Fluoroform (CHF3) has a central carbon (C) atom with 4 valence electrons, bonded to three fluorine (F) atoms and one hydrogen (H) atom. Each F contributes 7 valence electrons, and H contributes 1, totaling 26 electrons. The Lewis structure shows three single C-F bonds and one single C-H bond, with no lone pairs on carbon. CHF3 adopts a tetrahedral geometry with bond angles of approximately 109.5°. The molecule is polar due to the high electronegativity of fluorine (3.98) compared to carbon (2.55) and hydrogen (2.20), influencing its physical properties like boiling point and solubility, and its use as a refrigerant.
CHF3 is known as fluroform. It is a similar structure to methane and is also known as trifluoromethane. Three H atoms are replaced in methane by fluorine atoms. As it is similar to methane so the shape and bond angle is also similar to methane which is tetrahedral shape and bond angle near about 109.50. C-H and C-F bond lengths are different due to two substituents.
The hybridization of the CHF3 lewis structure is sp3. Due to the presence of different substituents and different electronegativity and asymmetric shapes, the molecule is polar. It can be soluble in organic non-polar solvents also. It is a greenhouse gas like chlorofluorocarbon.
Some important facts about CHF3
In the physical state, the CHF3 is a colorless gaseous molecule. As it is a gaseous species so it has some vapor pressure of about 4.38 MPa at 20 °C temperature. The melting point and boiling point of this molecule are 118 K and 191.1 K respectively. First, it was synthesized by the reaction of Iodoform and dry silver fluoride.
But in the laboratory, it is prepared by the reaction of Chloroform in the presence of Hydrogen fluoride.
CHCl3 + 3HF = CHF3 + 3HCl
Biologically, it can be produced by decarboxylation of trifluoroacetic acid.
In the organic reaction, it can act as a source of nucleophiles.
1. How to draw the CHF3 lewis structure?
Lewis structure is a very important tool for every covalent molecule. With the help of lewis’s structure, it can easily predict the bonding electrons, the shape of the molecule, lone pairs, and valence electrons of the molecule.
Before proceeding with the CHF3 lewis structure there are a few rules we should be kept in our mind.
First of all, we should count the valence electrons for all the individual atoms in the CHF3 molecule and then added together. Now we have to select the central atom based on less electronegativity. Based on the size and less electronegativity C is the central atom here and one H and three F atoms are the surrounding atoms here.
Now we will connect all the atoms via a single bond. The valence electrons of C are four, H is one, and F has seven electrons. In the CHF3 lewis structure, the number of electrons involved will be [4+1+ (3*7)] = 26 and from the octet rule the electrons needed [4*8 +1*2] = 34 electrons, and the required bonding electrons will be 34-26 = 8 electrons and the minimum bond required, 8/2 = 4 bonds.
So, in the CHF3 lewis structure, there will be a minimum of 4 bonds required and all the bonds are single. Attaching all the atoms with the central c atom via four bonds all the atoms completed their octet so no need to add multiple bonds here.
After that, the lone pairs are assigned to the respective atoms. F has seven electrons in its valence shell and the bond formation used only one electron so the remaining six electrons exit as lone pairs over F atoms.
2. CHF3 lewis structure shape
CHF3 lewis structure shape can be predicted from the Valence Shell Pair Electrons Repulsion theory. According to this theory if the bonding electrons count for any molecule will be 8 then the shape of the molecule will be tetrahedral.
8 electrons count molecule will adopt generally square planner or tetrahedral geometry. But in the square planner moiety, the bond angle in between atoms will be 900 and there is a high chance of steric crowding.
But in the tetrahedral geometry, the bond angle increases, and the free space among the molecule also increases so the chance of steric crowding of any kind of repulsion will be minimized.
In the CHF3 lewis structure, the central atom is here C and the surrounding atoms H and three F atoms are adjusted at the four vertices of the tetrahedral moiety and arranged with proper bond angle and spacing.
3. CHF3 valence electrons
In the CHF3 lewis structure, the valence electrons are considered for C, H, and F atoms which are present at their outermost or valence orbitals. Maybe they are involved in the bond formation or maybe exist as lone pairs.
The electronic configuration of H, C and F are 1s1, [He]2s22p2, [He]2s22p2 respectively. So, we can say that there is one electron from H which is also a valence electron, C has four electrons in its valence shell and F has seven electrons.
H and F involved one electron to form a covalent bond with C, and the rest of the six electrons of F exist as lone pairs and all the four valence electrons of C are involved with one H and three F to form the CHF3 lewis structure.
So, the total valence electrons in this molecule are the summation of three atoms valence electrons and the number of valence electrons will be, 1+4+(7*3) = 26 electrons.
4. CHF3 lewis structure octet rule
In the CHF3 lewis structure, all the individual atoms will follow the octet rule to complete their valence shell and gain the nearest noble gas configuration by accepting a suitable number of electrons.
From the electronic configuration of every atom, we see that H has one electron in its valence shell and it needs one more to gain the same configuration as He. So, one electron of H and one electron of C share in a bond and complete the octet of H.
F has seven electrons in its outermost orbital and among them, six exist as lone pairs, and one electron shares with one electron of C in a covalent bond and complete the octet of F by gaining eight electrons in its valence orbital.
C has four electrons in its valence shell and its hare has four electrons with three F atoms and one H atom and also gains eight electrons in its valence orbital to complete the octet.
According to octet, S orbital contains a maximum of two electrons like H atoms and p orbitals contain six electrons like C and F.
5. CHF3 lewis structure formal charge
The formal charge is a hypothetical concept like resonance and by this concept, we can predict the charge over a particular atom in a CHF3 molecule by their bonding electrons.
The formula we can use to calculate the formal charge, F.C. = Nv – Nl.p. -1/2 Nb.p.
Where Nv is the number of electrons in the valence shell or outermost orbital, Nl.p is the number of electrons in the lone pair, and Nb.p is the total number of electrons that are involved in the bond formation only.
In the CHF3 lewis structure, C and H are different substituents so we have to calculate the formal charge of C, H, and F individually.
The formal charge over the C atom is, 4-0-(8/2) = 0
The formal charge over the H atom is, 1-0-(2/2) = 0
The formal charge over the F atom is, 7-6-(2/2) = 0
So, the formal charge over the CHF3 lewis structure is zero as no individual charge contains any formal charge.
6. CHF3 lewis structure lone pairs
Lone pairs are those electrons that are present as valence shells but do not participate in the bond formation they are valence electrons also. In the CHF3 lewis structure, only F has lone pairs, and H and C lack lone pairs.
From the electronic configuration, we can say that F has six electrons in its valence shell and according to the octet rule, it shares one electron with C to complete its octet via the formation of one single covalent bond. The remaining six electrons are present as three pairs of lone pairs.
For H and C after bond formation, they have no electrons in their valence shell, so they lack lone pairs.
So, the total lone pairs in the CHF3 lewis structure will be, 3*3 = 9 pairs of lone pairs.
7. CHF3 lewis structure bond angle
The bond angle will be 109.50 which will be for ABX3 or AX4 molecules like CHF3. It adopts a tetrahedral structure so the bond angel is perfect for that geometry.
The CHF3 lewis structure adopts tetrahedral geometry according to the VSEPR theory. According to this theory, the bond angle of the molecule will be 109.50. The size of F and H is very small so there is no chance for lone pairs- bond pair repulsion and for this reason, there is no deviation of the actual bond angle.
But due to electronegativity F try to pull the electron density towards it and for this reason, the F-C-F bond angle is about 1080 but the F-C-H bond angle remains 109.50.
8. CHF3 lewis structure resonance
There is no resonance structure observed for the CHF3 lewis structure. Resonance is the concept by which in a molecule the delocalization of electron occurs in its different skeleton structure.
For the CHF3 lewis structure, there is a different skeleton structure is not possible, F is most electro-negative so it does not release the electron density from it and H is lack electron density. So, there is no possibility to form the resonating structure for the CHF3 lewis structure.
9. CHF3 hybridization
Hybridization is also a hypothetical concept by which the mixing of different orbitals of different energy to form a new hybrid orbital of equivalent energy. For the CHF3 lewis structure, the orbitals of C, H, and F get mixed to form an sp3 hybrid orbital.
We calculate the CHF3 hybridization by using the following formula,
H = 0.5(V+M-C+A), where H= hybridization value, V is the number of valence electrons in the central atom, M = monovalent atoms surrounded, C=no. of cation, A=no. of the anion.
For the CHF3 lewis structure, C has 4 valence electrons which are involved in the bond formation, and one H and three F atoms are present.
So, the central C in the CHF3 lewis structure is, ½(4+4+0+0) = 4 (sp3) hybridized.
| Structure | Hybridization value | State of hybridization of central atom | Bond angle |
| Linear | 2 | sp /sd / pd | 1800 |
| Planner trigonal | 3 | sp2 | 1200 |
| Tetrahedral | 4 | sd3/ sp3 | 109.50 |
| Trigonal bipyramidal | 5 | sp3d/dsp3 | 900 (axial), 1200(equatorial) |
| Octahedral | 6 | sp3d2/ d2sp3 | 900 |
| Pentagonal bipyramidal | 7 | sp3d3/d3sp3 | 900,720 |
According to VSEPR theory we can say that from the above table, if the central atom hybridization value is 4 then it is sp3 hybridized.
In the box diagram, it is shown that one s orbital and three p orbitals or C undergo missing to form an sp3 hybrid orbital. Only sigma bonds are allowed in the hybridization.
10. CHF3 solubility
CHF3 is an organic molecule so it is expected to be soluble in organic solvents like benzene, toluene, ethanol, etc. But it has a solubility in water.
Although CHF3 is an organic molecule it is a polar molecule and water is a polar solvent so it gets dissolved in a water molecule (like dissolve like).
11. Is CHF3 ionic?
All the covalent molecule has some % of ionic character according to Fajan’s rule. So, it is expected that the CHF3 lewis structure also has an ionic character.
F is the most electronegative atom and in the ionization form of CHF3 lewis structure, it can ionize Fluoride. Again, from the ionic potential of this molecule, we can say that the molecule can be polarizable so it has some ionic character.
12. Is CHF3 acidic or basic?
CHF3 is lesser acidic. It has acidic proton in it.
Due to the presence of three electronegative atoms F they will drag the electron density towards itself and for this reason, the C_H bond becomes weaker and it can easily be cleaved and H released easily.
So, we can say that the CHF3 molecule donates proton or H atom and behaves as an acid but from the pka value, it is less acidic.
13. Is CHF3 polar or nonpolar?
From the CHF3 lewis structure, we can say that the molecule is asymmetric due for this reason it is a polar molecule. Because it has a permanent dipole moment.
In the CHF3 lewis structure, the dipole moment acts from C to more electronegative F atoms. For the asymmetric structure, there is no chance to cancel out the dipole moment and the molecule has some resultant dipole moment and making it polar.
14. Is CHF3 tetrahedral?
Yes, the CHF3 molecule is tetrahedral. The hybridization value and according to the VSEPR theory, also confirmed its structure.
15. Is CHF3 linear?
No, the molecule is not linear. As discussed earlier it is tetrahedral geometry and it has a permanent dipole moment for its asymmetric structure.
Conclusion
From the whole discussion about the CHF3 lewis structure, we can conclude that the molecule is tetrahedral with sp3 hybridization. The molecule is acidic due to the presence of acidic proton and the molecule is also polar for its asymmetric structure.
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Hi……I am Biswarup Chandra Dey, I have completed my Master’s in Chemistry from the Central University of Punjab. My area of specialization is Inorganic Chemistry. Chemistry is not all about reading line by line and memorizing, it is a concept to understand in an easy way and here I am sharing with you the concept about chemistry which I learn because knowledge is worth to share it.
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