Direct Synthesis reaction

Direct Synthesis reaction, 6 393-408 Discrete monomeric anions, halogenocuprate and halogenorgenate(I) ions, 37 2-6 Disilacyclohexadienes, 29 12-13 Disilacyclohexanes, 29 12 Disilanes... 

Direct Synthesis reaction of, 6 395 fluoride, 21 235, 237, 239, 249 homopolyatomic cations, 17 82 ion, stereochemistry, 2 40-41, 44-45 isocyanates, preparation, 9 158 properties, 9 157 isothiocyanates, properties, 9 177 mixed valence compounds of, 10 375-381 crystal structure of, 10 376 diffuse reflectance spectrum of, 10 380 structure of Pb," ion, 10 381 nuclear magnetic shielding, 22 224 organometallic compounds, 2 82, 88, 89 oxide, neutron diffraction studies on, 8 231-233... 

Fig. 1 (a) Schematic representation of the "indirect" anthraquinone process for the production of hydrogen peroxide using 2-alkyl-anthraquinone (1) and 2-all lhydroan-thraquinone (2). (b) Schematic representation of the direct synthesis of hydrogen peroxide from H2 and O2 (route A). Other reactions that decrease the selectivity of direct synthesis reaction are decomposition of hydrogen peroxide (route B) to water and hydrogenation of hydrogen peroxide (route C) to water. 

Due to an erroneous assignment of mass numbers and decay properties in the physics discovery experiment [37], it was believed that also in the chemistry experiments two different isotopes of Sg, namely Sg and Sg were observed [36, 38, 39]. After, the discovery of (the a-decay mother of Sg) it became evident, that all decay chains observed in the Sg chemistry experiments are due to Sg only [13, 14]. There is now conclusive evidence for two isomeric states in Sg [40]. Sg decays with a half-life of about 9 s preferentially to Rf , which further decays by a-particle emission and a half-life of 68 s to No, whereas Sg with a half-life of about 14 s decays preferentially to Rf, which undergoes spontaneous fission with a half-life of about 3 s [40, 41]. Both states are formed in the direct synthesis reaction Vm( Ne,5n) Sg . See detailed discussion in Sect. 6.5 and Fig. 31. 

Derivatives of polyisobutylene (6. in Figure 9.1) offer the advantage of control over the molecular weight of the polyisobutylene obtained by cationic polymerization of isobutylene. Condensation on maleic anhydride can be done directly either by thermal activation ( ene-synthesis reaction) (2.1), or by chlorinated polyisobutylene intermediates (2.2). The condensation of the PIBSA on polyethylene polyamines leads to succinimides. Note that one can obtain mono- or disuccinimides. The mono-succinimides are used as... 

Imino-4-thiazolines are far more basic than their isomeric 2-aminothiazoles (see Table VI-1). They react with most electrophDic centers through the exocyclic nitrogen and are easily acylated (37, 477, 706) and sulfonated (652). The reaction of 2-imino-3-methyi-4-thiazoline (378) with a-chloracetic anhydride yields 379 (Scheme 217) (707). This exclusive reactivity of the exocyclic nitrogen precludes the direct synthesis of endocyclic quaternary salts of 2-imino-4-thiazolines. although this class of compounds was prepared recently according to Scheme 218 (493). 

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. 

However, BASF developed a two-step process (25). After methyl formate [107-31-3] became available in satisfactory yields at high pressure and low temperatures, its conversion to formamide by reaction with ammonia gave a product of improved quaUty and yield in comparison with the earlier direct synthesis. 

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). 

Tris(2,4-pentanedionato)iron(III) [14024-18-1], Fe(C H202)3 or Fe(acac)3, forms mby red rhombic crystals that melt at 184°C. This high spin complex is obtained by reaction of iron(III) hydroxide and excess ligand. It is only slightly soluble in water, but is soluble in alcohol, acetone, chloroform, or benzene. The stmcture has a near-octahedral arrangement of the six oxygen atoms. Related complexes can be formed with other P-diketones by either direct synthesis or exchange of the diketone into Fe(acac)3. The complex is used as a catalyst in oxidation and polymerization reactions. 

Organoaluminum Compounds. Apphcation of aluminum compounds in organic chemistry came of age in the 1950s when the direct synthesis of trialkylalurninum compounds, particularly triethylalurninum and triisobutylalurninum from metallic aluminum, hydrogen, and the olefins ethylene and isobutylene, made available economic organoalurninum raw materials for a wide variety of chemical reactions (see a-BONDED alkyls and aryls). 

Asymmetric synthesis is a method for direct synthesis of optically active amino acids and finding efficient catalysts is a great target for researchers. Many exceUent reviews have been pubHshed (72). Asymmetric syntheses are classified as either enantioselective or diastereoselective reactions. Asymmetric hydrogenation has been appHed for practical manufacturing of l-DOPA and t-phenylalanine, but conventional methods have not been exceeded because of the short life of catalysts. An example of an enantio selective reaction, asymmetric hydrogenation of a-acetamidoacryHc acid derivatives, eg, Z-2-acetamidocinnamic acid [55065-02-6] (6), is shown below and in Table 4 (73). 

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). 

Other preparative methods include direct synthesis from the elements, reaction between gaseous hydrogen fluoride and titanium tetrachloride, and decomposition of barium hexafluorotitanate [31252-69-6] BaTiF, or ammonium, (NH 2TiFg. 

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. 

Titanium Silicides. The titanium—silicon system includes Ti Si, Ti Si, TiSi, and TiSi (154). Physical properties are summarized in Table 18. Direct synthesis by heating the elements in vacuo or in a protective atmosphere is possible. In the latter case, it is convenient to use titanium hydride instead of titanium metal. Other preparative methods include high temperature electrolysis of molten salt baths containing titanium dioxide and alkalifluorosiUcate (155) reaction of TiCl, SiCl, and H2 at ca 1150°C, using appropriate reactant quantities for both TiSi and TiSi2 (156) and, for Ti Si, reaction between titanium dioxide and calcium siUcide at ca 1200°C, followed by dissolution of excess lime and calcium siUcate in acetic acid. 

Numerous other methods are available for the preparation of amino derivatives, and these include direct synthesis (see Section 2.14.3.2) and more traditional transformations such as the Hofmann reaction. Aminopyrazine has been prepared from pyrazinamide (60G1807) and 2-aminoquinoxaline from the corresponding carboxamide (71JOC1158). The... 

Avery direct synthesis of certain lactones can be achieved by heating an alkene, a carboxylic acid, and the Mn(III) salt of the acid. Suggest a mechanism by which this reaction might proceed. 

Direct synthesis of HCl by the burning of hydrogen in chlorine is the favoured process when high-purity HCl is required. The reaction is highly exothermic ( 92kJ/mol HCl) and requires specially designed burners and absorption systems,... 

The three isomers constituting n-hutenes are 1-hutene, cis-2-hutene, and trans-2-hutene. This gas mixture is usually obtained from the olefinic C4 fraction of catalytic cracking and steam cracking processes after separation of isobutene (Chapter 2). The mixture of isomers may be used directly for reactions that are common for the three isomers and produce the same intermediates and hence the same products. Alternatively, the mixture may be separated into two streams, one constituted of 1-butene and the other of cis-and trans-2-butene mixture. Each stream produces specific chemicals. Approximately 70% of 1-butene is used as a comonomer with ethylene to produce linear low-density polyethylene (LLDPE). Another use of 1-butene is for the synthesis of butylene oxide. The rest is used with the 2-butenes to produce other chemicals. n-Butene could also be isomerized to isobutene. ... 

With OH and SH, the nucleophilic substitution of Cl has been reported. Thus, with NaOH, there is a report of successful nucleophilic substitution in 50% aq. acetone at room temperature to give the phenol complex in 36% yield. The latter is then spontaneously deprotonated to give the cyclohexadienyl complex (Eq. (24)). An identical reaction was carried out using NaSH in MeCN (50% yield) to give the thiophenol complex which was deprotonated [72] Eq. (25). These reactions would be especially valuable because direct synthesis of the phenol or thiophenol complexes from ferrocene is not possible due to the strong interaction between the heteroatom and A1C13 [11, 19]. Recent improvement and use of this reaction were achieved [88],... 

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 ... 

Schneider and Simon82 prepared / -ketosulfoxides 47a and 47b by sulfinylation of the dianions of the methyl acetoacetates 48a and 48b with sulfinate ester 19 followed by decarboxylation of the intermediate products (Scheme 2). Apparently this avoids racemiz-ation experienced by others in the direct synthesis of these compounds9. /J-Ketosulfoxides are also available from the reaction of the anion derived from methyl p-tolyl sulfoxide with esters (see Section II.E). They can also be obtained, in some cases, through the hydrolysis of a-sulfinylhydrazones whose synthesis is described below. Mention has already been made of the synthesis of 2-p-tolylsulfinylcycloalkanones such as 32. 

In many cases, these cyclic siloxanes have to be removed from the system by distillation or fractionation, in order to obtain pure products. On the other hand, cyclic siloxanes where n = 3 and n = 4 are the two most important monomers used in the commercial production of various siloxane polymers or oligomers via the so-called equilibration or redistribution reactions which will be discussed in detail in Sect. 2.4. Therefore, in modern silicone technology, aqueous hydrolysis of chloro-silanes is usually employed for the preparation of cyclic siloxane monomers 122> more than for the direct synthesis of the (Si—X) functional oligomers. Equilibration reactions are the method of choice for the synthesis of functionally terminated siloxane oligomers. 

---