Question 1

Phenol is more acidic than aliphatic alcohols because:

Accepted Answer

Phenol's acidity arises from resonance stabilization of the phenoxide anion by the aromatic ring, making H⁺ loss easier.

Question 2

Which reagent is commonly used to distinguish between primary and secondary alcohols?

Accepted Answer

Acidic KMnO₄ oxidizes primary alcohols to carboxylic acids (decolorizes) and secondary to ketones, while tertiary alcohols are unaffected.

Question 3

Which hydrocarbon shows the phenomenon of isomerism first appearing in its series?

Accepted Answer

Butane is the first alkane to exhibit structural isomerism, existing as n-butane and isobutane (2-methylpropane).

Question 4

What is the IUPAC name of the compound with structure CH₃OCH₂CH₃?

Accepted Answer

The IUPAC name for CH₃OCH₂CH₃ is methoxyethane, where methoxy is the substituent on the ethane backbone.

Question 5

What is the IUPAC name of the compound CH3-CH2-CH2-CH3?

Accepted Answer

This straight-chain hydrocarbon contains 4 carbon atoms, making it butane according to IUPAC nomenclature.

Question 6

Which of the following represents a primary alcohol?

Accepted Answer

A primary alcohol has the hydroxyl group (-OH) attached to a carbon bonded to only one alkyl group; CH3CH2OH fits this definition.

Question 7

What is the general molecular formula for alkanes?

Accepted Answer

Alkanes are saturated hydrocarbons with only single bonds, following the formula CₙH₂ₙ₊₂ for acyclic chains.

Question 8

What is the IUPAC name of the hydrocarbon with the structure CH₃-CH₂-CH₂-CH₃?

Accepted Answer

This four-carbon alkane with only single bonds is named butane according to IUPAC nomenclature.

Question 9

Which of the following compounds is classified as a primary alcohol?

Accepted Answer

Primary alcohols have the OH group attached to a carbon bonded to only one other carbon; CH₃CH₂OH (ethanol) fits this definition.

Question 10

Which of the following haloalkanes undergoes SN2 reaction most readily?

Accepted Answer

Primary haloalkanes are most reactive in SN2 reactions due to least steric hindrance around the carbon bearing the halogen.

Question 11

What is the IUPAC name of the compound CH₃CHBrCH₂CH₃?

Accepted Answer

The main chain has 4 carbons (butane), and the bromine is attached to carbon 2 when numbered from the nearest end, giving 2-bromobutane.

Question 12

Which haloarene is most resistant to nucleophilic aromatic substitution?

Accepted Answer

The methoxy group (-OCH₃) is an electron-donating group that increases electron density on the benzene ring, making the C-Cl bond stronger and more resistant to nucleophilic attack.

Question 13

In the reaction of 1-bromobutane with KOH in alcoholic solution, the major product is:

Accepted Answer

Alcoholic KOH promotes elimination (E2 reaction) rather than substitution, producing 1-butene as the major product from a primary haloalkane.

Question 14

Which of the following statements about haloarenes is correct?

Accepted Answer

The C-X bond in haloarenes is shorter and stronger due to sp² hybridization of the aromatic carbon, making haloarenes less reactive towards nucleophilic substitution.

Question 15

Identify the functional group present in CH3COCH3.

Accepted Answer

CH3COCH3 contains a carbonyl group (C=O) bonded to two alkyl groups, which defines a ketone.

Question 16

Which pair of compounds represents isomers?

Accepted Answer

Both CH3CH2CH3 (n-propane) and CH3CH(CH3)2 (isopropane) have the molecular formula C3H8, making them constitutional isomers.

Question 17

Which of the following is an example of an alkene?

Accepted Answer

Ethene (C₂H₄) is an alkene containing one C=C double bond; alkenes follow the formula CₙH₂ₙ.

Question 18

How many sigma (σ) and pi (π) bonds are present in a molecule of ethyne (C₂H₂)?

Accepted Answer

Ethyne has a C≡C triple bond (1 σ and 2 π bonds between carbons) plus 2 C-H σ bonds, totaling 3 σ and 2 π bonds.

Question 19

What is the general formula for alkanes?

Accepted Answer

Alkanes are saturated hydrocarbons with only single C-C bonds, following the formula CnH2n+2 for acyclic compounds.

Question 20

The dehydration of ethanol (C₂H₅OH) with concentrated H₂SO₄ at 170°C produces:

Accepted Answer

Dehydration of ethanol at 170°C with concentrated H₂SO₄ removes water and forms ethene (C₂H₄) via an E1 mechanism.

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