Is CH3NH2 polar or non-polar? - Polarity of CH3NH2
CH3NH2 is the chemical formula of an organic compound, a derivative of ammonia known as methylamine. It is a colorless gas with a pungent fishy odor resembling the odor of ammonia.
CH3NH2 has a molar mass of 31.05 g/mol. It is used in making pharmaceuticals, insecticides, paint removers, surfactants, and rubber chemicals.
So are you excited to find out whether the methylamine CH3NH2 molecule is polar or non-polar? If yes, then continue reading this article.
Is CH3NH2 polar or non-polar?
Methylamine (CH3NH2) is a polar molecule. It consists of one carbon (C) atom, one nitrogen (N) atom, and five hydrogens (H) atoms. The carbon and nitrogen atoms are kept at the central position making a C-N bond. The hydrogen atoms are at the surrounding positions.
The carbon atom is surrounded by three H-atoms, while the nitrogen atom is surrounded by two H-atoms. The molecular geometry of CH3NH2, with respect to C-atom, is tetrahedral, while with respect to N-atom, it is trigonal pyramidal.
Between bonded atoms, an electronegativity difference of 0.49 units exists in the C-N bond, 0.35 units exist in C-H bonds, and 0.84 units exist between atoms in the N-H bonds.
Thus, C-N, C-H, and N-H bonds are individually polar in the CH3NH2 molecule and possess a specific dipole moment value (symbol µ).
In CH3NH2, the nitrogen atom contains one lone pair of electrons and also is strongly electronegative, so it attracts electrons from each of the C-N and N-H bonds to a large extent.
The electron cloud in CH3NH2 does not stay uniformly distributed in the molecule overall due to its asymmetric shape. As a result, the CH3NH2 molecule is overall polar (net µ= 1.31 Debye).
|Name of molecule||Methylamine (CH3NH2)|
|Bond type||Polar covalent|
Tetrahedral (w.r.t. C-atom)
Trigonal pyramidal (w.r.t. N-atom)
|Polar or Non-polar?||Polar molecule|
|Dipole moment||1.31 Debye|
∠ (H-N-H) = 106°
∠ (H-C-H) = 108°
∠ (C-N-H) = 109°
∠ (H-C-N) = 112°
What makes a molecule polar or non-polar?
A molecule is polar if there is a non-uniform charge distribution present in it. If the charge distribution gets equally balanced in different parts, then that molecule or molecular ion is considered non-polar.
The following three factors mainly influence the polarity of a molecule:
- The electronegativity difference between two or more covalently bonded atoms
- Dipole moment
- Molecular geometry or shape
Now, let us discuss the effect of the above three factors one by one to prove that the methylamine (CH3NH2) molecule is overall a polar molecule.
Factors affecting the polarity of CH3NH2
It is defined as the ability of an elemental atom to attract a shared pair of electrons from a covalent chemical bond.
Electronegativity increases across a period in the Periodic Table while it decreases down the group.
Greater the electronegativity difference between bonded atoms in a molecule, the higher the bond polarity.
Carbon (C) is present in Group IV A of the Periodic Table. The electronic configuration of carbon is 1s2 2s2 2p2. As per this electronic configuration, a C-atom has a total of 4 valence electrons. It is thus short of 4 more electrons that are required so that the carbon atom can achieve a complete octet electronic configuration.
Hydrogen (H) is present in Group IA of the Periodic Table. The electronic configuration of hydrogen is 1s1. According to this electronic configuration, an H-atom has 1 electron in its only shell, thus lacking one more electron to complete its duplet.
Conversely, Nitrogen (N) is present in Group VA of the Periodic Table. The electronic configuration of nitrogen is 1s2 2s2 2p3 which translates as a total of 5 valence electrons. It has a deficiency of three electrons to complete its stable octet configuration.
In CH3NH2, the central C-atom is bonded to 3 H-atoms and an N-atom. All four valence electrons of carbon get consumed in covalent bonding which denotes there is no lone pair of electrons on the central C-atom in CH3NH2.
In contrast, the N-atom is single covalently bonded to the C-atom and 2 H-atoms. 3 valence electrons of nitrogen get consumed in covalent bonding out of the 5 initially available. It thus has a lone pair of electrons.
In this way, the central C-atom and the N-atom attain a complete octet, while each of the five H-atoms obtains complete duplet electronic configuration via chemical bonding in the methylamine Lewis structure shown above.
All the valence electrons of carbon atom get consumed in the bond formation, so it has no lone pair, but there is one lone pair of electrons on the central N-atom in CH3NH2. Hence, there is distortion in the shape or geometry of the molecule w.r.t N-atom.
|Atom||Electronic configuration||Valence electrons|
CH3NH2 contains a C-atom (E. N= 2.55), an N-atom (E. N= 3.04), and H-atoms (E. N= 2.20). Hence, between bonded atoms, the electronegativity difference in the C-N bond is 0.49 units, in each C-H bond is 0.35 units, and in each N-H bond is 0.84 units, respectively.
The more electronegative N-atom (E. N= 3.04), along with having a lone pair of electrons, not only strongly attracts the shared electron cloud away from the central C-atom in the C-N bond but also attracts C-H bonded electrons in the CH3NH2 molecule.
Thus, the nitrogen atom present in CH3NH2 gains a partial negative (Nδ-) charge, while the central carbon atom obtains a partial positive (Cδ+) charge. All hydrogen atoms also gain partial positive (Hδ+) charges, as shown below.
As a result, with specific electronegativity differences, all of the N-H, C-H, and C-N bonds are individually polar in CH3NH2 (as shown below).
Dipole moment (μ) is a vector quantity that points from the positive pole to the negative pole of a bond or a molecule.
It is mathematically calculated as a product of the magnitude of charge (Q) and charges separation (r). The dipole moment is expressed in a unit called Debye (D).
The dipole moment of a polar covalent bond conventionally points from the positive center to the center of the negative charge.
So in CH3NH2, the dipole moment of polar C-N bond points from Cδ+ to Nδ-. The dipole moment of N-H bonds also points from Hδ+ to Nδ-.
Nitrogen being strongly electronegative, not only attracts C-N and N-H bonded electrons but also attracts C-H electrons; thus, the H-atoms bonded to the C-atom gains Hδ++ charges, indicating an extreme electron deficiency. The dipole moments of weakly polar C-H bonds thus point from Hδ++ to Cδ+.
The CH3NH2 molecule adopts two different shapes according to the valence shell electron pair repulsion (VSEPR) theory of chemical bonding. It is an AX4-type molecule as per the least electronegative C-atom. However, considering the more electronegative nitrogen (N) atom as the central atom, CH3NH2 is an AX3E1-type molecule.
To one C-atom at the center (A), four bonded atoms (X) are attached (three H-atoms and one N-atom), and the central C-atom contains no lone pair of electrons (E). So, w.r.t C-atom, the molecular geometry or shape of CH3NH2 is identical to its ideal electron pair geometry, i.e., tetrahedral.
In contrast, to one N-atom at the center (A), three bonded atoms (X) are attached (two H-atoms and one C-atom), and the central N-atom contains one lone pair of electrons (E). Hence the molecular geometry or shape of CH3NH2 w.r.t N-atom is trigonal pyramidal.
To minimize electronic repulsions and to attain stability, the bonded atoms of the CH3NH2 molecule possess bond angles of ∠ (H-N-H) = 106°, ∠ (H-C-H) = 108°, ∠ (C-N-H) = 109°, and ∠ (H-C-N) = 112°.
In conclusion, it is due to the asymmetric trigonal pyramidal shape of CH3NH2 w.r.t N-atom that the dipole moments of individually polar C-N, N-H, and C-H bonds do not get canceled overall in the molecule.
Nitrogen being strongly electronegative, not only strongly attracts the shared electron cloud from each of the C-N and the N-H bonds but also attracts C-H bonded electrons. This leads to a non-uniform charge distribution in the molecule.
Consequently, methylamine (CH3NH2) is overall a polar molecule (net µ = 1.31 D).
Difference between polar and nonpolar?
|Polar molecule||Non-polar molecule|
|Atoms must have a difference in|
|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), phosphorus trifluoride (PF3), Methylamine (CH3NH2), etc.||Examples include oxygen (O2), nitrogen (N2), methane (CH4), carbon disulfide (CS2), ethane (C2H6), propane (C3H8), etc.|
Also, check –
- CH3NH2 lewis structure, molecular geometry, bond angle, hybridization
- How to tell if a molecule is polar or nonpolar?
- Is CH2Cl2 polar or nonpolar?
- Is CH3F polar or nonpolar?
- Is NCl3 polar or nonpolar?
- Is NO3– polar or nonpolar?
- Is BrF5 polar or nonpolar?
- Is SF4 polar or nonpolar?
- Is CO2 polar or nonpolar?
- Is NH3 polar or nonpolar?
- Is SO2 polar or nonpolar?
- Is SO3 polar or nonpolar?
- Is H2O polar or nonpolar?
- Is H2S polar or nonpolar?
- Is HCN polar or nonpolar?
- Is CCl4 polar or nonpolar?
- Is XeF4 polar or nonpolar?
- Is CH2O polar or nonpolar?
- Is CHCl3 polar or nonpolar?
- Is SF6 polar or nonpolar?
- Is BF3 polar or nonpolar?
- Is PCl5 polar or nonpolar?
- Is CH3Cl polar or nonpolar?
Why is methylamine (CH3NH2) a polar molecule?
In conclusion, CH3NH2 is a polar molecule having a net dipole moment of µ = 1.31 D.
Which bond of CH3NH2 among N-H, C-H, and C-N is most polar?
The most polar bond is the one that has a connection between atoms of large electronegativity difference.
Methylamine (CH3NH2) has an electronegativity difference between the bonded atoms in the C-N bond (0.49 units), C-H bonds (0.35 units), and N-H bonds (0.84 units).
Therefore, among the three types of bonds, the larger electronegative difference is found between the single covalently bonded N-atom and H-atoms.
Hence, the N-H bonds of methylamine are the most polar.
Which one is the most polar molecule? CH3Cl, CH3NH2, CH3OH or CH3SH.
All four molecules mentioned above possess a tetrahedral shape and geometry with respect to the central C-atom.
An electronegative difference of 0.35 units exists between the C-H bonds present in all four molecules.
The CH3SH molecule consists of a slightly polar C-S bond with an electronegativity difference of only 0.03 units.
In CH3NH2, electronegative differences of 0.84 and 0.49 units exist between N-H and C-N bonded atoms.
In CH3Cl, an electronegative difference of 0.61 units exists between the bonded atoms in C-Cl.
The CH3OH molecule, however, contains a strongly polar O-H bond with an electronegative difference of 1.24 units between the bonded atoms.
Hence, CH3OH is the most polar molecule (net µ = 1.69 D) out of all four given.
Is there a formal charge on the bonded atoms in the CH3NH2 molecule?
Formal charge of an atom = [ valence electrons – non-bonding electrons- ½ (bonding electrons)]
For the central C-atom
∴ Formal charge on central C-atom = 4 – 0 – 8/2 = 4 – 0 – 4 = 4 – 4 = 0
For the N-atom
∴ Formal charge on the N-atom = 5 – 2 – 6/2 = 5 – 2 – 3 = 5 – 5 = 0
∴ Formal charge on each H-atom = 1 – 0 – 2/2 = 1 – 0 – 1 = 1 – 1 = 0
All atoms in the CH3NH2 molecule, including carbon, nitrogen, and hydrogen, obtain a formal charge equal to zero.
Hence, there are no or zero overall formal charges present on the methylamine CH3NH2 molecule.
- Methylamine (CH3NH2) is a polar molecule.
- It consists of one C-N bond, three C-H, and two N-H bonds with specific electronegativity differences of 0.49, 0.35, and 0.84 units, respectively.
- C-N and N-H bonds are strongly polar, while the C-H bonds are only weakly polar.
- Methylamine CH3NH2, with respect to the central C-atom, has a tetrahedral molecular shape, while with respect to N-atom, it has a trigonal pyramidal molecular shape and geometry.
- Due to the presence of one lone pair of electrons on the N-atom and the asymmetric trigonal pyramidal shape of the molecule w.r.t this atom, the individual dipole moments do not get canceled, and the electron cloud stays non-uniformly spread over the molecule.
- The net dipole moment in CH3NH2 is µ = 1.31 Debye, so it is overall a polar molecule.
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