Solvent anhydrous

Step 2 On reaction with hydrogen chloride m an anhydrous solvent the thiocarbonyl sulfur of the PTC derivative attacks the carbonyl carbon of the N terminal ammo acid The N terminal ammo acid is cleaved as a thiazolone derivative from the remainder of the peptide... 

The free maleic acid content in maleic anhydride is determined by direct potentiometric titration (166). The procedure involves the use of a tertiary amine, A/-ethylpipetidine [766-09-6J, as a titrant. A tertiary amine is chosen as a titrant since it is nonreactive with anhydrides (166,167). The titration is conducted in an anhydrous solvent system. Only one of the carboxyhc acid groups is titrated by this procedure. The second hydrogen s dissociation constant is too weak to titrate (166). This test method is not only used to determine the latent acid content in refined maleic acid, but also as a measure of the sample exposure to moisture during shipping. 

By working in anhydrous solvents even aldimines like (296) could be prepared (79TL3201). 

Although the catalysis of the dimerization of aldehydes to acyloins by thiazolium ion has been known for some tlrae, the development of procedures using anhydrous solvents which give satisfactory yields of acyloins on a preparative scale was first realized in the submitters laboratories. The mechanism proposed by Breslow - for the thiazolium ion-catalyzed reactions is similar to the Lapworth mechanism for the benzoin condensation with a thiazolium ylide replacing the cyanide ion. Similar mechanisms are involved... 

It is interesting to note that 4-aminopent-3-en-2-one (85), which is held in a cisoid arrangement by hydrogen bonding, gives the product 86, which is stable in anhydrous solvent, but which cyclizes under the influence of water to give methyl 2-methyl-5-oxo-4-(2-oxopropylidene)-2-pyrroline-3-carboxylate (87). 

Another anhydrous solvent that is frequently used for the synthesis of tantalum and niobium fluoride compounds is bromine trifluoride, BrF3. At ambient temperature, bromine trifluoride is light yellow liquid characterized by a boiling point of 126°C, a melting point of 9°C and a density of 2.84 g/cm3 at melting temperature. 

Acetyl eneozonide. C2H2 03, has never been isolated, According to Briner et al (Ref 3), ozoniza-tion of acetylene in gaseous form resulted in expins. However, when the ozonization was conducted in an anhydr solvent by one of the methods described by Harries (Ref 2) for ozonization of unsaturated hydrocarbons, Briner was able to obtain some crystals which were unstable and exploded before they could be examined. When the solvent used in the prepn was rapidly evaporated, the residue exploded... 

According to the processes mentioned above, MA was reacted with a primary or secondary amine, as shown in Scheme 5. Amidation usually occures in 1 h at a temperature below 100°C either in suitable anhydrous solvents or in the absence of solvents. Then the resulting maleamic acid can be esterified with or... 

The diazo transfer reaction between p-toluenesulfonyl azide and active methylene compounds is a useful synthetic method for the preparation of a-diazo carbonyl compounds. However, the reaction of di-tert-butyl malonate and p-toluenesulfonyl azide to form di-tert-butyl diazomalonate proceeded to the extent of only 47% after 4 weeks with the usual procedure." The present procedure, which utilizes a two-phase medium and methyltri-n-octylammonium chloride (Aliquat 336) as phase-transfer catalyst, effects this same diazo transfer in 2 hours and has the additional advantage of avoiding the use of anhydrous solvents. This procedure has been employed for the preparation of diazoacetoacetates, diazoacetates, and diazomalonates (Table I). Ethyl and ten-butyl acetoacetate are converted to the corresponding a-diazoacetoacetates with saturated sodium carbonate as the aqueous phase. When aqueous sodium hydroxide is used with the acetoace-tates, the initially formed a-diazoacetoacetates undergo deacylation to the diazoacetates. Methyl esters are not suitable substrates, since they are too easily saponified under these conditions. 

Although solutions of bromine pentafluoride in acetonitrile were reported stable at ambient temperature [1], it has been found that a 9% solution in the anhydrous solvent prepared at — 196°C decomposed violently, bursting the container, about 1 h after attaining ambient temperature [2],... 

PPL catalyzed polycondensation of bis(2,2,2-trichloroethyl) alkanediaoates with glycols in anhydrous solvents of low polarity to produce the polyesters [34, 35]. In the polymerization of bis(2-chloroethyl) succinate and 1,4-butanediol using Pseudomonas fluorescens lipase (lipase PF) as catalyst, the polyester with low molecular weight was formed [36]. This may be due to the low enzymatic reactivity of the succinate substrate. 

Wash the activated particles 3 times with anhydrous solvent to remove excess DSC and reaction by-products. After the final wash, remove the solvent and perform a quick wash with ice-cold water to remove most traces of solvent in the particle pellet. 

The carboxymethyl-dextran derivative may be used to couple amine-containing molecules by the carbodiimide reaction. Heindel et al. (1994) prepared the lactone derivative of carboxymethyl-dextran by refluxing for 5 hours in toluene or other anhydrous solvents. The lactone derivative is highly reactive toward amine-containing molecules, thus creating a preactivated polymer for conjugation purposes. 

The use of anhydrous solvents is necessary to avoid hydrolytic decomposition of 2,3-dichloro-5,6-dicyano-l,4-benzoquinone. 

This reaction is also used to characterise organic bases and to identify through a melting-point determination small amounts, particularly of the liquid bases, by converting them into their usually crystalline acyl derivatives. In order to cause the whole of the base to react—one mole is fixed by the hydrochloric acid liberated—alkali or carbonate is added when aqueous solutions or suspensions are used and dry potassium carbonate or pyridine when anhydrous solvents are employed. Since tertiary bases do not react with acid (acyl) chlorides, no further replaceable hydrogen atom being present, it is possible by the use of an acid chloride to determine also whether a base is, on the one hand, primary or secondary, or, on the other hand, tertiary. 

Secondary amines such as methylaniline and diphenylamine also form nitrosamines very rapidly. By means of gaseous hydrochloric acid in anhydrous solvents they undergo rearrangement to the isomeric p-nitroso-bases. 

Anhydrous solvents such as diethyl ether, N,N-dimethylformamide, toluene, and methanol were purchased from Mallinckrodt Inc. and were used without further drying. Concentrated hydrochloric acid and ammonium hydroxide were also purchased from Mallinckrodt Inc. 

Chemicals and Nanoparticles. All chemicals were used without further treatment. Anhydrous solvents and chemicals were stored in a drybox and used under dry nitrogen gas. 

Chromium (I I) salts are widely used in organic synthesis. However, the high sensitivity to air and the low solubility of Cr(III) salts in anhydrous solvents prevent their synthetic use as electrocatalysts. The electroreduction of both CO2 and CO to methanol has been achieved by the... 

A major cause of suboptimal activity in organic solvent results from the removal of essential water during enzyme dehydration. All enzymes require some water in order to retain activity through the provision of conformational flexibihty. Particularly in the case of lipases, the amount of water can be so low that it appears that none is required. For example, following the development of suitable techniques to analyse low water concentrations, it has been reported that the lipase from Rhizomucor miehei retains 30 % of its optimum activity with as little as two or three water molecules per molecule of enzyme.Owing to the apparent absence of water in some exceptional cases, the term biocatalysis in anhydrous solvent is commonly used, although in the vast majority of cases a monolayer of water is required for optimal activity (although this is often stUl well below its solubility limit in water-immiscible solvent). ... 

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