Waste-free large-scale syntheses without auxiliaries for sustainable production omitting purifying workup

Organic Solid-State Reactions

“…For example, the cocrystal out of two benzoic acids per aniline is not a mixture of acid dimer and aniline (the common acid dimer substructures are absent), but four hydrogen bonds to the carboxyl oxygens of four benzoic acid units with distances of 2.783, 2.792, 2.797, and 2.981 Å start from the N-atom of all aniline units in the crystal as evidenced from the crystal structure [57]. Large-scale well-defined 1 : 1 complexations with very weak acids (such as the hydroxyls in glucose) and very weak bases (such as urea) also provide hydrogen-bond interactions in the cocrystal [25]. However, also the 2 : 1 cocrystal of caffeine and oxalic acid is a hydrogen bond complex [58].…”

“…It is obtained by stoichiometric milling of o-phenylenediamine with its dihydrochloride. The latter is obtained from o-phenylenediamine and gaseous HCl [25]. Both the mono-and the di-hydrochloride are undoubtedly salts.…”

“…As a rule, these cocrystals are quantitatively obtained without forming wastes, upon stoichiometric comilling of the components (Scheme 4). Organic salts such as, for example, (l)-(+)-sodium tartrate (as obtained large scale by milling of (l)-(+)-tartaric acid with stoichiometric sodium hydrogen carbonate) [25] are not considered cocrystals. It is also possible to obtain the disodium salt (with stoichiometric sodium carbonate).…”

“…below, irradiation of solid material as embedded in KBr pellets for preliminary detection of photoreactivity by IR analysis without efficient temperature control, IR, X-ray, and so on analysis to check for transformations to give cocrystals, application of reactive gases to solids at appropriate temperatures (−100 to >100 ∘ C), reactive cogrinding with pestle and mortar, ball milling at constant temperature (−78 to >100 ∘ C), and large-scale industrial milling at controlled temperatures and not too high mechanical impact. These techniques have been amply described in Refs [7,8,23,24] (laboratory scale), and [25] (large scale). This shall not be repeated here in detail, but it must be stressed here that too high impact and absence of temperature control as in planetary mills are counterproductive, because this often leads to extremely long milling times due to clogging (kneading instead of milling) and/or liquefaction (melt reaction), which is much easily reached by conventional heating.…”

Effects of Ultrasound and Microwaves on Selective Reduction: Catalyst Preparation and Reactions

“…Supported catalysts are key systems in sustainable chemical processes because they are readily reused and recycled, and generally have low toxicity. [3,4] Metal nanoparticles based heterogeneous catalysts have been widely investigated, due to their high activity. Nano-scale metal colloids and clusters have unique physical and chemical properties, [5] which are absent in the bulk phase, and find very important applications in many fields of academic and industrial interest, in particular heterogeneous catalysis.…”