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Commercial Methods For the Synthesis of Methanol and Ethanol: Practice Problems and Frequently Asked Questions(FAQs)

Commercial Methods For the Synthesis of Methanol and Ethanol: Practice Problems and Frequently Asked Questions(FAQs)

Is drinking denatured alcohol safe?

Denatured alcohol is not fit for human consumption.

Denatured ethanol is ethanol that has been tainted with denaturing agents.

We know that in some regions, alcohol is taxed by many governments. If we make pure alcohol available in household products, it can be a convenient source of drinking. So, if we do not denature that alcohol, people would drink it.

In most cases, methanol is added to ethyl alcohol, which is harmful to us. Denatured alcohol is also referred to as methylated spirit. It is also known as denatured rectified spirit or wood spirit. When methanol is added to ethanol, the alcohol solution becomes poisonous, has a foul odor, a bad taste, and is nauseating.

Methanol is the most commonly used alcohol denaturant.

Table of content:

Commercial methods for the synthesis of Methanol:

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 sp3hybridization, the molecule has a tetrahedral structure with respect to carbon, but due to the lone pair of electrons on oxygen, there would be lone pair-lone pair repulsion, due to which the bond angle H-O-C is less than 109.5o

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Conventional Method of Production:

The oldest yet most used method for the production of methanol involves the reaction between carbon monoxide and hydrogen gas. 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.

CO + 2 H+ Zn/CuO → CH3OH

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 into 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.

Commercial methods for the synthesis of Ethanol:

Ethanol has two carbon atoms and one oxygen atom along with the six hydrogen atoms in its chemical formula C2H6O. The structural formula for ethanol C2H5OH, adds a little more detail, indicating that the 2-carbon chain ends in a hydroxyl group (-OH).

Preparations of ethanol

1. By fermentation of carbohydrates in presence of anaerobic bacteria:

Ethanol is manufactured on an industrial scale by fermenting molasses. Molasses is the mother liquor left over when sugarcane juice crystallizes, and it contains roughly 60% fermentable sugar. The steps are as follows:

(a) Molasses dilution: Molasses is first diluted in a 1:5 (molasses: water) volume ratio with water.

(b) Ammonium sulfate fortification: Ammonium sulfate fortification supplies yeast with an appropriate source of nitrogen.

(c) Sulphuric acid addition: A little amount of sulphuric acid is added to the fortified molasses solution. This promotes yeast development while inhibiting the growth of harmful bacteria.

(d) Fractional distillation: The alcohol obtained during fermentation is known as "wash," and it is around 15% to 18% pure. It is turned into 92 percent pure alcohol known as rectified spirit or commercial alcohol via fractional distillation.

We will also learn about one of the products of the fermentation reaction. Specifically, glucose.

Glucose is a carbohydrate and a vital biomolecule that contributes to the body's metabolism. It has a chemical formula C6H12O6 and is a simple sugar. It is made up of six carbon atoms, twelve hydrogen atoms, and six oxygen atoms..

Glucose, often known as dextrose or blood sugar, is an easily accessible monosaccharide. Glucose is primarily produced by plants and the majority of algae during the photosynthesis process.

To put it precisely, Glucose is a type of sugar. We don't only mean the white crystals we sprinkle on our cuisine when we say sugar. These sugars are a subgroup of carbohydrates, which are energy-giving chemicals found in food.

Practice problems:

Q.1. What does synthesis gas consist of?

(A) Mixture of H+ CO+ CO + N2
(B) Mixture of CH+ H+ CO
(C) Mixture of CO + H2
(D) Mixture of H+ O2

Answer: (C)

Solution: Synthesis gas is a mainly a mixture of CO + H2. The name comes from its use as an intermediate in creating SNG (Synthetic natural gas). Mixture of CO + N2 is called producer gas. Mixture of CH+ H+ CO is called coal gas.

Q.2. In liquid methanol, a reagent is employed to eliminate ketones and aldehydes is

(A) Manganate
(B) Chromate
(C) Di-chromate
(D) Per-manganate

Answer: (D)

Solution: Ketones and aldehydes are removed from depressurized liquid methanol using per-manganate, and light ends are removed using a stripper. Fractionation is used to separate molecules with a high molecular weight.

Q.3. In the production of ethanol, the pH of the molasses solution should be

(A) 1-2
(B) 2-3
(C) 7-9
(D) 4-5

Answer: (D)

Solution: To promote yeast growth that produces invertase and zymase, the pH of the molasses solution must be in the range of 4-5. Sulfuric acid is used to alter the pH.

Q.4. What is mash made up of in the manufacture of ethanol from molasses?

(A) Ammonium nitrate + Magnesium nitrate
(B) Ammonium nitrate + Magnesium nitrate + Phosphorus
(C) Ammonium sulfate + Magnesium sulfate
(D) Ammonium sulfate + Magnesium sulfate + Phosphorus

Answer: (D)

Solution: Nutrients such as Ammonium sulfate, Magnesium sulfate and Phosphorus are added to molasses to support the yeast growth.

Frequently asked questions:

Q1. Why is ethanol mixed with gasoline?

Answer: Ethanol can be mixed with gasoline to create various blends. Because the ethanol molecule contains oxygen, it allows the engine to more completely combust the fuel, resulting in fewer emissions and thus less environmental pollution.

Q2. Why is methanol referred to as wood spirit?

Answer: Methanol, also known as methyl alcohol, wood alcohol, or wood spirit, is the most basic of a long series of organic compounds known as alcohols, consisting of methyl group which is linked to hydroxyl group.

Previously, methanol was produced through the destructive distillation of wood. Modern methanol production is based on the direct reaction of carbon monoxide gas and hydrogen in the presence of a catalyst. Syngas, a mixture of hydrogen and carbon monoxide derived from biomass, is increasingly being used for methanol production.

As a result, Methanol is also known as wood spirit.

Q3. Why is ethanol used for DNA extraction?

Answer: The primary function of monovalent cations and ethanol is to dissolve the solvation shell that surrounds the DNA, allowing it to precipitate in pellet form. Furthermore, ethanol promotes DNA aggregation. During the DNA washing steps, approximately 70 % ethanol solution is typically used.

Q4. What makes methanol more toxic than ethanol?

Answer: 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 10 ml, 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.

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