Tetraethylammonium hydroxide

As expected, HTMAB made a respectable showing in these experiments. Trioctylmethylammonium chloride (TOMAC) and trioctylmetliylammonium bromide (TOMAB) outperformed all other catalysts. It was postulated that the three octyl groups were the proper length for solvation of the polymer while at the same time small enough to avoid sterically hindering the reaction. In order to determine if TOMAB could be used to catalyze PET depolymerization for more than one treatment cycle, the catalyst was recovered upon completion of one treatment and added to a second run for 60 min. Tetraethylammonium hydroxide (TEAOH) was studied as a catalyst in order to demonstrate the effect of hydroxide ion as a counterion. The percent PET conversion for the second cycle was 85.7% compared to a conversion of 90.4% for the first treatment cycle. 

In a 300-mL round-bottom flask, a 5% sodium hydroxide solution (250 mL) was heated to 80° C in a constant-temperature bath. The catalysts were added in the following amounts in separate experiments trioctylmethy-lammonium chloride (TOMAC) (0.04 g, 0.0001 mol) trioctylmethylammo-nium bromide (TOMAB) (0.045 g, 0.0001 mol) hexadecyltrimethylammo-nium bromide (HTMAB) (0.045 g, 0.0001 mol) tetraethylammonium hydroxide (TEAOH) (0.015 g, 0.0001 mol) and phenyltrimethylammonium chloride (PTMAC) (0.02 g, 0.0001 mol). PET fibers (1.98 g, 0.01 mol) were added to the mixture and allowed to react for 30, 60, 90, 150, and 240 min. Upon filtration, any remaining fibers were washed several times with water, dried in an oven at 130-150°C, and weighed. The results are shown in Table 10.1. 

The exact nature of the zeolite is determined by the reaction conditions, the silica to alumina ratio and the base used. For example zeolite /3, a class of zeolites with relatively large pores, in the range of 0.7 nm, of which mordenite is an example, are usually made using tetraethylammonium hydroxide as the base. This acts as a template for the formation of 12-membered ring apertures (Figure 4.3). 

In an attempt to produce TS-1 at low cost, alternative, cheaper sources of Ti and Si and other bases such as binary mixtures of (tetrabutylammonium and tetraethylammonium hydroxides), (tetrabutylphosphonium and tetraethylpho-sphonium hydroxides), (tetrapropylammonium bromide and ammonia, water, hexanediamine, n-butylamine, diethylamine, ethylenediamine, or triethanolamine) in place of TPAOH have been used (284—294). TS-1 was synthesized in the presence of fluoride ions but the material thus formed contained extraframework Ti species (295-297). 

The application of phase-transfer catalysis to the Williamson synthesis of ethers has been exploited widely and is far superior to any classical method for the synthesis of aliphatic ethers. Probably the first example of the use of a quaternary ammonium salt to promote a nucleophilic substitution reaction is the formation of a benzyl ether using a stoichiometric amount of tetraethylammonium hydroxide [1]. Starks mentions the potential value of the quaternary ammonium catalyst for Williamson synthesis of ethers [2] and its versatility in the synthesis of methyl ethers and other alkyl ethers was soon established [3-5]. The procedure has considerable advantages over the classical Williamson synthesis both in reaction time and yields and is certainly more convenient than the use of diazomethane for the preparation of methyl ethers. Under liquidrliquid two-phase conditions, tertiary and secondary alcohols react less readily than do primary alcohols, and secondary alkyl halides tend to be ineffective. However, reactions which one might expect to be sterically inhibited are successful under phase-transfer catalytic conditions [e.g. 6]. Microwave irradiation and solidrliquid phase-transfer catalytic conditions reduce reaction times considerably [7]. 

Figure 13 Cyclic voltammogram recorded at a platinum electrode in a dmso solution of [V(hidpa)2]2 (after addition of tetraethylammonium hydroxide). Scan rate 0.2 V s ...

A series of Beta zeolites have been synthesized in the presence of tetraethylammonium hydroxide (TEA). Samples with Si/Al ratio in the 7-100 range have been characterized by X-ray powder diffraction, I.R. spectroscopy, and pyridine adsorption. The fraction of TEA which is compensating the charge of the framework aluminum is removed at temperatures higher than those required to remove "occluded" TEA. Three hydroxyl bands are observed at 3740 cm l (silanol groups), 3680 cm" (extraframework Al) and 3615 cm 1 (acid hydroxyl groups interacting with pyridine). 

Tetramethyammonium hydroxide Tetraethylammonium hydroxide Tetrapropylammonium hydroxide... 

Polarographic Halt-Wave Potentials El, in Volts (vs. SCE), for Certain Metal Cations in the Presence of Either Amirfonia-Ammonium Chloride Mixture or Tetraethylammonium Hydroxide as the Indifferent Electrolyte... 

Protecting groups were removed by treatment of the polymer with sodium methoxide in p-dioxane, followed by tetraethylammonium hydroxide. Although nitrogen-free polymers were obtained by this procedure, the polymers had suffered a 16-20% decrease in PH. The resulting polymers were insoluble in water, sodium hydroxide, N, -dimethylformamide, and methyl sulfoxide, but were soluble in tetraethylammonium hydroxide and in Schweizer reagent. 

Total hydrolysis of the polymers gave D-glucose only. Water-soluble derivatives (ethyl or carboxymethyl ethers) of the polymers were unaffected by a-amylase, but were partially hydrolyzed by a ceUulase preparation from Acdobader xylinum. The optical rotations of several preparations of this polyglucose and of cellulose (P 1150) in tetraethylammonium hydroxide were all 0°, thereby strongly suggesting that the polyglucoses are /S-D-linked.109... 

Ion-pair chromatography has also been used for the determination of dulcin. Wu et al. (47) added the ion pair tetraethylammonium hydroxide to the mobile-phase methanol 85% phosphoric acid, pH 6 (2 8), for the separation of dulcin from saccharin, cyclamate, aspartame, and acesulfame-K on /xBondapak 08. Herrmann et al. (24) separated dulcin from saccharin, cyclamate, and aspartame on Hypersil MOS 3 using a mobile phase consisting of 5 mM tetrabutylam-... 

Tetracyanoethylene, A 143 Tetraethylammonium bisulfate, A057 Tetraethylammonium chloride, A053 Tetraethylammonium formate, AQ.24 Tetraethylammonium hydroxide, AO56 Tetraethylthiuram disulfide, AS76... 

Abbreviations p, ratio between ionic radii of cation and anion TBHP, rm-butyl hydroperoxide EBHP, ethylbenzene hydroperoxide PO, propylene oxide TBOT, tetrabutyl orthotitanate TEOT, tetraethyl orthotitanate TIOT, tetraisopropyl orthotitanate TEOS, tetraethyl orthosilicate THF, tetrahydrofuran TPA-OH, tetrapropylammonium hydroxide TMOS, tetramethyl orthosilicate TBA-OH, tetrabutylammonium hydroxide TBP-OH, tetrabutylphophonium hydroxide TEA-OH, tetraethylammonium hydroxide TMA-OH, tetramethylammonium hydroxide. 

See Periodic acid Tetraethylammonium hydroxide See also Tetramethylammonium periodate... 

Figure 8.6 Voltammograms for the oxidation of dissolved H2 (1 atm) in DMF [(0.5 M TEAP) (EUNCIOJ] and with 20 raM additions of triethylamine (Et3N), tetraethyl-ammonium benzoate (PhC(O)O-), and tetraethylammonium hydroxide (HO-). The Pt electrode (area 0.23 cm2) was preanodized at +1.8 V versus SCE for 2 min prior to each voltammogram scan rate 0.1 V s-1.

Figure 12.2 Cyclic voltammograms of (a) 2.0 mM 3,5-di-rert-butyl-o-benzoquinone (b) 2.0 mM, 3,5-di-ferf-butyl-o-semiquinone anion (formed by controlled potential electrolysis at —0.80 V (c) solution b plus 2.0 mM tetraethylammonium hydroxide, initial cathodic scan and (d) solution c, initial anodic scan. All solutions were in dimethyl-formamide that contained 0.1 M TEAP at a Pt electrode (surface area 0.23 cm2). Scan rate was 0.1 V s-1.

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