Fluoroform is an important haloform represented by the chemical formula CHF3. It exists as a colorless, odorless, non-toxic, and flammable gas at room temperature. It is also known as Freon-23, HFC-23, methyl trifluoride, and carbon trifluoride.
The IUPAC name of CHF3 is trifluoromethane. It is used as a refrigerant and is widely used in organic synthesis.
If you are looking to check the chemical nature of the fluoroform (CHF3) molecule, i.e., is it a polar or a non-polar molecule? Then your problem is solved here in this article.
Is CHF3 polar or non-polar?
Fluoroform (CHF3) is a polar molecule. The central carbon (C) atom in the CHF3molecule is surrounded by three fluorine (F) atoms and one hydrogen (H) atom via single covalent bonds, forming an asymmetric tetrahedral molecule.
The electronegativity of the fluorine (F) atom is greater than the carbon (C) and hydrogen (H) atoms. The higher electronegative F atoms attract the shared electron pairs in the CHF3 molecule with more influence.
Thus, all the bonds are individually polar and possess a specific dipole moment value.
The unsymmetric arrangement of atoms in the tetrahedral CHF3 molecule further enhances the polarity effect as the dipole moments of the bonds do not get canceled in the molecule overall. Thus, CHF3 is a polar molecule with a net dipole moment greater than 0.
In chemistry, a molecule with unequal charge distribution between different centers of bonded atoms is a polar molecule.
It is formed by the covalent bond between two different atoms leading to an asymmetric electron density.
In this case, the atoms acquire partial positive (δ+) and partial negative (δ–) charges.
If the dipole moments of individually polar bonds are not cancelled due to the asymmetrical shape of the molecule, the molecule will be polar, such as CHF3.
Hence a polar molecule has an unequal distribution of the electronic charge. Contrarily, if the electronic charge is evenly distributed over the molecule, in that case, it will be a non-polar molecule overall.
The following three factors influence the polarity of any covalent molecule:
Electronegativity.
Dipole moment.
Molecular geometry or shape.
In the next section, we will discuss how these three factors control the polarity of the CHF3 molecule.
Factors affecting the polarity of CHF3
Electronegativity
It is defined as the ability of an atom to attract a shared pair of electrons from a covalent chemical bond.
Electronegativity decreases down the group in the Periodic Table of elements while it increases across a period.
Greater the electronegativity difference between the bonded atoms in a molecule, the higher the bond polarity.
Hydrogen belongs to group 1-A (or 1) of the Periodic Table. The electronic configuration of hydrogen is 1s1, so it has 1 valence electron available for bonding.
Carbon belongs to group IV-A (or 14) of the Periodic Table. The electronic configuration of carbon is 1s2 2s2 2p2, so it has 4 electrons in the outermost shell.
In contrast, fluorine belongs to group VII-A (or 17) of the Periodic Table. The electronic configuration of fluorine is 1s2 2s2 2p5, which hints at the presence of 7 valence electrons.
The three F-atoms and one H-atom thus form a single covalent bond with the central C-atom on each side of the CHF3 molecule.
Atom
Electronic configuration
Valence electrons
Hydrogen (1H)
1s1
1
Fluorine (9F)
1s22s22p5
7
Carbon (6C)
1s22s22p2
4
According to Pauling’s scale, a covalent bond is polar if the bonded atoms have an electronegativity difference greater than 0.5 units.
Carbon (E.N = 2.55) is slightly more electronegative than the hydrogen atom (E.N = 2.20). There is an electronegativity difference of only 0.35 units between these two atoms. Therefore, the C-H bond is weakly polar.
On the other hand, fluorine is more electronegative (E.N = 3.98) than the carbon atom. There is an electronegativity difference of 1.43 units between these two atoms. Hence, each C-F bond is extremely polar in the CHF3 molecule.
Due to this electronegativity difference, the F-atom strongly attracts the shared electron cloud from the bonds. The bonded electrons are held significantly close to the fluorine atoms.
The central C-atom and H-atoms thus gain a partial positive charge (Cδ+ and H δ+), while the fluorine atom being more electronegative, obtains a partial negative (Fδ-) charge.
The F atoms not only attract the shared electron cloud of each C-F bond but also attracts C-H electrons. As a result, the electron cloud distribution in the molecule is unequal overall. Thus, CHF3 is a polar molecule.
Dipole Moment
The dipole moment is the product of electrical charge (Q) and bond length (r) between two bonded atoms. It is a vector quantity expressed in Debye (D) units.
It is represented by a Greek symbol µ and measures the polarity of a bond.
The dipole moment of any molecule depends on the difference in electronegativity between the bonded atoms. The greater the electronegativity difference, the higher the bond polarity, resulting in a high dipole moment value.
It points from the partial positive (δ+) center to the partial negative (δ–) center of a bond or molecule.
The difference in electronegativity between the bonded atoms in the CHF3 molecule leads to dipoles pointing from Cδ+and Hδ+ to Fδ-.
Thus, each bond in the CHF3 molecule is polar, with a net dipole moment > 0.
Molecular geometry
As discussed earlier, a fluoroform (CHF3) molecule consists of three single C-F covalent and one C-H covalent bond. There are a total of 26 valence electrons in the overall molecule.
According to the Valence Shell Electron Pair Repulsion Theory (VSEPR) theory of chemical bonding, CHF3 is an AX4-type molecule. Around the central carbon atom (A) are four bond pairs of electrons (X).
To minimize the electronic repulsions between the atoms, the fluoroform (CHF3) molecule adopts a tetrahedral geometry with a bond angle of 109.5°.
As a result of the asymmetric arrangement of atoms around the central carbon, the individual dipole moments of the bonds do not get canceled in the fluoroform (CHF3) molecule. There is an unequal distribution of electron clouds over the molecule.
Thus, CHF3 is an overall polar molecule with a net dipole moment (µ = 1.8 D).
Difference between polar and nonpolar?
Polar molecule
Non-polar molecule
Atoms must have a difference in
electronegativity
Atoms may have the same or different electronegativity values
Unequal charge distribution overall
Equal charge distribution overall
Net dipole moment greater than zero
Net dipole moment equals to zero
Examples include water (H2O), ethanol (CH3CH2OH), ammonia (NH3), sulfur dioxide (SO2), bromine trifluoride (BrF3), fluoroform (CHF3), bromine pentafluoride (BrF5), etc.
Examples include oxygen (O2), nitrogen (N2), methane (CH4), carbon disulfide (CS2), etc.
Due to a great electronegativity difference between the bonded fluorine, hydrogen, and carbon atoms, polar covalent bonds are generated in the CHF3
As a result of the unsymmetrical arrangement of atoms in the tetrahedral CHF3 molecule, the individual dipole moments of the bonds are not canceled.
Thus, CHF3 is a polar molecule.
CHF3 is a polar molecule but is considered a non-polar solvent. Why?
CHF3 is a polar molecule because of the difference in the electronegativity in the bonded C, H, and F atoms.
CHF3 is regarded as a non-polar solvent because a large number of CHF3 molecules together have a low dielectric constant.
CHF3 is polar, yet it is only sparingly soluble in water (a polar solvent). Why?
CHF3 is sparingly soluble in water due to its polar ends but lacks the ability to form hydrogen bonding with H2O molecules.
Thus, CHF3 does not completely dissolve in water. For H-bonding, hydrogen atoms must be directly bonded to the electronegative atoms.
Which is more polar, CHF3 or CHI3?
The greater the electronegativity difference between the bonded atoms, the higher the bond polarity, resulting in a high dipole moment value.
Fluorine ( E.N = 3.98) is more electronegative than the iodine atom (E.N = 2.66). Thus, fluorine will attract the shared electron pairs in the CHF3 molecule with more influence than the iodine atom in the CHI3.
As a result, the C-F bond is more polar than the C-I bond. Thus, CHF3 is more polar than the CHI3 molecule.
Is there a formal charge on the bonded atoms in the CHF3 molecule?
Formal charge of an atom = [ valence electrons – non-bonding electrons- ½ (bonding electrons)]
For hydrogen atom
Valence electrons = 1
Bonding electrons = 2
Non-bonding electrons = 0
∴ The formal charge on the hydrogen atom = 1-0-2/2 = 1-1 = 0
For fluorine atoms
Valence electrons = 7
Bonding electrons = 2
Non-bonding electrons = 6
∴ The formal charge on the fluorine atoms = 7-6-2/2 = 1-1 = 0
For carbon atom
Valence electrons = 4
Bonding electrons = 8
Non-bonding electrons = 0
∴ The formal charge on the central carbon atom = 4-0-8/2 = 4-4 = 0
Thus, no formal charge is present on the trifluoromethane (CHF3) molecule.
Summary
Fluoroform/trifluoromethane (CHF3) is a polar molecule.
Due to a great electronegativity difference between fluorine, hydrogen, and carbon, polar covalent bonds are generated.
The fluorine atom attracts the shared electron cloud strongly from the CHF3.
The difference in electronegativity between the bonded atoms leads to the formation of dipoles pointing from C δ+and Hδ+ to F δ-.
The AX4 type CHF3 molecule adopts a tetrahedral geometry with a bond angle of 109.5°.
Due to the unsymmetrical arrangement of atoms in the tetrahedral molecule, the individual dipole moments of the bonds are not canceled in the molecule overall. Thus, CHF3 is a polar molecule (μ = 1.8 D).
Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/
Topblogtenz is a website dedicated to providing informative and engaging content related to the field of chemistry and science. We aim to make complex subjects, like chemistry, approachable and enjoyable for everyone.
