Solution crowding

One physical consequence of the excluded volume effect is that solutions crowded with macromolecules tend to be highly nonideal. In an ideal solution, a particle has access to any region of the solution. This is clearly not true for the intracellular milieu (figure 6.22). As a result of excluded volume effects, the chemical activities of both large and small solutes are considerably higher than their actual concentrations (this is another aspect of the nonideality of the intracellular milieu). The nonideal characteristics of the intracellular solution favor a minimization of excluded volume, that is, they... 

Observed deviations from ideality are attributable to thiazole selfassociation. Such self-association is influenced by steric crowding as indicated by the behavior of methylthiazoles. The constants of selfassociation have been estimated for benzene solutions of thiazole (Kassoc = 3.2 at 5.5°C) and 5-methylthiazole at 6.5°C). 

It IS not possible to tell by inspection whether the a or p pyranose form of a par ticular carbohydrate predominates at equilibrium As just described the p pyranose form IS the major species present m an aqueous solution of d glucose whereas the a pyranose form predominates m a solution of d mannose (Problem 25 8) The relative abundance of a and p pyranose forms m solution depends on two factors The first is solvation of the anomeric hydroxyl group An equatorial OH is less crowded and better solvated by water than an axial one This effect stabilizes the p pyranose form m aqueous solution The other factor called the anomeric effect, involves an electronic interaction between the nng oxygen and the anomeric substituent and preferentially stabilizes the axial OH of the a pyranose form Because the two effects operate m different directions but are com parable m magnitude m aqueous solution the a pyranose form is more abundant for some carbohydrates and the p pyranose form for others... 

A mechanistic study6 5 of the reaction of sulphoxides with the sodium salt of 1 -methyl-1 -phenylethyl hydroperoxide in benzene-alcohol solutions at room temperature showed that the reaction is first order with respect to sulphoxide and the hydroperoxide salt. The rate was also shown to be inversely proportional to the alcohol concentration in the solvent and this dependence was shown to increase with increasing pH. Also, more sterically crowded alcohols caused a decreased rate of reaction. 

The vector of properties is a kind of chromosome, a code that defines the genotype of the individual. This sequence of values specifies the "genetic makeup" that (possibly uniquely) defines the animal. In Daisy s case, not all of the animal s characteristics are defined by her biological genetic code we have included in the vector other characteristics that would help to pick her out from the kine (cattle) crowd. In a similar way, a single GA solution can be constructed as a "chromosome" or genome in vector form, which contains all the information needed to define the potential solution to a scientific problem. 

As would be expected, the slopes are almost identical the intercept difference shows that methyl benzoate reacts about 1.5 times as fast as does ethyl benzoate in the standard state, a result easily attributable to the slight increase in steric crowding to the equation (42) hydrolysis in the latter case. The order of the A2 ester hydrolysis reaction in water is thus two, a result quite difficult to obtain in other ways, even in dilute solution, perhaps requiring a proton inventory study of a reaction that is very slow in water. 

Compound 87 was the first case found of a stannanethione stable in solution. It was synthesized via the organotin(II) intermediate 71 reaction 11 was followed by UVV spectrophotometry. When the less crowded Ar4 was used instead of substituent Ar1 (see formula 5), the stannathione underwent dimerization to 88199. See also Table 7. 

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