By Direct Synthesis

The synthesis of 2-amino-5-chloromethyl-3-cyanopyrazine 1-oxide (529) from aminomalononitrile and chloromethyl hydroxyiminomethyl ketone, and of 2-amino-6-chloromethyl(and chloroalkyl)-3-cyanopyrazine 1-oxide (534) from aminomalononitrile and -chloro-a-hydroxyiminopropionaldehyde (prepared from the addition of nitrosyl chloride to acrolein) has been described in Section III.l. 

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The 2-anilinoselenazoles follow an analogous reaction path. The entry of bromine into the 5-position is in agreement as seen in Scheme 35. The 2-anilino-4-phenylselenazole gives a 5-bromo derivative by bromination. It is not identical with either of the bromo derivatives prepared by direct synthesis (Scheme 35) (99). 

Even though form amide was synthesized as early as 1863 by W. A. Hoffmann from ethyl formate [109-94-4] and ammonia, it only became accessible on a large scale, and thus iadustrially important, after development of high pressure production technology. In the 1990s, form amide is mainly manufactured either by direct synthesis from carbon monoxide and ammonia, or more importandy ia a two-stage process by reaction of methyl formate (from carbon monoxide and methanol) with ammonia. 

The estimated capacity of formamide was approximately 100,000 t/yr worldwide in 1990. In 1993, there are only three significant producers BASE in Germany is the leading manufacturer. Smaller quantities of formamide are produced in the former Czechoslovakia (Sokolov) and Japan (Nitto) by direct synthesis from carbon monoxide and ammonia. Most of the formamide produced is utilized direcdy by the manufacturers. The market price for formamide (ca 1993) is about 2.00/kg. 

Hafnium Boride. Hafnium diboride [12007-23-7] HfB2, is a gray crystalline soHd. It is usually prepared by the reaction of hafnium oxide with carbon and either boron oxide or boron carbide, but it can also be prepared from mixtures of hafnium tetrachloride, boron trichloride, and hydrogen above 2000°C, or by direct synthesis from the elements. Hafnium diboride is attacked by hydrofluoric acid but is resistant to nearly all other reagents at room temperature. Hafnium dodecaboride [32342-52-2] has been prepared by direct synthesis from the elements (56). 

Tantalum Nitrides. Tantalum nitride [12033-62-4] TaN, is produced by direct synthesis of the elements at 1100°C. Very pure TaN has been produced by spontaneous reaction of lithium amide, L1NH2, and TaCl ( )- The compound is often added to cermets in 3—18 wt %. Ta N [12033-94-2] is used as a red pigment in plastics and paints (78). 

Titanium Dibromide. Titanium dibromide [13873-04-5] a black crystalline soHd, density 4310 kg/m, mp 1025°C, has a cadmium iodide-type stmcture and is readily oxidized to trivalent titanium by water. Spontaneously flammable in air (142), it can be prepared by direct synthesis from the elements, by reaction of the tetrabromide with titanium, or by thermal decomposition of titanium tribromide. This last reaction must be carried out either at or below 400°C, because at higher temperatures the dibromide itself disproportionates. 

Pyrazinones and quinoxalinones both play important roles in the chemistry of pyrazines and quinoxalines respectively, in that they are usually available by direct synthesis and serve as important starting points for halo derivatives, which in turn lead to a range of substitution products (e.g. see Section 2.14.3.3). 

Cycloserine may be made by a fermentation process or by direct synthesis. The fermentation process is described in U.S. Patent 2,773,878. A fermentation medium containing the following proportions of ingredients was prepared ... 

It was first prepd by Milone Massa (Ref 2) by nitrating phenyldinitromethane with strong nitric acid (a i.52g/cc). Fieser et al (Ref 3) prepd it using two methods a) nitration of phenyldinitromethane and b) by direct synthesis using the Ponzio reaction in which an ethereal soln of m-nitrobenzaldoxime is added dropwise and under reflux to an ethereal soln of nitrogen peroxide ... 

The first compound of this series, CeSI, was reported by Carter (68) in 1961, and later discussed by Dagron (93). It was obtained by the reaction of iodine with cerium sulfide at 430 C, or by direct synthesis from the elements at 500°C. This was the start of a detailed investigation of this group of compounds mainly by Dagron and co-workers. The present situation is presented in Table VII. No scandium compounds are known thus far, and the same is true for selenium and tellurium halides of these elements. 

Since metals react with B only at > 700°C, and since alkali-metal borides are thermally unstable, the preparation of these borides by direct synthesis can be carried out at high T only with an excess of metal in sealed containers. 

The formation of alkali-metal borides by direct synthesis requires temperatures of 750-1200°C, depending on the variety of boron utilized and the specific metal. This leads to two important consequences ... 

The B-Na system includes two phases with different thermal stabilities. Either of these two borides can be obtained by direct synthesis on adjusting the alkali-metal pressure in the vapor phase. Thus, the preparation of NaB can be carried out in isothermal reactors at < 1100°C (p a = 45 X 10 N m" ) where the equilibrium... 

Sn -I- 2RI R2Snl2 (where R is the alkyl group and I is the anion). Methyltin stabilizers are produced by direct synthesis in the United States. Dibutyltin dichloride is manufactured from crude tetrabutyltin and tin tetrachloride and is usually catalysed with aluminium trichloride (Blunden Evans, 1989 Gaver, 1997 Thoonen et al, 2001). 

Fuels Chemicals Co. Ltd., China. Table 1 shows the comparisons of these three different processes for DME production by direct synthesis from synthesis gas. 

We have already referred to the Mo/Ru/S Chevrel phases and related catalysts which have long been under investigation for their oxygen reduction properties. Reeve et al. [19] evaluated the methanol tolerance, along with oxygen reduction activity, of a range of transition metal sulfide electrocatalysts, in a liquid-feed solid-polymer-electrolyte DMFC. The catalysts were prepared in high surface area by direct synthesis onto various surface-functionalized carbon blacks. The intrinsic... 

In addition to these monostannylene complexes, distannylene-metal complexes have also been prepared, either in competition with monosubstituted species (Eq. (21)) or by direct synthesis (Eq. (22)). 

Purely siliceous SBA-15 was synthesized according to previously published method [2]. Al incorporation in SBA-15 lattice was performed either by direct synthesis for which we have applied an already known method, but improved in some details [3], or by post-synthesis according to the reported procedure [4, 5], Modified SBA-15 are denoted as Al-SBA-15. 

The uptake values obtained for MEC adsorption are in good agreement with the results obtained for nitrogen sorption. As expected, the lower adsorption capacity belongs to SBA-15. After Al incorporation by direct-synthesis, the surface areas and pore volumes... 

The formation of such bonds during the heat treatment of dealuminated mordenite has also been suggested by Rubinshtein et al. (72-74), in some instances without the intermediate formation of SiOH groups. The hydrophobic nature of the zeolite also increases with progressive dealumination. Chen (71) has shown that aluminum-deficient mordenite zeolites with SiO /Al O ratios over 80 absorb little or no water at low pressure. These highly silicious zeolites are truly hydrophobic and in this respect are similar to highly silicious zeolites prepared by direct synthesis (e.g. ZSM-5) (75). 

The synthesis of chalcogenides such as those of the rare earth elements has traditionally been performed through the reaction of rare earth metals or oxides with a molten or vaporous chalcogen source in a high-temperature environment. Soft synthetic methods utilizing lower temperature conditions, such as hydrothermal or flux syntheses, can allow access also to thermodynamically metastable phases. Flux syntheses of R chalcogenides via an alkali poly-chalcogenide flux have been shown to be extremely versatile for the preparation of many new structures, some of which cannot be obtained by direct synthesis from the elements. 

Preparation of InAs by direct synthesis from the elements... 

Some fimctionalized materials have also been prepared by coprecipitation at low supersaturation. A perylene chromophore, for example, has been intercalated into LDH in an attempt to prepare stabihzed pigments [40]. Catalyt-ically active species have also been introduced into the interlayers of LDHs by direct synthesis, e.g. the intercalation of (PWi204o) or (SiWi204o) gives catalysts or catalyst precursors containing interlayer polyoxometalate anions [41]. Vein et al. reported the synthesis of Zr-containing LDH-Hke... 

The high silica zeolites with Si/Al of 10-100 can be generated by either thermochemical framework modification of hydrophilic zeolites or by direct synthesis. In... 

Fung P. C. and Shaw D. M. (1978). Na, Rb and T1 distributions between phlogopite and sani-dine by direct synthesis in a common vapour phase. Geochim. Cosmochim. Acta, 42 703-708. 

We then studied group 5 metals, especially tantalum-for which the laboratory already had great experience. Because of the studied reaction, alkyl or hydride-type compounds such as those developed in the laboratory could not be employed. Consequently, we became interested in alkoxo-type derivatives, either synthesized by reaction of the grafted complex with an alcohol or obtained by direct synthesis starting from an alkoxy-tantalum compound grafted on silica. In all cases, resulting complexes have been characterized by surface organometallic chemistry techniques, especially EXAFS and solid-state NMR (ID and 2D with C-labeled compounds). Indeed various compounds bonded by one, two or three surface bonds have been prepared and characterized. 

P6 Preparation of new materials by directed synthesis at molecular-length scales is the object of much current research in materials science, surface chemistry, and the emerging held of crystal engineering. (Erom Patrick, 2000)... 

Table 1 summarises the list of ferrisllicate zeolites that have been prepared to-date by direct synthesis in basic media. Ferrisllicate pentasll zeolites have also been synthesised hydrothermally in an acidic, fluoride-containing medium [18,19]. Such samples, however, sometimes,... 

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