3- -1,1-dimethyl-urea Compound

Substituted urea compounds are often used as accelerators for DICY cure, specifically 3-(4-chlorophenyl)-l,l-dimethylurea (Monuron) and the 3-(3,4-dichlorophenyl) derivative (Diuron). This introduces a further level of complexity to the curing mechanism. Son and Weber 62) showed that Monuron could dissociate to form dimethyl-amine and 4-chlorophenylisocyanate and that this is facilitated by the reaction of DICY with the isocyanate to form a carbanilinoguanidine ... 

The first compound with significant herbicidal action discovered among aliphatic urea derivatives, N-butyl-N, N -dimethylurea (Searle, 1954) was never put on the market. Others, for example, halo and polyhaloallyl-N,N-dimethyl ureas, also have herbicidal properties, while symmetric tetraalkyl-ureas are inactive. 

EtNH)2C-S-Me, BF3]I has a shift of -I-18-5, slightly lower than the thiourea complex. The disproportionation of the syw-dimethyl-urea—boron trichloride complex was followed by means of the spectra, and the formation of the tetrachloroborate ion and of a cyclic compound was suggested from the shift data. 

The determination of the vapor pressure of various compounds was reviewed by Wiedemann (49). He discussed the determination of vapor pressure by TG techniques based on the Knudsen effusion method. The sample holder that was employed is illustrated in Chapter 3 (Figure 3.6). For some measurements, a Pyrex glass cell having a diameter of about 15 mm was used. Four organic compounds were studied p-chlorophenyl-AT. Af-dimethyl urea (Monuron. a herbicide), p-phenacetin, anthracene, and benzoic acid, in the temperature range of 250-400 K. The vapor-pressure curves of these compounds, in the range from 0 10 Torr, are shown in Figure 4.49. The AHs values calculated were Monuron. 27.4 p-phenacetin 27.6 anthracene, 20.1 and benzoic acid. 20.7 kcalmole. 

Dimethyl urea is prepared by the interaetion of urea and methylamine, whieh upon treatment with eyanoaeetie aeid yields an open-chain nitrite with the elimination of a molecule of water. This resulting compoimd undergoes cyclization in the presence of alkali. The cyclized compound on treatment with nitrous acid, followed by reduction, reaction with formic acid and subsequently with alkali gives rise to the formation of theophylline, which upon methylation finally yields caffeine. 

Urea-formaldehyde resins and similar aminoplast precondensates form the greatest proportion of all the resins used as additives. Mono-methylated and dimethylated ureas are used, as are the analogous condensation products of formaldehyde with melamine. The monomeric compounds penetrate into the intermicellar space in the cellulose in aqueous solution, and there harden with heat to form insoluble resins (cf. also Section 28.2). Since the formation of mono- and dimethylated urea is reversible, CH2O occurs in equilibrium. Formaldehyde can form methylene cross-link bridges between the individual chains. In addition, longer cross-linking... 

Under the same conditions the even more reactive compounds 1,6-dimethylnaphthalene, phenol, and wt-cresol were nitrated very rapidly by an autocatalytic process [nitrous acid being generated in the way already discussed ( 4.3.3)]. However, by adding urea to the solutions the autocatalytic reaction could be suppressed, and 1,6-dimethyl-naphthalene and phenol were found to be nitrated about 700 times faster than benzene. Again, the barrier of the encounter rate of reaction with nitronium ions was broken, and the occurrence of nitration by the special mechanism, via nitrosation, demonstrated. 

In the hands of Collie and Tickle in 1899 this reaction gave the first crystalline pyrylium salts. The salt character of the compounds was proved by conductivity measurements the basicity of 2,6-dimethylpyrone was found to be a little higher than that of urea. Basicities of other pyrones decrease in the order 2,6-dimethyl-> 2-phenyl-6-methyl-> 2,6-diphenylpyrone, paralleling the dipole moments. These hydroxypyrylium salts hydrolyze in water to pyrones. " The formation of salts of 2,6-dimethylpyrone with organic acids was investigated by Kendall,and with mineral acids by Cook. 11 ... 

See Chlorine Nitrogen compounds, or Dimethyl phosphoramidate Phosphorus pentachloride Urea Sodium chloride Nitrogen compounds See other irradiation decomposition incidents... 

Diphenylurea Crystallization. 1,3-hfsphenylurea (13) is the parent compound of a large family of derivatives, most of which do not cocrystallize with guest molecules (Etter et al. 1990). Even when put into solution with strong hydrogen bond acceptors, e.g., dimethyl sulfoxide (DMSO), triphenylphosphineoxide (TPPO) and tetrahydrofuran (THF), most diphenyl ureas crystallize with other molecules of the same kind in a connectivity pattern viewed as is shown below (14), instead of forming cocrystals (e.g., 15). 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

As we learned in Chapters 3 and 4, many inorganic compounds, not just ammonia, are derived from synthesis gas, made from methane by steam-reforming. In the top 50 this would include carbon dioxide, ammonia, nitric acid, ammonium nitrate, and urea. No further mention need be made of these important processes. We discussed MTBE in Chapter 7, Section 4, and Chapter 10, Section 9, since it is an important gasoline additive and C4 derivative. In Chapter 10, Section 6, we presented -butyraldehyde, made by the 0x0 process with propylene and synthesis gas, which is made from methane. In Chapter 11, Section 8, we discussed dimethyl terephthalate. Review these pertinent sections. That leaves only two chemicals, methanol and formaldehyde, as derivatives of methane that have not been discussed. We will take up the carbonylation of methanol to acetic acid, now the most important process for making this acid. Vinyl acetate is made from acetic... 

Series of various mono,- bi-, and poly-(thio)urea-functionalized (poly)saccha-rides have already been synthesized and studied for molecular recognition of, e.g., dimethyl and phenylphosphate as model compounds for monoanionic and polyanionic phosphate esters, respechvely [111]. Thiourea derivatives such as 195-197 were analyhcally identified to provide double hydrogen bonding mediated host-guest complexes of well-defined dimension and orientations and were also reported to serve as phosphate binders even in the hydrogen bonding environment of water (Figure 6.57) [111]. 

Thin-layer chromatography has also been employed in the analysis of these compounds (9,38,150,155-159). Several developers, such as silver nitrate (150,158), / -dimethyl-aminobenz-aldehyde (38), or UV light (150,158) have been used. Derivatization techniques, based on the urea hydrolysis to the corresponding aniline and ulterior reaction with dansyl chloride, have also been carried out (9,159). Moreover, TLC is frequently employed in studies of metabolization with radiolabeled compounds (155-157). 

One of the most reactive 1,3-dicarbonyl compounds used in the domino-Knoevenagel-hetero-Diels-Alder reaction is N,N-dimethyl barbituric acid 2. It has been shown that the fairly stable products can easily been transformed into other compounds via a reduction of the urea moiety with DIBAL-H [20]. Thus, reaction of 30 with DIBAL-H at 78 °C led to 46, which can be hydrolyzed to give 47 (Scheme 5.9). In a similar way, 48 was transformed into 50 via 49 and 12 to 52 via 51. The obtained compounds containing a lactone and an amide moiety can again be further transformed using DIBAL-H followed by an elimination. In this way, dihydropyran 54 is obtained from 50 via 53 as one example. 

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