Effective molarity values, influencing

Pintre IC, Pierrefixe S, Hamilton A, Valderrey V, Bo C, BaUester P. Influence of the solvent and metal center on supramolecular chirahty induction with bisporphyrin tweezer receptors. Strong metal modulation of effective molarity values. Inorg Chem. 2012 51 4620-4635. 

Toluene alkylation with isopropyl alcohol was chosen as the test reaction as we can follow in a detail the effect of zeolite structural parameters on the toluene conversion, selectivity to cymenes, selectivity to para-cymene, and isopropyl/n-propyl ratio. It should be stressed that toluene/isopropyl alcohol molar ratio used in the feed was 9.6, which indicates the theoretical toluene conversion around 10.4 %. As you can see from Fig. 2 conversion of toluene over SSZ-33 after 15 min of T-O-S is 21 %, which is almost two times higher than the theoretical toluene conversion for alkylation reaction. The value of toluene conversion over SSZ-33 is influenced by a high rate of toluene disproportionation. About 50 % of toluene converted is transformed into benzene and xylenes. Toluene conversion over zeolites Beta and SSZ-35 is around 12 %, which is due to a much smaller contribution of toluene disproportionation to the overall toluene conversion. A slight increase in toluene conversion over ZSM-5 zeolite is connected with the fact that desorption and transport of products in toluene alkylation with isopropyl alcohol is the rate controlling step of this reaction [9]... 

The positive intercepts in Figure 7 show that post-gel(inelastic) loop formation is influenced by the same factors as pre-gel intramolecular reaction but is not determined solely by them. The important conclusion is that imperfections still occur in the limit of infinite reactant molar masses or very stiff chains (vb - ). They are a demonstration of a law-of-mass-action effect. Because they are intercepts in the limit vb - >, spatial correlations between reacting groups are absent and random reaction occurs. Intramolecular reaction occurs post-gel simply because of the unlimited number of groups per molecule in the gel fraction. The present values of p , (0.06 for f=3 and 0.03 for f=4 are derived from modulus measure- ments, assuming two junction points per lost per inelastic loop in f=3 networks and one junction point lost per loop in f=4 networks. 

A useful plot for identifying factors that are important is a Pareto chart. The graph in Fig. 1 shows the t-test values in the horizontal axis and also includes a vertical line to indicate the p value (an effect that exceeds the vertical line maybe considered significant). As observed in the Pareto chart, enzyme concentration is the most significant variable influencing monolaurin molar fraction. 

INFLUENCE OF SUBSTITUENTS ON BIOLOGICAL ACTIVITY. The following table illustrates effects of alterations in the sn-1 and sn-2 position of the PAF molecule on its ability to aggregate platelets. The numbers are the EC50 values in molarity, M. 

The reaction of XIII with EtOH in CHjCl EtOH, in 1 1 molar ratio, affords the ethoxy-derivative, [8,8-(q2-dppp)-9-(OEt)-nido-RhSB,H,] (XIV) behavior which is seen in the series of related compounds.12,111 This suggests that the boron vertex at the 9-position in Xm, and the related series of compounds, is prone to nucleophilic substitution reactions. XIV was characterized by NMR spectroscopy, mass spectrometry and X-ray diffraction. In contrast to the parent rhodathiaborane IV, and XIII, compound XIV does not feature fluxional behavior, even at 373 K implying, perhaps, AG values greater than 64 kjmol 1 for a possible dynamic process in XIV. The apparent large difference in the activation energy for the substituted versus the unsubstituted species may be due to either electronic or steric effects. The differences in the structures of XIII and XIV are minimal except for the B(9)-B(10) distances which differ by 0.083 A.4b This tends to suggest a role for this bond in the fluxional process although a purely steric influence of the substituent at the 9-position in XIV cannot be ruled out. 

If we compare the value (—61.7°) for a polymer prepared from 1 (calculated for the molar content of 1), still containing the template, with the value —448.9° for the template monomer 1, it becomes apparent that the molar optical rotation value is considerably decreased as a result of polymerisation. This can have several causes, one being the influence of the polymer matrix. Its effect can be determined by removing the optically active template la. If the boronic acids are then converted with ethylene glycol to the corresponding achiral ester, the polymer shows a positive molar rotation [M] °546 = -1- 110.0°. Apparently, in P-E the imprints generated in the polymer make a positive contribution to the optical rotation value. Measuring the optical rotation in the solid phase allows the... 

The pore shape influences the mass transfer rate and thus the efficiency of separation. The effective diameter of pores determines the range of separated molar masses. The pore size distribution and the pore volume are decisive for selectivity of separation (section 4.6.2.3). The pore sizes of commercially available gels cover the region necessary for separation of the wide spectrum of substances — from low molecular samples to very high polymers, colloidal particles and viruses. The mean values of pore diameters range from few nanometers to about 2.5 /xm. Gels with various pore sizes, but of the same type, can be combined within the same column. 

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