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Uses of Formaldehyde

Uses of Formaldehyde: Structure, Preparations, Physical Properties, Uses of Formaldehyde, Practice Problems & Frequently Asked Questions

If you have visited a zoology laboratory, you might have observed dead animals small to big placed in glass containers covered with a transparent liquid. The liquid is not water but a dilute solution of formaldehyde.

A dilute 4% aqueous solution of formaldehyde called formalin is used in biology laboratories for preserving the decay of dead biological species. Formaldehyde polymerises to form -CH2 linkages, which bond with nitrogen atoms present in the primary amino acids of the protein chains present in biological samples.

Table of content:

  • Structure of Formaldehyde
  • Preparations of Formaldehyde
  • Physical Properties of Formaldehyde
  • Uses of Formaldehyde
  • Practice Problems
  • Frequently Asked Questions

Structure of Formaldehyde:

Methanal is the IUPAC name for Formaldehyde, and its condensed chemical formula is CH2O. The functional group is an aldehyde -CHO, with one carbon atom, two hydrogen atoms, and one oxygen atom. Formaldehyde has the chemical formula HCHO, which is represented below.

Formaldehyde is the simplest aldehyde and is a one-carbon compound. The only carbon atom in its formula is sp2 hybridised and belongs to the aldehyde functional group.

Three sigma bonds are formed by the sp2 hybridised carbon. In the ideal case, the creation of three sigma bonds give formaldehyde a basic trigonal planar geometry with bond angles of 120o. Because only two of the three carbon p orbitals participate in hybridisation, one p orbital remains unhybridized. This unhybridized p orbital forms a pi bond with the oxygen atom's unhybridized p orbital.

Preparations of Formaldehyde:

(i) At 300 o C, a combination of methyl alcohol vapours and the air is passed over a platinised asbestos or copper or silver catalyst.

(ii) A mixture of methanol vapours and air is passed over an iron oxide-molybdenum oxide or silver driver at 500 o C in the industrial method of producing formaldehyde.

Physical Properties of Formaldehyde:

CH2O

Formaldehyde

Density

815 kg m-3

Molecular Weight/ Molar Mass

30.031 g mol-1

Boiling Point

-19 o C

Melting Point

-92o C

Chemical Formula

HCHO

Uses of Formaldehyde:

  • Many packaged foods use very trace amounts of diluted formaldehyde as a preservative.
  • Several paint-related products, such as paints and primers used to give walls clear coatings, are made with formaldehyde.
  • Formaldehyde, though not used directly as a component, it is often released from preservatives like DMDM hydantoin, imidazolidinyl urea, sodium hydroxymethylglycinate, and 2-bromo-2-nitropropane-1, 3-diol used in a beauty product. Hence caution is needed in the use of such preservatives containing beauty products as formaldehyde will be affecting the skin on continuous usage. Additionally, it has been known to be a carcinogen.
  • It is antibacterial and antifungal and hence acts as an antiseptic in dilute solutions. Formaldehyde is used as a methylating agent, to methylate the proteins which disrupt the structure of proteins resulting in denaturation and destruction of the microorganisms.
  • It was used as a chemical disinfectant. Additionally, it is used in places where corpses are stored, to disinfect the place, as a disinfectant.
  • The ingredients that go into making RDX explosive is formaldehyde.
  • It is frequently blended with fossil fuels for vehicles, like natural gas and petroleum, to increase the vehicles' fuel efficiency while at the same time using less of it. The Blend seems to be less dense making the vehicle relatively lighter compared to the use of other fuel. However, in addition to formaldehyde, which is a plentiful resource in our environment, formaldehyde technology is occasionally advised to help preserve other resources that are more vulnerable to depletion.
  • Printing ink, namely Hematin, is prepared using formaldehyde..
  • Formaldehyde polymerises with many organic compounds like phenols melamine and urea etc. to form products with water resistance, materials of high tensile strength and mite resistance and heat resistance. Hence the formaldehyde polymers find many uses in place of natural wood, ceramics, electrical insulators, etc.
  • The most resilient formaldehyde-based resins are likely formaldehyde melamine resins, which are created when formaldehyde reacts with melamine. It is used to create flooring laminates that are water-resistant, rain-resistant laminates, and water-cleaning material coats for vehicles.
  • Certain vaccines have historically been produced and sanitised using formaldehyde. It has frequently been used with influenza vaccines as it acts as an antiviral agent and can synergistically act with the vaccine's active ingredient. Additionally, it is used against bacterial endotoxins that are administered as vaccinations for the diagnosis of some pathogenic bacteria.
  • Due to its antibacterial qualities, formaldehyde was once used to treat some UTI infections. Methylamine, a formaldehyde-derived chemical compound, now performs the same function. It is also present in a number of topical ointments that are utilised to fight fungal infections. However, the Food and Drug Administration has set limits on its concentrations, due to its poisonous and adverse actions on the skin. Furthermore, you should always speak with your doctor before using such products..
  • Formaldehyde is used to make use of and throw sanitisers like facial wipes, tissue papers, and paper napkins in the sanitary products industry.
  • Formalin, a 37 per cent formaldehyde solution, has disinfectant properties and also acts as an antiperspirant. Fungus growth is higher in water contact areas of the skin. Formaldehyde not only prevents sweat formation and collection of water over the skin and also prevents fungal growth as a disinfectant. that can be used to clean a wide range of surfaces.
  • Formaldehyde is used to prepare polymers with high bonding quality to be used as adhesives. It has superior binding capabilities. Formaldehyde-based adhesives and resins work very well. It is also a more affordable option because it is more readily available and less expensive than other synthetic adhesives.
  • Formaldehyde and phenol react to create resins that are used to make brake liners or cushions for automobiles. These resins are particularly fire resistant because they can withstand the highest temperatures without deteriorating or decomposing.
  • While the earth’s upper atmosphere contains a high amount of formaldehyde, in the lower atmosphere it is broken down by the sun’s heat energy to CO2. The atmosphere of Venus is formed by clouds of polymerized formaldehyde.
  • One of the intermediates created during the burning of methane gas before it is transformed into CO2 is formaldehyde. It is also one of the main substances created and released into the atmosphere whenever organic material burns, including when trees burn during forest fires when fuel burns in cars and trucks to produce waste heat, and when people smoke tobacco.
  • Formaldehyde is used in the textile industry as a binder, to bind the pigments to the fabric. Formaldehyde bonded colour shows greater resistance to fading than by the other binders during washing.
  • Formaldehyde resins are useful in the textile sector to give fibres wrinkle-free properties. Clothing made with formaldehyde-based resins is less likely to wrinkle and crease.

Practice Problems:

Q.1. The reaction of formaldehyde with ammonia produces

(A) Bakelite
(B) Urea
(C) Triethylene tetramine
(D) Hexamethylene tetramine

Answer: (D)
Solution: Formaldehyde reacts with ammonia to produce hexamethylenetetramine, which is known as urotropine and is used as a urinary antiseptic.

6 HCHO + 4 NH3 → (CH2)6N4 + 6 H2O

Q.2. Formaldehyde on reaction with base sodium hydroxide will give sodium formate and

(A) CH3OH
(B) CH3CH2OH
(C) CH3CH2CH2OH
(D) None of the above

Answer: (A)
Solution: When formalin reacts with a base, such as sodium hydroxide, it produces sodium formate and methanol. The chemical formula is depicted below.

2 HCHO + NaOH → HCOONa + CH3OH

Q.3. Which of the following reagents is required to distinguish between formaldehyde and acetaldehyde?

(A) Tollens’ reagent
(B) Fehling’s solution
(C) Schiff’s reagent
(D) Caustic soda solution

Answer: (D)
Solution: When formaldehyde reacts with Conc. NaOH(Caustic soda), it undergoes a Cannizzaro reaction. When acetaldehyde reacts with dil. NaOH(caustic soda), an aldol condensation reaction takes place.

Q.4. Which of the following aldehydes is present in the form of gas?

(A) Acetaldehyde
(B) Formaldehyde
(C) Butyraldehyde
(D) Benzaldehyde

Answer: (B)
Solution: Methanal is a gas with a boiling point of -21o C, while ethanal has a boiling point of +21o C. That means ethanal boils at nearly room temperature. The other aldehydes and ketones are liquids, with increasing boiling points as the molecules get bigger.

Frequently Asked Questions:

Q1. Why is formaldehyde more reactive in nucleophilic addition reactions than other aldehydes?
Answer:
Formaldehyde is the most reactive aldehyde because there is no electron-donating group in formaldehyde(HCHO) to diminish the density of carbon atoms in the -CHO group. Other higher members have an electron donating group, which means an alkyl group, which increases electron density at the carbon atom of the -CHO group via the positive inductive effect.

Q2. Is formaldehyde and formalin the same?
Answer:
Both formalin and formaldehyde have the same chemical formula, which is HCHO. However, they differ in their physical states and chemical activities. Formaldehyde is a colourless, water-soluble, flammable gas at room temperature with a strong, unpleasant odour. Formalin, on the other hand, is a liquid that is made by combining formaldehyde gas with water. This is the key difference between formalin and formaldehyde. A saturated solution of formalin typically contains around 40 % (by volume) or 37 % (by weight) formaldehyde gas and a stabiliser to prevent formaldehyde polymerization.

Q3. Does formaldehyde have a dipole moment?
Answer:
The dipole moment in formaldehyde is primarily due to the -CHO group's C=O bond. Because of the electronegativity of carbon and oxygen, the C=O bond is polar. Because the oxygen atom pulls the shared pair of electrons more strongly than the carbon atom, the molecule has a partial negative charge at one end and a partial positive charge at the other.

Because there is only one polar link, no cancelling can occur, and the formaldehyde molecule's dipole moment is found to be 2.3 Debye.

Q4. Why does formaldehyde give a Cannizzaro reaction?
Answer:
The Cannizzaro reaction is a chemical reaction in which an aldehyde without a hydrogen atom in the alpha position or an alpha-hydrogen undergoes base-induced disproportionation. Because formaldehyde (HCHO) lacks alpha hydrogen, it can undergo the Cannizzaro reaction.

Related Topics

Aldehyde

Structure of aldehyde

Aldol condensation

Tollens’ test

Acetone

Ketone

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