CH₄ — Methane

Methane (CH₄) is the simplest member of the alkane series and one of the most abundant organic compounds in nature. It consists of one carbon atom covalently bonded to four hydrogen atoms. Methane is a major component of natural gas and is an important fuel used for cooking, heating, and electricity generation. It also plays a crucial role in the carbon cycle and acts as a potent greenhouse gas in Earth's atmosphere.

Methane is produced naturally through anaerobic decomposition of organic matter in wetlands, landfills, and digestive tracts of ruminant animals. Industrially, it is obtained from natural gas wells or as a by-product of petroleum refining. Its simple structure makes it a fundamental compound in organic chemistry and an essential starting material for various chemical syntheses.

Methane has a tetrahedral molecular geometry, with the carbon atom at the center and four hydrogen atoms at the corners of a tetrahedron. The bond angle between two hydrogen atoms is approximately 109.5°. The carbon atom undergoes sp³ hybridization, forming four equivalent C–H sigma (σ) bonds. Each bond is formed by the overlap of one sp³ orbital of carbon with the 1s orbital of hydrogen.

The molecule is nonpolar because of its symmetrical geometry and uniform distribution of charge. This explains methane’s low solubility in water and its volatility under standard conditions.

Methane can be prepared in laboratories and obtained naturally. Some important methods are:

• From sodium acetate: When sodium acetate reacts with soda lime (a mixture of NaOH and CaO), methane gas is produced.

• From aluminum carbide: When aluminum carbide reacts with water, methane is formed.

Natural sources include biogas plants, decaying vegetation, and volcanic emissions.

Methane is a colorless, odorless, tasteless gas lighter than air. It is non-toxic but highly flammable, forming explosive mixtures with air. The gas liquefies easily under pressure at low temperatures.

Chemically, methane is quite stable due to its strong C–H bonds. However, under suitable conditions, it participates in several reactions such as combustion, halogenation, and oxidation.

• Combustion: Methane burns in oxygen to form carbon dioxide and water, releasing a large amount of energy.

• Halogenation: In the presence of ultraviolet light, methane reacts with chlorine to form chloromethane and hydrogen chloride.

Methane has a wide range of industrial and domestic applications:

• Fuel: Used in household gas supply (piped natural gas) and power generation.
• Chemical feedstock: Used in manufacturing methanol, hydrogen gas, and ammonia.
• Transportation fuel: As Compressed Natural Gas (CNG), methane is used in eco-friendly vehicles.
• Research: Used in calibration gases and laboratory studies involving combustion chemistry.

Because of its clean-burning nature, methane is an environmentally preferred alternative to coal or petroleum-based fuels.

Although methane is an efficient and clean-burning fuel, it is also a potent greenhouse gas. Its global warming potential is approximately 28 times higher than that of carbon dioxide over a 100-year period. Leakage from pipelines, landfills, and livestock contributes significantly to climate change.

Efforts are underway globally to reduce methane emissions by improving pipeline infrastructure, promoting biogas utilization, and capturing methane from waste sources to use it as renewable energy.