Ureas carboxylic acid amides

Isocyanates are quite reactive and they react with compounds which contain active hydrogen such as hydroxy, amine, carboxylic acids, amide, urea, etc. They can also undergo addition reaction ... 

The instability of primary nitramines in acidic solution means that the nitration of the parent amine with nitric acid or its mixtures is not a feasible route to these compounds. The hydrolysis of secondary nitramides is probably the single most important route to primary nitramines. Accordingly, primary nitramines are often prepared by an indirect four step route (1) acylation of a primary amine to an amide, (2) A-nitration to a secondary nitramide, (3) hydrolysis or ammonolysis with aqueous base and (4) subsequent acidification to release the free nitramine (Equation 5.17). Substrates used in these reactions include sulfonamides, carbamates (urethanes), ureas and carboxylic acid amides like acetamides and formamides etc. The nitration of amides and related compounds has been discussed in Section 5.5. 

Eutectics formed between quaternary ammonium salts and hydrogen bond donors (HBD) have potential windows that tend to be controlled by the stability of the carboxylic acid, amide or alcohol. In general the potential windows depend upon the pfCa of the HBD. Figure 4.13 shows the potential windows of eutectics formed between ChCl with ethylene glycol, urea and malonic acid. 

We selected a novel approach to design a masked or blocked aliphatic diisocyanate based on the fact that 1,3-disubstituted ureas undergo facile thermal dissociation to produce an isocyanate and an amine derivative. ) In the dissociation of mono acyl and aroyl ureas an isocyanate and a carboxylic acid amide is simultaneously produced. If the urea group is part of a cyclic system both fragments are parts of the same molecule. 

Carboxylic acid amides from carboxylic acids and ureas... 

If the imidoyl halides are generated from N,N -disubstituted carboxylic acid amides, or from tetrasubstituted ureas, only iminium salts are formed. 

The reactivity of different isocyanates varies widely, and the most reactive NCO groups can react with almost any compound that contains an active hydrogen [1, 2, 16]. The reactivity of the nucleophilic groups also varies primary amines are more reactive towards NCO than primary alcohols, followed by water, secondary and tertiary alcohols, other urethanes, carboxylic acids, and carboxylic acid amides in that order [16]. The isocyanate will, of course, react with the water present in the EPI formulation to form amines followed by further reactions producing urea and biuret. The mechanism of this reaction is shown in Pig. 5. As can be seen from the reaction mechanism CO2 is a byproduct of this reaction. 

Synthesis of enamines from carboxylic acid amides via 1-alkoxyazomethi-nium salts and amide acetals—Gyclic enamines via lactam acetals— Easy reaction of amide acetals with nucleophiles, urea acetals s. 16, 785 Enamines from carboxylic acid amides GHg + OG N < G G N <... 

N-Carbamylamidinium chlorides from ureas and carboxylic acid amides... 

Hexamethylolmelamine can further condense in the presence of an acid catalyst ether linkages can also form (see Urea Eormaldehyde ). A wide variety of resins can be obtained by careful selection of pH, reaction temperature, reactant ratio, amino monomer, and extent of condensation. Eiquid coating resins are prepared by reacting methanol or butanol with the initial methylolated products. These can be used to produce hard, solvent-resistant coatings by heating with a variety of hydroxy, carboxyl, and amide functional polymers to produce a cross-linked film. 

A/,0-Bis(trimethylsilyl)trifluoroacetamide. This reagent is suitable for the silylation of carboxylic acids, alcohols, phenols, amides, and ureas. It has the advantage over bis(trimethylsilyl)acetamide in that the byproducts are more volatile. 

In the course of this study, the authors determined /Lvalues for dibenzyl, methyl phenyl, methyl p-nitrophenyl, di-p-tolyl, di-isopropyl and tetramethylene sulphoxides and for diethyl, dipropyl and dibutyl sulphites. The /Lscales are applied to the various reactions or the spectral measurements. The /Lscales have been divided into either family-dependent (FD) types, which means two or more compounds can share the same /Lscale, family-independent (FI) types. Consequently, a variety of /Lscales are now available for various families of the bases, including 29 aldehydes and ketones, 17 carboxylic amides and ureas, 14 carboxylic acids esters, 4 acyl halides, 5 nitriles, 10 ethers, 16 phosphine oxides, 12 sulphinyl compounds, 15 pyridines and pyrimidines, 16 sp3 hybridized amines and 10 alcohols. The enthalpies of formation of the hydrogen bond of 4-fluorophenol with both sulphoxides and phosphine oxides and related derivatives fit the empirical equation 18, where the standard deviation is y = 0.983. Several averaged scales are shown in Table 1588. 

Isocyanates react with carboxylic acids to form amides, ureas, anhydrides, and carbon dioxide, depending on reaction conditions and the structure of the starting materials (Scheme 4.13). Aliphatic isocyanates more readily give amides. Aromatic isocyanates tend to react with carboxylic acids to first generate anhydrides and ureas, which at elevated temperatures (ca. 160°C) may further react to give amides. In practice, the isocyanate reaction with carboxylic acid is rarely utilized deliberately but can be an unwanted side reaction resulting from residual C02H functionality in polyester polyols. 

Nitrosation of primary amides results in deamination to produce carboxylic acid and nitrogen as products. Secondary amides, when nitrosated, give the corresponding nitrosamides in a reversible process [51]. In order to obtain good yields of the nitrosamides, it is best to add a base to remove the acid formed (Scheme 3.2). This reaction also occurs with ureas and carbamates. 

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