HCOOH or CH2O2 is the chemical formula for formic acid, which is the simplest carboxylic acid with a hydrogen atom connected to the -COOH group. Methanoic acid is another name for it.
Do you know that formic acid can be found in a variety of insect species, including ants and stingless bees?
In industries, we use the formulae below to make HCOOH:
CH3OH + CO ——> HCO2CH3 (1)
HCO2CH3 + H2O ——> HCOOH + CH3OH (2)
In laboratory preparation, the necessary chemical reactions are:
C2O4H2 ——-> CO2H2 + CO2
Pb(HCOO)2 + H2S ——-> 2HCOOH + PbS
Formic acid has a molecular weight of 47.018 g/mol and a density of 1.220 g/ml. It takes the form of a whitish fuming liquid with a strong, penetrating odour.
It’s utilised in fuel cells and in reverse-phase high-performance liquid chromatography procedures as a component of the mobile phase.
Apart from that, HCOOH can be employed as miticides and antibacterial agents in the leather and dyeing industries.
Let’s look at how this carboxylic acid compound’s chemical bonds work.
Lewis Structure of CH2O2
We need to design the Lewis Structure to figure out the type of chemical bonding inside any polyatomic molecule.
Lewis Structure shows us how to create a 2D schematic depiction of a molecule step by step. The concept of valence electrons is used to determine the type of bond formation in this case.
Two hydrogen atoms, one carbon atom, and two oxygen atoms make up HCOOH, or methanoic acid.
The current Periodic Table is seen in this image.
Carbon has a valency of 4 and 4 valence electrons, as can be shown. Oxygen has 6 valence electrons and belongs to group 16 (chalcogen family).
Hydrogen is a member of group 1 and only possesses one electron in its outermost shell (valence electron).
The total number of valence electrons is equal to 12 + 4 + 6 = 18.
The least electronegativity value among the three elements is hydrogen, followed by carbon, and finally oxygen.
The least electronegative element must be in the centre, according to the usual rule.
Due to its single valence electron, hydrogen, on the other hand, tends to stay in the corners and does not become the core atom.
As a result, carbon will be the central atom in formic acid.
The atoms will appear as follows:
The valence electrons will now be placed around each constituent atom, and the diagram will look like this:
This is where the Octet rule, a crucial notion, comes into play. According to this criterion, every element in groups 1-17 (the main groups) has an octet configuration in its valence shell, similar to noble gas elements.
Nitrogen, for example, will have a Neon configuration, while Chlorine will have an Argon configuration.
You may have heard that chemistry is full of exceptions, and one of them is that Hydrogen tends to take on the Helium structure, necessitating the use of two electrons to complete the valence shell.
Carbon has not yet reached the octet fulfilment state, as seen in the diagram above. To do so, we’ll add two more electrons to the atom’s orbit.
The needed sketch is as follows:
If we add up the formal charges, we get:
The formula for calculating formal charge values is as follows:
C’s formal charge is calculated as 4 – 0.5*8 – 0 = 0.
For each H, the formal charge is 1 – 0.5*2 – 0 = 0.
O bound to H and C both have a formal charge of 6 – 0.5*4 – 4 = 0.
O bound to C has a formal charge of 6 – 0.5*4 – 4 = 0.
As a result, the atoms are in their least formal charge states.
For methanoic acid, the best Lewis Structure is:
Molecular Geometry of CH2O2
Valence Shell Electron Pair Repulsion Theory (VSEPR) is an acronym for Valence Shell Electron Pair Repulsion Theory. In chemistry, this model is used to predict the molecular geometry of a compound based on its Lewis Structure.
While the Lewis Structure provides a 2D picture of a chemical molecule, the VSEPR model provides a foundation for deciphering the molecular form in three dimensions.
This is important for molecules that are covalently bound. It discusses the concept of minimal repulsion and considers electron pairs (both bound and unbonded).
The electrons generate a negatively charged atmosphere around the atomic nuclei, according to VSEPR theory, which creates a repulsive force between like charges.
The molecules’ stability is maintained by increasing the distance between electrons, which reduces the repulsive force.
We can anticipate molecular geometry using VSEPR notations in VSEPR theory.
The core atom is denoted by A, and the surrounding atoms are denoted by X. (in VSEPR, we also consider triple and double bonds to be one bonding group),
The number of lone pairs linked to the core atom is denoted by the letter E.
Carbon is the central atom in this diagram (A). X is made up of two oxygen atoms and one hydrogen atom.
n = 3 is the number of people in the group.
E: there are no lone pairs of A, x = 0.
The VSEPR nomenclature for formic acid is AX3E0.
The molecular geometry of HCOOH is trigonal planar, as seen in the diagram.
Hybridization of CH2O2
Orbital hybridization is one of the most fundamental models for describing the nature of chemical bonding.
Hybridization is a concept that deals with atomic orbitals (AOs). Hybrid orbitals are formed when the orbitals of the same atom with equivalent energies merge and fuse. The electrons in the valence shell are involved. These hybrid orbitals are thus thought to have a role in bond formation.
Let’s look at the hybridization type for methanoic acid now.
Number of atoms bound to the core atom inside a molecule + Number of lone pairs of electrons attached to the central atom = Steric number
The centre carbon atom is double bound to an oxygen atom, single bonded to another oxygen atom, and single bonded to a hydrogen atom in HCOOH.
In formic acid, there are no lone or unbonded pairs of electrons.
3 + 0 = 3 is the steric number.
As a result, we have carbon sp2 hybridization.
We have sp2 hybridization for the oxygen in C=O because it has two lone pairs and one bound atom, whereas we have sp3 hybridization for the oxygen in C-O because it has two lone pairs and two sigma bonds.
Polarity of CH2O2
Let’s talk about polarity now.
A chemical molecule’s polarity is an important trait or property. It has something to do with the distribution of electric charges among the atoms that make up a molecule.
When is a molecule considered polar? When the distribution of electrons among the atoms is not even, i.e. there is an asymmetric charge distribution within the molecular composition, we call it polar.
The idea of electronegativity can be used to verify this. Polar covalent bonds are defined as a difference in electronegativity between two atomic elements in the range of 0.4–2.
A schematic of the Pauling electronegativity chart is shown below:
The difference in the C-H bond is 2.55 – 2.20 = 0.35.
The difference between C and O bonds is 3.44 – 2.55 = 0.89.
The difference in the O-H bond is 3.44 – 2.20 = 1.24.
As can be seen, the bonds have a tendency to be polar in character. In addition, the structure is asymmetric, with the hydrogen end on the positive side and the oxygen end on the negative.
HCOOH is a polar compound. In water and polar organic solvents, it is miscible.
The simplest carboxylic acid is HCOOH, which is an important organic compound. In this article, we went into chemical bonding in depth.
Good luck with your studies!