Micellar catalysis of organic reactions. X. Further evidence for the partial failure of the pseudophase kinetic model of micellar catalysis for reactions of hydroxide ions

1983 ◽  
Vol 36 (4) ◽  
pp. 711 ◽  
Author(s):  
TJ Broxton ◽  
DB Sango
Keyword(s):  
Kinetic Model ◽  
Cetyltrimethylammonium Bromide ◽  
Micellar Catalysis ◽  
Aryl Halides ◽  
Organic Reactions ◽  
Partial Failure ◽  
Pseudophase Model ◽  
Rate Ratios

Rates of hydrolysis for a number of amides and hydroxydehalogenation of some activated aryl halides have been determined in the presence of micelles of cetyltrimethylammonium bromide (ctab) and cetyltrimethylammonium fluoride (ctaf). The rates of reaction in micelles of ctaf are greater than in micelles of ctab in each case but the ctaflctab rate ratios are smaller than predicted by the pseudophase model of micellar catalysis. The results are discussed in terms of reactions in ctaf occurring within the micelle but reactions in ctab occurring both within the micelle and across the micellar interface. The extent of reaction across the micellar interface is shown to be dependent on the structure of the substrate. Substrates chosen were those bearing hydrophobic or hydrophilic substituents, designed to orient the substrate molecules in predictable ways within the micelles.

Tests of the pseudophase model of micellar catalysis: its partial failure

1979 ◽  
Vol 101 (5) ◽  
pp. 1253-1259 ◽  
Author(s):  
Clifford A. Bunton ◽  
Laurence S. Romsted ◽  
Gianfranco Savelli
Keyword(s):  
Micellar Catalysis ◽  
Partial Failure ◽  
Pseudophase Model

Micellar Catalysis of Organic Reactions. XXXVIII A Study of the Catalytic Effect of Micelles of 3-Hydroxymethyl-1-tetradecylpyridinium Bromide on Amide Hydrolysis and Nucleophilic Aromatic Substitution

1998 ◽  
Vol 51 (7) ◽  
pp. 541 ◽  
Author(s):  
Trevor J. Broxton
Keyword(s):  
Catalytic Effect ◽  
Micellar Catalysis ◽  
Aryl Halides ◽  
Organic Reactions ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Rate Determining Step ◽  
Amide Hydrolysis

The preparation of 3-hydroxymethyl-1-tetradecylpyridinium bromide and its use as a catalyst of nucleophilic aromatic substitution and also amide hydrolysis are reported. It was found that the hydroxydehalogenation of nitro-activated aryl halides was much faster in these micelles than in the presence of cetyl(2-hydroxyethyl)dimethylammonium bromide. It was concluded that the increased catalysis of nucleophilic aromatic substitution by this micelle was due to a faster decomposition of the aryl micellar ether which must occur before the phenolate product is released. No such difference in the two micelles was found for amide or thioamide hydrolysis since in these reactions the product amine is produced in the first step of the reaction and decomposition of the acylated micelle is not required in the rate-determining step of the reaction.

Micellar catalysis of organic reactions. IX. The reaction of sodium azide with activated aromatic halides and the subsequent decomposition of the initially formed aryl azide

1982 ◽  
Vol 35 (12) ◽  
pp. 2557 ◽  
Author(s):  
TJ Broxton ◽  
AC Jakovljevic
Keyword(s):  
Sodium Azide ◽  
Substitution Reaction ◽  
Cetyltrimethylammonium Bromide ◽  
Micellar Catalysis ◽  
Organic Reactions ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Aryl Azide ◽  
Snar Reaction ◽  
Subsequent Decomposition

The effect of micelles of cetyltrimethylammonium bromide on the SNAr reaction of azide ions with 1-halogeno-2,4-dinitrobenzenes and on the subsequent decomposition of the aryl azide product has been measured. The nucleophilic aromatic substitution reaction is shown to be subject to significant micellar catalysis whereas the subsequent decomposition of the aryl azide is not.

Micellar catalysis of organic reactions. XII. Basic hydrolysis of some alkyl and aryl N-(4-Nitrophenyl)carbamates

1984 ◽  
Vol 37 (1) ◽  
pp. 47 ◽  
Author(s):  
TJ Broxton
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Kinetic Studies ◽  
Micellar Catalysis ◽  
Organic Reactions ◽  
Bond Breaking ◽  
Tetrahedral Intermediate ◽  
Stable Product ◽  
Methyl Derivatives ◽  
Basic Hydrolysis ◽  
Hydrolysis Of

The basic hydrolysis of a number of alkyl and aryl N-(4-nitrophenyl)carbamates in the presence and absence of micelles of cetyltrimethylammonium bromide (ctab) are reported. In water the stable product at 26�C was N-(4-nitrophenyl)carbamate ion (3). At higher temperatures this carbamate ion slowly decomposed to 4-nitroaniline. In ctab the decarboxylation of the N-(4-nitrophenyl)carbamate ion was strongly catalysed (× 45) and thus the observed final product even at 26�C was 4-nitroaniline. Kinetic studies in water and in ctab were consistent with decomposition of the methyl carbamate (la) by a BAC2 mechanism and the 2,2,2-trifluoroethyl carbamate (lc) by an E1cB mechanism. The extent of ionization of the substrate carbamates to nitranion (4) was enhanced in ctab as was the rate of spontaneous decomposition of the nitranion. This is in contrast to other E1cB reactions reported in the literature, for which the rate of spontaneous decomposition of the carbanion was inhibited by ctab. For compounds reacting by the BAC2 mechanism, the tetrahedral intermediate (2) partitioned in favour of C-OR bond breaking rather than C-N bond breaking observed previously for some N-methyl derivatives.

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