Yield experimental

The theoretical yield is the maximum amount of product that can be obtained. In calculating the theoretical yield, it is assumed that the limiting reactant is 100% converted to product. In the real world, that is unlikely to happen. Some of the limiting reactant may be consumed in competing reactions. Some of the product may be lost in separating it from the reaction mixture. For these and other reasons, the experimental yield is ordinarily less than the theoretical yield. Put another way, the percent yield is expected to be less than 100% ... 

Experimental yield The amount of product actually obtained in a reaction, 65 Exponential notation, 643-645 Extensive property A property of a... 

Model GASPP was also used to correlate the results for polymerization at 20 atm, a 33% reduction in reactor pressure. Using the parameters for the most active BASF TiCil3, the model yields were 13% and 40% higher than the experimental yields. The 13% is... 

Under similar conditions, reactions between pyrrolidine derivatives 632 and MTAD proceed much more slowly and less cleanly with formation of a polymeric material. When the reaction is stopped before 50% conversion is reached, starting compound 632 is isolated as the main component (c. 40%) and compound 637 as a minor product (10-14%). Mechanistically, the most difficult problem lies in the fact that a reduction step has to be involved and no particular reduction agent is present. A proposed mechanism is shown in Scheme 103. The pathway includes a Cannizzaro-type hydride transfer between dipole 633 and product 634 (keto tautomer), resulting in the formation of the iminium derivative 635, which might be responsible for the polymeric material, and hydroxy derivative 636, the direct precursor of the final products 637. The low experimental yield of 637 could be explained by this mechanism <2003EJ01438>. 

The first subnanosecond experiments on the eh yield were performed at Toronto (Hunt et al., 1973 Wolff et al., 1973). These were followed by the subnanosecond work of Jonah et al. (1976) and the subpicosecond works of Migus et al. (1987) and of Lu et al. (1989). Summarizing, we may note the following (1) the initial (-100 ps) yield of the hydrated electron is 4.6 0.2, which, together with the yield of 0.8 for dry neutralization, gives the total ionization yield in liquid water as 5.4 (2) there is -17% decay of the eh yield at 3 ns, of which about half occurs at 700 ps and (3) there is a relatively fast decay of the yield between 1 and 10 ns. Of these, items (1) and (3) are consistent with the Schwarz form of the diffusion model, but item (2) is not. In the time scale of 0.1-10 ns, the experimental yield is consistently greater than the calculated value. The subpicosecond experiments corroborated this finding and determined the evolution of the absorption spectrum of the trapped electron as well. 

Clifford et ah (1987a,b) considered acid spurs (primary radicals H and OH) and computed the evolution of radical and molecular products by the master equation (ME) and IRT methods. Reasonable values were assumed for initial yields, diffusion constants, and rate constants, and a distribution of spur size was included. To be consistent with experimental yields at 100 ns, however, they found it necessary that the spur radius be small—for example, the radius of H distribution (standard deviation in a gaussian distribution) for a spur of one dissociation was only in the 0.4—0.75 nm range. Since in acid spurs H atoms inherit the distribution of eh, this is considered too low. This preliminary finding has later been revised in favor of spurs of much greater radius. 

To place this argument in perspective assume that both trans and cis adducts were equally likely. Then stereoselectivity would not be observed. All of the adducts to base atoms listed in Table XII for trans addition correspond to the sterically forbidden possibilities for cis addition and vice versa. Therefore, l(+) and i(-) isomers would bind equally well to N2(g). This does not occur. Rather the favored Sjj2 reaction over the Sjjl reaction weights trans addition heavily. Therefore, in our interpretation of experimental yields, the smaller yield of i(-) with N2(G) is predicted to be a cis addition product. The argument can be extended to demonstrate that trans l(-)-N6(A) and 06(G) and cis l(+)-N6(A) and 06(G) adducts should be expected. 

Haworth methylation of methyl /3-D-glucopyranoside and its 4-benzyl and 4-(tetrahydropyran-2-yl) ethers was investigated in connection with partial-methylation studies on cellulose.267 For the unsubstituted glycoside, the ratios of relative rate-constants k2 k3 k4 k were estimated to be 8 2 1 8, and, for the 4-ethers, it was found that ke> k2> k3 best agreements between calculated and experimental yields were found with the assumption that the rate constant for reaction at HO-3 is doubled when HO-2 is substituted. Later methylation studies,268 performed to low degrees of substitution, with analysis by gas-liquid chromatography, gave k2> k4> k3 for the reactivity... 

Intratrack Reactions. Earlier It was noted that chemical reactions could occur between the species before they could diffuse away from each other. In the case of Irradiated water, for example, this will result In a greater yield of the molecular species, H2 and H202, and a lower yield of the radical species, 0H, e and H. Additionally, the amount of solute present In a short track or blob Is limited and this may conceivably alter the course of reactions. In other respects, once the radlolytlc species diffuse away from their place of origin Into the bulk of the solution, they follow conventional solution behaviour. However, even In homogeneous solutions there will be differences attributable to the three track entitles because of differences In the yields of molecular products formed by reactions between primary radicals and the yields of radical species which are able to escape out of the tracks. Thus It Is possible to consider the overall yield of products as the sum of the Individual yields from the three track entitles, duly adjusted for the relative contributions from each, giving a weighted average equivalent to the observed experimental yields (10,19). 

In reaction (17), 67% of the boron in B3Ha is converted to Bi+Hio. This percent conversion agrees closely with experimental yields. It suggests that the preparative procedure is quantitative with respect to the theoretical amount of Bi+Hio which can be produced. This is by far the safest route to B Hj g available. It is also attractive because of the commercial availability of [N(CH2) ][B Hg] (Alfa Products, Danvers, MA 01923). 

In reaction (18) 63% of the boron in the Bi+Hg is converted to B5HH. Thus the experimental yield, 60%, is close to the theoretical limit of B5H11 available from (18). This is the safest route to... 

In reaction (19) 56% of the boron in the BgHm is converted to BioHm. The experimental yield of BioHm, 50%, suggests that the theoretical limit defined by Reaction (19) is approached. 

Fig. 32. (a) Comparison of random distribution calculated yields and (A) experimental yields of poly U photoproducts as functions... 

Fig. 33. Comparison of random distribution calculated yields and experimental yields of photoproducts formed by irradiation of poly U at 225 nm. The photoproduct yields are given as percentages of initial activity in the poly U (Pearson, Whillans, LeBlanc, and Johns138).

Table 1.1 clearly shows that the major pathway in the photochemistry of pentanal is the y-H transfer, followed by the C—C cleavage. The H detachment is only a minor pathway. A high percentage of trajectories are unreactive in this timescale. The relative yield of Norrish type I versus Norrish type II reaction from this table is 66% Norrish type II reaction and 34% Norrish type I reaction. This compares well to the observed experimental yield of 80% for Norrish type II reaction [16, 70]. 

A quantitative surface compositional analysis requires the comparison of the experimental yield of the individual clusters with corresponding yields obtained theoretically this may be done by numerical simulation of the complex collision process but the accuracy of the result cannot yet be ascertained. The accuracy of the compositional analysis depends to some extent on such poorly known factors as the interatomic potential, ionization cross-sections and quantum-mechanical corrections to a treatment based on classical trajectories. 

Fig. 24. Energy of the excited singlet state Si and triplet state T% of rhodamine 10) (Si = ID, Xi=3D ) and of the organic crystals (Si=1C, Ti =3C ) 74-78). The energy of the reduced dye-hole pair (2D. .. 2C+) is also shown as derived from the experimental yield curve (compare Figs. 31 and 32)...

Note that FO theory gives here fairly good results. According to 3-21G calculations (see Vedejs et al.S9), the major product is B when the larger LUMO coefficient is at carbon and A when it is at sulfur. An anomalous result occurs with Z = CN the two coefficients are equal, but the experimental yields are 4% for B and 70% for A. 

Fig. 4 Relationship between time, concentration, yield and ee in asymmetric autocatalysis of alkanol 12. a Enantiopure (> 99.5% ee) asymmetric autocatalyst was used. Experimental concentration of alkanol (filled circle), simulation (solid line), b Asymmetric autocatalyst with 59% ee was used. Experimental yield (open circle), experimental ee (filled circle)...

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