-state syntheses) is overcome, and what the physical reasons are for long range anisotropic molecular migrations along crystallographic channels, cleavage planes, or to voids. It is again shown that local melting is not required. Staying below the lowest eutectic temperature is essential. The basic reasons and technical requirement for the wealth of thermodynamic controlled solid-state reactions (as opposed to counter-thermodynamic mechanochemistry) are summarized in this mini review with a short selection from the striking synthetic advancements to remind the mostly disregarded top of sustainability also against some habits with the 12 commandments of “green chemistry”. These do not require avoiding unnecessary catalysis (on the contrary) or solvents (“green solvents” are also deactivating), or to completely avoid (instead of “decrease”) dangerous wastes by solvent consuming chromatographic workup, etc. This holds for particularly easy gas-solid productions and to solid-solid reactions, where mills are presently often misused heating/melting devices.

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