Paraformaldehyde

• Polyoxymethylene
• ParaForm
• P- formaldehyde
• Polyformaldehyd

White solid with a characteristic odor

Fixed

1.39 g · cm -3 ( 20 ° C)

About 130 ° C ( closed vessel ) 120-170 ° C

Sparingly soluble in water (20 ° C)

Attention

• 592 mg · kg -1 ( LD50, rat, oral)
• 1.07 mg · l-1 · 4 h ( LC50, rat, inh. )
• 10,000 mg · kg -1 ( LDLO, rat, transdermal)

Paraformaldehyde short chain polymer of the formaldehyde, the degree of polymerization is 8 to 100. It is a white powder which is split once again in formaldehyde at low pH or by heating. Degradation occurs via the terminal groups. If these are protected by esterification or etherification, a sturdy plastic is obtained which polyoxymethylene.

Upon heating of paraformaldehyde in water or an aqueous buffer solution it breaks, you get a formaldehyde solution. This is sometimes referred to as " paraformaldehyde solution " to distinguish it from formaldehyde solutions which are caused by dilution of formalin, a concentrated formaldehyde solution, which also contains methanol for stabilization. Strictly speaking, however, the designation paraformaldehyde solution is incorrect because the polymer is insoluble in water. This solution is used in biology for the fixation of tissue or cell cultures, usually in concentrations between 1 and 4% buffered to neutral pH. The effect is based on the reversible cross-linking of proteins.

Paraformaldehyde is a harmful and is suspected to be carcinogenic. The oral LD50 value for rats is 592 mg / kg. The vapor pressure at 25 ° C is 2hPa. The maximum allowable concentration is 0.3 ml · m-3 and 0.37 mg · m- third

In preparative chemistry can paraformaldehyde for formylation reactions and syntheses thereof are derived using, e.g., Mannich reaction, Blanc reaction ( " chloromethylation ").