Insoluble Products

A precipitation reaction occurs when two or more soluble species combine to form an insoluble product that we call a precipitate. The most common precipitation reaction is a metathesis reaction, in which two soluble ionic compounds exchange parts. When a solution of lead nitrate is added to a solution of potassium chloride, for example, a precipitate of lead chloride forms. We usually write the balanced reaction as a net ionic equation, in which only the precipitate and those ions involved in the reaction are included. Thus, the precipitation of PbCl2 is written as... 

The most important types of reactions are precipitation reactions, acid-base reactions, metal-ligand complexation reactions, and redox reactions. In a precipitation reaction two or more soluble species combine to produce an insoluble product called a precipitate. The equilibrium properties of a precipitation reaction are described by a solubility product. 

Biacetyl is produced by the dehydrogenation of 2,3-butanediol with a copper catalyst (290,291). Prior to the availabiUty of 2,3-butanediol, biacetyl was prepared by the nitrosation of methyl ethyl ketone and the hydrolysis of the resultant oxime. Other commercial routes include passing vinylacetylene into a solution of mercuric sulfate in sulfuric acid and decomposing the insoluble product with dilute hydrochloric acid (292), by the reaction of acetal with formaldehyde (293), by the acid-cataly2ed condensation of 1-hydroxyacetone with formaldehyde (294), and by fermentation of lactic acid bacterium (295—297). Acetoin [513-86-0] (3-hydroxy-2-butanone) is also coproduced in lactic acid fermentation. 

Many techniques have been developed to accomplish this, for example, the use of a cooled recirculating system in which the chlorine is dissolved in one part and the allyl chloride is dissolved and suspended in another (61). The streams are brought together in the main reaction zone and thence to a separator to remove water-insoluble products. Another method involves maintaining any organic phase present in the reaction zone in a highly dispersed condition (62). A continuous reactor consists of a recycle system in which make-up water and allyl chloride in a volume ratio of 10—50 1 are added... 

In the early stages, considerable foaming usually occurs, and care must be exercised that the foam does not carry part of the insoluble product into the condenser. The insoluble material accumulating on the walls of the flask is occasionally returned to the liquid portion by whirling the flask. 

When one equiualini of cuprous iodide was treated with one equivalent of methyliithium the yelU)w, ether-insoLubli product wasfonved. Both the precipitate and thi eihir solution... 

Preparation of 7-amino-3-chloro-3-cephem-4-carboxylic acid To a solution of 750 mg (1 55 mmol) of p-nitrobenzyl 7-amino-3-chloro-3-cephem-4-carboxylate hydrochloride in 20 ml of tetrahydrofuran and 40 ml of methanol was added a suspension of 750 mg of prereduced 5% palladium on carbon catalyst in 20 ml of ethanol and the suspension was hydrogenated under 50 psi of hydrogen at room temperature for 45 minutes. The catalyst was filtered and washed with THF and water. The filtrate and catalyst washes were combined and evaporated to dryness. The residue was dissolved in a water-ethyl acetate mixture and the pH adjusted to pH 3. The insoluble product was filtered and triturated with acetone. The product was then dried to yield 115 mg of 7-amlno-3-chloro-3-cephem-4-carboxylic acid. 

The soiution was treated with 0.01 mol of formaldehyde in aqueous solution, with agitation. The solution was then filtered to eliminate traces of insoluble product and the filtrate was lyophilized. Sodium 6-[ D(-)-alpha-(methylene-amino-phenylacetamido)] -penicillanate was obtained. 

In practice, however, the soluble components are often contained in a matrix of insoluble product and formation of electrolyte by both capillary and chemical condensation may occur in the same humidity range. 

In the above equilibria it has been assumed that no insoluble products are formed nor any polynuclear species. 

It should form no volatile or insoluble product with the precipitate. 

Generally, wet chemical methods require the availability of compounds which are soluble in water or in another solvent. The dissolution in a solvent allows intimate mixture on an atomic or molecular scale. However, it has to be ensured that no compound precipitates before the others when the solvent is evaporated, or else insoluble products are formed. The importance of wet chemical methods lies in the possibility of simple upscaling to industrial needs. 

Triallyl monomers [e.g. (21) or salts thereof] can potentially undergo two successive intramolecular cyclizationsX15 1 However, in practice these materials give insoluble products. 

Tetrachlorodibenzo- -dioxm- C, U.L. 2,7-Dichlorodibenzo-p-dioxin- C, U.L. (0.500 gram) was stirred with 10 ml of chloroform containing trace amounts of FeCls and L and heated to reflux temperature while chlorine gas was passed into the mixture for 18 hours. After cooling, the white insoluble product was collected by filtration and triturated with 15 ml of boiling chloroform. The insoluble portion was transferred to a sublimation flask where it was vacuum-sublimed at 140 °C. The sublimate was recrystallized from 2.5 ml of anisole and washed with chloroform. The product weighed 0.229 gram and contained 2.9 /xCi of radioactivity per mg. 

Flory (5) states that gelled, insoluble products are formed by the inter-molecular reaction of units which are trifunctional or higher. An infinite network structure is formed however, it is limited only by the volume of the reaction mixture. The monomer size controls the rate of reaction. 

Attempts to oxidise silver dithiocarbamato complexes with halogens to compounds with the metal in higher oxidation states obviously failed. By addition of iodine to a solution of [Ag(Bu2 fc)]g in CHQ3, an insoluble product is formed with the composition rjA% S> X2dtc) 141). With other alkyl groups similar complexes are obtained. Investigations about the nature of this type of compounds are in progress. 

Not surprisingly, The amount of di-t-butylperoxide (DtBP) is an important factor affecting the outcome of the reaction. The level of incorporation increases in proportion to the amount of DtBP (compare samples 1, 2, 6). Too much of the radical promoter is deleterious, since sample 6 was partially orosslinked, and an attempted modification reaction using 6.53 mmol of DtBP produced a completely insoluble product, which apparently was highly crosslinked. 

Copolymerization reactions with p-methoxy-a-methylstyrene were also attempted at 0°C, and a methanol-insoluble product having an Mjj of 1600 was obtained over a period of 36 h. From the 250-MHz 1h-NMR spectrum, it was found that p-methoxy-a-methylstyrene was present in the polymer to the extent of 14%. 

Procedure To a dry Erlenmeyer flask of appropriate size, add one half of the reaction solvent. All reactants, including the dry mass of the hydroperoxide, should not constitute more than 23 weight percent of the reaction mixture or an insoluble product may be produced. Add dry lignin and dry calcium chloride to the reaction vessel and cap with a septum or rubber stopper. In a separate vessel, dissolve 2-propenamide in about one quarter of the DMSO solvent and, in a third vessel, dissolve the sulfonated monomer in the final one quarter of the solvent. Saturate both monomer solutions with by bubbling with the gas for 10 minutes. Saturate the lignin solution with for 10 minutes. Add the hydroperoxide to... 

When unamalgamated zinc dust is used, a considerable proportion of yellow insoluble product is often noted at this point. Since the disulfide has been isolated as an intermediate in a similar reduction of m-chlorosulfonylbenzoic acid,4 it is probable that this material is a mixture of disulfides of varying molecular weight. 

The reactive crystallization has some peculiar characteristics like insoluble product, initiation of reaction by change in pH and conductivity. In this case the solution becomes saturated and eventually supersaturated with respect to reactant nucleation [30], The ultrasound assisted decomposition precursors includes dissolving metal organic precursors in organic solvents/water with the assistance of surfactants leads to monodisperse and reduced metal/metal oxide nanoparticles. 

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