Organic Chemistry

1. Consider the following: 1. Aerosols 2. Foam agents 3. Fire retardants

Consider the following:
1. Aerosols
2. Foam agents
3. Fire retardants
4. Lubricants
In the making of how many of the above are hydrofluorocarbons used?

Only one
Only two
Only three
All four
This question was previously asked in
UPSC IAS – 2023
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Hydrofluorocarbons (HFCs) are used in the making of all four of the listed items.
HFCs were developed as substitutes for ozone-depleting substances (like CFCs and HCFCs) in various applications.
1. **Aerosols:** HFCs are used as propellants in various aerosol products.
2. **Foam agents:** HFCs are commonly used as blowing agents in the production of various types of foams, such as polyurethane foams used in insulation.
3. **Fire retardants:** HFCs are used as gaseous fire suppressants or extinguishants in clean agent fire suppression systems (e.g., HFC-227ea, HFC-125). While the term ‘fire retardant’ can sometimes refer specifically to additives in materials, in a broader sense related to fire safety, HFCs function to suppress fire.
4. **Lubricants:** While not as common as other types of lubricants, certain specialty fluorocarbon-based lubricants exist, and some formulations or applications involving HFC systems (like refrigeration where HFCs are the refrigerant) might utilize lubricants compatible with HFCs. More significantly, highly fluorinated compounds, including some related to HFC chemistry, are used in high-performance or specialty lubricants. Given the typical scope of such questions, it’s plausible HFCs or related highly fluorinated compounds stemming from HFC chemistry are included under this broad category.
While the primary uses of HFCs are in refrigeration, air conditioning, aerosols, and foam blowing, and as fire suppressants, the formulation of specialty lubricants can also involve fluorinated compounds, sometimes including those related to the HFC family, particularly for applications where chemical inertness and thermal stability are required. Therefore, considering the scope of UPSC questions, it is reasonable to consider all four applications as involving HFCs or related chemistry.

2. Which one of the following is NOT a heterocyclic aromatic compound ?

Which one of the following is NOT a heterocyclic aromatic compound ?

Tropolone
Furan
Thiophene
Pyridine
This question was previously asked in
UPSC CAPF – 2020
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Tropolone is a seven-membered carbocyclic compound containing a ketone and a hydroxyl group. Its aromaticity arises from the cyclic conjugated system within the carbon ring, but the ring itself is made entirely of carbon atoms. Furan, Thiophene, and Pyridine are all five- or six-membered rings containing heteroatoms (Oxygen in Furan, Sulfur in Thiophene, Nitrogen in Pyridine) within the ring structure, along with conjugated pi systems that satisfy Hückel’s rule, making them heterocyclic aromatic compounds.
A heterocyclic compound contains at least one atom other than carbon (such as O, N, S) in its ring structure. An aromatic compound is cyclic, planar, conjugated, and obeys Hückel’s rule (4n+2 pi electrons).
Tropolone is a carbocyclic aromatic compound. Common examples of heterocyclic aromatic compounds include pyridine, furan, thiophene, pyrrole, and imidazole.

3. Leakage of which one of the following gases had caused Bhopal Gas Trag

Leakage of which one of the following gases had caused Bhopal Gas Tragedy in the year 1984 ?

Methyl isocyanate
Hexamethylene diisocyanate
Isophorone diisocyanate
Isothiocyanate
This question was previously asked in
UPSC CAPF – 2017
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The leakage of Methyl Isocyanate (MIC) gas caused the Bhopal Gas Tragedy in 1984.
The Bhopal Gas Tragedy occurred on the night of December 2–3, 1984, at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh. A leak of methyl isocyanate gas and other chemicals resulted in thousands of deaths and long-term health issues for many more.
Methyl Isocyanate (MIC) is a highly toxic organic compound used in the production of pesticides. It is a volatile, flammable liquid. The incident is considered one of the world’s worst industrial disasters.

4. Which one of the following is NOT an example of organic compound ?

Which one of the following is NOT an example of organic compound ?

Ammonium cyanate
Marsh gas
Urea
Cane sugar
This question was previously asked in
UPSC NDA-2 – 2023
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A) Ammonium cyanate is NOT an example of an organic compound.
– Organic compounds are generally defined as compounds containing carbon, especially those with C-H bonds. They typically originate from biological sources or contain carbon in combination with hydrogen, oxygen, nitrogen, sulfur, etc.
– There are exceptions to the “contains carbon” rule for inorganic compounds, which include oxides of carbon (CO, CO₂), carbonates, bicarbonates, cyanides, cyanates, thiocyanates, carbides, and elemental carbon forms.
– Ammonium cyanate (NH₄OCN) is an ionic salt formed from the ammonium ion (NH₄⁺) and the cyanate ion (OCN⁻). It is classified as an inorganic salt. Historically, it is famous because Friedrich Wöhler synthesized urea (an organic compound) from it in 1828, which was a significant step in disproving the vital force theory.
– Marsh gas is Methane (CH₄), a simple hydrocarbon (alkane) and a classic organic compound.
– Urea ((NH₂)₂CO) contains a carbonyl group (C=O) and amine groups (NH₂). It is an organic compound, specifically an amide.
– Cane sugar is Sucrose (C₁₂H₂₂O₁₁), a disaccharide carbohydrate, which is a large class of organic compounds.
– Therefore, Ammonium cyanate is the only compound in the list that is considered inorganic.

5. Liquid vegetable oils are converted to solid margarine by the use of

Liquid vegetable oils are converted to solid margarine by the use of

hydrogen gas
chlorine gas
carbon dioxide gas
oxygen gas
This question was previously asked in
UPSC NDA-2 – 2022
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The correct answer is hydrogen gas.
Liquid vegetable oils are typically unsaturated fats, meaning they contain carbon-carbon double bonds. To convert these liquid oils into solid or semi-solid fats like margarine, hydrogen gas is added across the double bonds in the presence of a catalyst (usually nickel, palladium, or platinum). This process is called hydrogenation.
Partial hydrogenation can lead to the formation of trans fats, which have been linked to negative health effects. Modern hydrogenation processes aim to minimize trans fat formation while achieving the desired consistency.

6. What is the total number of covalent bonds in methanol ?

What is the total number of covalent bonds in methanol ?

3
4
5
6
This question was previously asked in
UPSC NDA-2 – 2021
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The correct option is C. Methanol has the chemical formula $\text{CH}_3\text{OH}$. To find the number of covalent bonds, we need to consider its molecular structure.
The structure of methanol involves a central carbon atom bonded to three hydrogen atoms, one oxygen atom, and the oxygen atom is bonded to one hydrogen atom.
Drawing the Lewis structure or structural formula:
Carbon (C) forms single bonds with 3 Hydrogen atoms (H) and 1 Oxygen atom (O).
Oxygen (O) forms a single bond with the Carbon atom (C) and a single bond with 1 Hydrogen atom (H).
The bonds are: 3 C-H single bonds, 1 C-O single bond, and 1 O-H single bond.
Total number of covalent bonds = 3 (C-H) + 1 (C-O) + 1 (O-H) = 5.
Each line in the structural formula represents a single covalent bond, which is a pair of shared electrons. Carbon typically forms 4 bonds, Oxygen typically forms 2 bonds and has 2 lone pairs, and Hydrogen forms 1 bond. This structure satisfies the valency rules for all atoms.

7. How many covalent bonds are present in a Chloropropane molecule having

How many covalent bonds are present in a Chloropropane molecule having molecular formula, C₃H₇Cl ?

6
8
9
10
This question was previously asked in
UPSC NDA-2 – 2020
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The correct answer is (D) 10. The molecular formula is C₃H₇Cl. This represents a chloropropane molecule, which is derived from propane (C₃H₈) by replacing one hydrogen atom with a chlorine atom. Let’s consider the structure of propan-1-ol (CH₃-CH₂-CH₂-Cl) or propan-2-ol (CH₃-CHCl-CH₃). Counting the single covalent bonds:
In CH₃-CH₂-CH₂-Cl:
C1-H (3 bonds)
C1-C2 (1 bond)
C2-H (2 bonds)
C2-C3 (1 bond)
C3-H (2 bonds)
C3-Cl (1 bond)
Total = 3 + 1 + 2 + 1 + 2 + 1 = 10 covalent bonds.
In CH₃-CHCl-CH₃:
C1-H (3 bonds)
C1-C2 (1 bond)
C2-H (1 bond)
C2-Cl (1 bond)
C2-C3 (1 bond)
C3-H (3 bonds)
Total = 3 + 1 + 1 + 1 + 1 + 3 = 10 covalent bonds.
A covalent bond is formed by the sharing of electron pairs between atoms. To find the total number of covalent bonds in a simple organic molecule, you need to count all the single, double, and triple bonds between atoms.
In organic molecules, carbon typically forms 4 bonds, hydrogen forms 1 bond, and chlorine forms 1 bond. By drawing the skeletal structure and adding hydrogens to satisfy valency, one can systematically count the bonds.

8. Which one among the following compounds has a sweet and fruity smell ?

Which one among the following compounds has a sweet and fruity smell ?

Ethyl alcohol
Acetic acid
Ethyl acetate
Acetophenone
This question was previously asked in
UPSC NDA-1 – 2024
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Ethyl acetate has a sweet and fruity smell.
Esters are a class of organic compounds formed from an alcohol and a carboxylic acid, and they are commonly known for their pleasant, often fruity or flowery odors. Ethyl acetate is an ester derived from ethanol and acetic acid.
Ethyl alcohol (ethanol) has a characteristic alcoholic smell. Acetic acid is a carboxylic acid with a pungent, vinegar-like smell. Acetophenone is a ketone with a sweet, sometimes described as almond-like or floral, smell.

9. Which one of the following statements is not correct?

Which one of the following statements is not correct?

Most carbon compounds are good conductors of electricity.
Bonding in organic compounds is covalent.
Graphite is used as a lubricant.
Diamond is an allotrope of carbon.
This question was previously asked in
UPSC NDA-1 – 2022
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The correct answer is A) Most carbon compounds are good conductors of electricity. This statement is incorrect; most organic (carbon) compounds are covalent and do not conduct electricity well in their solid or liquid state.
– Conductivity of electricity requires the presence of free-moving charged particles (electrons or ions).
– Most carbon compounds (organic compounds) are formed by covalent bonds between nonmetal atoms (C, H, O, N, S, halogens, etc.). Covalent compounds typically do not form free ions or mobile electrons, so they are poor conductors or insulators.
– Statement B is correct: The primary bonding in organic compounds is covalent.
– Statement C is correct: Graphite, an allotrope of carbon, has a layered structure with delocalized electrons within the layers, which makes it a conductor and a good solid lubricant. However, graphite is an *exception* among carbon compounds regarding conductivity.
– Statement D is correct: Diamond is another well-known crystalline allotrope of carbon.
– The statement claims *most* carbon compounds are good conductors, which is false. The vast majority of organic molecules (e.g., sugars, plastics, oils, alcohols, proteins) are electrical insulators.
Exceptions to the non-conductivity of carbon compounds include graphite, some conjugated polymers, and ionic carbides (though ionic carbides are not typically considered “organic” compounds in the traditional sense). However, the general rule for the vast class of organic compounds is that they are poor conductors of electricity.

10. Hydrogenation of vegetable oils using nickel catalyst is an example of

Hydrogenation of vegetable oils using nickel catalyst is an example of

Substitution reaction.
Elimination reaction.
Addition reaction.
Free-radical polymerization.
This question was previously asked in
UPSC NDA-1 – 2021
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Hydrogenation is a chemical reaction that involves the addition of hydrogen gas (H₂) to a compound. Vegetable oils are unsaturated fats containing carbon-carbon double bonds (C=C). In the presence of a catalyst like nickel, hydrogen atoms add across these double bonds, converting them into single bonds (C-C) and making the oil saturated or partially saturated (like in the production of vanaspati ghee). This type of reaction, where atoms are added across a double or triple bond, is an addition reaction.
Addition reactions are characteristic of unsaturated compounds (alkenes, alkynes, etc.). Hydrogenation specifically involves the addition of hydrogen. Catalysts (like Ni, Pt, or Pd) are typically used to speed up the reaction rate.
Substitution reactions involve the replacement of one atom or group by another. Elimination reactions involve the removal of atoms or groups from a molecule to form a double or triple bond. Free-radical polymerization is a process where monomers join together to form a polymer chain via a free-radical mechanism.
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