Do you know which liquid is used by the carpenters for polishing wooden objects?
Ok! I am giving one hint that it belongs to the same family which is also used frequently for drinking. I think most of you have got it right.
It is nothing but methanol which is also known as wood alcohol or wood spirit.
We all are familiar with the term "alcohol", which is used in different dimensions such as recreational drink, medical purpose, wood spirit etc. In chemistry, alcohol represents a class of organic compounds in which at least one hydroxyl group (-OH) is attached to a saturated carbon atom. And the general formula of alcohols is CnH2n+1OH . For example, the alcohol used for recreational purposes is ethyl alcohol, which has a chemical formula C2H5OH.
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Methanol, also known as methyl alcohol, is the simplest alcohol with a chemical formula CH3OH A volatile, colorless, flammable liquid with an ethanol-like odor. The original method of producing methanol was the destructive distillation of wood, which was given its common name, woody alcohol. Today, methanol is produced industrially by hydrogenating carbon monoxide. Methane is primarily used as a raw material chemical for the synthesis of other compounds, but it can also be used as a fuel for some internal combustion engines. The chemical reaction formula for burning methanol is given by,
Methanol is not ideally used as a fuel because of its reactivity with metals that can cause engine corrosion. Nonetheless, with only minor engine changes, methanol helps the environment by significantly reducing the emission of sulfur oxides, nitrogen oxides, and particulate matter into the atmosphere, making it an excellent choice in the marine industry. It is an alternative fuel. Methanol is also used as a denatured substance to prevent abuse of recreational ethanol. Governments around the world have their own rules and regulations regarding the licensed and licensed sale of denatured alcohol. Another use of methanol in everyday life is as a solvent and as an antifreeze for pipe and windshield washer fluid.
Methanol (CH3OH) is composed of one carbon, one oxygen and four hydrogen atoms. Carbon (6) has a valency of four, which means it needs four electrons to achieve stability. In methanol, carbon achieves this stability by forming covalent bonds with three hydrogens and one oxygen atom of the hydroxyl group.
In the molecule of methanol, both carbon and oxygen are SP3 hybridized. Because of SP3 hybridization, the molecule has a tetrahedral structure, but due to the lone pair of electrons on oxygen, the bond angle H-O-C is less than 109.5o
Conventional Method of Production:
The oldest yet most used method for the production of methanol involves the reaction between carbon monoxide and hydrogen. This carbon monoxide was initially obtained from fossil fuels, but now agricultural wastes are used to produce methanol in a much greener environment-friendly way.
The direct combustion reaction between carbon monoxide and hydrogen is facilitated by the catalyst zinc or cupric oxide, which is coated on the surface of alumina. The reaction is also used for the commercial production of methanol because of its high selectivity.
Biosynthetic Production of Methanol:
Methane can be converted to methanol with the help of the enzyme methane monooxygenase. However, this zinc or copper-dependent enzyme is not selective in nature, so the methanol produced at the end of the process is very little. Many investigations are underway to overcome this problem.
The oxidation reaction of methanol is used to form an industrially and commercially used chemical called formaldehyde. The reaction proceeds as follows. Formaldehyde and water are produced when methanol is reacted with oxygen in the presence of potassium dichromate in an acidic medium. The reaction is shown below.
When alcohol reacts with carboxylic acids, it forms another class of organic compounds found in organic chemistry called esters. An example of the formation of an ester (methyl ethanoate) in the reaction of methanol and acetic acid is shown below.
This reaction takes place in an acidic medium (preferably a dilute sulfuric acid solution is commonly used). Because methanol is simple alcohol, it easily reacts with any member of the carboxylic acid family to form a fruity scented ester. Esters have excellent industrial and commercial applicability in various industries such as the food industry and the perfume industry.
Reaction with halogen acids:
The reaction of alcohol with a halogen acid (also commonly known as a halo acid) is one of the most preferred methods for producing alkyl chlorides. When methanol reacts with halogen acids (such as hydrochloric acid, the most common acid in this family), it produces water as a by-product and methyl chloride. The reaction is explained as follows:
Although consumption of methanol by an individual is a rare incident to occur, its adverse effects on the body can not be ignored. Methanol in itself is non-toxic but, on consumption, gets converted to formic acid in the body. This formic acid is highly toxic and can lead to severe metabolic acidosis. In addition, methanol, in low concentrations of 10ml, can disrupt the optic nerve and cause permanent blindness. Ethanol is much safer than methanol and hence is used in the preparation of hand sanitizers.
Q1. Methyl alcohol on reaction with grignard reagent () gives
(A) Methane (B) Ethane
(C) propane (D) Butane
Solution: Methyl alcohol on reaction with grignard reagent gives methane. The reaction as follows
Q2. Formaldehyde on reaction with grignard reagent followed by hydrolysis gives
(A) Primary alcohol (B) Secondary alcohol
(C) Tertiary alcohol (D) None of the above
Solution: Formaldehyde forms primary alcohol while all other aldehydes form secondary alcohols on reaction with a grignard reagent followed by hydrolysis.
Q3. Methanol on reaction with sodium metal gives
(A) Sodium methoxide (B) Sodium ethoxide
(C) Sodium propoxide (D) None of the above
Solution: Methanol in reaction with sodium metal gives Sodium methoxide and hydrogen. The reaction is as follows
Q4. Methyl alcohol on oxidation in the presence of sodium dichromate and sulphuric acid gives
(A) Formaldehyde (B) Acetaldehyde
(C) Propionaldehyde (D) propanone
Solution: Methyl alcohol on oxidation in the presence of sodium dichromate and sulphuric acid gives formaldehyde and water. The reaction is as follows
Question 1. Why is methanol more acidic than water?
Answer: Methanol is more acidic than water because the conjugate base of methanol (methoxide ion) is a weaker base than the hydroxide ion. Methyl slightly withdraws electron density from the oxygen atom unlike hydrogen which donates electrons to the oxygen atom.
Question 2. Can we drink Methanol?
Answer: Methanol is also known as wood alcohol. It is highly toxic to neurons and quickly blinds you as it kills your brain cells. (Most of your brain is dedicated to vision). Therefore, do not use it for drinking. When ingested, the body metabolizes methanol into formaldehyde and formic acid, which in large amounts are toxic and even fatal.
Question 3. What is Biodiesel?
Answer: Biodiesel is produced by reacting vegetable oils with methanol. The main product is a methyl ester of a long-chain fatty acid, which is used as biodiesel. Glycerol is produced as a by-product in the reaction. Biodiesel can be used as a replacement fuel in most modern diesel engines – unlike raw vegetable oil, which can only be used in converted or old-fashioned diesel engines.
Question 4. What is the purpose of adding methanol to ethyl alcohol for denaturation?
Answer: Ethanol is naturally produced when yeast and other microbes ferment plant sugar found in plants. Denatured alcohol is ethanol that has been tainted with substances that render it unfit for human consumption. When methanol and pyridine are mixed with ethanol, the alcohol solution becomes poisonous, foul-smelling, bad-tasting, and nauseating. Methanol is the most commonly used alcohol denaturant.
Pinacol pinacolone rearrangement