Is CH3Br a polar or a non-polar compound?

Bromomethane (CH3Br) is a colourless, non-flammable gas with no discernible odour. It is a manmade chemical compound that is generated biologically and industrially. It is also known as methyl bromide, methyl fume, and mono-bromomethane. The substance has a high toxicity and is classified as an ozone depleting substance. When we discuss its polarity, pupils frequently express scepticism.

The polar nature of CH3Br will be discussed in this article.

Is CH3Br polar or nonpolar, then? Because the molecule’s structure is tetrahedral and bromine (2.96) has a higher electronegativity than carbon (2.55), Ch3Br (Bromomethane) is a polar compound with a high electron density towards the Bromine atom. As a result, the dipole force is directed towards bromine, resulting in the formation of a polar molecule, CH3Br.

It is made up of Carbon, Hydrogen, and Bromine and has a molecular weight of 94.94 g/mol. Bromomethane comes from both natural and anthropogenic sources.

Every year, marine organisms produce around 56,000 tonnes of CH3Br. Bromomethane is also produced by terrestrial plants, with the Brassicaceae family being a notable example.

It was once widely utilised in the form of insecticides, but due to its ozone-depleting properties, it is no longer used in agriculture.

It’s made by curing methanol with Br in the presence of sulphur and hydrogen sulphide. The chemical reaction that follows is as follows:

6CH3OH   +   3Br2   +   S    ——->      6CH3Br   +   2H2O   +   H2SO4

Is CH3Br a polar or a non-polar compound?

This question does not have a simple answer. Bromomethane, often known as Ch3Br, is a somewhat polar gas.

The presence of a negative dipole in the Br molecule, which is the most electronegative element in the entire structure, is the reason for this.

If we compare the electronegativity of Carbon, Hydrogen, and Bromine, which is 2.55, 2.20, and 2.96, we can assume that all of their underlying bonds are covalent and thus non-polar, making the molecule non-polar.

A polar dipole in a compound is formed mathematically by adding the differences between the component molecules.

Due to Hydrogen and Carbon, there is a very little electron pull towards the molecule’s epicentre. The higher difference between Carbon and Bromine has a greater impact, causing electrons to be drawn to Bromine, resulting in a dipole that is slightly negative in nature.

When these effects are added together, the absolute outcome is the formation of partially positive dipoles on the Hydrogen atom.

CH3Br has a low boiling point of 4 degrees Celsius. The molecule’s dipole moments are also weak. All of this is due to the compound’s molecules having extremely low polar charge.

This means that, despite the fact that a CH3Br molecule exists as a gas at standard pressure and temperature, it has a far higher molar mass than other compounds such as H2O, which exists as a liquid at standard pressure and temperature.

Polar and Non-Polar Molecules: An Overview

To come together and achieve stability, all chemical elements react with one another. They create compounds as a means of achieving stability by filling their quota of lacking electrons.

The creation of various sorts of bonds brings these chemical substances together. The following are some of the numerous types of bonds that we commonly see:

Hydrogen Bonds: Hydrogen bonds are generated by the electrostatic attraction of a hydrogen atom bound covalently to an atom or group with a higher electronegative characteristic.

Second-tier elements like Nitrogen, Fluorine, and Oxygen, as well as other atoms with strong electronegativity, are commonly used to generate hydrogen bonds.

Metallic Bonds: Metallic bonds are formed when metal ions with a positive charge interact with conduction electrons via the Electrostatic Attractive Force, or ESF.

A metallic bond can be described as an arrangement of positively charged ions sharing free electrons.

When two atoms with opposite charges combine to form a molecule, the bond produced between them is known as an Ionic Bond.

Two differently(opposite) charged atoms come together to achieve stability in this situation.

When there is a significant difference in the electronegativities of the interacting atoms, this type of connection is formed.

In the case of ionic bonding, a complete electron transaction occurs.

Covalent Bonds: Covalent Bonds are the bonds produced when two or more atoms come together in an electron sharing transaction to establish stability.

Depending on the number of involved electrons, a covalent bond can be single, double, or even triple. The density of an atom is affected by the establishment of a covalent bond.

The electron density of atoms varies when they join together to form covalent bonds.

The unequal distribution of charge on two atoms in the covalent bond is caused by this variation in electron density; the covalent bond is said to be polar in nature.

When this happens, one of the interacting atoms develops a partial or fragmented ionic charge. Such instances are more common in compounds with a bigger difference in electronegativity between the underlying atoms.

As a result, one atom is strongly positive while the other is extremely negative, resulting in the formation of an ionic partial charge.

For example, CH2Cl2 is a nonpolar molecule that is similar to CH2Cl2. You should also check out our article on CH2Cl2 polarity.

The resultant molecule is called a Non-Polar when the atoms involved in the creation of a covalent bond come together in a symmetric arrangement with an identical ionic charge on both atoms.

For instance, O2 and CO2 have a symmetric linear shape and are nonpolar. You can also look up CO2 polarity in the Wikipedia article.

When the electronegativity of all participating atoms is equivalent, if not identical, a non-polar molecule is created.

As a result, the bonds have no higher or lower level of electronegativity, and no bond may behave as a pole.

What causes CH3Br to be polar?

CH3Br is made up of one carbon atom, three hydrogen atoms, and one bromine atom. The single Carbon atom is in the centre, surrounded by the remaining atoms.

There are 14 valence electrons in CH3Br. Hydrogen stays outside, and Carbon stays in the middle because it is less electronegative than Bromine.

Carbon and hydrogen bonds each take up two of the 14 valence electrons, leaving the rest as follows:

Step 1: Each C-H bond has two electrons. There are 2 x 3 = 6 valence electrons in three C-H bonds. Count of electrons left = 14 – 6 = 8.

Step 2: There are two electrons in the C-Br bond. There are 8 – 2 = 6 valence electrons left.

Step 3: Due to Bromine’s increased electronegativity, the remaining 6 valence electrons are modified along with it.

The structure of CH3Br tends to be polar due to the increased amount of electrons in the case of Bromine.

The remaining non-negative bonds generate a net positive polarity, resulting in the polarity of the CH3Br molecule.

The importance of electronegativity in defining a molecule’s polarity

Electronegativity is also important in defining a compound’s polarity. In a polar bond, electrons gravitate toward the atom with the highest electronegativity.

Because of the difference in electronegativity of Carbon and Bromine, the bond between the centrally located Carbon atom and Bromine, C-Br, is polar.

The polar character of CH3Br is due to the sharp disparity in electronegativity of Bromine, Carbon, and Hydrogen.

Geometry’s Role in Determining a Molecule’s Polarity

CH3Br Molecular Geometry:

Understanding the geometry of a chemical is necessary for determining its polarity. The structure of a molecule is crucial in determining the orientation of each solitary bond dipole, which affects its polarity.

The structure of a CH3Br molecule is tetrahedral, similar to that of Methane (CH4).

The sole difference is that one of the Hydrogen atoms is substituted by a Bromine atom in this example.

The core Carbon atom has four electron zones surrounding it, owing to the presence of three hydrogen atoms and one bromine atom.

The following figure shows the structural composition of a CH3Br molecule.

Conclusion

To summarise, the differential in electronegativity shown by distinct elements in the atoms of a CH3Br molecule is responsible for the majority of Bromomethane’s physical features and applications.

Because of the bending force imposed by the C-Br bond on the simpler C-H bonds, the compound is polar and has a bent, tetrahedral shape.

As a result, it’s commonly employed in the production of solvents, chemicals, and pesticides. It is also exceedingly potent and reactive in its natural gaseous form, and its use is presently restricted due to its role in the ozone layer’s depletion.

Read more: Potato pH: Is it Acidic or Alkaline?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.

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