Halides, quaternary ammonium

When quaternary ammonium halides are treated with strong bases (e.g., PhLi, KNH2 in liquid an elimination can occur that is similar in products, though not in... 

The phase-transfer catalyst (Q+X-) is usually a quaternary ammonium halide (R4N+X ) such as tetrabutylammonium halide (CH3CH2CH2CH2)4N+X. ... 

Another approach for ion-sensing (here copper and zinc) is based on the water-soluble ligand zincon and the ion pair with quaternary ammonium halides shown in Figure 17 which can be homogeneously dissolved in polymers such as plasticized poly(vinyl acetate), ethyl cellulose, and polyurethane. 

Because of their high lipophobic character, compared with other ammonium salts, quaternary ammonium hydroxides are not readily prepared by liquidrliquid anion exchange. Only with quaternary ammonium hydrogen sulphates is it possible to transfer the ammonium hydroxide into the organic phase in any viable degree of concentration [30] and this procedure remains the cheapest and simplest procedure. Other methods include treatment of quaternary ammonium halides with silver oxide [31] and by anion exchange using polymer bound hydroxide [e.g. 32]. 

Lower molecular-weight quaternary ammonium halides, which partition across the two-phase system, transfer anions in measurable concentrations from the aqueous to the organic phase but, in contrast, many of the higher-molecular-weight quaternary ammonium halides with more than ca. 30 carbon atoms are virtually insoluble in aqueous media and their partition coefficients between aqueous and organic phases preclude the transfer of anions efficiently across the interface by the extraction process and yet catalysts, such as Aliquat 336 and Adogen 464, are extremely effective catalysts. 

The ability of quaternary ammonium halides to form weakly H-bonded complex ion-pairs with acids is well established, as illustrated by the stability of quaternary ammonium hydrogen difluoride and dihydrogen trifluorides [e.g. 60] and the extractability of halogen acids [61]. It has also been shown that weaker acids, such as hypochlorous acid, carboxylic acids, phenols, alcohols and hydrogen peroxide [61-64] also form complex ion-pairs. Such ion-pairs can often be beneficial in phase-transfer reactions, but the lipophilic nature of H-bonded complex ion-pairs with oxy acids, e.g. [Q+X HOAr] or [Q+X HO.CO.R], inhibits O-alkylation reactions necessitating the maintenance of the aqueous phase at pH > 7.0 with sodium or potassium carbonate to ensure effective formation of ethers or esterification [49,64]. 

It is noteworthy that benzyltriethylammonium chloride is a slightly better catalyst than the more lipophilic Aliquat or tetra-n-butylammonium salts (Table 5.2). These observations obviously point to a mechanism in which deprotonation of the amine is not a key catalysed step. As an extension of the known ability of quaternary ammonium halides to form complex ion-pairs with halogen acids in dichloromethane [8], it has been proposed that a hydrogen-bonded ion-pair is formed between the catalyst and the amine of the type [Q+X—H-NRAr] [5]. Subsequent alkylation of this ion-pair, followed by release of the cationic alkylated species, ArRR NH4, from the ion-pair and its deprotonation at the phase boundary is compatible with all of the observed facts. 

Oxiranes undergo ring-opening with cerium(VI) ammonium nitrate and an excess of a quaternary ammonium halide to yield haloethanols [34], The reaction occurs with high regio- and stereo-selectivity, for example, / (+)-styrene oxide produces S(+)-2-chloro-2-phenylethanol in 85% yield with 96% ee. 

A compound whose addition to a two-phase organic water system helps to transfer a water soluble ionic reactant across the interface to the organic phase where a homogeneous reaction can take place is called a phase transfer catalyst. These catalysts enhance the rate of a reaction. A quaternary ammonium halide R4N+ X- e.g., tetrabutylammonium halide is phase transfer catalyst. It can cause the transfer of the... 

The synthetic efficiency compares favorably with existing methods that largely use quaternary ammonium halides and chlorohydrocarbon solvents (Arends et al 1997). Sato and co-workers (Sato et al., 1997) provide several tables of primary and secondary alcohols that were successfully oxidized with aqueous hydrogen peroxide. 

Propylene carbonate [108-32-7] M 102.1, b 110°/0.5-lmm, 238-239°/760mm, d 1.204, n 1.423. Manufactured by reaction of 1,2-propylene oxide with CO2 in the presence of a catalyst (quaternary ammonium halide). Contaminants include propylene oxide, carbon dioxide, 1,2- and 1,3-propanediols, allyl alcohol and ethylene carbonate. It can be purified by percolation through molecular sieves (Linde 5A, dried at 350° for 14h under a stream of argon), followed by distn under vac. [Jasinski and Kirkland AC 39 163 1967], It can be stored over molecular sieves under an inert gas atmosphere. When purified in this way it contains less... 

The use of mixtures of sodium hydroxide and benzyltrimethylammonium chloride or tetrabutylammonium bromide failed to enhance the DPGE alkylation of HEC by the in situ formation of the corresponding quaternary ammonium hydroxide phase transfer catalyst. These quaternary ammonium halides are too soluble in aqueous /-butyl alcohol and are preferentially extracted into the organic phase. Mixtures of benzyltrimethylammonium hydroxide and sodium acetate were also ineffective in enhancing the DPGE alkylation of HEC for the same reason, namely preferential solubility of benzyltrimethylammonium acetate in the organic phase. 

Copper and silver will dissolve in nitric acid or hot sulfuric acid. A mixture of hydrochloric and nitric acids (aqua regia) will dissolve gold. It has recently been reported lhat mixtures of halngcns and quaternary ammonium halides in organic solvents dissolve gold faster ihan does aqua regia, see Nakao, Y. J. Chem. Soc. Chem. Ccmmun. 1992. 426-427. 

The substitution of allyl and benzyl halides is also catalyzed by quaternary ammonium halides. In fact, the method was discovered with tributylstannyl ethers [15]. The conversion of tributylstannyl ethers to ketones with AMnomosuccinimide is an alternative to the bromine oxidation of stannylenes [12,13]. Again, the disposal of the tin by-product Bt SnX may be a problem in large-scale wotk. It may be fairly efficiently extracted with hexane from a solution of the reaction mixture in acetonitrile. 

Tertiary amines do not react with nitrous acid, acetyl chloride, benzoyl chloride, benzenesulfonyl chloride, but react with alkyl halides to form quaternary ammonium halides, which are converted by silver hydroxide to quaternary ammonium hydroxides. Quaternary ammonium hydroxides upon heating yield (1) tertiary amine pins alcohol (or, for higher members, olefin plus water). Tertiary amines may also be formed (2) by alkylation of secondary amines, e.g., by dimethyl sulfate, (3) from amino acids by living organisms, e g, decomposition of fish in the case of trimethylamine. 

EMDE DEGRADATION. Modification of the Hofmann degradation method for reductive cleavage of the carbon-nitrogen bond by treatment of an alcoholic or aqueous solution of a quaternary ammonium halide with sodium amalgam. Also used as a catalytic method with palladium and platinum catalysts. The method succeeds with ring compounds not degraded by the Hofmann procedure. 

CeH5.CH2(CH3)2.N(C16H33)Cl. A quaternary ammonium halide recommended by McDonatd(Ref 2) as satisfactory for the decontamination of waters coatg dissolved expl wastes. This, or other halide salts, can be added to a tank along with the waste water the expl material settles as an insol addn compd Refs l)Beil- not found 2)L.McDonald,USP 2647084(1953) CA 47,10853(1953)... 

Following the findings of Butler et al. [5], that diallyl quaternary ammonium halides form water soluble polymers, the structures of polymers produced via a ring-closing mechanism have been the subject of intensive research. A cyclic structure was elucidated and the mechanism was defined as an alternating intra-intermolecular chain propagation, later termed cyclopolymerization [3]. Based on the general scheme presented in Fig. 6 the chemical structure of PDADMAC is determined by... 

Quaternary ammonium halides are formed by reaction of alkyl halides and tertiary amines. 

An extensive range of metal salts [96] have been studied but the only ones which produce ionic liquids (i.e. liquid below 100°C) with pyridinium, imidazolium and quaternary ammonium halides are FeCh, ZnC, SnC, CuCl [105], InCh [100] andAuCb [106,107],... 

Acetylcholine was separated by Paul and Ebrahimian from adrenaline and serotonin [125]. The thin layer chromatographic behavior of acetylcholine and other quaternary ammonium halides were studied on silica gel by Iorio et al. [126]. 

What is especially intriguing is the reverse behavior exhibited by the use of ruthenium carbonyl as the metal carbonyl. This reaction, which is catalytic in both Ru3(CO)2 and quaternary ammonium halide (which accelerates the rate of formation of the hydride intermediate), occurs in much higher yield under a carbon monoxide than a nitrogen atmosphere (22). The reaction conditions used for the Ru3(CO)12-catalyzed reaction are much milder than those reported using the water gas shift reaction [100°C, 500 psi] (25). 

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