Impurities product yield

The catalytic hyilrcgonatiou of tho j5 Jactoi e in the preaenoe of Haney niokel, a pi-oceea v liioh ia frequently carried nut iuduistriaUy with impure products, yields organic acids.> . which can be... 

An impure product was obtained in a considerably lower yield. 

Jote 2. We have also carried out this synthesis in ethanol as a solvent but the results were not reproducible. Although a series of experiments with zinc powder from one flask gave reasonable results (50-78% yields), a new flask with the same batch number gave low yields of impure products. The main impurity was probably the non-conjugated diene, H2C=CH-CH2-CH=CH-CH3, possibly resulting from reduction of the 1,2,4-triene by the zinc. The... 

A vapor-phase process primarily for ECC off-gas feeds was developed by Sinopec Technology Company based on a 2eoHte catalyst of the Pentasd type (24,25). It reHes on frequent regeneration of the catalyst to minimi2e pretreatment of the ECC off-gas and allows the impurities in the feed gas to react with ben2ene to form by-products. Consequently, the product yield and purity are low. Joint licensing by ABB Lummus Crest and Sinopec was announced in 1994. 

The only practical method of preparing 1,4-aminonaphthol is from a-naphthol through an azo dye, the nitroso compound not being readily available. The majority of investigators have reduced technical Orange I with stannous chloride Mi.is.is.ir.is by the procedures discussed above, and benzeneazo-a-naphthol has been reduced by the same reagent. In order to make possible the use of crude, technical a-naphthol a method has been developed for the preparation of the benzeneazo compound, its separation from the isomeric dye coming from the d-naphthol present as well as from any disazo compound by extraction with alkali, and the reduction of the azo compound in alkaline solution with sodium hydrosulfite. The process, however, is tedious and yields an impure product. 

The presence of impurities such as butadiene affects the product yield and properties. Butadiene tends to polymerize and form acid-soluble oils, which increases acid makeup requirements. For every pound of butadiene in the feed, ten pounds of additional make-up acid will be required. ... 

Hydroxyphenylpyruvic acid plays an important role in the biogenesis of compounds with a phenylpropane skeleton, and it has been used as substrate in several enzyme studies. Published procedures for its preparation are unsatisfactory in many ways. The alkaline hydrolysis of the azlactone of a-bcnzoylamino- -acetoxycinnamic acid 7 makes necessary a tedious separation of the resulting benzoic acid, and the yield is only 34% based on -hydroxybenzaldehyde. The hydrolysis of 5- ( -hydroxybenzal)-3-phenylhydantoin 9 requires a separation of phenylurea. Finally, the two-step cleavage of the azlactone of a-acetamino- -acetoxycinnamic acid 8 does not proceed easily, and impure products are obtained. In applying this procedure to the synthesis of a carboxyl-labeled -hydroxyphenylpyruvic acid, the overall yield was only 9%.u It must be kept in mind that any prolonged isolation procedure will cause some decomposition of this sensitive compound. 

The superiority of extractive hydrolysis over acid hydrolysis with respect to its productivity, yield, raw materials, and waste streams, for the transformation of drug intermediates (e.g. for Primaxin) in formate ester form to the corresponding alcohol, has been effectively demonstrated by King et al. (1985). They carried out the hydrolysis of the relevant formate ester with simultaneous extraction of the desired product from the undesired impurities by two-phase reaction/extraction with a base. 

N, and solute passage Si needed to produce desired retentate product with impurity concentrations Cj and retentate product yield Mj/Mjo. Permeate product characteristics for batch operation can be determined by mass balances using a permeate volume of Vp = Vo(l 1/X + N/X), a mass of solute i in the permeate as Mj perme e = Mjo(l — and the permeate concentration as the ratio of the... 

Concentration of the filtrate yields a second crop of impure product, which is recrystallized from toluene and then melts at 119-120°. The combined yield of pure white o-phenylene carbonate from the first and second crops is 107-116 g. (79-86%). 

Nitric acid of lower specific gravity than 1.42 at 15.5° yields an impure product. Ordinary concentrated nitric acid usually has to be strengthened by the addition of fuming nitric add. 

Most early publications on bacterial polysaccharides were concerned with impure products and poorly-described organisms. Many more recent papers are of limited value also, due to low yields, lack of characterization of products and arbitrary interpretations of data. Low yields of methylated polysaccharides may be due to degradation of the bacterial polysaccharide during methylation, or to degradation of the hydrolytic products of the methylated polysaccharide (to form methyl levulinate, etc.46). The great importance of (a) complete methylation of polysaccharide products prior to structural determination by hydrolysis and (6) quantitative identification of the hydrolytic products, has been emphasized previously. Other difficulties in end group analysis have been discussed recently.7... 

Early reports on levan are obscured by incomplete descriptions of impure products.2 96 Greig-Smith found that Bacillus levaniformans(1) produced levan from sucrose96" in suitable nutrient solutions, but not from D-glucose, D-fructose, lactose or maltose.966 He therefore assumed that levan could only be formed from the nascent D-fructose and D-glucose resulting from the inversion of sucrose. Hydrolysis of levan yielded D-fructose only, and analysis of levan agreed with the empirical formula (C HiriOi) it was noted that levan was closely related to inulin but was not identical with it. 

A dual-bed catalyst system has been developed to tackle the key problems in benzene product impurity during heavy aromatics transalkylation processing over metal-supported zeolite catalysts. It was found that by introducing zeolite H-Beta as a complementary component to the conventional single-bed Pt/ZSM-12 catalyst, the cascaded dual-bed catalyst shows synergistic effect not only in catalytic stability but also in adjustments of benzene product purity and product yields and hence should represent a versatile catalyst system for heavy aromatics transalkylation. 

What was the actual percentage yield of the impure product ... 

The coupling of Naphtol AS or its phenyl-substituted derivatives with diazonium salts from variously substituted anilines in aqueous alkaline solution (section 4-11) gave incomplete reactions and impure products in some instances, probably because these coupling components have inadequate solubility in aqueous media. Pure dyes in ca. 90% yields were obtained by reaction in dimethylformamide in the presence of sodium acetate. Metallisation of these o,o -dihydroxyazo ligands with sodium chromium salicylate or a cobalt(II) salt gave metal-complex dyes in 80-100% yields [22]. Specific structural isomers of these complexes were identified by i.r., n.m.r., Raman and UV/visible spectroscopy [23]. 

N-(3-ethvnvlphenvl)maleimide—N-(3-ethynylphenyl)maleamic acid (21.5 g 0.100 mol), anhydrous sodium acetate (6.0 g 0.0731 mol), and 175 mL of acetic anhydride (1.86 mol) were stirred together and heated at 50°C for 3 hr. The reaction mixture was cooled to room temperature and filtered. The filtrate was precipitated in an ice-water mixture to yield an impure product. This product was dissolved in hot ethanol and recrystallized by addition of cold water to yield 5.3 g (27% of theory) of a fine yellow powder, m.p. 130-131°C. 

If the first two extractions with alcohol do not yield about 90 g. of crude product, a third extraction of the sand and residue is well worth while (the yield of impure product was never less than 90 g. when this procedure was carried out). 

The order and timing of the addition of reagents in the KA-process is varied but in a typical procedure three reagents, namely, acetic anhydride, a solution of ammonium nitrate in nitric acid, and solid hexamine dinitrate, are added slowly, in small portions and in parallel, into the reaction vessel which is preheated to 60-80 °C. On completion the reaction mixture is often cooled to 50-60 °C and the RDX filtered and sometimes washed with acetic acid. This process produces a product which melts over a 2 °C range but the RDX still contains up to 10 % HMX as a by-product. Dilution of the reaction mixture with water before removing the RDX produces a very impure product containing numerous unstable linear nitramine-nitrates. Based on the assumption that one mole of hexamine dinitrate produces two mole of RDX the KA-process commonly yields 75-80 % of RDX. 

Excellent yields can be obtained when the mixture of RC=CLi and the epoxide in ammonia is allowed to stand for 12 to 24 hours [2]. With sodium acetylides, there is some risk of subsequent attack of the acetylenic alcoholate on the epoxide, especially when the latter compound is used in excess. The reaction of acetylenic magnesium halides, RCsCMgX, with epoxides also leads to homopropargylic alcohols, but this is generally not recommended as a satisfactory method, as impure products are often obtained [62], Coordination of the epoxide-oxygen atom with the Lewis acid may give rise to a Sjql-like attack of RCaC on... 

Compared to the reaction in exp. 30, the conversion of 2,3-dibromotetrahydrofuran with propynylmagnesium bromide can be carried out at higher temperatures, so that the reaction time can be shortened to 2 h at 50 C. When propynyUithium is used instead of the Griguard reagent, a very impure product is obtained in low yield. Elimination possibly predominates with the more strongly basic lithium alkynylides (compare exp. 28). 

In one experiment with 750 ml. of acetic acid, the resulting impure product was washed first with water to remove acetic acid and then with 1 N sodium hydroxide to remove />-tolylsul-fonylmethylamide (the nitroso compound is not attacked by cold aqueous sodium hydroxide). The yield of />-tolylsulfonylmethyl-nitrosamide was 76%, m.p. 58-60°. Acidification of the alkaline wash yielded (9% recovery) the jb-tolylsulfonylmethylamide, m.p. 77.5-78.5°. 

The methods for producing diacetone alcohol are the action of barium hydroxide on acetone 1 the action of calcium hydroxide on acetone 2 the action of concentrated sodium hydroxide or potassium hydroxide on acetone 3 the action of magnesium amalgam on acetone 4 and the action of nitrous acid on diace-tonamine.5 The last method was not considered because of the difficulty of preparing diacetonamine. Of the methods employing acetone only, the first two seemed more promising, since the others are reported as giving low yields of impure product. It was soon found that barium hydroxide acted more rapidly than calcium hydroxide (as reported by L. P. Kyriakides) and this method was therefore employed. 

If the mother liquor is further evaporated to 300ml additional impure product is obtained, which is contaminated with tris(ethylenediamine) cobalt fill) chloride and ethyl-enediamine dihydrochloride. After it is dried at 100° C, the yield is about 18g of solid. 

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