We discuss the molecular geometry, hybridization, bond angle , octet rule, dipole moment and other related facts in detail and some frequently asked questions.
Dichloromethane ,mainly called as methylene chloride, is a polar organic solvent that is mostly used in various type of chemical research and manufacturing purpose also. It is a highly volatile liquid. Molar mass of DCM is 84.93gm/mol. Melting point and boiling point of CH2Cl2 are -96.7 and 39.6 degree celcius respectively.
In this article the lewis structure of CH2Cl2 and other detailed facts are discussed briefly.
CH2Cl2 lewis structure molecular geometry
Molecular geometry of any molecule can be determined by using VSEPR (Valence Shell Electron Pair Repulsion) Theory.. The main agenda to determine the structure of any compound using this VSEPR theory that the atoms or substituents around the central atom will adopt such an arrangement that the repulsion between the valence shell electrons will be minimum.
Analysing VSEPR theory it can be concluded that CH2Cl2 possesses a tetrahedral like molecular geometry (Methane like structure) as the carbon atom ( central atom) have two different types of atoms ( two hydrogen and two chlorine) around it.
CH2Cl2 lewis structure valence electrons
From the Lewis structure we can easily decide the number of bonds, lone pairs on each atom and be sure whether each of the atom fulfill their respective octer rule or not.
Valence shell electrons of every atoms should be calculated first to determine the Lewis dot structure of any molecule.
Carbon has six electrons. Among these 6 electrons there are 2 electrons in its 1s orbital and 2 electrons in its 2s orbital and rest of the two electrons in its 2p orbital.
The total numbers of its valence shell electrons of carbon is 4. Thus carbon needs four more electrons to achieve its octet ( to have eight electrons in its valence shell that is outermost shell).
Hydrogen has atomic number 1, thus each H has 1 electron in its 1s orbital and needs 1 more to achieve duplet( to have 2 electrons in its valence shell) as 1s orbtal can only have two electrons.
The atomic number of chlorine is 17. 1s orbital contains 2, 2s orbital 2 and 2p contains 6 electrons. Rest of the seven electrons will fill 3s and 3p orbitals respectively. So 3s orbital will have two and 3p orital will have the last 5 electrons.
The total number of valence shell electrons are 7 in chlorine so it needs 1 more electron to fulfill its octet.
In this CH2Cl2 molecule carbon is central atom( it has the highest bonding capacity and it is the shortest of the octet). Carbon needs 4 more electrons to complete its octet.
Two hydrogen and two chlorine atoms share those 4 electrons with carbon to achieve the octet.
Hydrogen has 1 electron in its 1s orbital and a s orbital
can only accommodate two electrons. Thus hydrogen
can only fulfil duplet (having two electrons in its valence shell) rather than octet.
Carbon forms sigma bond ( single bond) with two hydrogenand chlorine atoms as shown in Lewis structure.
There is no other different acceptable lewis structure for CH2Cl2. Moving the chlorine atoms around does not produce a new structure. That’s because the molecule is actually tetrahedral in shape and not flat as is classically drawn in Lewis structure.
Does CH2Cl2 follow octet rule
Octet rule states that an element is surrounded by eight electrobs in its Lewis structure.
Analysing the Lewis structure of CH2Cl2 it is clear that it does not violate the octet rule.
CH2Cl2 lewis structure lone pairs
Dichloromethane has one carbon two hydrpgen and two chlorine atoms. In the lewis structure of CH2Cl2, carbon atom is the center atom as it has the highest valancy (four) with comparing to hydrogen and chlorine atoms. Both the chlorine atoms have three lone pairs in each and carbon or hydrogen atom does not have any lone pairs.
CH2Cl2 lewis structure valence electrons
Let’s calculate the electrons in valence shell (valence electrons) on each atom ( two chlorine, two hydrogen, and one carbon).
Valence electrons in Carbon atom is four (2s2 2p2).
Valence electrons in each of the Hydrogen atom is one ( 1s1).
Valence electrons in each of the Chlorine atom are seven ( 3s2 3p5).
Thus the total valence electrons in CH2Cl2 molecule are –
= 4 + (2 × 1) + ( 7 × 2)
CH2Cl2 lewis structure formal charge
Formal charge of any atom in any molecule canbe calculated by the formula mentioned below.
FC = V- N- (B/2)
FC= Formal charge N= Number of nonbonding valence electrons
V= Number of valence electrons
B= Total numbers of bonded electrons.
Formal charge on Carbon
FC= 4-0-(8/2) [V=4 , N=0, B=8]
=(4-4) = 0
Formal charge on Chlorine
FC= 7-6-(2/2) [V=7, N=6, B=2]
Formal charge on Hydrogen
FC= 1-0-(2/2) [V=1, N=0, B=2]
To know more please follow Triple Bond Examples: Detailed Insights And Facts
Hybridisation is mainly defined as the mixing of orbitals which have comparable in their energies, symmetries and shapes. This phenomenon is actually suitable to pair up the electrons and form chemical bonds (sigma, pi).
When two molecules participate in bond formation overlapping of the orbitals happen due to sharing of electrons. These overlapped orbitals are denoted as hybrid orbitals.
There are different types of hybridization due to different type of orbital overlap.
Let us look at the ground state electronic configuration of each atom in CH2Cl2 molecule .
Carbon (C) : 1s2 2s2 2px1 2py1
Hydrogen (H): 1s1
Chlorine (Cl): 1s2 2s2 2p6 3s2 3px2 3py2 3pz1
In the excited state Carbon has one of the 2s electrons jumped into the 2p orbital; therefore the electronic configuration ( in excited state) will be: 1s2 2s1 2p3. Thus the 2s, 2px, 2py, 2pz orbitals are now half filled.
Now these four hybrid orbitals together form four identical sp3 hybrid orbitals (having same energy). Each of these 4 orbitals has one electron and can accept one more ( the capacity of each orbitals can accommodate maximum two electrons).
Two electrons comes from each of the two hydrogen and rest of the two electrons come from each of the chlorine atoms and form four single or sigma bonds.
To know more please follow 15 Coordinate Covalent Bond Examples: Detailed Insight And Facts
A bond angle is defined as the the angle between two bonds or three atoms that form the two bonds. VSEPR theory helps to determine the molecular geometry as well as the bond angle of a molecule.
There are some parameters which help to assign the bond angle . They are Bond pair – bond pair repulsion(bp-bp repulsion), lone pair- lone pair repulsion(lp-lp repulsion), bond pair- lone pair repulsion9 lp-bp repulsion), electronegativity of the central atom as well as the substituent atoms arount the central atom.
From the point of molecular Geometry” we conclude that CH2Cl2 has tetrahedral like structure but due to presence of two different type of substituents ( H and Cl) it is slightly deviated from ideal tetrahedral structure and the ideal bond angle (109.50) like methane ( CH4), as it has four same atoms surrounded the central carbon atom.
The reason for not having the ideal tetrahedral structure is discussed below.
Chlorine is the most electronegative atom followed by carbon and then hydrogen in this CH2Cl2 molecule. Thus chlorine attracts the electron pais of C-Cl bond towards itself more with comparing to the carbon. Therefore the bond pair- bond pair electron repulsion in two C-Cl bond will be less than the bond pair – bond pair repulsion in two C-H bonds as the bonded electrons in C-H bond is shifted towards the carbon atom.
Therefore the the bond angle of <H-C-H Will be slightly greater than the <Cl-C-Cl angle and this molecule does not show the actual bond angle 109.5 0.
To know more please follow 4 nonpolar covalent bond examples:
CH2Cl2 lewis structure dipole
A dipole moment occurs in any system in which there is a separation between the charges.
Dipole moment (mu) = charge× inter nuclear separation between two atoms.
Dipole moment of any molecule is denoted by Greek letter “mu”( µ) and the unit of dipole moment is debye.
Analysing the structure (tetrahedral) of CH2Cl2 molecule it is concluded that this molecule possesses some non zero dipole moment. In CH2Cl2 dipole moment of H-H atoms and Cl-Cl atoms do not cancel each other because they are not in linear position ( bond angle between them is not 180 0.
Studying the arrangement of the molecules around the carbon atom it is clear that the bond dipole moment of two C-Cl bonds cannot cancel the dipole of each other. Due to the difference in electronegativity of chlorine and carbon and carbon and hydrogen produces a net nonzero dipole moment (µ≠0) and thus it is a polar molecule. According to the study that CH2Cl2 shws dipole moment 1.6 debye.
Read more about Hydrogen Bond Examples
Does CH2Cl2 have isomers
Isomers have same chemical formula but different chemical rearrangement. For this they differ in their physical and chemical properties from each other.
Isomers are classified in the below terms-
There are no stereoisomers possible for CH2Cl2 as the carbon is not a chiral center, it requires carbon to be bonded with four different atoms to be a chiral center . Moreover there are no constitutional isomers ( same molecular formula but different structural formula).
Read more about SN1 Examples
What is the point group of CH2Cl2
Point groups are mainly used to describe molecular symmetry and it is arepresentation of the symmetry elements. Point groups are used in group theory which helps to determine the properties like molecular orbitals.
Point groups usually consist of the following elements:
E- Identity operator.
Cn– n fold axis of rotation.
σ (sigma)- The mirror plane
Dichloromethane, CH2Cl2. There is a C2 (2 fold axis of rotation) rotation axis , identity operator ( which is present in every molecule), σ(xz plane) containing CH2 and σ( yz plane) containing CCl2.
These four symmetry element is present in CH2Cl2 molecule which indicates the molecule C2V point group.