With urea

C10H16N2O3. White crystalline powder, m.p. I22-124°C. Prepared by condensing ethyl butylethylmalonate with urea. It is used as a sedative and hypnotic. 

C8H10N4O2. An alkaloid occurring in tea, coffee and guarana, from which it may be prepared by extraction, It is also manufactured by the methylation of theobromine and by the condensation of cyanoacetic acid with urea. Crystallizes with H2O or anhydrous from organic solvents. M.p. (anhydrous) 235"C, sublimes at 176 C. Odourless, and with a very bitter taste. Caffeine acts as a stimulant and diuretic, and is a constituent of cola drinks, tea and coffee. 

C12H12N2O3. White crystals, m.p. 174°C. Prepared by condensing the ethyl ester of phenylethylmalonic acid with urea. It is a more active hypnotic than barbitone. It and its sodium salt - soluble phenobarbitone - are used as sedatives and in treating epilepsy. 

Treatment with PCI5 gives phthalyl chloride reduction with zinc and ethanoic acid or NaOH gives phthalide. Fusion with urea gives phthalimide. 

Heating phthalic anhydride with urea (or ammonia) and a metallic salt. 

For physical processes, two examples are the elimination of normal paraffins from a mixture by their adsorption on 5 A molecular sieves or by their selective formation of solids with urea (clathrates)... 

Barbituric acid and 2-thiobarbituric acid are readily prepared by the condensation of diethylmalonate with urea and thiourea respectively, in the presence of sodium ethoxide. The use of substituted derivatives of urea and thiourea and of diethyl malonate will clearly lead to a wide range of barbituric and thiobarbituric acids having substituents in the i, 3, or 5 positions. 

Determine the melting point of pure cinnamic acid (133°) and pure urea (133°). Intimately mix approximately equal weights (ca. 01 g.) of the two finely-powdered compounds and determine the melting point a considerable depression of melting point will be observed. Obtain an unknown substance from the demonstrator and, by means of a mixed melting point determination, discover whether it is identical with urea or cinnamic acid. 

By heating the acid or its ammonium salt with urea ... 

The reaction commences at about 120° the carbamic acid formed decomposes immediately into carbon dioxide and ammonia. The latter may form the ammonium salt with unreacted acid the ammonium salt also reacts with urea at temperatures above 120° to yield the amide ... 

Hydantoins with one or two substituents in the 5-position may be obtained by heating cyanohydrins with ammonium carbonate or with urea. Thus ... 

An alternative method of preparation involves the interaction of methylamine hydrochloride with urea to give methylurea, followed by interaction with nitrous acid as above ... 

MO-Valeric acid is converted by phosphorus and bromine into a-bromo-tso-valeryl bromide the latter upon beating with urea gives bromural ... 

Ethyl malonate condenses with urea in the presence of sodium ethoxide to yield barbituric acid (malonylurea) ... 

Evidence from the viscosities, densities, refractive indices and measurements of the vapour pressure of these mixtures also supports the above conclusions. Acetyl nitrate has been prepared from a mixture of acetic anhydride and dinitrogen pentoxide, and characterised, showing that the equilibria discussed do lead to the formation of that compound. The initial reaction between nitric acid and acetic anhydride is rapid at room temperature nitric acid (0-05 mol 1 ) is reported to be converted into acetyl nitrate with a half-life of about i minute. This observation is consistent with the results of some preparative experiments, in which it was found that nitric acid could be precipitated quantitatively with urea from solutions of it in acetic anhydride at —10 °C, whereas similar solutions prepared at room temperature and cooled rapidly to — 10 °C yielded only a part of their nitric acid ( 5.3.2). The following equilibrium has been investigated in detail ... 

Certain features of the addition of acetyl nitrate to olefins in acetic anhydride may be relevant to the mechanism of aromatic nitration by this reagent. The rapid reaction results in predominantly cw-addition to yield a mixture of the y -nitro-acetate and y5-nitro-nitrate. The reaction was facilitated by the addition of sulphuric acid, in which case the 3rield of / -nitro-nitrate was reduced, whereas the addition of sodium nitrate favoured the formation of this compound over that of the acetate. As already mentioned ( 5.3. i), a solution of nitric acid (c. i 6 mol 1 ) in acetic anhydride prepared at — 10 °C would yield 95-97 % of the nitric acid by precipitation with urea, whereas from a similar solution prepared at 20-25 °C and cooled rapidly to —10 °C only 30% of the acid could be recovered. The difference between these values was attributed to the formation of acetyl nitrate. A solution prepared at room... 

Condensation of 2-phenyl-4-amino-5-benzoylthiazole with urea yields thiazolo[4.5-d]pyrimidines 127 (Scheme 84) (49). 

Diethyl malonate has uses other than m the synthesis of carboxylic acids One particu larly valuable application lies m the preparation of barbituric acid by nucleophilic acyl substitution with urea... 

These compounds are prepared m a manner analogous to that of barbituric acid itself Diethyl malonate is alkylated twice then treated with urea... 

Section 21 8 Alkylation of diethyl malonate followed by reaction with urea gives derivatives of barbituric acid called barbiturates, which are useful sleep promoting drugs... 

Furfural has been used as a component in many resin appHcations, most of them thermosetting. A comprehensive review of the patent Hterature describing these uses is beyond the scope of this review. A few, selected recent patents and journal articles have been referenced. Resins prepared from the condensation products of furfural with urea (47), formaldehyde (48), phenols (49,50), etc, modified by appropriate binders and fillers are described in the technical Hterature for earlier appHcations, see reference 1, which contains many references in an appendix. 

In 1987, Toray Industries, Inc., announced the development of a new process for making aromatic nitriles which reportedly halved the production cost, reduced waste treatment requirements, and reduced production time by more than two-thirds, compared with the vapor-phase process used by most producers. The process iavolves the reaction of ben2oic acid (or substituted ben2oic acid) with urea at 220—240°C ia the presence of a metallic catalyst (78). 

During the late 1970s, concerns were raised about levels of airborne formaldehyde in buildings resulting primarily from constmction using composite panels bonded with urea—formaldehyde resins and combined with energy-efficient building practices which reduced air losses. 

Both melamine—formaldehyde (MF) and resorcinol—formaldehyde (RF) foUowed the eadier developments of phenol—, and urea—formaldehyde. Melamine has a more complex stmcture than urea and is also more expensive. Melamine-base resins requite heat to cure, produce colorless gluelines, and are much more water-resistant than urea resins but stiU are not quite waterproof. Because of melamine s similarity to urea, it is often used in fairly small amounts with urea to produce melamine—urea—formaldehyde (MUF) resins. Thus, the improved characteristics of melamine can be combined with the economy of urea to provide an improved adhesive at a moderate increase in cost. The improvement is roughly proportional to the amount of melamine used the range of addition may be from 5 to 35%, with 5—10% most common. 

For most crops, other than rice, urea in the soil must first undergo hydrolysis to ammonia and then nitrification to nitrate before it can be absorbed by plant roots. One problem is that in relatively cool climates these processes are slow thus plants may be slow to respond to urea fertilization. Another problem, more likely in warmer climates, is that ammonia formed in the soil hydrolysis step may be lost as vapor. This problem is particularly likely when surface appHcation is used, but can be avoided by incorporation of the urea under the soil surface. Another problem that has been encountered with urea is phytotoxicity, the poisoning of seed by contact with the ammonia released during urea hydrolysis in the soil. Placement of urea away from the seed is a solution to this problem. In view of the growing popularity of urea, it appears that its favorable characteristics outweigh the extra care requited in its use. 

Phosphoric Acid-Based Systems for Cellulosics. Semidurable flame-retardant treatments for cotton (qv) or wood (qv) can be attained by phosphorylation of cellulose, preferably in the presence of a nitrogenous compound. Commercial leach-resistant flame-retardant treatments for wood have been developed based on a reaction product of phosphoric acid with urea—formaldehyde and dicyandiamide resins (59,60). 

LRC-100Finish. The use of LRC-100 flame retardant for 50/50 polyester cotton blends has been reported (144). It is a condensation product of tetrakis(hydroxymethyl)-phosphonium salt (THP salt) and A/A7,A7 -trimethylphosphoramide [6326-72-3] (TMPA). The precondensate is prepared by heating the THP salt and TMPA in a 2.3-to-l.0-mole ratio for one hour at 60—65°C. It is appUed in conjunction with urea and trimethylolmelamine in a pad-dry-cure oxidation wash procedure. Phosphoms contents of 3.5—4.0% are needed to enable blends to pass the FF 3-71 Test. 

A variety of a-amino acid derivatives, including the acids themselves, haUdes, esters, and amides can be transformed iato hydantoias by coadeasatioa with urea (67). a-Hydroxy acids and thek nitriles give a similar reaction (68) ... 

Channels in crystals of thiourea [62-56-6] (87) are comparable but, as a consequence of the larger size of the sulfur atom, have larger cross-sectional areas (0.7 nm) and can trap branched-chain, aUcychc, and other molecules of similar dimensions including polychlorinated hydrocarbons. But they do not include the straight-chain hydrocarbons that work so well with urea. 

Reactions. The chemical properties of cyanoacetates ate quite similar to those of the malonates. The carbonyl activity of the ester function is increased by the cyano group s tendency to withdraw electrons. Therefore, amidation with ammonia [7664-41-7] to cyanoacetamide [107-91-5] (55) or with urea to cyanoacetylurea [448-98-2] (56) proceeds very easily. An interesting reaction of cyanoacetic acid is the Knoevenagel condensation with aldehydes followed by decarboxylation which leads to substituted acrylonitriles (57) such as (29), or with ketones followed by decarboxylation with a shift of the double bond to give P,y-unsaturated nitriles (58) such as (30) when cyclohexanone [108-94-1] is used. 

Particle board and wood chip products have evolved from efforts to make profitable use of the large volumes of sawdust generated aimually. These products are used for floor undedayment and decorative laminates. Most particle board had been produced with urea—formaldehyde adhesive for interior use resin demand per board is high due to the high surface area requiring bonding. Nevertheless, substantial quantities of phenol—formaldehyde-bonded particle board are produced for water-resistant and low formaldehyde appHcations. 

Phthabc anhydride reacts with urea and metal diacetates to form metal phthalocyanines (qv). 

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