Methanol (CH3OH) Lewis dot structure, molecular geometry or shape, electron geometry, bond angle, hybridization, formal charges, polar vs non-polar
CH3OH is the chemical formula for methanol or methyl alcohol, a colorless sweet smelling, extremely volatile alcohol. The commercial name for methanol is wood alcohol. It is the primary member of the alcohol family.
It is used as a building block for the synthesis of paints and plastics. Methanol is a safe energy source, an antifreeze agent, and a popular energy carrier.
In this article we will discuss everything you need to know about methanol (CH3OH) such as how to draw its Lewis dot structure, what is its molecular geometry or shape, electron geometry, bond angle, hybridization, formal charges, polarity nature, etc.
The Lewis structure of methanol (CH3OH) consists of a carbon (C) atom at the center which is bonded to three atoms of hydrogen (H) and a hydroxyl (OH) functional group. In this way, there are a total of 4 electron density regions around the central C-atom in the CH3OH Lewis structure.
All four electron density regions are comprised of bond pairs. Thus, there is no lone pair of electrons on the central C-atom in this Lewis structure.
Drawing the Lewis dot structure of methanol (CH3OH) is quite an easy task if you follow the simple steps given below.
Steps for drawing the Lewis dot structure of CH3OH
1. Count the total valence electrons in CH3OH
The first step while drawing the Lewis structure of a molecule is to count the total valence electrons present in it. The number of valence electrons present in an elemental atom can be easily determined by identifying its Group number from the Periodic Table of elements.
As there are atoms from three different elements of the Periodic Table in CH3OH. So you need to look for these elements in the Periodic Table.
Carbon (C) belongs to Group IV A (or 14) so it has a total of 4 valence electrons. Oxygen (O) is present in Group VI A (or 16) so it has 6 valence electrons while hydrogen (H) lies at the top of the Periodic Table containing a single valence electron only.
∴ The CH3OH molecule consists of 1 C-atom, 1 O-atom, and 4 H-atoms. Therefore, the total valence electrons available for drawing the Lewis dot structure of CH3OH = 1(4) + 6 + 4(1) = 14 valence electrons.
2. Choose the central atom
In this second step, usually the least electronegative atom out of all the concerned atoms is chosen as the central atom.
This is because the least electronegative atom is the one that is most likely to share its electrons with the atoms spread around it.
Oxygen is more electronegative than both carbon and hydrogen. Hydrogen (E.N = 2.20) is less electronegative than carbon (E.N = 2.55) but it cannot be chosen as the central atom because a hydrogen (H) atom can accommodate only 2 electrons so it can form a bond with a single adjacent atom only. This denotes that H is always placed as an outer atom in a Lewis structure.
As a result, the carbon (C) atom is chosen as the central atom in the Lewis dot structure of methanol (CH3OH) while the O and H atoms occupy terminal positions, as shown in the figure below.
3. Connect outer atoms with the central atom
Now we need to connect the outer atoms with the central atom of the Lewis structure using single straight lines.
The four hydrogens and one oxygen atom are the outer atoms in the Lewis structure of methanol. The terminal H-atom at the right-hand side is joined to the O-atom using a single bond.
As we already told you H can form a single bond with one adjacent atom only. So except for this H-atom, all the other outer atoms are directly joined to the central C-atom using straight lines, as shown below.
Each straight line represents a single covalent bond i.e., a bond pair containing 2 electrons. There are a total of 5 single bonds in the above diagram. As 5(2) = 10, that means 10 valence electrons are already consumed out of the 14 initially available.
4. Complete the duplet and/or octet of the outer atoms
As we already identified, the hydrogen and oxygens atoms are the outer atoms in the Lewis dot structure of CH3OH.
Each hydrogen (H) atom requires a total of 2 valence electrons in order to achieve a stable duplet electronic configuration.
A C-H and an O-H single bond already represent 2 valence electrons around each H-atom. This means all four H-atoms already have a complete duplet in the Lewis structure drawn till yet. Thus, we do not need to make any changes with regard to the hydrogen atoms in this structure.
In contrast to that, an O-atom needs a total of 8 valence electrons to achieve a stable octet electronic configuration. A C-O bond and an O-H bond represent 2(2) = 4 electrons which denotes the outer O atom needs 4 more electrons to complete its octet.
Consequently, these 4 valence electrons are placed as 2 lone pairs on the oxygen (O) atom in the CH3OH, as shown below.
5. Complete the octet of the central atom
In the Lewis structure drawn till step 4, the central carbon (C) atom has four single bonds around it i.e., 3 C-H single bonds and 1 C-O single bond. Four single covalent bonds represent a total of 4(2) = 8 valence electrons. In short, the central C-atom already has a complete octet electronic configuration.
Total valence electrons used till step 5 = 5 single bonds + electrons placed around the O-atom, shown as dots = 5(2) + 4 = 14 valence electrons.
Total valence electrons – electrons used till step 5 = 14 – 14 = 0 valence electrons.
All the valence electrons initially available are now used up therefore there is no lone pair of electrons on the central C-atom in the Lewis dot structure of CH3OH.
The final step is to check the stability of the Lewis structure of CH3OH obtained in this step. Let us do that using the formal charge concept.
6. Check the stability of the CH3OH Lewis structure using the formal charge concept
The less the formal charge on the atoms of a molecule, the better the stability of its Lewis structure.
The formal charge can be calculated using the formula given below.
Zero formal charges on all the bonded atoms in the CH3OH Lewis structure marks the incredible stability of this structure.
Now that we have obtained the correct and best Lewis representation of methanol, let us move ahead and discuss other interesting facts related to CH3OH such as its shape and geometry.
What are the electron and molecular geometry of CH3OH?
The methanol (CH3OH) molecule has an identical electron geometry and molecular geometry or shape i.e., tetrahedral.
There are a total of 4 electron density regions around the central C-atom in CH3OH and there is no lone pair of electrons on this central atom. Thus, there is no distortion witnessed in the shape and geometry of the molecule.
Molecular geometry of CH3OH
The molecular geometry or shape of methanol (CH3OH) is tetrahedral.
The absence of any lone pair of electrons on the central C-atom in CH3OH means there are no lone pair-lone pair and lone pair-bond pair electronic repulsions present in the molecule.
A bond pair-bond pair repulsive effect exists which makes the bonded electron pairs occupy the four corners of a tetrahedron, as shown in the figure below.
Electron geometry of CH3OH
According to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding, the ideal electron geometry of a molecule containing a total of 4 electron density regions around the central atom is tetrahedral.
In CH3OH, there are 4 single bonds around the central carbon atom which makes a total of 4 electron density regions. Thus, its electron geometry is also tetrahedral.
A shortcut to finding the electron and the molecular geometry of a molecule is by using the AXN method.
AXN is a simple formula to represent the number of atoms bonded to the central atom in a molecule and the number of lone pairs present on it.
It is used to predict the geometry or shape of a molecule using the VSEPR concept.
AXN notation for CH3OH molecule
A in the AXN formula represents the central atom. In the CH3OH molecule, a carbon (C) atom is present at the center so A = C.
X denotes the atoms bonded to the central atom. In CH3OH, three hydrogens (H) atoms and one OH functional group are bonded to the central carbon. The OH group is considered 1 region of electron density. In short, X = 3+1 = 4 for CH3OH.
N stands for the lone pairs present on the central atom. As per the Lewis structure of CH3OH, there are no lone pairs of electrons on the central carbon so N = 0.
As a result, the AXN generic formula for CH3OH is AX4.
Now, you may have a look at the VSEPR chart below.
The VSEPR chart confirms that the molecular geometry or shape of a molecule with an AX4 generic formula is identical to its electron pair geometry i.e., tetrahedral, as we already noted down for methanol (CH3OH).
Hybridization of CH3OH
The central carbon (C) atom in methanol (CH3OH) is sp3 hybridized.
The electronic configuration of carbon is 1s2 2s2 2p2.
During chemical bonding, the 2s electrons of carbon get unpaired. One of the two electrons shifts to the empty 2p atomic orbital. The 2s orbital and three half-filled 2p atomic orbitals of carbon consequently hybridize to yield four sp3 hybrid orbitals.
Each sp3 hybrid orbital is equivalent and contains a single electron only. It possesses a 25% s character and a 75% p-character.
Three of the four sp3 hybrid orbitals of carbon form C-H sigma (σ) bonds by overlapping with the s-orbitals of the hydrogen atoms.
The remaining sp3 hybrid orbital of carbon forms the C-O sigma (σ) bond by overlapping with the sp3 hybridized orbital of the oxygen atom in CH3OH.
Another shortcut to finding the hybridization present in a molecule is by using its steric number against the table given below. The steric number of central C in CH3OH is 4 so it has sp3 hybridization.
Steric number
Hybridization
2
sp
3
sp2
4
sp3
5
sp3d
6
sp3d2
The CH3OH bond angle
The H-C-H bond angle is 109.5° in the CH3OH molecule as expected in a symmetrical tetrahedral shape. Contrarily, the C-O-H bond angle is 104.5 ° due to the repulsive effect between two lone pairs on the O-atom and the bond pairs respectively.
According to Pauling’s electronegativity scale, a covalent bond is considered polar if the concerned atoms have an electronegativity difference greater than 0.5 units.
An electronegativity difference of 0.35 units exists between a carbon (E.N = 2.55) and a hydrogen (E.N = 2.20). Therefore, the C-H bond is only weakly polar.
In contrast to that, the oxygen atom is highly electronegative. An electronegativity difference of 0.89 units exists between the carbon and chlorine (E.N = 3.44) atoms.
Hence the C-O bond is extremely polar in nature and it possesses a high dipole moment value (symbol µ). Similarly, the O-H bond is polar as an even higher electronegative difference of 1.24 units exists between an O and an H-atom.
As a result, the O atom obtains a partial negative (δ–) charge while the C atom and the H-atoms attain partial positive (δ+) charges in CH3OH.
The highly electronegative oxygen atom not only attracts the shared electron cloud of the C-O bond but also attracts C-H and O-H bonded electrons. The electron cloud stays non-uniformly distributed in the molecule overall. In conclusion, CH3OH is a polar molecule (net µ = 1.69 D).
It is due to this polar nature of methanol (CH3OH) that it is fairly water soluble. Like dissolves like. Polar (H2O) molecules attract polar CH3OH molecules and overcome the intermolecular forces of attraction between CH3OH molecules to a large extent.
Also, hydrogen bonding can develop between water and methanol molecules that speed up the dissolution of CH3OH in H2O.
The Lewis structure of methanol (CH3OH) consists of a carbon (C) atom at the center which is bonded to 3 H-atoms and an OH functional group.
This Lewis structure displays a total of 14 valence electrons i.e., 14/2 = 7 electron pairs.
The 7 electron pairs comprise 5bond pairs and 2 lone pairs of electrons.
The 5 bond pairs are made up of 3 C-H bond pairs, 1 C-O bond pair, and 1 O-H bond pair.
The 2 lone pairs are present on the outer O-atom while there is no lone pair on the central C-atoms in the CH3OH lewis structure.
How many lone pairs are there in the Lewis structure of CH3OH?
There are a total of 2 lone pairs in the Methanol (CH3OH) Lewis structure. Both the lone pairs of electrons are present on the oxygen (O) atom bonded to the central C-atom.
What shape is CH3OH?
The CH3OH molecule has a tetrahedral shape and molecular geometry which is identical to its ideal electron pair geometry.
According to some online sources, methanol occupies a bent shape due to lone pair-bond pair repulsions if oxygen is considered the main geometric center.
But that is out of the scope of this article. Since carbon is less electronegative than oxygen so we are considering C as the only geometric center while discussing the shape of CH3OH.
What are the similarities and differences between CH4 and CH3OH in terms of molecular shapes and polarity?
Both methane (CH4) and methanol (CH3OH) molecules have an identical shape and molecular geometry as per the VSEPR concept i.e., tetrahedral.
There are a total of 4 electron density regions around the central C-atom in both molecules and it has no lone pairs of electrons. Thus, maintaining a symmetrical tetrahedral shape.
However, CH4 is a non-polar molecule (net µ = 0) while CH3OH is polar (net µ = 1.69 D). The difference in polarity exists due to the presence of an extremely electronegative oxygen atom in CH3OH while there is no such atom in the CH4 molecule.
The total number of valence electrons available for drawing methyl alcohol or methanol (CH3OH) Lewis structure is 14.
CH3OH has an identical electron and molecular geometry or shape i.e., tetrahedral.
The CH3OH molecule has sp3 hybridization.
The bonded atoms form a mutual bond angle of 109.5° in the tetrahedral CH3OH molecule.
The CH3OH molecule is overall polar (net µ > 0) due to the high electronegativity of the oxygen atom which attracts each C-H electron cloud in addition to attracting the C-O and O-H bonded electrons.
Zero formal charges present on all the bonded atoms in the CH3OH molecule account for the extraordinary stability of the Lewis structure drawn in this article.
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/
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