Organic Chemistry
Q. How does the presence of a +M group affect the stability of a carbocation?
-
A.
Increases stability
-
B.
Decreases stability
-
C.
No effect
-
D.
Depends on the solvent
Solution
A +M group increases the stability of a carbocation by donating electron density through resonance.
Correct Answer: A — Increases stability
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Q. How many isomers does C4H10 have?
Solution
C4H10 has 2 structural isomers: n-butane and isobutane.
Correct Answer: B — 2
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Q. How many isomers does C5H12 have?
Solution
C5H12 has 3 structural isomers: pentane, isopentane, and neopentane.
Correct Answer: C — 4
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Q. Identify the group that shows a -I effect.
-
A.
-NH2
-
B.
-CH3
-
C.
-F
-
D.
-OCH3
Solution
The -F group shows a -I effect as it withdraws electron density through its electronegativity.
Correct Answer: C — -F
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Q. Identify the IUPAC name for the compound with the structure CH3-CH(CH3)-C(CH3)2-CH2-CH3.
-
A.
2,3-Dimethylpentane
-
B.
3,3-Dimethylpentane
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C.
2-Methylhexane
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D.
3-Methylhexane
Solution
The longest chain has 5 carbons, and there are two methyl groups on the third carbon, making it 3,3-Dimethylpentane.
Correct Answer: B — 3,3-Dimethylpentane
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Q. Identify the IUPAC name for the compound with the structure CH3-CH(CH3)-C(CH3)2-COOH.
-
A.
3-Methylbutanoic acid
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B.
2-Methylbutanoic acid
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C.
3,3-Dimethylbutanoic acid
-
D.
2,3-Dimethylbutanoic acid
Solution
The compound has a carboxylic acid group and a total of 5 carbons with two methyl groups on the third carbon, making it 3,3-Dimethylbutanoic acid.
Correct Answer: C — 3,3-Dimethylbutanoic acid
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Q. In which of the following cases does the mesomeric effect dominate over the inductive effect?
-
A.
Aromatic compounds
-
B.
Aliphatic compounds
-
C.
Alkynes
-
D.
Alkenes
Solution
In aromatic compounds, the mesomeric effect dominates due to resonance stabilization.
Correct Answer: A — Aromatic compounds
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Q. In which of the following compounds does the inductive effect play a significant role?
-
A.
Benzene
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B.
Acetic acid
-
C.
Cyclohexane
-
D.
Ethylene
Solution
In acetic acid, the inductive effect of the –COOH group influences the acidity of the compound.
Correct Answer: B — Acetic acid
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Q. What are the building blocks of nucleic acids?
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A.
Amino acids
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B.
Fatty acids
-
C.
Nucleotides
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D.
Monosaccharides
Solution
Nucleotides are the building blocks of nucleic acids like DNA and RNA.
Correct Answer: C — Nucleotides
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Q. What is denaturation of proteins?
-
A.
The process of protein synthesis
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B.
The loss of protein function due to structural changes
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C.
The formation of peptide bonds
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D.
The folding of proteins into their functional shape
Solution
Denaturation refers to the process where proteins lose their native structure and function due to external factors like heat or pH changes.
Correct Answer: B — The loss of protein function due to structural changes
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Q. What is the basic building block of proteins?
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A.
Nucleotides
-
B.
Fatty acids
-
C.
Amino acids
-
D.
Monosaccharides
Solution
Proteins are made up of amino acids, which are their basic building blocks.
Correct Answer: C — Amino acids
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Q. What is the basic structural unit of proteins?
-
A.
Nucleotide
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B.
Monosaccharide
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C.
Amino acid
-
D.
Fatty acid
Solution
Proteins are made up of long chains of amino acids.
Correct Answer: C — Amino acid
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Q. What is the basic unit of nucleic acids?
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A.
Amino acid
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B.
Nucleotide
-
C.
Monosaccharide
-
D.
Fatty acid
Solution
The basic unit of nucleic acids, such as DNA and RNA, is the nucleotide.
Correct Answer: B — Nucleotide
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Q. What is the basic unit of proteins?
-
A.
Nucleotide
-
B.
Monosaccharide
-
C.
Amino acid
-
D.
Fatty acid
Solution
Proteins are made up of amino acids, which are their basic building blocks.
Correct Answer: C — Amino acid
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Q. What is the boiling point trend among alcohols, ethers, and alkanes?
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A.
Alcohols > Ethers > Alkanes
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B.
Ethers > Alcohols > Alkanes
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C.
Alkanes > Ethers > Alcohols
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D.
All have the same boiling point
Solution
Alcohols have higher boiling points than ethers and alkanes due to hydrogen bonding.
Correct Answer: A — Alcohols > Ethers > Alkanes
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Q. What is the bond angle around the carbon atoms in an alkyne?
-
A.
120 degrees
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B.
180 degrees
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C.
109.5 degrees
-
D.
90 degrees
Solution
The bond angle around the carbon atoms in an alkyne is approximately 180 degrees due to linear geometry.
Correct Answer: B — 180 degrees
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Q. What is the effect of -NO2 group on the stability of benzene derivatives?
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A.
Stabilizing
-
B.
Destabilizing
-
C.
No effect
-
D.
Enhancing acidity
Solution
-NO2 is a strong electron-withdrawing group and destabilizes benzene derivatives.
Correct Answer: B — Destabilizing
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Q. What is the effect of a -CF3 group on the stability of a benzene ring?
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A.
Stabilizing
-
B.
Destabilizing
-
C.
No effect
-
D.
Depends on substituents
Solution
-CF3 is a strong electron-withdrawing group, which destabilizes the benzene ring.
Correct Answer: B — Destabilizing
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Q. What is the effect of a -CH3 group on the stability of a carbocation?
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A.
Destabilizes
-
B.
No effect
-
C.
Stabilizes
-
D.
Increases acidity
Solution
The -CH3 group is an electron-donating group and stabilizes the carbocation through hyperconjugation.
Correct Answer: C — Stabilizes
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Q. What is the effect of a -COOH group on the stability of a benzene ring?
-
A.
Stabilizing
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B.
Destabilizing
-
C.
No effect
-
D.
Depends on substituents
Solution
The -COOH group is a strong electron-withdrawing group, thus it destabilizes the benzene ring.
Correct Answer: B — Destabilizing
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Q. What is the effect of a -I group on the acidity of a carboxylic acid?
-
A.
Increases acidity
-
B.
Decreases acidity
-
C.
No effect
-
D.
Only affects basicity
Solution
A -I group increases the acidity of a carboxylic acid by stabilizing the negative charge on the conjugate base.
Correct Answer: A — Increases acidity
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Q. What is the effect of a -I group on the acidity of carboxylic acids?
-
A.
Increases acidity
-
B.
Decreases acidity
-
C.
No effect
-
D.
Depends on the solvent
Solution
A -I group increases the acidity of carboxylic acids by stabilizing the negative charge on the conjugate base.
Correct Answer: A — Increases acidity
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Q. What is the effect of a -NO2 group on the stability of a benzene ring?
-
A.
Stabilizing
-
B.
Destabilizing
-
C.
No effect
-
D.
Enhances reactivity
Solution
The -NO2 group is a strong electron-withdrawing group, which destabilizes the benzene ring.
Correct Answer: B — Destabilizing
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Q. What is the effect of alkyl groups on the basicity of amines?
-
A.
Decrease basicity
-
B.
Increase basicity
-
C.
No effect
-
D.
Depends on the size
Solution
Alkyl groups increase the basicity of amines due to their electron-donating effect.
Correct Answer: B — Increase basicity
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Q. What is the effect of electron-donating groups on the basicity of amines?
-
A.
Increase basicity
-
B.
Decrease basicity
-
C.
No effect
-
D.
Depends on the solvent
Solution
Electron-donating groups increase the electron density on the nitrogen atom, thus increasing the basicity of amines.
Correct Answer: A — Increase basicity
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Q. What is the effect of electron-withdrawing groups on the basicity of amines?
-
A.
Increase basicity
-
B.
Decrease basicity
-
C.
No effect
-
D.
Varies with the group
Solution
Electron-withdrawing groups decrease the basicity of amines by reducing the electron density on the nitrogen atom.
Correct Answer: B — Decrease basicity
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Q. What is the effect of increasing the carbon chain length on the boiling point of aldehydes?
-
A.
Decreases
-
B.
Increases
-
C.
Remains the same
-
D.
Varies randomly
Solution
The boiling point of aldehydes increases with the increase in carbon chain length due to increased van der Waals forces.
Correct Answer: B — Increases
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Q. What is the effect of increasing the number of carbon atoms in a carboxylic acid on its solubility in water?
-
A.
Increases solubility
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B.
Decreases solubility
-
C.
No effect
-
D.
First increases then decreases
Solution
As the number of carbon atoms increases, the solubility of carboxylic acids in water generally decreases due to the increasing hydrophobic character.
Correct Answer: B — Decreases solubility
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Q. What is the effect of increasing the number of carbon atoms in a carboxylic acid on its acidity?
-
A.
Increases acidity
-
B.
Decreases acidity
-
C.
No effect
-
D.
Depends on the structure
Solution
As the number of carbon atoms increases, the acidity generally decreases due to the increasing electron-donating effect of alkyl groups.
Correct Answer: B — Decreases acidity
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Q. What is the effect of increasing the number of carbon atoms in aldehydes on their boiling points?
-
A.
Decreases
-
B.
Increases
-
C.
Remains constant
-
D.
Varies unpredictably
Solution
The boiling points of aldehydes increase with the number of carbon atoms due to increased van der Waals forces.
Correct Answer: B — Increases
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