Formaldehyde in aqueous solution

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. 

Butyne-l,4-diol and propargylalcohol are produced by reaction between formaldehyde in aqueous solution and gaseous acetylene in the presence of a copper acetylide catalyst supported on nickel. The process is carried out by trickle-flow operation (BIO, S4). 

Figure 15.1 Reactions of formaldehyde with peptides and amino acids. Shown are the four types of reaction products seen when peptides or amino acids are treated with formaldehyde in aqueous solution. These reaction products are methylol (hydroxymethyl) adduct (reaction 15.1), Schiff-base (reaction 15.2), 4-imidazolidinone adduct (reaction 15.3), and one type of methylene bridge [cross-link] (reaction 15.4).

A further quantity of arabinose may be isolated from the mother liquors by the use of diphenylhydrazine to a solution of 22 g. of diphenylhydrazine hydrochloride in 100 cc. of absolute methyl alcohol is added a solution of 3.3 g. of sodium in 50 cc. of methyl alcohol. After fifteen minutes standing the sodium chloride is removed by filtration and washed with methyl alcohol. The filtrate, which contains approximately 18 g. of free diphenylhydrazine, is added to the alcoholic mother liquor from the arabinose and the mixture is inoculated with diphenylhydrazone prepared from some of the crystalline arabinose. The mixture is allowed to stand overnight, and the crystalline diphenylhydrazone is filtered, washed with 95 per cent ethyl alcohol, and dried in a vacuum desiccator. In a preparation in which the yield of crystalline arabinose had been 23.5 g., the yield of diphenylhydrazone was 16.5 g., corresponding to 7.8 g. of the sugar. Arabinose can be recovered from the diphenylhydrazone by treatment with formaldehyde in aqueous solution. In view of the... 

The synthetic applications of these reactions are considered in Section 61.4.15. Reaction of copper(II) glycinate with formaldehyde in aqueous solution at pH 12 gives serine, while reaction with acetaldehyde gives a mixture of threonine and allothreonine (Scheme 35). This reaction has been extended to a variety of aldehydes to obtain longer chain /3-hydroxyamino acids.439... 

Hydroxymethylation of N-unsubstituted tetrazoles. N-Unsubstituted tetrazoles react slowly with formaldehyde in aqueous solution at pH 5 to produce mixtures of 1- and 2-hydroxymethyl derivatives 223 and 224 <2000H(53)1421>. The use of acetic acid as the reaction medium shortens the reaction time and relieves the problems of solubility (Equation 28) <1997RJ0524>. 

Melamine, a white powder, was discovered and identified by Liebig in 1834 but commercial manufacture came only in 1939, by Cyanamid Company of America with dicyandiamide as raw material. Melamine is 2,4,6-triamino-l,3,5-triazine with a structure as shown in Figure 53. On reaction with formaldehyde in aqueous solution the melamine powder dissolves rapidly on heating to form various methylol melamines, as in Figure 54. After further heating and the elimination of water the methylol melamines condense to form resinous polymers. 

The type of polymer obtained depends on factors such as the pH and temperature of reaction, the ratio of melamine to formaldehyde, and the type of catalyst employed. For decorative laminates, melamine-formaldehyde is prepared by reacting melamine in stainless steel kettles under reflux, alkaline conditions with 37% to 46% formaldehyde in aqueous solution. The reaction temperatures used vary from 80 to 100°C and are maintained until the condensation has reached the desired end point—that is, reacted sufficiently but still water-soluble. The end point is checked by measurements of viscosity, cure time, and water tolerance. Depending on the type of laminate to be produced, other constituents (surfactants, plasticizers, release and anti-foam agents) normally are added to the base resin before impregnation of the surface papers. It is common practice also at this stage to adjust the pH by adding acid catalysts. 

Ureaform is produced by reaction of urea with formaldehyde in aqueous solution in the presence of an acid that catalyzes the reaction. The degree of polymerization depends on the mole ratio of urea to formaldehyde and on the pH, time, and temperature of reaction. The reaction is stopped by neutralizing the acid. Production processes have been described by Clark et al47 and by Kolterman and Rennie 48... 

IK Production of 2-butene-1.4-diol and propargyl alcohol by reaction between acetylene and formaldehyde in aqueous solution over a copper acetyhide catalyst supported on nickel 14, 52.99... 

The anodic reaction (34) is a catalytic process, and it proceeds in several distinct steps. Formaldehyde in aqueous solution is known to exist almost entirely in the form of methylene glycol [128] ... 

The racemic [Co(azasartacn)]Cl3 l/2CH30H C2H50H complex resulted fi om capping of [Co(taetacn)] + cation with ammonia and formaldehyde in aqueous solution in the presence of lithium carbonate. Only partial separation was achieved when attempts were made to resolve azasarcophaginate [Co(azasartacn)]- + cation into A- and A-forms by lEC. Therefore, the pre-resolved A- and A-[Co(taetacn)](C104)3 semiclathrochelates were used as initial compounds. As result, the A-and A-[Co(azasartacn)]2+ sarcophaginates were isolated as PFe salts and were additionally purified by fractional crystallization from aqueous solution [142]. 

Sodium hydroxymethanesulfinate Dithionites are the starting materials in the manufacture of sodium hydroxymethanesulfonate by the reaction of dithionites with formaldehyde in the presence of sodium hydroxide. In a variant of this process, zine dithionite, as starting material, reacts with formaldehyde in aqueous solution forming zinc salts of hydroxymethanesulfinic acid and hydroxymethanesulfonic acid. The latter is reduced to zinc hydroxymethanesulfinate with added zinc at 90 °C. 

Exposure to formaldehyde by the oral route can occur, but exposure is not as common as by the inhalation route because of the instability of formaldehyde in aqueous solution. Much of the information available about the effects of formaldehyde after oral exposure in humans comes from case reports of acute poisoning. Small amounts of formaldehyde can occur in foodstuffs, usually added as a preservative. 

Such solutions can contain up to 60 wt% formaldehyde in liquid form, while the solubility of formaldehyde in aqueous solutions is only 37 wt%. Modern resins are modified by second and third addition of urea to bring the over-all molar ratio sufficiently down to retain unreacted amino groups capable of acting as scavengers of... 

The pararosaniline method has been used widely for the determination of formaldehyde in aqueous solutions and in the atmosphere In this procedure mercury (II) - sulfite and acidified pararosaniline reagent were sequentially added to an aqueous formaldehyde solution (21.22). In 1965, an automated procedure for formaldehyde was described by Lyles et al (2L) Later, Lahmann and Jander ( 2) modified the reagent concentrations to enhance sensitivity This method has been adapted to the CEA 555... 

This product is known as hexamine in the plastics industry and urotropin in the pharmaceutical industry. The reaction is rapid and the yield is above 96%. In order to carry out the reaction, formaldehyde in aqueous solution reacts with anhydrous ammonia in a cooled reactor. The reaction product is purified by evaporation, centrifuging, and drying. The centrifuge wash liquors are virtually all recycled. 

Notably, formaldehyde in aqueous solutions is hydrated to methylene glycol [84] (D2C(OH)2 for the case of deuterated formaldehyde) with pK= 13, indicating that at pH= 13 methylene glycol is present at equal amounts with its anion [23,24]. Nevertheless, due to the absence of hydrogen... 

The first anticoagulant rodenticide was dicoumarin (19). Its anticoagulant effect was first observed on cattle. Coumarin has an odour reminiscent of hay. When mown sweet clover (Melilotus albe) becomes mouldy, dicoumarin is formed from coumarin, and cattle fed with such mouldy, sweet clover hay bleed to deat when injured because of reduced blood coagulation (Campbell and Link, 1941 Stahmann et al., 1941). Dicoumarin, 3,3 -methylene-bis(4-hydroxycoumarin), is obtained by the condensation of 2 moles of 4-hydroxycoumarin (20) and 1 mole of formaldehyde in aqueous solution. 

Two phenomena that have received much attention in studies of solvent effects on carbonyl additions are catalysis of formaldehyde hydration and the effect of solvation on the energy profile for the addition of hydroxide ion to formaldehyde in aqueous solution. 

The carbonyl component has been almost exclusively formaldehyde, in aqueous solution or as paraformaldehyde, and only rarely other aldehydes such as acetaldehyde.699... 

The first step in the preparation of urea or melamine resins is the reaction with formaldehyde in aqueous solution to form methylol compounds. 

Leptodactylus pentadactylus and L. ocellatus native to South and Central America, contain considerable amounts of 5-hydroxytryptamine derivatives, like N-methylserotonine, bufotenin and bufotenidin as well as leptodactylin and candicin (ref. 4). Of a new type are substances like histamin, methyl-, and acetyl-histamins, and spinaceamin. Spinaceamin can be synthesized in vitro by a biomimetic reaction of histamin and formaldehyde in aqueous solution at pH 6.8, and room temperature (ref. 5). 

SpN readily takes up only one mole of formaldehyde in aqueous solution to give an N-oxymethyl derivative with an unidentified structure, possibly 583 or 583a,b. When this derivative is either heated or acidified, one mole of formaldehyde is liberated (44BJ309). 

There is another electrophilic substitution reaction described in the literature where the results may be interpreted by general acid catalysis of the second step. Dijkstra et al. (1962) found that the rate of the reaction of phenol and formaldehyde in aqueous solution forming o-and p-methylolphenol is compatible with a mechanism involving pheno-late ion and formaldehyde in the first step. The steady-state intermediate forms the products with the aid of an additional phenol molecule and not a phenolate anion. In the opinion of the present author this phenol molecule may act as a proton donor to the carbonyl oxygen in the intermediate similar to mechanism (21). 

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