P-Bromobenzenesulfonic acid

However, if the desired product is p-bromobenzenesulfonic acid, then the order of the two reactions must be reversed because only the bromo substituent is an ortho-para director. 

Table S.16 presents data on some representative nucleophilic substitution processes. The first entry illustrates the use of 1-butyl-l-r/p-bromobenzenesulfonate to dononstrate at primary systems react with inversion, even under solvolysis conditkms in formic acid. The observation of inversion indicates a concerted mechanism in fids weakly nucleophilic solvent.

Figure 5.1 Effect of added LiC104 on ka and kt in solvolysis of threo-3-p-anisyl-2-butyl-p-bromobenzenesulfonate (3) in acetic acid. Reprinted with permission from S. Winstein and G. C. Robinson, J. Amer. Chem. Soc., 80, 169 (1958). Copyright by the American Chemical Society.

Table 4.12. Relative Solvolysis Rates of Some w-Metboxyalkyl p-Bromobenzenesulfonates in Acetic Acid ...

The most frequently synthesized and used cellulose sulfonates are the p-toluenesulfonates (tosylates), methanesulfo-nates (mesylates), p-bromobenzenesulfonates (brosylates), and ttifluoromethanesulfonates (Inflates). The synthesis of sulfonates through simple esterification of the -OH groups of cellulose with the corresponding sulfonic acid chlorides or anhydride is a way to attach nucleofuge groups to... 

TFA is 99 vol. % trifluoroacetic acid, 1 vol. % water. The sulfonate esters used were in 90E the p-bromobenzenesulfonate in 50E and 97TFE isopropyl-p-bromobenzenesulfonate and 2,2,2-trifluoroethanesulfonate, pinacolyl p-bromobenzenesulfonate and 2-adamantyl 2,2,2-trifluoroethanesuifonate in 99TFA, isopropyl and p-bromobenzenesulfonate, pinacolyl p-toluenesulfonate and 2-adamantyl p-toluenesulfonate and p-bromobenzenesulfonate. 

Relative solvolysis rates of some 6>-methoxyalkyl p- bromobenzenesulfonates in acetic acid... 

The rates of solvolysis in ethanol, formic acid, and acetic acid of l-(p-methoxyphenyl)ethyl toluene-p-sulfonate (65) are approximately the same as those of its para isomer (66). Because of the lack of product analyses and therefore quantitative knowledge of the importance of aryl participation " and the pathway,it is not possible to determine the extent of o-MeO-5 participation. However, o-MeO-6 participation occurs extensively in the acetolysis and formolysis of the analogous 3-(o-methoxyphenyl)-l-propyl p-bromobenzenesulfonate (73) and 3-(o-methoxyphenyl)-3-methyl-l-butyl toluene-p-sulfonate (74) (see Table 6). Any competing aryl participation would be Ari-4 participation and, as shown by the reaction rates for the para isomers, is unimportant. The reaction products (Table 6) contain large amounts of the pyran derivatives (75) and (76) and of the methyl arenesulfonates, and the reactions may therefore be formulated as shown in... 

When the ether oxygen is substituted for C-6 of a bicyclo[2.2.1]heptyl ester, a dramatically different result is observed. Thus the solvolysis of exo-p-bromobenzenesulfonate (124) in buffered acetic acid offers an extraordinary demonstration of anchimeric assistance. While the endo isomer (125) undergoes solvolysis at the rate predicted by the Foote-Schleyer method, the exo isomer (124) reacts some 7 x 10 times faster. This suggests that the ring oxygen is unusually capable of interacting with the back-side lobe of the sp orbital of the exo substituent. R2O-3 participation after ionization was suggested for the endo isomer from product analysis of solvolysis of the deuterated derivative (126). The endo derivative produced 85 %... 

The stereochemistry of nucleophilic substitution reactions has been examined for substrates ranging in complexity from primary alkyl to triarylmethyl. A summary of representative examples is presented in Table 5.14. Chiral 1-butanol-l-d and its derivatives have small, but measurable, optical rotations and provide useful substrates for the important case of substitution in primary systems. Entry 1 in Table 5.14 illustrates the stereospecific inversion observed in 1-butyl-1-d p-bromobenzenesulfonate, even toward nucleophiles as weak as formic acid. This inversion is indicative of a high degree of solvent participation in the displacement... 

H-Di-Me, Na salt Used as aq. soln as acid-base indicator (pH range 1.6 - 3.6 colour change red yellow). Orange-red cryst. (EtOH). Sol. H2O, EtOH insol. QH. N-P/z. 4-[ 4-Phenylaminopheny[)azoy3-bromobenzenesulfonic acid... 

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