Formaldehyde Formula: IUPAC, Structure, & Properties

What solution is used to preserve biological species? It is Formaldehyde. Scientifically known as Methanal. Formaldehyde is a colourless, strong-smelling gas used in making building materials and many household products. Formaldehyde Formula is represented as \(\mathrm{CH}_{2} \mathrm{O}\).

Formaldehyde in water is known as formalin, which is commonly used as an industrial disinfectant and as a preservative in funeral homes and medical labs. In this article, we will discuss about Formaldehyde formula in detail. Continue reading to find out more about the Formaldehyde formula!

Formaldehyde Formula

The IUPAC name of Formaldehyde is Methanal with a condensed chemical formula \(\mathrm{CH}_{2} \mathrm{O}\). The functional group is an aldehyde; \(-\mathrm{CHO}\) and is made up of one carbon atom, two hydrogen atoms, and one oxygen atom. The chemical formula of Formaldehyde is \(\mathrm{HCHO}\) and is represented as below.

Formaldehyde Molar Mass

The molar mass of Formaldehyde, \(\text {HCHO}\) is:

\(=(\text {The atomic mass of carbon})+2\text {x}(\text {The atomic mass of hydrogen})+\)
\(\text {Atomic mass of Oxygen}\)

\(=(12.01)+2 \text {x}\left(1.007)+15.999=30.023 \mathrm{~g} \mathrm{~mol}^{-1}\right.\)

Hence, one mole of Formaldehyde weighs \(30.023\) grams.

Formaldehyde Hybridisation

Formaldehyde is a one-carbon compound and is the simplest aldehyde. The only carbon atom present in its formula belongs to the aldehyde functional group and is \(\text {sp}^{2}\) hybridised.

Steric number of the aldehydic carbon atom \(=\) Number of atoms attached \(+\) Lone pairs

\(=3+0=3\left(\text {sp}^{2}\right)\)

The carbon atom of Methanal is \(\text {sp}^{2}\) hybridised \(\left(\text {1s + 2p = 3 sp}^{2}\right)\). The atomic orbitals of the carbon atom undergo intermixing to form \(3\,\text {sp}^{2}\) hybridised orbitals.

The \(\text {sp}^{2}\) hybridised carbon forms \(3\) sigma bonds. The formation of \(3\) sigma bonds gives Formaldehyde a basic trigonal shape with bond angles of \(120\) degrees in the ideal case. Only two out of three \(\text {p}\) orbitals of carbon participate in hybridisation; hence, one \(\text {p}\) orbital is unhybridized. This unhybridized \(\text {p}\) orbital forms a pi bond with the unhybridized \(\text {p}\) orbital of the oxygen atom. This \(\text {p}\) orbital is directed above and below the plane of the paper.

Molecular Geometry of Formaldehyde

In Formaldehyde, the \(\text {C}\) atom from the aldehyde has a \(\text {sp}^{2}\) hybridisation and has a trigonal-planar geometry.

Bond Angle of Formaldehyde

The \(-\text {CHO}\) group in Methanal is \(\text {sp}^{2}\) hybridised, hence the \(\mathrm{O}-\mathrm{C}-\mathrm{H}\) bond angle is \(121^\circ\) due to higher electronic repulsion between single bond and double bond, and \(\mathrm{C}-\mathrm{H}\) bond length is \(1.11\,\overset{^\circ }{\mathop {\text{A}}} \), and \(\mathrm{C}=\mathrm{O}\) bond length is \(1.22\,\overset{^\circ }{\mathop {\text{A}}} \).

Dipole Moment of Formaldehyde

The dipole moment in Formaldehyde is mainly due to the \(\mathrm{C}=\mathrm{O}\) bond of the \(-\text {CHO}\) group. This is due to the electronegativity between carbon and oxygen, which makes the \(\mathrm{C}=\mathrm{O}\) bond polar. The oxygen pulls the shared pair of electrons more strongly than the carbon atom, resulting in a partial negative charge at one end of the compound and a partial positive charge at the other.

As there is only one polar bond, no cancelling can happen, and the dipole moment of the formaldehyde molecule is found to be \(2.3\) Debye.

Lewis Structure of Formaldehyde

Methanal, the first member of the aldehyde functional group, comprises a single Carbon atom that forms a double-bond with an oxygen atom. In the Lewis structure for Formaldehyde, there are a total of \(12\) valence electrons. These electrons are distributed as shown below:

Skeletal Formula of Formaldehyde

Formaldehyde consists of a carbon atom that shares a double bond with an oxygen atom. Two hydrogen atoms occupy the carbon’s remaining electron-sharing slots. It has three sigma bonds and one \(\text {π}\) bond. The skeletal structure of Formaldehyde is shown below:

Three-Dimensional Representation of Formaldehyde

The three-dimensional structure of Methanal can not be represented by the Wedge-Dash method because it is a planar molecule with \(\text {sp}^{2}\) carbon atom having trigonal planar geometry.

Preparation of Formaldehyde

The preparations of formaldehyde is explained below:

(i) Formaldehyde Preparation Through Lab Method

The laboratory preparation of Methanal involves passing a mixture of methyl alcohol vapours and air over platinised asbestos or copper or silver catalyst at \(300^\circ {\text{C}}\).

The air is drawn into Methyl alcohol with the help of a suction pump, where it is oxidised to gaseous Formaldehyde. It is then absorbed in water. The resulting mix is called formalin which is a mix of \(40\,\% \) formaldehyde, \(8\,\% \) methyl alcohol, and \(52\,\% \) water.

(ii) Formaldehyde Preparation Through Industrial Method

In the industrial method of manufacturing Formaldehyde, a mixture of methanol vapours and the air is passed over iron oxide-molybdenum oxide or silver driver at \(500^\circ {\text{C}}\).

Physical Properties of Formaldehyde

The formaldehyde physical properties are explained below:

Chemical Properties of Formaldehyde

The formaldehyde chemical properties are explained below:

1. Formaldehyde is polarised due to the \(-\text {C}=\text {O}\) bond of the \(-\text {CHO}\) functional group.

2. The presence of positively and negatively charged centres helps nucleophilic molecules attack the carbonyl carbon which is deficient in electrons. At the same time, electrophiles attack the negatively charged oxygen atom.

3. Formaldehyde readily oxidized to formic acid in the presence of atmospheric oxygen. 

4. Formaldehyde undergoes electrophilic aromatic substitution reactions with aromatic compounds resulting in hydroxymethylated derivatives.

\({\text{ArH}} + {\text{C}}{{\text{H}}_2}{\text{O}} \to {\text{ArC}}{{\text{H}}_2}{\text{OH}}\)

5. Formaldehyde also participates in the Cannizzaro reaction in the presence of basic catalysts to produce formic acid and methanol.

Uses of Formaldehyde

The uses of formaldehyde are as follows:

1. It is utilised in the manufacturing of resins like urea-formaldehyde and plastics such as Bakelite.
2. It is used in the manufacturing of dyes such as indigo, para-rosaniline, and so on.
3. \(40\,\% \) aqueous solution of formic acid is called formalin. It is used as an antiseptic, a disinfectant, a germicide, a fungicide, and for maintaining animal specimens and sterilising surgical instruments.
4. It is used as a decolourising agent in barrel dyeing.
5. It is used in the silvering of mirrors.
6. It is utilised in the processing of the anti-polio vaccine.

Phenol-formaldehyde Polymer

Phenol reacts with Formaldehyde and polymerises to form phenol-formaldehyde resins, commercially known as Bakelite. This resin is used to manufacture switches, cabinets, doors, etc. It can withstand extreme conditions, and hence, is used in various electrical and automobile industries.

The reaction between Phenol and Formaldehyde also forms a sun-like compound called Novolac. Novolac has adhesive properties and is used as a binding agent in different industries.

Urea-formaldehyde Resin Formula

Urea-formaldehyde \(\left( {{\text{UF}}} \right)\), also known as urea-methanal, is a non-transparent thermosetting synthetic resin or polymer. It is produced from urea and Formaldehyde and consists of \({\left[{({\text{O}}){\text{CNHC}}{{\text{H}}_2}{\text{NH}}}\right]_{\text{n}}}\) repeat units. These resins are used in adhesives, finishes, particleboard, medium-density fibreboard \(\left( {{\text{MDF}}} \right)\), and moulded objects.

Summary

Formaldehyde is widely used as a specimen preserver in medical labs. Formaldehyde is acidic in nature. Furthermore, it is important to note that formaldehyde is also referred to as Methanal. It is named Methanal as it is produced by formic acid. Its compound with urea and phenol is a crucial polymer extensively used in adhesives and the automobile industry.

Formaldehyde is used in barrel dyeing as a decolourising agent. It is also used as an important component in the silvering of mirrors. However, it also has some disadvantages. If kept at higher concentrations, formaldehyde may result in headaches, a burning sensation in the throat, etc.

FAQs on Formaldehyde Polymer

Q.1. What is \({\text{C}}{{\text{H}}_2}{\text{O}}\) called?
Ans: \({\text{C}}{{\text{H}}_2}{\text{O}}\) is the condensed formula of Formaldehyde or Methanal. It is the simplest aldehyde and is represented as \(\mathrm{HCHO}\).

Q.2. What is Formaldehyde used in?
Ans: Formaldehyde is a colourless, strong-smelling gas used in pressed-wood products, such as particleboard, plywood, and fiberboard; glues and adhesives; permanent-press fabrics; paper product coatings; and certain insulation materials. It is one of the key ingredients in preserving animal specimens.

Q.3. Is Formaldehyde a base or acid?
Ans: Formaldehyde is acidic in nature with a \(\text {pH}\) range of \(3\) to \(3.5\).

Q.4. Why is Methanal called Formaldehyde?
Ans: Methanal is named “Formaldehyde” because it was produced by a reaction with “formic acid”. Formic acid was named after Latin Formica meaning “ant”.

Q.5. Is Formaldehyde an explosive?
Ans: Formaldehyde is highly flammable. Its gas or air mixture is explosive.

Q.6. What is the disadvantage of Formaldehyde?
Ans: Formaldehyde at concentrations above \(0.1\,\text {ppm}\) can irritate the eyes and mucous membranes, resulting in watery eyes. It may cause headaches, a burning sensation in the throat, and difficulty in breathing at higher concentrations.

Learn About Hydrogen Bonding Here

We hope this detailed article on Formaldehyde Formula is helpful to you. If you have any queries on this page or in general about the formaldehyde formula, ping us through the comment box below and we will get back to you as soon as possible.