Isocyanates amines

Industrially, polyurethane flexible foam manufacturers combine a version of the carbamate-forming reaction and the amine—isocyanate reaction to provide both density reduction and elastic modulus increases. The overall scheme involves the reaction of one mole of water with one mole of isocyanate to produce a carbamic acid intermediate. The carbamic acid intermediate spontaneously loses carbon dioxide to yield a primary amine which reacts with a second mole of isocyanate to yield a substituted urea. 

Ammonia is used in the fibers and plastic industry as the source of nitrogen for the production of caprolactam, the monomer for nylon 6. Oxidation of propylene with ammonia gives acrylonitrile (qv), used for the manufacture of acryHc fibers, resins, and elastomers. Hexamethylenetetramine (HMTA), produced from ammonia and formaldehyde, is used in the manufacture of phenoHc thermosetting resins (see Phenolic resins). Toluene 2,4-cHisocyanate (TDI), employed in the production of polyurethane foam, indirectly consumes ammonia because nitric acid is a raw material in the TDI manufacturing process (see Amines Isocyanates). Urea, which is produced from ammonia, is used in the manufacture of urea—formaldehyde synthetic resins (see Amino resins). Melamine is produced by polymerization of dicyanodiamine and high pressure, high temperature pyrolysis of urea, both in the presence of ammonia (see Cyanamides). 

Open times of two-component urethanes can vary widely, depending on the level of catalyst. Reaction times can vary from 90 s to over 8 h. Dibutyltin dilaurate is the most common catalyst employed to catalyze the urethane reaction. This is normally added to the polyol side. A tertiary amine may also be added in small amounts. Tin catalysts do not catalyze the amine/isocyanate reaction very well. Acids, such as 2-ethyl hexanoic acid, may be employed to catalyze the amine/isocyanate reaction where needed. 

Ammonia and primary and secondary amines can be added to isocyanates to give substituted ureas. Isothiocyanates give thioureas. This is an excellent method for the preparation of ureas and thioureas, and these compounds are often used as derivatives for primary and secondary amines. Isocyanic acid (HNCO) also gives the reaction usually its salts (e.g., NaNCO) are used. Wohler s famous synthesis of urea involved the addition of ammonia to a salt of this acid. "... 

Kaldor [49 i, 55] demonstrated the advantages of applying solid-supported scavengers to the preparation of parallel arrays in a multi-step fashion. In these studies he examined the clean-up of multiple amine alkylation and acylation reactions using a variety of immobilized electrophilic and nucleophilic scavenger reagents including an amine, isocyanate, aldehyde and acid chloride (Tab. 2.1). 

De Mello et al. have constructed a so-called pSYNTAS (miniaturized synthesis and total analysis system). The system was used to perform an Ugi-type reaction to form several a-aminoacetamides from amines, isocyanates and formaldehyde in the presence of water (Scheme 25) [56-58]. The reported system consists of a glass/silicon nanoreactor [59] in connection to a TOF-MS for the real-time online analysis of the reaction stream. Reactions were conducted in the 600 nl volume chip under continuous flow of 20-2 pl/min flow rate. Reduced flow rates resulted in increased outputs. The analyzed outlet flow showed high yields of the desired products with small quantities of starting materials and intermediates (no exact yields were reported). 

The carbonylation of nitro arenes can lead to amines, isocyanates, carbamates, azo compounds, or ureas.80 Iron, ruthenium, rhodium, or palladium complexes have been used as catalysts. The carbonylation to give isocyanates, for example, involves the steps... 

In this section isocyanate-based polyurea foams ja-oduced by the reaction of the water-isocyanate or amine-isocyanate reactions will be described. Urea-formaldehyde foams will be excluded. The isocyanate-based urea-linkage formation is shown by the following model reactions ... 

Priester et al (141) have found a method of controlling the amine-isocyanate reaction by using substituted-amine-terminated polyethers, and they obtained high-resiliency polyurea foams by this method. Ashida et al (81) prepared low-density flexible polyurea foams by using a primary-amine-terminated polyether (Jefhunine D-2000, Texaco Chemical). 

This paper will describe the reactions of ketene aminals, 1, more highly activated electron-rich alkenes, with isocyanates to again afford amide products. We shall initially discuss the chemistry of the ketene aminal/isocyanate reaction, the preparation of these activated monomers and sane properties of solution-derived model "hard segments". 

Uracils can be prepared via reaction of primary amines with 3-ethoxyacryloyl isocyanate this method is particularly snitable for complex amines and has fonnd much use in recent years in the synthesis of, for example, carbocyclic nncleoside analogues as potential anti-viral agents. The immediate product of amine/isocyanate interaction can be cyclised under either acidic or basic conditions the method can also be applied to thionracil synthesis by the use of the corresponding isothiocyanate. 

ACETIC ACID, 1,3-DIMETHYLBUTYL ESTER (108-84-9) CgHi Oj Forms explosive mixture with air (flash point 113°F/45°C). Violent reaction with strong oxidizers. Incompatible with sulfuric acid, nitric acid, caustics, aliphatic amines, isocyanates. Will swell rubber and can dissolve certain coatings. 

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