Formaldehyde

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-92 °C (pure)
−15 °C (37% solution)

-21 °C (pure)
96 °C (37% solution)

Formaldehyde (systematic name: methanal) is an organic compound with the formula CH2O. As the simplest aldehyde, it is an important precursor to many other chemical compounds, especially for polymers. In 2005, annual world production of formaldehyde was estimated to be 23 million tons (50 billion pounds).[2] In view of its widespread use, toxicity and volatility, exposure to formaldehyde is a significant consideration for human health.[3]

Contents

Forms of formaldehyde

Formaldehyde is more complicated than many simple carbon compounds because it adopts different forms. Formaldehyde is a gas at room temperature, but the gas readily converts to a variety of derivatives. These derivatives generally behave similarly to gaseous formaldehyde and are used in industry. One important derivative is the cyclic compound trioxane, the "trimer" of formaldehyde with formula is (CH2O)3. When dissolved in water, formaldehyde converts to H2C(OH)2, a diol (i.e. a compound with two hydroxy groups). Aqueous solutions of formaldehyde are referred to as formalin. "100%" formalin consists of a saturated solution of formaldehyde (this is about 40% by volume or 37% by mass) in water, with a small amount of stabilizer, usually methanol to limit oxidation and degree of polymerization. A typical commercial grade formalin may contain 10–12% methanol in addition to various metallic impurities. The diol also exists in equilibrium with a series of short polymers (called oligomers), depending on the concentration and temperature. The infinite polymer formed from formaldehyde is called paraformaldehyde. The cyclic trimer is called metaformaldehyde (or 1,3,5-trioxane).

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