Solvents, acidic unreactive

The molecular weight of the polymers is controlled by temperature (for the homopolymer), or by the addition of organic acid anhydrides and acid hahdes (37). Although most of the product is made in the first reactor, the background monomer continues to react in a second reactor which is placed in series with the first. When the reaction is complete, a hindered phenoHc or metal antioxidant is added to improve shelf life and processibiUty. The catalyst is deactivated during steam coagulation, which also removes solvent and unreacted monomer. The cmmbs of water-swoUen product are dried and pressed into bale form. This is the only form in which the mbber is commercially available. The mbber may be converted into a latex form, but this has not found commercial appHcation (38). 

Add 20 g of clean sodium methal to 325 ml of cooled (-16°) dry ethanol. Add 100 g of 3-methyl-cyclohexanone in small amounts over a period of 1 hour and 150 g of diethyloxylate while keeping Ae temp below -11°. Maintain this temp for 3 hours, then 12 hours at room temperature. Make a solution of 1.3 liters of water and 60 ml of 2 N sulfuric acid and add this to the reaction mixture. The resulting yellow brown oil is separated and the water is extracted with ether until the yellow color is removed. Combine the oil and the extracts and distill off the solvent and unreacted starting material at 100° with 13 mm of vacuo. Slowly heat the residue to 220° and hold there for 90 min. Fractionally distill 2 times to get a little over 80 g of colorless oily product. 

A broad spectrum of racemic 2-hydroxy acids 65 were resolved via lipase-catalyzed enantioselective acetylation to their corresponding 2-acetoxy acids 66 using vinyl acetate as acyl donor in methyl Art-butyl ether as organic solvent. The unreacted enantiomer (R)-65 was recovered with ee values up to >99%.80... 

Benzoic acid prepared catalytically from phthalic anhydride may contain certain undesirable compounds, tars, and coloring materials and must of necessity be purified in some cases to obtain a marketable product. Naphthoquinone impurities are reduced to naphthohydroquinones by treatment of the product with sulfur dioxide or sodium bisulfite at 40° to 50° C. for 3 to 4 hours. Any phthalic anhydride remaining is converted to phthalic acid at the same time. Leaching with water is used to remove the reduced impurities.72 Unconverted phthalic acid may also be separated from benzoic by treatment of the mass with sodium carbonate so as to convert the polycarboxylic acid into a primary salt while leaving the mono-carboxylic acid unreacted. Solvent leaching is then used to separate the salt from the acid.78 Colored impurities in benzoates from synthetic benzoic acid may be removed by oxidation with potassium permanganate.71... 

A flask was charged with 4-chloronitrobenzene (3.0 g, 0.019 mol) and KCN (6.45 g, 0.099 mol) in 26 mL of 48% aqueous ethanol, and the reaction mixture was refluxed for 48h. The mixture was allowed to cool to rt and transferred into a flask with the aid of water, then the solution was made basic with the addition of NaOH. Organic solvent and unreacted starting material were removed by steam distillation and then the residue was acidified. Steam was again passed through the acidified solution until 1.5 L of distillate was collected. The pH of the distillate was adjusted with NaHCOs, and the volume of the solution was reduced via distillation to approximately 200 mL. Then the residue was acidified. The resulting precipitate was collected by filtration to give 1.2 g (0.0076 mol) 3-chlorobenzoic acid. 

A major advantage of this technique is that these reactions usually proceed very rapidly at room temperature and atmospheric pressure, in contrast to the long times, high temperatures, and vacuums usually associated with polycondensations. This must be balanced against the cost of preparing the special monomers, such as the acid chloride above, and the need to separate and recycle solvents and unreacted monomers. 

A combination of the promoting effects of Lewis acids and water is a logical next step. However, to say the least, water has not been a very popular medium for Lewis-acid catalysed Diels-Alder reactions, which is not surprising since water molecules interact strongly with Lewis-acidic and the Lewis-basic atoms of the reacting system. In 1994, when the research described in this thesis was initiated, only one example of Lewis-acid catalysis of a Diels-Alder reaction in water was published Lubineau and co-workers employed lanthanide triflates as a catalyst for the Diels-Alder reaction of glyoxylate to a relatively unreactive diene . No comparison was made between the process in water and in organic solvents. 

Direct, acid catalyzed esterification of acryhc acid is the main route for the manufacture of higher alkyl esters. The most important higher alkyl acrylate is 2-ethyIhexyi acrylate prepared from the available 0x0 alcohol 2-ethyl-1-hexanol (see Alcohols, higher aliphatic). The most common catalysts are sulfuric or toluenesulfonic acid and sulfonic acid functional cation-exchange resins. Solvents are used as entraining agents for the removal of water of reaction. The product is washed with base to remove unreacted acryhc acid and catalyst and then purified by distillation. The esters are obtained in 80—90% yield and in exceUent purity. 

C, which decomposes when heated above the melting point. Its solubility at 25°C in g/100 g solvent is water. 111 methanol, 5 ethanol, 1.4 acetone, 0.04 and carbon tetrachloride, 0.004. Because its carbon—fluorine bond is unreactive under most conditions, this salt can be converted by standard procedures to typical carboxylic acid derivatives such as fluoroacetyl esters (11,12), fluoroacetyl chloride [359-06-8] (13), fluoroacetamide (14), or fluoroacetonitrile [503-20-8] (14). 

Titrations with dibutylamine [111-92-2] can also be used to determine the NCO content of isocyanates and prepolymers. Generally, an excess of amine in a suitable solvent such as chlorobenzene [108-90-7] is added to the sample. The resulting solution is allowed to react and the unreacted amine is back- titrated with dilute hydrochloric acid. For low NCO content levels, a colorimetric method is often used. The isocyanate-containing species is titrated with amine and the unreacted amine is deterrnined using malachite green [569-64-2]. 

Hydrochloric acid [7647-01-0], which is formed as by-product from unreacted chloroacetic acid, is fed into an absorption column. After the addition of acid and alcohol is complete, the mixture is heated at reflux for 6—8 h, whereby the intermediate malonic acid ester monoamide is hydroly2ed to a dialkyl malonate. The pure ester is obtained from the mixture of cmde esters by extraction with ben2ene [71-43-2], toluene [108-88-3], or xylene [1330-20-7]. The organic phase is washed with dilute sodium hydroxide [1310-73-2] to remove small amounts of the monoester. The diester is then separated from solvent by distillation at atmospheric pressure, and the malonic ester obtained by redistillation under vacuum as a colorless Hquid with a minimum assay of 99%. The aqueous phase contains considerable amounts of mineral acid and salts and must be treated before being fed to the waste treatment plant. The process is suitable for both the dimethyl and diethyl esters. The yield based on sodium chloroacetate is 75—85%. Various low molecular mass hydrocarbons, some of them partially chlorinated, are formed as by-products. Although a relatively simple plant is sufficient for the reaction itself, a si2eable investment is required for treatment of the wastewater and exhaust gas. 

An excess of crotonaldehyde or aUphatic, ahcyhc, and aromatic hydrocarbons and their derivatives is used as a solvent to produce compounds of molecular weights of 1000—5000 (25—28). After removal of unreacted components and solvent, the adduct referred to as polyester is decomposed in acidic media or by pyrolysis (29—36). Proper operation of acidic decomposition can give high yields of pure /n j ,/n7 j -2,4-hexadienoic acid, whereas the pyrolysis gives a mixture of isomers that must be converted to the pure trans,trans form. The thermal decomposition is carried out in the presence of alkaU or amine catalysts. A simultaneous codistillation of the sorbic acid as it forms and the component used as the solvent can simplify the process scheme. The catalyst remains in the reaction batch. Suitable solvents and entraining agents include most inert Hquids that bod at 200—300°C, eg, aUphatic hydrocarbons. When the polyester is spHt thermally at 170—180°C and the sorbic acid is distilled direcdy with the solvent, production and purification can be combined in a single step. The solvent can be reused after removal of the sorbic acid (34). The isomeric mixture can be converted to the thermodynamically more stable trans,trans form in the presence of iodine, alkaU, or sulfuric or hydrochloric acid (37,38). 

The yields of primary chloroformates are usually well above 90%. The secondary chloroformates give yields of 80—90%. In cases where the alcohols are most unreactive, an acid acceptor may be used to drive the reaction. Commercial processes are usually mn neat, although solvents such as chloroform, toluene, dioxane, or THE are sometimes used to dissolve the starting alcohol or the product chloroformate as maybe necessary. 

A water-reducible coating or resin is one that is diluted with water before use. Water-reducible alkyds give comparable drying performance to solvent-bome alkyds. However, they are not widely used because film properties tend to be poorer than those of solvent-bome alkyds, especially in air-dry systems (26). This is pardy because of alcoholysis of the alkyd by primary alcohols such as 1-butanol [71-36-3] C H qO, a common solvent in water-reducible alkyds (27,28) secondary alcohols such as 2-butanol [78-92-2] C qH O, minimize this problem (27). In any case, the slow loss of amine or ammonia leads to short-term high sensitivity to water. Even in the fully dry films, the presence of unreacted carboxyHc acid groups leads to films having comparatively poor water resistance limiting their usehilness. 

The propionamide can be dried over CaO. H2O and unreacted propionic acid were removed as their xylene azeotropes. It was vacuum dried. Material used as an electrolyte solvent (specific conductance less than 10 ohm cm" ) was obtained by fractional distn under reduced pressure, and stored over BaO or molecular sieves because it readily absorbs moisture from the atmosphere on prolonged storage. [Hoover Pure Appl Chem 37 581 I974 Recommended Methods for Purification of Solvents and Tests for Impurities, Coetzee Ed., Pergamon Press, 1982.]... 

The reactivity of mercury salts is a fimction of both the solvent and the counterion in the mercury salt. Mercuric chloride, for example, is unreactive, and mercuric acetate is usually used. When higher reactivity is required, salts of electronegatively substituted carboxylic acids such as mercuric trifiuoroacetate can be used. Mercuric nitrate and mercuric perchlorate are also highly reactive. Soft anions reduce the reactivity of the Hg " son by coordination, which reduces the electrophilicity of the cation. The harder oxygen anions leave the mercuric ion in a more reactive state. Organomercury compounds have a number of valuable synthetic applications, and these will be discussed in Chapter 8 of Part B. 

When diazomethane is slowly added to excess lactam, the anions formed can interact with unreacted lactam by means of hydrogen bonds to form ion pairs similar to those formed by acetic acid-tri-ethylamine mixtures in nonpolar solvents. The methyldiazonium ion is then involved in an ion association wdth the mono-anion of a dimeric lactam which is naturally less reactive than a free lactam anion. The velocity of the Sn2 reaction, Eq. (7), is thus decreased. However, the decomposition velocity of the methyldiazonium ion, Eq. (6a), is constant and, hence, the S l character of the reaction is increased which favors 0-methylation. It is possible that this effect is also involved in kinetic dependence investigations have shown that with higher saccharin concentrations more 0-methylsaccharin is formed. 

After cooling, unreacted ethylenediamine is neutralized in a cooling mixture with the absolute ethanolic hydrochloric acid, filtered off from any components that are insoluble in ethanol and approximately two-thirds of the solvent filtered off under suction in a water jet pump vacuum. Residual quantities of ethylenediamine dihydrochloride are precipitated in fractions by the careful addition of ethyl methyl ketone, after which the imidazoline hydrochloride is separated off by the addition of dry ether. Following repeated recrystallization from ethanol ether, 2-[0(-(2,6-dichlorophenoxy)ethyl] -A -imidazoline hydrochloride is obtained in the form of small white crystals melting at 221°C to 223°C. 

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