Formaldehyde preparation

Pure formaldehyde, prepared by vacuum depolymerisation of paraldehyde, was collected as a solid at — 189°C. When the flask was transferred to a Cardice-ethanol bath, the contents began to repolymerise exothermally and ignited. 

Experiment 6. Reaction with Ammonia.—Of the formaldehyde prepared 10 c.c. are mixed with a small excess of ammonia and the mixture is evaporated in a small glass dish on the water bath. The colourless crystals which remain consist of hexamethylenetetramine (CH2)6N4 (urotropine.) This reaction proceeds quantitatively. It should be so carried out and the result compared with that obtained by titration. 

Experiment 12. Schardinger s Reaction.—Of two 25 c.c. portions of fresh milk one is boiled for a short time and cooled then 1 C.c. of the formaldehyde (prepared in an earlier experiment) and a few drops of an aqueous solution of methylene blue are added to each portion. When the two samples are now warmed to about 50° the dye in the unboiled milk is very rapidly decolorised and the same happens to further amounts added. In the boiled milk the colour remains unaltered. 

Addition of organometallic reagent to formaldehyde preparation of primary alcohols... 

Formaldehyde. Preparation of phenol-formaldehyde resins can result in uncontrollable... 

Production/preparation of particular products Sulfuric and nitric acid manufacture Formaldehyde preparation Chemical synthesis 4, 26, 86... 

Some hetero double bond systems have been shown to enter [3 + 2] cycloaddition reactions with the mesoionic 1,3-dithiolones. Thus, the mesoionic 1,3-dithiolones (2) react with formaldehyde, prepared in situ by depolymerization of paraformaldehyde, with regiospecific formation of the 2-oxa-6,7-dithiabicyclo[2.2.1]heptanone derivatives (131). The corresponding reaction of (2) with the N=N double bond of dimethyl azodicarboxylate proceeds via cycloaddition yielding (132), and a similar reaction takes place between (2) and 4-phenyl-l,2,4-triazoline-3,5-dione (78CB3171). 

Acidity (as acetic acid) Mix 38 mL of sample with an equal volume of carbon dioxide-free water, add 0.1 mL of phenol-phthalein TS, and titrate with 0.1 A sodium hydroxide. Not more than 0.1 mL is required to produce a pink color. Aldehydes (as formaldehyde) Prepare a Sample Solution by diluting 2.5 mL of sample with 7.5 mL of water. Prepare a Standard Solution containing 40 p,g of formaldehyde in 10 mL of water. Add 0.15 mL of a 5% solution of 5,5-dimethyl-1,3-cyclohexanedione in alcohol to each solution, and evaporate on a steam bath until the Acetone is volatilized. Dilute to 10 mL with water, and cool quickly in an ice bath while stirring vigorously. Any turbidity produced in the Sample Solution does not exceed that produced in the Standard Solution. 

CHEMICAL PROPERTIES volatile liquid polymerization may be caused by oxidizers, peroxides, elevated temperature, or sunlight reacts with water to form hydrochloric acid and formaldehyde prepared by passing hydrochloric acid through a mixture of fomalin and methanol FP(15°C, 60°F). 

Methoxyhexylmagnesium chloride, obtained from l-chloro-5-methoxyhexane and Mg in anhydrous ether with ethylene bromide and ethyl bromide as initial activators, treated at reflux with anhydrous gaseous formaldehyde prepared by heating a soln. of hydroxymethoxycyclohexane 6-methoxyheptanol. Y 78%. F. e. s. G. Michel and S. Tchelitcheff, Bl. 196A, 2230 ethylene bromide as entrainer s. D. E. Pearson and D. Gowan, Org. Synth. 44, 78 (1964). 

Formaldehyde Prepare stock standards by diluting known volumes of 37% formaldehyde solution with methanol. A procedure to determine the formaldehyde content of these standards is presented in Section 4. A standard containing 7.7 mg/mL formaldehyde was prepared by diluting 1 mL of the 37% reagent to 50 mL with methanol. 

Highly dispersed crosslinked melamine-formaldehyde structures have been prepared by Reimer [37]. In a typical open pore melamine-formaldehyde preparation, a melamine resin that has a low memelamine fonnaldehyde molar ratio (1 1.6) and that contains 15% sucrose as an additive was converted into an open pore melamine—formaldehyde oligomer by acidification with 7% phosphoric acid (based on resin solid) at 50-60°C. 

Methoxy-l-p-tolylsulfonyIacetone in abs. acetonitrile added dropwise under dry Ng to a stirred suspension of NaH in acetonitrile, stirring continued several hrs. at 20°, then formaldehyde prepared by heating a mixture of trioxymethylene and PgOg at 180-200° carried by a Na-stream into the mixture -> l-methoxy-l-(p-tolylsulfonyl)ethylene Y 92%. F. e. and comparison with other methods of carbonylolefination s. G. Ferdinand, K. Schank, and A. Weber, A. 1975, 1484. 

Apparatus for preparing liquid formaldehyde. Preparation of crude... 

In addition to the syntheses described above, many other processes for the use of formaldehyde in the production of dyes and dy e intermediates are described in the patent hterature. Recent patents,for example, includethe production of benzene-soluble azo dyes by coupling diazotized arj lamines with aromatic hydroxy compounds plus formaldehyde , preparation of vat dyes by condensation of formaldehyde with ST-dihy di O-l,2,T,2 -anthra-quinone azities , synthesis of nitroso dy es by. reacting formaldehyde viith p-X-alky laminonitrosoben2ene del i atives, formation of thiazole dyes from mercaptothiazoles, primary amines, and foimaldehyde , production of diphenyimethane intermediates , etc. 

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