Product yields/formation

Results obtained for two mixed plastics are summarized in Table 4. A balance exists between process temperature, plastics feed rate, and product yields (67). For example, lower temperatures increase wax formation due to incomplete depolymerization. Slower feed rates and increased residence times reduce wax formation and increase the yield of Hquids. The data summarized in Table 4 illustrate that the addition of PET to a HDPE PP PS mixture changes the performance of the Conrad process. Compared to the reference HDPE PP PS mixture, increased amounts of soHds ate formed. These are 95% terephthahc acid and 5% mono- and bis-hydroxyethyl esters. At higher temperatures, apparentiy enough water remains to promote decarboxylation. 

Benzyl Chloride. Benzyl chloride is manufactured by high temperature free-radical chlorination of toluene. The yield of benzyl chloride is maximized by use of excess toluene in the feed. More than half of the benzyl chloride produced is converted by butyl benzyl phthalate by reaction with monosodium butyl phthalate. The remainder is hydrolyzed to benzyl alcohol, which is converted to ahphatic esters for use in soaps, perfume, and davors. Benzyl salicylate is used as a sunscreen in lotions and creams. By-product benzal chloride can be converted to benzaldehyde, which is also produced directiy by oxidation of toluene and as a by-product during formation of benzoic acid. By-product ben zotrichl oride is not hydrolyzed to make benzoic acid but is allowed to react with benzoic acid to yield benzoyl chloride. 

In order to optimi2e selectivity for any particular system, unwanted by-products must be identified, and reaction conditions and catalyst components that are not favorable to their formation selected. For many reactions, selectivity is found to decrease as the activity increases. Thus sometimes it is necessary to accept a compromise in which some activity or selectivity or both is sacrificed so that the overall product yield or process economics is maximi2ed. 

In the chlorination of 2,4-dichlorophenol it has been found that traces of amine (23), onium salts (24), or triphenylphosphine oxide (25) are excellent catalysts to further chlorination by chlorine ia the ortho position with respect to the hydroxyl function. During chlorination (80°C, without solvent) these catalysts cause traces of 2,4,5-trichlorophenol ( 500 1000 ppm) to be transformed iato tetrachlorophenol. Thus these techniques leave no 2,4,5-trichlorophenol ia the final product, yielding a 2,4,6-trichlorophenol of outstanding quaUty. The possibiUty of chlorination usiag SO2CI2 ia the presence of Lewis catalysts has been discussed (26), but no mention is made of 2,4,5-trichlorophenol formation or content. 

The reaction rates and product yields of [2+2] cycloadditions are expectedly enhanced by electronic factors that favor radical formation. Olefins with geminal capto-dative substituents are especially efficient partners (equations 33 and 34) because of the synergistic effect of the electron acceptor (capto) with the electron donor (dative) substituents on radical stability [95]... 

A mixture of nitromethane and hexafluorobenzene, when thermolyzed at 550 °C, yields pentafluorotoluene and pentafluorophenol as major products- The formation of nitrosyl and mtryl fluondes is probably a dnving force in this transfor-madon [705] A potential general preparative route to various perfluorovmyl amines is pyrolytic decarboxylation of potassium salts of perfluoro-2-(dialky-... 

The first compound containing a telluroazepine ring, ll-(4-methylphenyl) dibenzo[d,/][l,4]telluroazepine 62 was obtained in 21% yield upon heating p-xylene solution of 9-azido-9-(4-methylphenyl)telluroxanthene at 130-140°C (87KGS279). Other products of this pyrolitic process are the imine 63 (32% yield) and phenanthridine 64 (21% yield). Formation of the latter implies extrusion of the tellurium atom from dibenzotelluroazepine 62. 

As you might have already gathered, the majority of industrial fermentations are batch processes. In closed batch systems, the growth medium is inoculated with cells and growth and product formation is allowed to proceed until the required amount of conversion has taken place. After harvesting the culture the vessel is cleaned, sterilised and filled with fresh medium prior to inoculation. For some processes, addition of all the feedstock prior to inoculation, as is done in closed batch fermentations, is undesirable and it is preferable to incrementally add the carbon source as the fermentation proceeds. Such a process is known as fed-batch culture and the approach is often used to extend the lifetime of batch cultures and thus product yields fed-batch cultures are considered further in Section 2.7.4. 

Product formation stoichiometry can be used to estimate the upper bounds for product yields in processes. A relatively simple example is the anaerobic fermentation of glucose by yeast. Here, carbon dioxide and ethanol are the only products. Modification of (E -3.9) then becomes ... 

Product yields may also be determined by magnetic measurements, as in the formation of ferrites [340], where kinetic data were obtained at reaction temperature. Quantitative applications of Mossbauer spectroscopy have also been described [326]. 

Product yield The yield of an irradiation process [39] can be defined as the amount of a particular reaction (cross-Unking, degradation, gas formation, formation of unsaturation, etc.) produced per 100 eV of absorbed energy. It is expressed as the G value, for example. 

The superiority of extractive hydrolysis over acid hydrolysis with respect to its productivity, yield, raw materials, and waste streams, for the transformation of drug intermediates (e.g. for Primaxin) in formate ester form to the corresponding alcohol, has been effectively demonstrated by King et al. (1985). They carried out the hydrolysis of the relevant formate ester with simultaneous extraction of the desired product from the undesired impurities by two-phase reaction/extraction with a base. 

Sodium alkylamides can also be generated in situ by reacting the amine with sodium naphthalene in THF [207, 208]. This procedure has been used for the condensation of secondary amines with different 1,3-dienes to give high yields of monoalky-lated products without formation of 1 2 telomers. In the case of primary amines, mixtures of mono- and dialkylated products are obtained together with unidentified... 

C(l)-Acylation of the l,4-dihydro-277-pyrazino[2,TA]quinazoline-3,6-diones 57 (R4 = Me, Rz = Bn, CH2-C6H4-MeO-/>) by treatment with LHDMS at — 78 °C followed by addition of acyl chlorides resulted in the as- 1-acyl derivatives with de > 95% in good yield. Formation of the air-product was explained by equilibration through the anion formed by deprotonation at C-l. The 1-acyl compounds were unstable and easily retransformed into the starting 57 <1998TA249>. 

The Cu(acac)2-promoted transformation 368 - 369 represents an intramolecular carbenoid insertion into the penicillin C5—S bond 347). The original report did not mention the low-yield formation of a second product to which the tricyclic structure 370 was assigned 348,349 >. In both 369 and 370, the original stereochemistry at C-5 of 368 has been inverted this is seen as a consequence of intramolecular nucleophilic a-face attack in a presumed azetidinium enolate intermediate. Attempts to realize a more flexible intermediate which then would have a chance to undergo p-face attack centered on the chain-extended diazoketone 371. Its catalytic decomposition led to the tricycle 372 exclusively, however, C7/N rather than C5/S insertion having taken place 349). 

One of the most recent developments in the field of Ni-catalyzed reactions of alkyl halides with organozinc derivatives is a study of Terao et al.411 They reported the use of three additives in the couplings 1,3-butadiene, N,N-bis(penta-2,4-dienyl)benzylamine 308a, and 2,2-bis(penta-2,4-dienyl)malonic acid dimethyl ester 308b. Addition of tetraene 308b to the reaction mixtures significantly increased the product yields (Scheme 157). The remarkable effect of these additives was explained by the formation of the bis-7r-allylic complex 309 as the key intermediate (Scheme 158). 

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