Aqueous formalin

The formaldehyde solutions were prepared by diluting 35.5% aqueous formalin with water. Synthesis of 1 was performed in a two-chamber electrodialyzer described in (8,9). To 30 ml of an aqueous solution of 0.2 M NaxSiW 039... 

Despite occasional admonitions to avoid alcoholic formalin for certain IHC procedures, there is no reason to think that this fixative would do more harm than a functionally equivalent degree of fixation with aqueous formalin since tissues go through 70% alcohol during processing. The degree of fixation, not the type of fixation, is the major difference if alcoholic formalin is used. When trying to standardize IHC procedures, keep this in mind if some specimens have been exposed to alcoholic formalin and others have not. 

The yield of 3-hydroxymethyl-4,5-dimethyl-4/7-l,2,4-triazole 45a could be increased to 73% by reacting the precursor 1,2,4-triazole in 37% aqueous formalin at 90 °C for 3h <2006S156>. 

Aromatic Mannich reactions have been reviewed290. Recent examples are the formation of 254 from p-cresol, paraformaldehyde and 1-methylpiperazine and of 255 from salicylaldehyde, aqueous formalin and 1-methylpiperazine291. 

More recently, Tietze s group adapted the well-known domino Knoevenagel-Hetero-Diels-Alder MCR to the efficient synthesis of the deoxyaminosugar (-l-)-D-Forosamine starting from nitroacetone, aqueous formaline, and ethyl vinyl ether (Scheme 65) [169]. The expected racemic dihydropyran was obtained in 37% yield and further transformed to the optically pure product in eight steps in chiral resolution with chiral HPLC. 

The reaction of 3-aminopyridopyrimidin-4-one 330 with acetone in boiling dichloromethane in the presence of a catalytic amount of acetic acid for 5 hours followed by 24-hour stirring at room temperature or with 37% aqueous formalin in boiling ethanol for 2 hours afforded tricyclic oxazolo[5,4-c/]pyrido[l,2-a]pyrimidinones 462 [91IJC(B)839]. 

This catalytic system could be applied to the enantioselective hydroxymethylation of silyl enol ethers with aqueous formalin (Scheme 9.12).21 Doyle and coworkers have successfully applied the catalyst system of BINAP-AgOTf, KF, and %-crown-6 for Mukaiyama aldol reaction of a-diazo silyl enol ether (Scheme 9.13).22... 

By careful choice of conditions, the simplest dipyrromethane, bis(pyrrol-2-yl)methane, can be obtained directly from pyrrole with aqueous formalin in acetic acid reaction in the presence of potassium carbonate allows 2,5-bis-hydroxymethylpyrrole to be isolated. This diol reacts with pyrrole in dilute acid to give tripyrrane and from this, reaction with 2,5-bis(hydroxymethyl)pyrrole gives porphyrinogen, which can be oxidised with chloranil (2,3,5,6-tetrachloro-p-benzoquinone) to porphine, the simplest porphyrin. 

The reaction of 5-methoxy-1-naphthol with cyclohexylamine (Imole) and aqueous formalin (2moles) at ambient temperature gave 3-cyclohexyl-... 

Phenol resins, both resols and novolacs, are exclusively made in batch processes. In the production of novolacs, molten phenol is charged into the heated and stirred reaction tank together with the weak acidic catalyst (for estample, oxalic add). At 95°C, the aqueous formalin solution is slowly added, while the reaction heat is removed through distillation of water at slightly diminished pressure. When all the formaldehyde has reacted, the water is distilled off and the reaction with the excess phenol is continued at higher temperature (140-160°C). When the desired viscosity is reached, the excess of unreacted phenol is removed by distillation as well. The molten resin is let down onto a cooling belt, and broken into small glassy lumps. 

Formaldehyde for use as a disinfectant is usually marketed as formalin, a solution of about 37 percent concentration, or as paraformaldehyde, a solid polymerized compound. The substance can be utilized for decontamination of large areas (427) or surfaces (451). Formaldehyde in a concentration of 5 percent active ingredient is an effective liquid disinfectant. Formaldehyde at 0.2 to 4.7 percent is often used to inactivate viruses in the preparation of vaccines. Formaldehyde seems to be more effective as a disinfectant against hydrophilic viruses than against lipophilic viruses. Forty percent aqueous formalin (16 percent formaldehyde) is effective in inactivating hepatitis B virus, using a contact time of 12 hours. A 20 percent formalin solution in 70 percent... 

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