Scale reaction yield

It was found that N-arylation reactions could be carried out in solventless conditions with all the six catalysts 222-227. However, with the presence of a little NMP (1 ml at a 5 mmol scale), reaction yields were higher in all cases. In the presence of NMP, the yields were 77-100%, wheareas for the neat case, the yields were 56-68% (Scheme 54). 

It has been found that the yield of product is generally higher when the reaction is performed on a smaller scale. Reactions carried out on approximately one third of the above scale have given yields of approximately 60ii. 

In this process the reduction of the ferric components of the scale is coupled to oxidation of the base metal, both reactions yielding ferrous species readily soluble in the acid. For magnetite the processes are as shown in equations 11.1 and 11.2. 

The commercially available chloramine-T trihydrate (TsNNaCl 3H20) could also be used directly as the oxidant, although slightly more dilute concentrations (0.2 m vs. 0.5 m) had to be employed to ensure comparable yields. The applicability of this trihydrate version to large-scale syntheses was demonstrated by the aziridination of cyclopentene on a 0,5 mol scale reaction, providing 6-tosylazabicyclo-[3.1.0]hexane in 80% isolated yield (Scheme 12.14). 

Metallic Sr can be prepared by methods similar to those used for Ca manufacture (sec 7.2.3.3.1). Thus thermal reduction of SrO using A1 and electrolysis of anhyd SrCU both yield pure Sr. Reduction of SrO by CH4 is also successful on a pilot scale. Metallic Ba is produced by thermal reduction of BaO by Al alternative reducing agents arc Na, Mg, Si and FeSi. Electrolysis of fused anhydrous halides (c.g., BaCK) is not applicable since the reaction yields a subhalide rather than the pure metal. 

The yield is typically 72-78 g. (90-100%). An excess of the reagent is not detrimental to the procedures in Parts B and C. The submitters have doubled the scale of this procedure with no change in the yield. For smaller-scale reactions the submitters recommend that the reagent be purchased from Alfa Division, Ventron Corporation. The checkers used the commercially available reagent successfully in one run, the material having been transferred to the reaction vessel in a dry box. 

It is important to realize that though the formulas for RME explicitly do not depend on reaction scale, x, since this variable cancels out in the computation, RME does in fact implicitly depend on reaction scale because reaction yields are scale dependent and RME in turn depends on reaction yield. Reaction yields are parameters whose magnitude cannot be predicted theoretically but must be verified experimentally. It does not always follow that a reported yield for a given reaction at a given scale will be the same at another scale. This requires experimental verification. Moreover, the direction of change as the scale is changed is also not predictable. AH of this means that when the same synthesis plan is run at a different scale, different reaction yields will be determined and hence different material efficiency performance values of RME, Em and mass of waste will be obtained. However, the... 

D-Saccharic acid 1,4-lactone (SAL 5-10 mM), a selective inhibitor of/3-glucuronidase [29], is often included in UGT reactions for improving yield. As /3-glucuronidases and UGTs have different optimal pH ranges, use of SAL in preparative-scale reactions may be avoided. 

The octacyclic dimer (+)-94 could be obtained in short order from the tetracyclic bromide (+)-93 via a Co(I)-mediated reductive dimerization protocol first implemented in our prior syntheses of (+)-chimonanthine (7), (+)-folicanthine (8), and (—)-calycanthine (9) [7]. Simple exposure of intermediate (+)-93 to tris (triphenylphosphine)cobalt(I) chloride [48] in acetone under anaerobic conditions rapidly afforded dimer (+)-94 in 46 % yield. While higher yields (52 % yield) could be obtained in tetrahydrofuran on small scale, performing the reaction in acetone reproducibly afforded higher yields on gram scales. Notably, the product was obtained in similar efficiency on multi-gram scale (43 % yield on 8-g scale)... 

Oxidation of benzene to phenol. This was attempted in the former U.S.S.R. and Japan on a pilot-plant scale. High yields were reported, but full-scale operation apparently was discontinued because of destruction of product by irradiation and the possibility of explosion in the reaction vessel. The latter danger can be controlled in the oxidation of halo-genated hydrocarbons such as trichloro- or tetrachloroethylenes, where a chain reaction leads to the formation of dichloro- or trichloro-acetic acid chlorides through the respective oxides. 

Reliable mechanistic conclusions require high intrazeolite yields that account for the majority of the substrate mass balance. This can be a challenge because of the small-scale reactions often conducted for mechanistic studies. In addition, rapid removal of the products from the zeolite, and/or low conversions to decrease residence time, is occasionally necessary because of the sensitivity of the reaction products to the zeolite environment.44,45 Intrazeolite products are generally recovered by extractive techniques from either the intact zeolite, or from a mixture formed after mild digestion of the zeolite. Polar solvents such as tetrahydrofuran or acetonitrile coupled with a continuous extraction technique is in particular an effective means to remove polar products with an affinity for the interior of the zeolite.44 Zeolite digestion with mineral acids, in order to liberate the products, must be conducted with care in order to prevent acid catalyzed product decomposition or reaction.46,47... 

The repeated treatment with lithium aluminum hydride was necessary to obtain complete reduction, since use of the reducing agent in manyfold excess and longer reaction times failed to accomplish complete reduction in one step. If the product was purified by distillation without the second reduction, the yield of pure diimine amounted to 9.1 g. (71%). The submitters report that on ten times the scale the yield with one reduction was 81 g. (64%). 

Over a three-year period at Rheinau, 1922-1925, Bergius and his assistants tested more than 200 different kinds of coal. Starting from a relatively small scale, they eventually hydrogenated coal in quantities as large as 1,000 kg (1 ton). A typical reaction run contained 100 kg of coal mixed with 40 kg of heavy oil, 5 kg of hydrogen gas, and 5 kg of ferric oxide to remove any sulfur present in the coal. The reaction yielded 20 kg of gas and about 128 kg of oil and solids. Distillation of the oil produced 20 kg of gasoline. (14)... 

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