Alkoxy groups, determination

By determining ha for several different buffer catalysts and each of several alkoxy leaving groups, it was determined that there was a relationship between the Bronsted eoeffieient a and the strueture of the alkoxy leaving group. The data are given and show that a deereases as the alkoxy group beeomes less basie. 

Also A H+ as measured in these acidic solutions was 4 to 30 times less than when it was measured at pH 4.5-7.5 (Ahmad el al., 1977, 1979). Therefore in the acidic solutions the alkoxy group must have been lost before the rate-determining step in the formation of 2-hydroxyethyl benzoate and this step must therefore be breakdown of the hemiorthoester [70]. At higher pH breakdown of the hemiorthoester [70], which is also base-catalysed, becomes very fast, and cleavage of the exocyclic C— bond of the starting material [69], which depends on R, is rate-determining. 

For instance, in the polymerization of 1.3-pentadiene in the presence of a catalyst prepared from optically active titanium alcoholates and diethylaluminum monochloride, the diolefin might give a complex with a titanium atom before the polymerization (92) the steric structure of the complexed pentadiene molecule might be determined by the optically active alkoxy groups still bound to the titanium atom. However, the case of. the polymerization of diolefins is much more complex than the case of the polymerization of vinyl monomers owing to the possible... 

Chemically, the triarylmethane dyes are monomethine dyes with three terminal aryl systems of wind] one or more arc substituted with primary, secondary, or tertiary amino groups or hydroxyl groups in the para position to the methine carbon atom. Additional substituents such as carboxyl, sulfonic acid, halogen, alkyl, and alkoxy groups may be present on the aromatic rings. The number, nature, and position of these substituents determine both the hue or color of the dye and the application class to which the dye belongs. 

Methoxy- and amino-substituted disilenes behave differently from 1529. Irradiation of a hexane solution of 20 in the presence of various alcohols at room temperature afforded 1,1-dialkoxyhydrodisilanes 28a-32a together with a small amount of the regioisomers 28b-32b (Scheme 5). Thus alkoxy groups direct the alcohol addition to the alkoxy-substituted silicon atom. The ratios of regioisomers (a/b) were 100/0 (EtOH, 28), 96/4 (i-PrOH, 29) and 93/7 (t-BuOH, 30). Steric bulkiness is not the only factor that determines the regioselectivity, since bulky but acidic alcohols, such as 2,6-dimethylphenol... 

Chlorohydrins are compounds characterized by alpha halo-alpha alkoxy groups bound to a common carbon atom. These compounds undergo rapid hydrolysis at this shared carbon atom. Bis(2-chloroisopropyl)ether, a chlorohydrin, has two such carbon atoms, and both react very rapidly with water. In fact, the reactions are so fast that acid and alkaline contributions have not been determined. It is likely, however, that base accelerates the reaction kinetics. The proposed reaction pathway for this compound is based on the reported pathway for bis(chloroethyl)ether (Figure 13.4). The reported rate constant for bis(chlorome-thyl)ether, of 0.23 sec-1 was based on an observed half-life of a few minutes. Similarly, for bis(2-chloroisopropyl)ether, both of the chloro substituents are reactive, and a half-life of a few minutes can be assigned to this compound, as well. 

Recently crystal structure determinations of the complexes derived from 2,4,6-trinitroanisole and methoxide (Ueda et al., 1967) and 2,4,6-trinitrophenetole and ethoxide (Destro et al., 1967) have shown that the two alkoxy groups are indeed identical in the complex and that the plane defined by their oxygen atoms and Cl is orthogonal to the ring. The C6-C1-C2 bond angle is 109°, very close to the tetrahedral angle required for an sp3-hybridized carbon. 

Tellurium tetrakis[fluoroalkoxides] and tellurium tetrachloride reacted in refluxing benzene or tetrahydrofuran to produce fluoroalkoxy tellurium chlorides. The number of alkoxy groups in the product molecules is determined by the molar ratio of the reagents2. 

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