Organosilicon synthesis of isocyanates: III

Yakabe et al. (1994) studied the fate of PMDI in water under two conditions — namely, vigorous stirring and static conditions, which simulate two scenarios of accidental spills of PMDI. PMDI used in experiments is complex and composed of 5–6 major constituents having 2–4 aromatic rings. When MDI comes into contact with water, it does not disperse readily, but forms globules or solid masses, which react at their surface. Under such heterogeneous conditions, the disappearance of PMDI shows zero-order kinetics. Production of water-soluble MDA increases gradually with time, and the MDA reaches a nearly constant concentration after 16 h; the amount of MDA formed is less than 0.5% of the nominal concentration of PMDI initially added, and the major products of PMDI breakdown are solid, insoluble polyureas. The polyureas formed from MDI appear to be stable to chemical attack, as would be expected from its insolubility and the stability of ureas.

Preparation of aromatic isocyanates US 3674827 A

Its derivatives are widely used in manufacturing dyes, aroma compounds and pharmaceuticals.

Synthesis of isocyanates of the furan, thiophene, …

After widespread drying process chlorine in accordance with the prior art also produce large quantities of dilute sulphuric acid, which must be either concentrated with high energy consumption in the distillation installation, or excluded from the process of chlorine. When the nitration of aromatic compounds sulfuric acid used as the catalyst, concentrated for re-use after the reaction at high energy cost. In this way lost large amounts of sulfuric acid on the way the product/waste water, which must be replaced with fresh sulfuric acid. Sulfuric acid contained in the wastewater of the process of obtaining chlorine and nitration process, must be neutralized by the addition of large quantities of sodium Selo and, before the waste water can be fed to the cleaning device.

Method for combined synthesis of isocyanates and chlorine

EFFECT: method enables to cut power consumption and consumption of neutralising agents during combined synthesis of aromatic isocyanates and chlorine owing to treatment of the merged stream of diluted sulphuric acid obtained in each of said processes.

The condensation with diisocyanates was successful for the aliphatic hexamethylene diisocyanate.

Studies on polynucleotides. CII. The use of aromatic isocyanates …

N2 - The combination of an aluminium(heteroscorpionate) complex and tetrabutylammonium bromide acts as a highly efficient catalyst system for the synthesis of oxazolidinones from epoxides and isocyanates. Twenty two complexes were tested derived from a range of bispyrazole ligands and containing 1-3 aluminium atoms per complex. The optimal catalyst was found to be a bimetallic complex of a thioacetamidate ligand. Under the optimal reaction conditions (80°C in toluene for 24h using 5mol% of both aluminium catalyst and tetrabutylammonium bromide co-catalyst), six epoxides were reacted with six aromatic isocyanates, giving 25 oxazolidinones in moderate to excellent yields showing broad substrate scope. The regiochemistry of the reaction (to produce 3,4- or 3,5-oxazolidinones) is controlled by the substrate with epoxide ring opening occurring preferentially at the less hindered end of the epoxide unless a substituent on the epoxide can stabilise a positive charge.

It is used as a reaction solvent for the preparation of aromatic sulfonic acids, pyridines, isocyanates and pharmaceuticals.

Process for the preparation of aromatic carbamates and isocyanates ..

The condensation with aliphatic mono-isocyanates was relatively straightforward, however phenyl isocyanates only resulted in low yields together with the formation of a cyclic hemi-aminal during purification.

Syntheses of isocyanates via amines and carbonyl …

Typical examples of suitable aliphatic diamines described in particular in European patent application EP-A 0289840, typical examples of suitable aliphatic triamines described in particular in European patent application EP-A 749958. These diamines suitable for receiving the corresponding diisocyanates or triisocyanate method according to the invention.

One-pot process for the synthesis of isocyanates, ..

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