Aldehydes, Ketones and Carboxylic Acids

Formaldehyde

Formaldehyde is a kind of present compound having the formula \(CH_{2}O\). The pure compound is usually a pungent-smelling colourless gas that polymerises spontaneously into paraformaldehyde, hence it’s stored as a solution (formalin). The common name of this substance comes from its similarity and reference to formic acid.

Formaldehyde

What is Formaldehyde?

Formaldehyde is a flammable, colourless, strong pungent-smelling chemical that’s utilized in building materials and to supply many household products. It has a lot of utilization in pressed-wood products, like plywood, particleboard, and fiberboard; glues and adhesives; permanent-press fabrics; paper product coatings; and certain insulation materials. Formaldehyde also occurs naturally within the environment.

Forms of Formaldehyde

Molecular formaldehyde – It forms a colourless gas with a characteristic pungent, irritating odour. It is in stable form at around 150 °C but polymerizes when condensed to a liquid.

1,3,5-Trioxane- Its formula is \(\left ( CH_{2}O \right )_{3}\). It’s a white solid that dissolves without degradation in organic solvents.

Paraformaldehyde is a type of white solid with the formula \(HO\left ( CH_{2} O\right )nH\).

Methanediol – Its formula is \(CH_{2}\left ( OH \right )_{2}\). This compound also exists in equilibrium with various oligomers (short polymers), counting on the concentration and temperature.

Occurrence

Processes within the upper atmosphere contribute up to 90% of the entire formaldehyde within the environment. Formaldehyde is a median form within the oxidation (or combustion) of methane, also as of other carbon compounds. When produced within the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons, it becomes a part of smog. Formaldehyde has also been detected in space. It is also seen within the bloodstream of humans and other primates at concentrations of roughly 0.1 millimolar.

Formaldehyde doesn’t accumulate within the environment, because it’s weakened within a couple of hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, converting it to acid, so it doesn’t accumulate within the body.

Synthesis and Industrial Production

Russian chemist Aleksandr Butlerov (1828–86) first reported formaldehyde in 1859. Wilhelm von Hofmann, who first physically formed the formaldehyde and reported the assembly by passing methanol vapour in the air over the hot platinum wire.

Industrially formaldehyde is manufactured by the catalytic oxidation of methanol. The foremost common catalysts are silver metal or a mix of iron and molybdenum or vanadium oxides. In the most common used formox process, methanol and oxygen react at 250–400 °C in the existence of iron oxide together with molybdenum and/or vanadium to produce formaldehyde.

\(2CH_{3}OH + O_{2} \rightarrow 2CH_{2}O + 2H_{2}O\)

Uses of Formaldehyde

  • Industrial applications – Products generated from formaldehyde include urea-formaldehyde resin, synthetic resin, phenol-formaldehyde resin, polyoxymethylene plastics, etc. Formaldehyde-based resins are useful as finishers in the textile industry to form fabrics crease-resistant. Formaldehyde is in use to make various components for the transmission, electrical system, cylinder block, door panels, axles and brake shoes in the automobile industry. Formaldehyde when treated with urea, phenol or melamine produces, respectively hard thermoset phenol-formaldehyde resin, urea-formaldehyde resin, and synthetic resin. These polymers are common permanent adhesives useful in plywood and carpeting.
  • Medical Industry – An solution of formaldehyde acts as a useful disinfectant because it kills most bacteria and fungi (including their spores). It is in use as an additive in vaccine manufacturing to inactivate toxins and pathogens.
  • Photography – Formaldehyde is employed in low concentrations for process C-41 (colour negative film) stabilizer within the final wash step, also as within the process E-6 pre-bleach step, to form it unnecessary within the final wash.

Safety

Formaldehyde can act as a sensitizing agent and maybe a known human carcinogen that’s linked to nasal cancer and carcinoma. Acute exposure to formaldehyde is very irritating to the systema respiratorium and may cause headaches and eye and throat irritation at very low concentrations.

FAQs on Formaldehyde

Q.1. How does one remove formaldehyde?

Answer – The sole thanks to removing formaldehyde from indoor air is with an air purifier that contains a deep-bed activated charcoal filter. Not every air purifier can remove formaldehyde.

Q.2. What foods contain formaldehyde?

Answer – Formaldehyde often occurs naturally in food up to the amount of 300 to 400 mg/kg, including fruits and vegetables (e.g. apples, bananas, grapes, carrot, spinach), meats, fish (e.g., Bombay-duck, codfish), crustacean and dried mushroom, etc.

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