Information AboutFormaldehyde |
|
The Chemical Compound formaldehyde (also known as '''methanal'''), is a Gas with a pungent smell. It is the simplest Aldehyde . Its Chemical Formula is H2CO. Formaldehyde was first synthesized by the Russia n chemist Aleksandr Butlerov in 1859 but was conclusively identified by August Wilhelm van Hofmann in 1867. Formaldehyde readily results from the incomplete Combustion of Carbon -containing materials. It may be found in the smoke from Forest Fire s, in Automobile exhaust, and in Tobacco Smoke . In the Atmosphere , formaldehyde is produced by the action of sunlight and Oxygen on atmospheric Methane and other Hydrocarbon s. Small amounts of formaldehyde are produced as a Metabolic byproduct in most organisms, including humans. Properties Although formaldehyde is a gas at room temperature, it is readily soluble in water, and it is most commonly sold as a 37% Solution in water called by trade names such as formalin or '''formol'''. In water, formaldehyde Polymer izes, and formalin actually contains very little formaldehyde in the form of H2CO monomer. Usually, these solutions contain a few percent Methanol to limit the extent of polymerization. Formaldehyde exhibits most of the general chemical properties of the aldehydes, except that is generally more reactive than other aldehydes. Formaldehyde is a potent Electrophile . It can participate in Electrophilic Aromatic Substitution reactions with Aromatic Compound s and can undergo Electrophilic Addition reactions with Alkene s. In the presence of Basic Catalyst s, formaldehyde undergoes a Cannizaro Reaction to produce Formic Acid and methanol. Formaldehyde reversibly polymerizes to produce its cyclic trimer, 1,3,5-trioxane or the linear polymer Polyoxymethylene . Formation of these substances makes formaldehyde's gas behavior differ substantially from the Ideal Gas Law , especially at high pressure or low temperature. Formaldehyde is readily Oxidized by atmospheric oxygen to form Formic Acid . Formaldehyde solutions must be kept tightly sealed to prevent this from happening in storage. Production Industrially, formaldehyde is produced by the catalytic oxidation of Methanol . The most commonly used catalysts are Silver metal or a mixture of an Iron Oxide with Molybdenum and vanadium. In the more commonly used iron oxide system (Formox process), methanol and oxygen react at 250°C to produce formaldehyde according to the Chemical Equation :2 CH3OH + O2 → 2 H2CO + 2 H2O The silver-based catalyst is usually operated at a higher temperature, about 650 °C. On it, two chemical reactions simultaneously produce formaldehyde: the one shown above, and the dehydrogenation reaction : CH3OH → H2CO + H2 Further oxidation of the formaldehyde product during its production usually gives formic acid that is found in formaldehyde solution, found in ppm values. On a smaller scale, formalin can be produced using a whole range of other methods including conversion from ethanol instead of the normally-fed methanol feedstock. Such methods however are of less commercial importance. Uses Formaldehyde kills most ; trans. H. T. Lowe-Porter { 1927 ). It is also used to preserve biological specimens, and as a Preservative in Vaccination s. In medicine, formaldehyde solutions are applied topically to dry the skin, such as in the treatment of Wart s. Formaldehyde based solutions are used in Embalming to disinfect and temporarily preserve human remains pending final disposition. Most formaldehyde, however, is used in the production of polymers and other chemicals. When combined with Phenol , Urea , or Melamine , formaldehyde produces a hard Thermoset resin. These resins are commonly used in permanent adhesives, such as those used in Plywood or Carpet ing; and as the wet-strength resin added to sanitary paper products such as (listed in increasing concentrations injected into the paper machine headstock chest) facial tissue, table napkins, and roll towels. They are also foamed to make Insulation , or Cast into molded products. Production of formaldehyde resins accounts for more than half of formaldehyde consumption. Formaldehyde is still used in low concentrations for process C-41 (color negative film) stabilizer in the final wash step, as well as in the process E-6 pre-bleach step, to obviate the need for it in the final wash. Formaldehyde is also used to make numerous other chemicals, used even in personal care products such as Toothpaste . Many of these are polyfunctional Alcohol s such as Pentaerythritol , which is used to make Paint s and Explosive s. Other formaldehyde derivatives include Methylene Diphenyl Diisocyanate , an important component in Polyurethane paints and foams, and Hexamine , which is used in phenol-formaldehyde resins and to make the explosive RDX . Formaldehyde cross links Amino Group s. Health Effects Because formaldehyde resins are used in many construction materials, including plywood, carpet, and spray-on insulating foams, and because these resins slowly give off formaldehyde over time, formaldehyde is one of the more common indoor air pollutants. At concentrations above 0.1 mg/kg in air, inhaled formaldehyde can irritate the eyes and Mucous Membrane s, resulting in watery eyes, headache, a burning sensation in the throat, and difficulty breathing. Large formaldehyde exposures, for example from drinking formaldehyde solutions, are potentially lethal. Formaldehyde is converted to Formic Acid in the body, leading to a rise in blood acidity, rapid, shallow breathing, Hypothermia , and Coma or death. People who have ingested formaldehyde require immediate medical attention. In the body, formaldehyde can cause Protein s to irreversibly bind to DNA . Laboratory animals exposed to large doses of inhaled formaldehyde over their lifetimes have developed more Cancer s of the nose and throat than are usual, as have workers in particle-board Sawmill s. However, some studies suggest that smaller concentrations of formaldehyde like those encountered in most buildings have no Carcinogen ic effects. Formaldehyde is classifed as a probable human carcinogen by the U.S. Environmental Protection Agency and as a known human carcinogen by the International Agency For Research On Cancer . External links
|