Theoretical maximum yield

The theoretical maximum yield from an entrainer sublimation process is the difference between the calculated sublimation rates corresponding to the conditions in the vaporisation and condensation stages. 

The enzymatic resolution of racemic substrates now is a well-established approach for the synthesis of single enantiomers [1, 2]. A representative example is the kinetic resoluhon of secondary alcohols via lipase-catalyzed transesterification for the preparation of enantiomericaUy enriched alcohols and esters [3], The enzymatic resolution in general is straightforward and satisfactory in terms of optical purity, but it has an intrinsic Hmitation in that the theoretical maximum yield of a desirable enantiomer cannot exceed 50%. Accordingly, additional processes such as isolation, racemization and recycling of unwanted isomers are required to obtain the desirable isomer in a higher yield (Scheme 1.1). 

The enzyme-catalyzed regio- and enantioselective reduction of a- and/or y-alkyl-substituted p,5-diketo ester derivatives would enable the simultaneous introduction of up to four stereogenic centers into the molecule by two consecutive reduction steps through dynamic kinetic resolution with a theoretical maximum yield of 100%. Although the dynamic kinetic resolution of a-substituted P-keto esters by chemical [14] or biocatalytic [15] reduction has proven broad applicability in stereoselective synthesis, the corresponding dynamic kinetic resolution of 2-substituted 1,3-diketones is rarely found in the literature [16]. 

The oil yields calculated from the analyses of the denormal products in Table III are plotted versus denormal product pour point in Figure 12. It is seen that 60% of the ii-paraffins must be removed before the pour point begins to decrease. Further extraction of the ti-paraffins to 88% of the theoretical (maximum) yield of 16.7 wt % n-paraffins then reduces the pour point from 294 K to 266 K. It appears that extraction of the remaining n-paraffins may lower the pour point to the desirable range of 261-255 K. It would be interesting to determine the effect of pour point depressants on the denormal oil product. 

Hydrogen and Acetate Yields as Percentage of Theoretical Maximum Yield and Maximum Hydrogen Production Rates... 

With regard to the theoretical maximum yield the relative molar yield was approx. 40% cf. K. Li, J. W. Frost, Biotechnol. Prog. 1999, 35, 876—883. 

From a theoretical perspective, pure cellulose contains 44.4 wt % carbon, so the maximum theoretical yield of charcoal, assuming all of the cellulosics can be carbonized, is 44.4 wt %. But with dry wood chars containing about 60 to 70 wt % fixed carbon (c/. Table 8.6), the theoretical maximum yields of charcoal including volatile matter and ash from wood feedstocks then correspond to about 65 to 75% by weight of the dry wood. It is evident that if... 

Ignoring the small amount of sugars used by the organisms for growth and maintenance, the theoretical maximum yield of fermentation ethanol from the pentose sugars is 51.14 wt % of the sugars fermented, the same as the theoretical maximum yield from the hexose sugars. 

These values are the theoretical maximum yields (same as glucose fermentation) that represent the maximum value obtainable. This can be achieved only if no sugar is assimilated to cell mass or oxidized through the TCA cycle. Of the total carbon contained in xylose, two-thirds goes to ethanol and the other one-third is lost as CO2. On a weight basis, the yield of ethanol from both xylose and glucose is approximately 51 %. 

However, a general disadvantage of kinetic resolution is that the theoretical maximum yield is limited to 50%. To overcome this restriction, racemisation techniques during the resolution have been developed. However, only in a few cases are the optical purities comparable to those obtained with oxynitrilases [121-123]. 

Taking into account that fructose loses three molecules of water during dehydration towards HMF, from 1 kg of fructose calculating the theoretical maximum yield only 0.7 kg of HMF could be obtained. When considering a favorable average molar yield of 70% for the dehydration, from 1 kg of fructose only 490 g of HMF could be obtained. 

Because the resolution with acylase gave a theoretical maximum yield of only 50% and required separation of the desired product from the unreacted enantiomer at the end of the reaction, we next tried to prepare the amino acid by reductive amination of the corresponding ketoacid, a process with a theoretical maximum yield of 100%. A variety of ketoacids can be converted to L-amino acids by treatment with ammonia, reduced nicotinamide adenine dinucleotide (NADH), and a suitable amino acid dehydrogenase. 2-Keto-6-hydroxyhexanoic acid (in equilibrium with its cyclic hemiketal form) was prepared by chemical synthesis starting from 4-chloro-l-butanol, which was... 

Theoretical Maximum Yield of Ozone from CO Oxidation... 

The theoretical maximum yield of 03 per CO + OH reaction would occur if NO, concentrations were sufficiently high that every H02 radical reacts with NO rather than with itself and termination of the chain by the OH + N02 reaction were neglected. The resulting mechanism would be... 

The theoretical maximum yield of O3 from CH4 oxidation would occur when NO levels are sufficiently high that the peroxy radicals H02 and CH302 react exclusively with NO and all the formaldehyde formed photolyzes by the radical path. The theoretical maximum yield is 4 03 molecules per each CH4 molecule oxidized ... 

Since the theoretical maximum yield of 03 from oxidation of CO is one more molecule of O3, the theoretical maximum yield of 03 from one CH4 molecule, all the way to C02 and H20, is... 

In an alternate process for the preparation of the C-13 paclitaxel side chain, the enantioselective enzymatic hydrolysis of racemic acetate ci5 -3-(acetyloxy)-4-phenyl-2-azetidinone 38 (Eignre 16.10B), to the corresponding (S)-alcohol 39 and the nnreacted desired (l )-acetate 38 was demonstrated [63] nsing lipase PS-30 from Pseudomonas cepacia (Amano International Enzyme Company) and BMS lipase (extracellnlar lipase derived from the fermentation of Pseudomonas sp. SC 13856). Reaction yields of more than 48% (theoretical maximnm yield 50%) with EEs greater than 99.5% were obtained for the (R)-38. BMS lipase and lipase PS-30 were immobilized on Accnrel polypropylene (PP), and the immobilized lipases were reused (10 cycles) without loss of enzyme activity, productivity, or the EE of the product (R)-38. The enzymatic process was scaled up to 250 L (2.5 kg substrate input) using immobilized BMS lipase and lipase PS-30. Prom each reaction batch, R-acetate 38 was isolated in 45 mol% yield (theoretical maximum yield 50%) and 99.5% EE. The (R)-acetate was chemically converted to (R)-alcohol 39. The C-13 paclitaxel side-chain synthon (2R,3S-37 or R-39) produced by either the reductive or resolution process could be coupled to bacattin III 34 after protection and deprotection to prepare paclitaxel by a semisynthetic process [64]. 

Take about 150 ml of potassium acid sulphate in, preferably, a tall narrow electrolytic beaker, and surround the beaker by an ice bath. Add about 0.1 gram of sodium fluoride if desired, though it is not necessary. Insert the electrodes, and pass a current of 1 to 1.5 amp for 2 hours. Six volts will be sufficient potential and will not require a rheostat, since the current can be adjusted by moving the cathode up and down. Keep a record of the time and the current, and maintain the current constant to 0.1 amp, so that you can calculate the number of coulombs passed and thence the theoretical maximum yield for the reaction 2HS07 SaOr + 2H+ + 2e. 

When the electrolysis is finished, calculate the number of coulombs passed and the theoretical maximum yield of perchlorate in moles. Measure out an equal number of moles of potassium choride, in the form of a saturated (4M) solution, and stir this into the warm electrolyte. A fine perchlorate precipitate appears. Cool in ice and filter the potassium perchlorate on a small Buchner funnel. Wash with a little ice-cold water and suck as dry as possible then dissolve the crude product (which contains some chlorate) in 150 ml of hot water and recrystallize, cooling to below 10° before filtering off the crystals. Wash the crystals wdth about 50 ml of ice-cold 50 per cent alcohol, suck dry, and dry in air. The yield of recrystallized salt, based on the current consumption, is about 60 per cent. 

The theoretical maximum yield would be obtained if only the reaction 2CH4 -> C2H2 + 3H2 occnrred, the reaction went to completion, and all the C2H2 formed were recovered in the product gas. This yield is (1 mol C2H2/2 mol CH4) = 0.500 mol C2H2/2 mol CH4. 

Several solvents at 10% (vol/vol) were evaluated in an attempt to improve the e.e. and yield. Solvents had significant effects on both the extent of hydrolysis and the e.e. of unreacted (S)-epoxide (12). Most solvents gave a lower e.e. product and slower reaction rate than that of reactions without any solvent supplement. Methyl tertiary-butyl ether gave a reaction yield of 45% (theoretical maximum yield 50%) and an e.e. of 99.9% for unreacted (5)-epoxide (12). 

In this particular example, therefore, the loss from the condenser exit gases is only 0.22kgh and the theoretical maximum yield is virtually 137kgh . This maximum yield will only be obtained, however, if the air is saturated with salicylic acid vapour at 150 °C, and saturation will only be approached if the air and salicylic acid are eontaeted for a sufficient period of time at the required temperature. A fluidized-bed vaporizer may allow these optimum conditions to be approached but if air is simply blown over bins or trays containing the solid, saturation will not be reaehed and the actual rate of sublimation will be less than that ealeulated. In some eases the degree of saturation achieved may be as low as 10 per eent of the possible value. 

FIGURE 6.2 Theoretical maximum yield of isoprene from glucose (soM Rue), and oxygen consumed per mol of isoprene made (dotted Une), as a function of the ratio of the two... 

The theoretically maximum yield of PI (78 2)% was easily obtained. Without H2 bubbles, the yield of PI would have been about 57% [153]. 

A calculation of theoretical yield was done for Klebsiella pneumoniae. Two separate cases for ATP generation were assumed, one for acetic acid production and the other for ethanol. The acetic acid pathway was calculated to have a five times higher PDO yield than the ethanol pathway, while the ethanol pathway gave higher biomass and ATP yields. The theoretical maximum yield when acetate and not... 

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