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Methanol

What is methanol?

Methanol or methyl alcohol also called carbinol is a colourless, inflammable, poisonous alcohol with the chemical formula CH3OH. It is missable with water in all proportions and also missable with most organic solvents. It burns in air to form a faintly luminous flame. Methanol vapour forms an explosive mixture with air or oxygen when ignited. In the earliest time, it was obtained from wood. Destructive distillation of wood gives tar and pyroligneous acid. Pyroligneous acid contains three organic compounds like methanol, acetone, and acetic acid. Therefore, it was also named as wood spirit. It is used widely as a solvent for paints, varnishes, shellac, etc.

Structure of methanol

Molecular weight determination and analysis show that the molecular formula of methanol is CH4O. The quadrivalent carbon, bivalent oxygen, and univalent hydrogen in methanol form the following structure,

Structure and molecular formula of of methanol  or methyl alcohol

  • Only one hydrogen atom in methyl alcohol is replaceable by a sodium atom. It is suggested that the one hydrogen atom in methyl alcohol is different from the other three hydrogen atoms.
  • The presence of the hydroxyl group is confirmed by the reaction between methyl alcohol and phosphorus pentachloride. Methyl chloride, hydrogen chloride, and phosphoryl chloride are formed by this reaction.
  • Infrared spectroscopic studies show that the absorption band of hydroxyl compounds in the region of 3650 – 3580 cm-1. It is true if there is no hydrogen bonding. Intermolecular hydrogen bonding produces the absorption band in the region of 3550 – 3230 cm-1.

Chemical properties

Methanol is colourless, poisonous, and volatile liquid that burns in air with faintly luminous flame and forms an explosive mixture with air or oxygen. It contains a methyl group linked with the hydroxyl group. Some important properties of methanol are given below the table,

Properties of methanol
Chemical formula CH4O
Molar mass 32.04 g mol-1
Appearance colourless liquid
odor sweet and pungent
Density 0.792 g/cm3
Melting point -97.6 °C
Boling point 64.7 °C
Acidity (pka) 15.5
Conjugate acid base pair acid base
methyloxonium methanolate
Viscosity 0.545 mPa s at 25 °C
Dipole moment 1.69 debye

Methanol production

Production from synthesis gas

Methanol is produced from synthesis gas in 200 atmosphere pressures over a chemical catalyst containing oxides of copper, zinc, and chromium at 300 °C.
CO + 2H2 → CH3OH

The production of methanol is 100 percent if the proper precaution is taken. By change the catalyst and ratio of carbon monoxide to hydrogen, the product is a variety of higher alcohol.

Production of methanol from methane

Catalytic oxidation of methane produced CH3OH. A mixture of methane and oxygen (9:1 ratio) produced methyl alcohol when passed through a copper tube at 200 °C and 100 atmospheric pressure.
CH4 + ½O2 → CH3OH

Uses of methanol

  • Methanol is the type of alcohol produced mostly from natural gas. It is the base material for the production of acetic acid and formaldehyde. It is also used for the production of hydrocarbons like ethylene and propylene.
  • Methyl alcohol and its derivatives like formaldehyde and acetic acid are used for the production of acrylic plastic, synthetic fabrics, and fibers which are used in clothing.
  • It is used as a solvent for paints, varnishes, shellac, etc.
  • For the production of pharmaceuticals, agrichemicals, and perfumes, we used widely methyl alcohol.
  • It is an efficient energy carrier for factories and different types of energy generation processes. It is used as a fuel because it is easier to store than hydrogen and natural gas. It is biodegradable and renewable source of energy.
  • Methanol is also used for making methylated spirit and automobile antifreezing mixtures.