[Chemistry Class Notes] Methanol Pdf for Exam [2024]

Methanol gets its name due to its historical relevance when it was first discovered to be a product that forms when cellulose (the main sugar component present in wood) gets fermented by any form of bacteria. Earlier, with the process of Pyrolysis of wood, menthol was obtained as a product. Methanol (CH3OH), aka methyl alcohol, wood alcohol or wood spirit. Earlier methanol was produced by the process of destructive distillation of woods, which is used chiefly for rendering industrial alcohol and not fit to drink.

The modern preparation method is much easier and is prepared by directly combining carbon monoxide gas and hydrogen in the presence of a catalyst, we also know that increasingly, sent gas which is a mixture of hydrogen and carbon monoxide derived from biomass is used for methanol production as well. The purest form of methanol is considered to be an important material in chemical synthesis, the derivatives which we get from this are used in great quantities for building up a vast number of compounds, among them the very important is synthetic dyes stuff, resins, pharmaceuticals and different kind of perfumes. Along with their usage in smaller quantities, large quantities are first converted into dimethylaniline for dyestuffs and to formaldehyde for synthetic resin. This can also be used in automotive antifreeze, rocket fuels and in the general solvent that we use. There are many uses of methanol which is also a high octane, clean-burning fuel which can be used as a substitute for gasoline in automotive vehicles.

Characteristics of methanol or methyl alcohol

It is a colorless liquid that boils at 64.96° celsius and solidifies at -93.9° celsius. When mixed with air or comes in contact with air it forms explosive mixtures and burns with a non-luminous flame. Methanol is completely miscible in water, its order is similar to that of Ethyl alcohol.
Methanol’s odor resembles that of ethyl alcohol, an intoxicant of alcoholic beverages but along with this, it is also a very dangerous poison. It was also said to cause death if consumed.
It appears as a colorless, fairly volatile liquid. The vapors of methyl alcohol or slightly heavier than air and I travel to some distance to a source of ignition and flashback. With this characteristic, if there is an accumulation of zippers in confined spaces in the buildings or any other confined places such as sewers, it may explode if ignited.
Methanol works as an amphiprotic solvent. (Define) . It is majorly known as alkyl alcohol, which is the one-carbon compound, and also a girl child organic compound which categorizes as primary alcohol as well. It is the conjugate acid of methoxide.

Uses of methanol

It is used as a chemical building block for various everyday products such as plastics, beans, car parts and construction materials.
Given its property as a clean energy resource it is used to fuel cars, trucks, ships, boilers and cook stoves etc.
Acute or chronic exposure of methanol by humans through inhalation or injection might result in various complications such as blurred vision, headaches and nausea. Additionally birth defects have been observed in the offsprings of rats and mice which were exposed to methanol during experiments and naturally.
There is not enough information or data available on the effects of methanol on the reproductive, developmental front or any sign of carcinogenic effects of methanol in humans. Even the EPA has not classified methanol with respect to carcinogenicity.
The usage of methanol extends to pharmacology and biochemistry such as insolvent. A solvent is a liquid that dissolves another substance that is primarily known as a salute, generally solids without changing its chemical composition, for example, water containing sugar.
Since ancient times, Methanol was used as a fuel, particularly biofuel.
It is often used in car racing events or stunts performing tricks since it is comparatively less inflammable than other fuel options available and also due to its readily soluble nature with water.
Methanol is used as a laboratory solvent for carrying out a lot of reactions due to its polar nature.
Methanol is commercially used for the production of other industrially applicable chemicals such as formaldehyde, acetic acid and certain heavy chemicals such as methyl tertiary butyl ethers and other polymers.
Methanol is used in the production of alkyl halides which are a class of compounds from which other important compounds are readily formed by nucleophilic substitution reactions.
Methanol is used as an anti-freeze agent in many cold regions such as European countries.
Methanol is used as an alcohol denaturant during the commercial production of ethanol for keeping a check on prohibited access to ethanol by the factory workers.
Methanol can be used for the production of hydrocarbons such as gasoline and olefins and other higher complex aromatic compounds by undergoing condensation reactions catalyzed by heterogeneous catalysts such as zeolites.
Methanol is occasionally also used as an automobile fuel since on thermal decomposition it produces carbon dioxide and water. The carbon dioxide produced acts as a thermal energy source for the combustion engine of vehicles.
Many stove-based cooking appliances used methanol as their source of energy fuel.
In polyacrylamide gel electrophoresis (PAGE), methanol is used as a destaining agent to remove the dye initially added to detect proteins or nucleic acids in the gel.
Methanol is also used as one of the components in the perfume industry.
Methanol is a common medium for a lot of reactions involved in pharmaceuticals.
Methanol can be absorbed through inhalation or injection out of which inhalation is the major root or cause of absorption in the regular occupational environment, it can be a threat for both human beings and the environment but there is no steady agreement on the potential risk of dermal exposure to methanol.

Structure of Methanol

The chemical formula of Methanol is CH₃OH. Since its chemical structure is a linkage between a methyl (–CH₃) group and a hydroxyl group (–OH), it is sometimes also written as MeOH, where Me stands for Methyl. The molecular weight (or molar mass) of Methanol is 32.04 g/mol. The various forms in which the molecular structure of Methanol can be represented are given below:

The carbon present in the Methanol is sp³ hybridized. Due to the presence of hydroxyl group, the structure of Methanol can easily form intermolecular hydrogen bonds with hydrogen bond acceptors. The mixture of water-methanol mixtures is one of the classical examples studied for hydrogen bonding.

Physical Properties of Methanol

Methanol exists as a clear and colorless volatile liquid at room temperature
The density of Methanol is 792 kg/m³
The melting point of Methanol is -97.6 °C
Its odor is very similar to Ethanol (which is used as drinking alcohol) and is often mistaken for Ethanol and results in alcohol poisoning. (Note: Methanol is highly toxic if inhaled or ingested and may even lead to death. It causes retinal damage leading to terminal blindness. Inhaled fumes of Methanol may lead to coughing and/or headache. It is very harmful topically too and may cause skin damage if someone comes in direct contact with it. Its toxicity is basically due to the metabolic products it forms when acted upon by biological enzymes such as alcohol dehydrogenase and aldehyde dehydrogenase)
Methanol is a highly flammable liquid and hence should not be used near flame or in high-temperature surroundings as it may easily catch fire (Its boiling point is very low – 64.7 °C
Methanol is highly polar in nature due to the presence of the hydroxyl group, thus making it a good solvent
Methanol is completely miscible with water (solubility > 100 mg/Ml at 25 °C) and ethanol, benzene, ether and many other organic solvents. It is also soluble in acetone and chloroform
Methanol vapours are relatively higher than air
The flashpoint of Methanol is 9.7 °C
Its vapor pressure is 127 mm Hg at 25 °C
Its LogP is -0.77
It is generally stable at normal laboratory storage conditions
Its viscosity is 0.544 mPa at 25°C
Its heat of combustion and heat of vaporization are 726.1 Kj/mole and 37.34 Kj/mole (at 25 deg C), respectively, at 25 °C
Its surface tension is 22.07 Mn/m at 25 °C
Its pKa (dissociation constant) is 15.3

Chemical Properties of Methanol (Reactions of Methanol)

Oxidation Reaction:

The oxidation reaction of Methanol is used for the formation of industrially and commercially used chemicals named formaldehyde. The reaction occurs as follows – when Methanol is allowed to react with nascent oxygen in the presence of potassium dichromate as a catalyst in an acidic medium, it leads to the formation of formaldehyde and water. The elucidation of the reaction is given below:

CH₃OH + O → HCHO + H₂O

(Methanol) (Nascent oxygen) (Formaldehyde) (Water)

Ester formation

When alcohol is reacted with a carboxylic acid, it results in the formation of another class of compounds found in organic chemistry called the esters. An example of the formation of ester (methyl ethanoate) when Methanol reacts with acetic acid is given below:

CH₃OH + CH₃COOH → CH₃COOCH₃

(Methanol) (Acetic acid) (Methyl Ethanoate)

This reaction occurs in an acidic medium (preferably a dilute solution of sulfuric acid is generally used). Since Methanol is simple alcohol, it easily reacts with any member of the carboxylic acid family and leads to the formation of fruity smelled fragrant esters. Esters have a lot of industrial and commercial applicability in various industries such as the food industry and perfume industry.

Reaction with halo-acids

The reaction of alcohols with halogen acids (also commonly known as halo-acids) is one of the most preferred ways of producing alkyl chlorides. When Methanol is reacted with a halogen acid (such as hydrochloric acid, the most common acid of this family), it leads to the production of methyl chloride along with the formation of water as a by-product. The reaction is elucidated as follows:

CH₃OH + HCl → CH₃Cl + H₂O

Methods of Preparation of Methanol

Catalytic Hydrogenation

This is one of the oldest and most traditional methods of Methanol production in which carbon monoxide is hydrogenated in the presence of zinc oxide-chromium oxide catalysts (ZnO – Cr₂O₃) at high temperature and high pressure.

CO+ 2H₂→ CH₃OH

(Methanol) (Hydrogen (Methanol)

This method traditionally made use of coal, oil or natural gas as a source of carbon monoxide. However, this method was not environment-friendly and was resulting in the depletion of these limited natural resources and hence has now been replaced by a more environment-friendly method and is termed as “green” methanol production which makes use of agricultural, industrial and other urban wastes as a source of carbon monoxide. The use of carbon dioxide produced as a waste product from a number of processes is another “green” way to produce Methanol.

Commercial bioreactors

Methanol is nowadays prepared at a commercial level by using large fixed bed reactors which operate at high temperature (approximately 550-575 °C) and high-pressure conditions (around 100 atmospheric pressure) which utilizes alumina-coated copper and zinc oxides as a catalyst. This method is found to achieve a 97% conversion rate of the reactants into Methanol. Although the mechanism by which methanol is formed by this process is still not known, many theories have been hypothesized to explain its formation.

Biochemical method of production

Since the first natural occurrence of alcohol was discovered as an end product of fermentation, it is one of the cheapest and oldest used methods even today to do so. Certain enzymes, such as methane monooxygenases, can be used which perform the catalytic conversion of methane to methanol. These enzymes are oxygenases by origin and perform a mixed function, i.e. production of methanol by oxygenation is accompanied by the formation of other by-products such as water and NAD+ but is not a problem as these can be separated by end processing steps. The biochemical reaction of production of Methanol from Methane gas with the help of enzymes occurs as follows:

CH₄ + O₂+ NADPH + H+→ CH₃OH + H₂O + NAD+

In conclusion of the article, we have learned about the physical and chemical properties of methanol. We have also learnt about the chemical reactions and methods of preparation of the chemical.