Subject organic solvents

Another reason for discussing the mechanism of nitration in these media separately from that in inert organic solvents is that, as indicated above, the nature of the electrophile is not established, and has been the subject of controversy. The cases for the involvement of acetyl nitrate, protonated acetyl nitrate, dinitrogen pentoxide and the nitronium ion have been advocated. 

Pha.se-Tra.nsfer Ca.ta.lysts, Many quaternaries have been used as phase-transfer catalysts. A phase-transfer catalyst (PTC) increases the rate of reaction between reactants in different solvent phases. Usually, water is one phase and a water-iminiscible organic solvent is the other. An extensive amount has been pubHshed on the subject of phase-transfer catalysts (233). Both the industrial appHcations in commercial manufacturing processes (243) and their synthesis (244) have been reviewed. Common quaternaries employed as phase-transfer agents include benzyltriethylammonium chloride [56-37-17, tetrabutylammonium bromide [1643-19-2] tributylmethylammonium chloride [56375-79-2] and hexadecylpyridinium chloride [123-03-5]. 

The original scientific account of the preparation of this body stated that mcfa-isohutyl toluene was heated on a water-bath for twenty-four hours, with five times its weight of a mixture of sulphuric and nitric acids. The product was subjected to a repetition of the same treatment, so as to convert it into trinitro-butyl toluene, which crystallises from alcohol in white needles melting at 96° to 97°. It is insoluble in water, but soluble in organic solvents. Even in very dilute solutions this compound has a. 

The mixture was poured in water, acidified to pH 1 with dilute hydrochloric acid, heated on the steam bath for 30 minutes and then subjected to steam distillation to remove the organic solvents. The residue was filtered, dried and recystallized several times from ethyl acetate. The A -19-nor-17a-ethinylandrosten-17/3-ol-3-one thus obtained had a MP of 198° to 200°C (in sulfuric acid bath), 200° to 204°C (Kofler). 

As with organic solvents, proteins are not soluble in most of the ionic liquids when they are used as pure solvent. As a result, the enzyme is either applied in immobilized form, coupled to a support, or as a suspension in its native form. For production processes, the majority of enzymes are used as immobilized catalysts in order to facilitate handling and to improve their operational stability [24—26]. As support, either inorganic materials such as porous glass or different organic polymers are used [27]. These heterogeneous catalyst particles are subject to internal and external... 

Residues containing high levels of heavy metals are not suitable for catalytic cracking units. These feedstocks may be subjected to a demetallization process to reduce their metal contents. For example, the metal content of vacuum residues could be substantially reduced by using a selective organic solvent such as pentane or hexane, which separates the residue into an oil (with a low metal and asphaltene content) and asphalt (with high metal content). Demetallized oils could be processed by direct hydrocatalysis. 

Corrosion reactions in aggressive organic solvents are becoming a more frequent occurrence owing to developments in the chemical and petrochemical industries, and these reactions can lead to the deterioration of the metal and to undesirable changes in the solvent. This aspect of corrosion has recently been the subject of an extensive review by Heitz who has considered the mechanisms of the reactions, the similarities between corrt ion in organic solvents and in aqueous solutions, the methods of study and the occurrence of the phenomenon in industrial processes. 

A typical penicillin broth contains 20-35 mg/1 of antibiotic. Filtration is used to remove mycelial biomass from fermentation broth. The filtration may be subjected to filter aided polymers. Neutralisation of penicillin at pH 2-3 is required. Amyl acetate or butyl acetate is used as an organic solvent to remove most of the product from the fermentation broth. Finally, penicillin is removed as sodium penicillin and precipitated by a butanol-water mixture. 

Several reports deal also with the effects of ionic liquids on enzyme enantioselectivity, which is the subject of this chapter. Although in several cases there was no change or even a decrease in enantioselectivity compared to organic solvents [47], in other cases improved enantioselectivity was observed [47,49-56]. In the following text, the latter cases will be examined in some detail. 

Dohrn CS, Lichtor JL, Finn RS, et al Subjective and psychomotor effects of nitrous oxide in healthy volunteers. Behav Pharmacol 3 19-30, 1992 Dohrn CS, Lichtor JL, Coalson DW, et al Reinforcing effects of extended inhalation of nitrous oxide in humans. Drug Alcohol Depend 31 263-280, 1993 Evans AC, Raistrick D Phenomenology of intoxication with toluene-based adhesives and butane gas. Br J Psychiatry 130 769-773, 1987 Evans EB, Balster RL CNS depressant effects of volatile organic solvents. Neurosci Biobehav Rev 13 233—241, 1991... 

Whilst total elimination of volatile organic solvents from all chemical manufacturing processes is a worthy goal, the pursuit of this goal must be subject to some caution. Alternative organic solvent-free processes may have poor heat and/or mass transfer and/or viscosity limitations, which could result in excessive energy use or the production of less pure... 

Phenol, the simplest and industrially more important phenolic compound, is a multifunctional monomer when considered as a substrate for oxidative polymerizations, and hence conventional polymerization catalysts afford insoluble macromolecular products with non-controlled structure. Phenol was subjected to oxidative polymerization using HRP or soybean peroxidase (SBP) as catalyst in an aqueous-dioxane mixture, yielding a polymer consisting of phenylene and oxyphenylene units (Scheme 19). The polymer showed low solubility it was partly soluble in DMF and dimethyl sulfoxide (DMSO) and insoluble in other common organic solvents. 

Fluorinated phenols, 3- and 4-fiuorophenols, and 2,6-difluorophenol, were subjected to peroxidase-catalyzed polymerization in an aqueous organic solvent, yielding fluorine-containing polymers. Elimination of fluorine atom partly took place during the polymerization to give polymers with complicated structures. 

A homogenized sample of cereals, vegetables, fruits or potatoes (10-20 g) is extracted with an organic solvent such as acetone and methanol. After filtration, the extract is concentrated to about 20 mL by rotary evaporation below 40 °C. The residue is transferred with 5% sodium chloride (NaCl) aqueous solution and partitioned twice with n-hexane. The n-hexane extracts are dried with anhydrous sodium sulfate and subjected to a Florisil column chromatographic cleanup procedure. The eluate from the Horisil column is concentrated to dryness and the residue is dissolved in an appropriate amount of acetone for analysis by GC/NPD. ... 

While excited-state properties of monomeric carotenoids in organic solvents have been the subject of numerous experimental and theoretical studies (Polfvka and Sundstrom 2004), considerably less is known about excited states of carotenoid aggregates. Most of the knowledge gathered so far stems from studies of aggregation-induced spectral shifts of absorption bands of carotenoid aggregates that are explained in terms of excitonic interaction between the molecules in the aggregate. 

Substrate can be added to the cultures as a solid, a suspension, or a solution in DMSO, methanol, ethanol, acetonitrile or water. As the microbial culture generally has high tolerance toward organic solvents, there is less restriction on the choice and amount of solvent to be used for dispensing the substrate. Aqueous solubility of substrates normally will not affect compound loading, as a compound with poor aqueous solubility will likely be absorbed by the cells and still be subjected to biotransformation. 

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