Benzyltrimethylammonium effect

Compare electrostatic potential maps for tetrabenzyl-ammonium ion and tetraethylammonium ion with that of benzyltrimethylammonium ion. Are they likely to be as effective or more effective as phase-transfer catalysts as benzyltrimethylammonium ion Explain. (Hint Predict solubility properties for the three ions.)... 

Our recent studies on effective bromination and oxidation using benzyltrimethylammonium tribromide (BTMA Br3), stable solid, are described. Those involve electrophilic bromination of aromatic compounds such as phenols, aromatic amines, aromatic ethers, acetanilides, arenes, and thiophene, a-bromination of arenes and acetophenones, and also bromo-addition to alkenes by the use of BTMA Br3. Furthermore, oxidation of alcohols, ethers, 1,4-benzenediols, hindered phenols, primary amines, hydrazo compounds, sulfides, and thiols, haloform reaction of methylketones, N-bromination of amides, Hofmann degradation of amides, and preparation of acylureas and carbamates by the use of BTMA Br3 are also presented. 

A primary kinetic isotope effect (kn/ko = 6.03 at 298 K) was observed for the oxidation of formic and oxalic acids by benzyltrimethylammonium tribromide (BTMAB) to carbon dioxide. The kinetics of oxidation of pyridoxine to pyridoxal by broma-mine-T and bromamine-B ° and caffeine by bromamine-B have been investigated. 

Temperature Effects. The oxidation of 9,10-dihydroanthrafcene to anthraquinone in anhydrous pyridine solvent with benzyltrimethylammo-nium hydroxide as the base occurs over a wide temperature range (Table I). Some oxidation takes place at a temperature as low as — 20°C., but maximum anthraquinone conversions (about 70%) occur between 50° and 70°C. Above 70°C., the conversion decreases, probably as a result of thermal decomposition of the benzyltrimethylammonium hydroxide. 

Effects of polymer structure on reaction of phenylacetonitrile with excess 1-bromo-butane and 50% NaOH have been studied under conditions of constant particle size and 500 rpm stirring to prevent mass transfer limitations I03). All experiments used benzyltrimethylammonium ion catalysts 2 and addition of phenylacetonitrile before addition of 1-bromobutane as described earlier. With 16-17% RS the rate constant with a 10 % CL polymer was 0.033 times that with a 2 % CL polymer. Comparisons of 2 % CL catalysts with different % RS and Amberlyst macroporous ion exchange resins are in Table 6. The catalysts with at least 40% RS were more active that with 16 % RS, opposite to the relative activities in most nucleophilic displacement reactions. If the macroporous ion exchange resins were available in small particle sizes, they might be the most active catalysts available for alkylation of phenylacetonitrile. 

The phase transfer catalyzed alkylation reaction of dodecyl phenyl glycidyl ether (DPGE) with hydroxyethyl cellulose (HEC) was studied as a mechanistic model for the general PTC reaction with cellulose ethers. In this way, the most effective phase transfer catalysts and optimum reaction concentrations could be identified. As a model cellulose ether, CELLOSIZE HEC11 was chosen, and the phase transfer catalysts chosen for evaluation were aqueous solutions of choline hydroxide, tetramethyl-, tetrabutyl-, tetrahexyl-, and benzyltrimethylammonium hydroxides. The molar A/HEC ratio (molar ratio of alkali to HEC) used was 0.50, the diluent to HEC (D/HEC) weight ratio was 7.4, and the reaction diluent was aqueous /-butyl alcohol. Because some of the quaternary ammonium hydroxide charges would be accompanied by large additions of water, the initial water content of the diluent was adjusted so that the final diluent composition would be about 14.4% water in /-butyl alcohol. The results of these experiments are summarized in Table 2. 

The best alkylation efficiencies of DPGE were obtained with benzyltrimethyl- and tetrabutylammonium hydroxide. To explore the effect of the variation of A/HEC ratio on DPGE alkylation efficiency, experiments were conducted at varying A/HEC ratios (see Figure 3). The alkylation efficiency maximum occurs between about 0.25 and 0.50 A/HEC molar ratio. The observed alkylation efficiencies of DPGE with tetrabutylammonium hydroxide were comparable to the alkylation efficiencies with benzyltrimethylammonium hydroxide. 

The oxidation of a-hydroxy acids by benzyltrimethylammonium tribromide (BTMAB) to the corresponding carbonyl compounds shows a substantial solvent isotope effect, A (H20)/A (D20) = 3.57, but no KIE for a-deuteromandelic acid.133 The oxidation of glucose by hypobromous acid is first order in glucose and the acid.134 [l,l-2H2]Ethanol shows a substantial kinetic isotope effect when oxidized by hexamethylenetetramine-bromine (HABR) in acetic acid to aldehyde.135 Kinetics of the oxidation of aliphatic aldehydes by hexamethylenetetramine-bromine have been studied by the same group.136 Dioxoane dibromide oxidizes y-tocopherol to 5-bromomethyl-y-tocopherylquinone, which spontaneously cyclizes to 5-formyl-y-tocopherol.137... 

Brasen and Hauseri describe a procedure for effecting reductive rearrangement of benzyltrimethylammonium iodide (1) to the tertiary amine (2). 

Rearrangement catalyst. The reagent effects exclusive ortho rearrangement of benzyltrimethylammonium iodide to 2,N,N-trimethylbenzylamine.ub... 

Shechter and Wynstra ( ) also demonstrated that benzyldi-methylamine was a somewhat more effective catalyst than potassium hydroxide, and the quaternary compound benzyltrimethylammonium hydroxide was even more powerful. Each reaction was highly selective. 

Only a few departures from the basic Haloform reaction conditions (Section 7.3.5) have been developed. Both sodium bromite23 and benzyltrimethylammonium tribromide24 in aqueous sodium hydroxide are convenient alternatives to the use of bromine in the Haloform reaction (e.g., 13 to 14,23 15 to 1624). Both reagents also effect conversion of methyl carbinols to carboxylic acids. 

The use of benzyltrimethylammonium tribromide is particularly effective for the synthesis of aromatic and heteroaromatic carboxylic acids as shown in Table 1. 

A simple synthesis of cyanides that can be effected in an aqueous medium consists of treating the alkyl halides with benzyltrimethylammonium cyanide (prepared in situ from benzyltrimethylammonium chloride and sodium cyanide) 442... 

Benzyltrimethylammonium tetrachloroiodate was less effective although nevertheless a stable chlorinating agent which with anisoie in acetic acid at 70°C during 24 hours afforded 4- and 2-chloroanisole (6 1) in 73% yield (ref. 108). 

Large series of quaternary ammonium bases have further been synthesized. Some of those compounds have nicotinic actions and thus stimulate respiration, as acetylcholine. Diethylammonium and trimethylammo-nium chloride induce marked respiratory stimulation. Tetramethylammo-nium chloride first stimulates and then temporarily paralyzes respiration. Tetraethylammonium chloride has lesser respiratory effects. Phenyl- and benzyltrimethylammonium, and trimethylphenethylammonium are active nicotinic compounds (1, 18, 19) and stimulate reflexly the respiratory center. 

A soln. of acetanilide in 5 2 methylene chloride/methanol treated with benzyltrimethylammonium chlorobromate(l-) at room temp., and stirred for 20 min - 4-bromoacetanilide. Y 97%. Tetrabutylammonium and benzyltrimethylammonium tribromide were also effective in the presence of methanol, but reaction times were longer (cf. Synth. Meth. 42,471). F.e. incl. dibromination of amino- or hydroxy-subst. acetanilides s. S. Kajigaeshi et al.. Bull. Chem. Soc. Japan 61, 2681-3 (1988). 

Racemization via a reversible addition/elimination process under mild conditions can be used, with for example cyanohydrins, hemiacetals, hemiaminals and hemithioacetals. SiUca-supported benzyltrimethylammonium hydroxide (BTAH) was used to racemize cyanohydrins and effected an efficient DKR process in tandem with porous ceramic-immobilized lipase (lipase PS-C II) (Scheme 4.22) [57]. 

In their initial studies, Shechter and Wynstra had demonstrated that these catalysts could achieve high selectivity of the epoxy-phenol reaction in a solution of excess phenol. They later reversed the situation and studied the reaction selectivity in a solution of excess glycidyl ether in which the phenol was used as the limiting reagent. The excess of epoxide over phenol was measured until phenol had practically disappeared, and the results in all cases indicated high selectivity towards the epoxy-phenol reaction. The tertiary amine, ben ldimethylamine, was somewhat more effective than potassium hydroxide benzyltrimethylammonium hydroxide was even more powerful. First-order kinetics were observed for all reactions. Since it was postulated that the phenoxide ion was common to all these reactions, the observed diffCTences in reaction rates were linked to the cation. In was not determined, however, whether the cation effect is one of different degrees of dissociation of the phenol salts or of some other phenonomenon. 

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