Grinding alkyl

Titanium trichloride is almost always prepared by the reduction of TiCl, most commonly by hydrogen. Other reduciag agents iaclude titanium, aluminum, and 2iac. Reduction begias at temperatures of ca 500°C and under these conditions a-TiCl is formed. The product is cooled quickly to below 450°C to avoid disproportionation to the di- and tetrachlorides. P-TiCl is prepared by the reduction of titanium tetrachloride with aluminum alkyls at low (80°C) temperatures whereas y-TiCl is formed if titanium tetrachloride reacts with aluminum alkyls at 150—200°C. At ca 250°C, the P-form converts to d. d-TiCl is made by prolonged grinding of the d- or y-forms. 

If the salt is lumpy, it is best to grind it into a fine powder in an agate mortar before washing it with the hexane. The fine powder is more easily washed and reacts more readily in the alkylation reaction. 

Aluminum powder Aluminum alkyls Grinding Heating Carboxylic acid chlorides Ethers Tertiary amines Tertiary phosphines Metal chlorides... 

The explanation for the dependence of the kinetics on order of addition was that of competitive equilibrium in the formation of active centres from metal alkyl, TiCls and monomer. The build-up of polymerization is much faster than in those systems which rise to a steady rate, and the maximum rate is at least double the steady rate. The formation of the active but short-lived species in the example shown in Fig. 10a has not been associated with a large change in surface area since the steady rate is unchanged. However, more intensive grinding gives rise to a greater increase in the initial acceleration and to higher steady rates. 

Titanium dichloride gives catalysts with aluminium alkyls but alone is inactive for ethylene polymerization unless mechanically ground. Grinding... 

The A-Boc group is rapidly removed on reaction with AlClj under microwave irradiation. Friedel-Crafts reactions. Both alkylation and acylation of arenes can be performed without solvent, by thoroughly grinding the reagents in an agate mortar and pestle at room temperature. (This technique is also applicable to Beckmann rearrangement of oximes in nearly quantitative yields. )... 

Natta catalyst. A stereospecific catalyst made from titanium chloride and aluminum alkyl or similar materials by a special process that includes grinding the materials together to produce an active catalyst surface. 

It is not clear at this stage if the increase in snrface area on grinding is due to the same mechanism responsible for the high surface area of the para-alkyIphenol material. The para-alkyl material is extremely brittle and crumbly in texture, and it seems possible that the reduced functionality of the material has created a system of small domains, which on carbonization behave like finely ground phenol-formaldehyde resin. 

The Friedel-Crafts alkylation of benzene with isopropyl bromide (8.10) was run by grinding the ingredients in an... 

Usually wasabi is prepared by grinding the raw stem at room temperature. The pungency of wasabi decreases rapidly as time passes. The yields of the alkyl isothiocyanates in the different pHs at 3°C are shown in Figure 2 (top). The distinguishing increase in the yields of the alkyl isothiocyanates (1, 3 and 4) took place within 1 minute as a result of the rapid hydrolysis of thioglucoside. The yields of (1, 3 and 4) increased in the order pH 4 [Pg.69]

The Mhssbauer data unambigously demonstrate the high spin state of the perfluoro-aryl porphyrins and are in good agreement with a low spin state of the alkyl(aryl) ferriporphyrins independent of the grinding (Table 5). 

Organic sulfides are oxidized to sulfonyl chlorides by iodosylbenzene, activated by crushing and grinding with a HCl-treated silica gel [522,523], Sulfides 431 with benzylic substituents, such as dibenzyl, alkyl benzyl and benzyl phenyl sulfides, are converted by this reaction into the corresponding sulfonyl chlorides 432 and 433 in high yields (Scheme 3.173). Other types of sulfides, such as dialkyl and alkyl phenyl sulfides, give sulfonyl chlorides only in moderate yield. 

Asymmetric carbon-carbon bond formation reaction under solvent-free conditions was carried out by Bolm et al. in ball mill [58]. Here, nickel(II) complex 206 was used as a chiral auxiliary in alkylation with various bromides (Schane 2.67). Optimized reaction conditions were set to increase the stereoselectivity however, the desired monoalkylated product 207 was often accompanied by small amount of doubly alkylated side product 208. Two different bases were used (NaOMe/MgS04 or CS2CO3) and grinding of nickel complex 206 with bromides for 30-75 min afforded alkylation products in moderate to high yields and with complete stereoselectivity (selected examples. Table 2.54). 

Another synthetic approach was used by Lamaty et al. in asymmetric alkylation of Schiff bases in ball mill (Scheme 2.69) [59]. In optimized reaction conditions, grinding of Schiff base of glycine ester 213 with organic halides in the presence of... 

Optimal reaction conditions were used for ball milling of stoichiometric amounts of variety of Boc-protected a-amino acid A-carboxyanhydrides (Boc-AA-NCA) 92 or Boc-protected a-amino acid A-hydroxysuccinimide esters (Boc-AA-OSu) 95 with a-amino acid alkyl ester salts (Schemes 3.26 and 3.27, Tables 3.9 and 3.10). In this way, di- to pentapeptides 97 and 100 were produced in high yield and environmentally benign manner. For some of the reactions, iBuOAc was used as a grinding auxiliary. Furthermore, it was established that no racemization could be observed as the diastereomeric excess of some products was checked and was found to be superior to 98%. After completion of Boc-AA-OSu reactions, mixture was milled for 5 min at 30 Hz with aqneous NaOH solution, diluted with EtOAc, and washed with sodium carbonate and dilnted acid. Pentapeptide Boc-Tyr(Bn)-Gly-Gly-Phe-Leu-OBn product obtained mechanochemically was successfully converted to Leu-enkephaUn by classical methods. 

Addition of amines to acetylene carboxylates 246 in ball mill was studied by Stolle and Thorwirth (Scheme 3.65) [44]. Employing solvent-free protocol in planetary ball mill in conjunction with quartz sand as inert grinding auxiliary, a number of enamines 247 were prepared in high yield (Table 3.33). No further catalysts or additives was required to accomplish reaction within 5 min. Obtained E/Z ratios vary with amine applied in the case of dicarboxylates, mainly the E-isomers have been identified. In contrast, reactions with propiolates and anilines yielded favorably the Z-isomer, whereas secondary alkyl amines furnished the E-isomer preferably. Simple stirring of DMAD and aniline in flask afforded only 80% conversion and chemoselectivity was lower (E/Zratio of 87 13) in comparison to ball milling. A common method for synthesis is the reaction in solvent, for which was found to have a strong influence on the E/Z ratio of the product, while this influence is not present in solvent-free milling. 

Hydrazones prepared mechanochemically by Lamaty (Section 3.5) were further Af-alkylated in ball mill [15]. Optimal reaction conditions were grinding of mixture... 

Chem. Descrip. Alkyl naphthalene sulfonate Uses Freeze/thaw stabilizer, pigment dispersant, grinding aid, wetting agent for paints/coatings... 

Natta catalyst nat-(i)ta- n. Any of several catalysts used in the stereospecific polymerization of olefins, e.g., ethylene and propylene, particularly a catalyst made from titanium chloride and aluminum alkyl or similar materials by a special process including grinding the materials together to produce an active catalytic surface. Odian GC (2004) Principles of polymerization. John Wiley and Sons Inc., New York. 

Activation of MgCl2 is required to afford high specific surface areas > 40 m /g. This can be achieved by means of mechanical grinding or by in situ preparation of MgClj, e.g. by chlorinating magnesium alkyls. 

---