1. Which of the following is the correct IUPAC name for the compound CH₃-CH₂-CH₂-CH(OH)-CH₃?
A. 3-Hydroxy-2-pentanol
B. 2-Pentanol
C. 3-Pentanol
D. Pentan-2-ol
Answer: D. Pentan-2-ol
Explanation:
The longest carbon chain contains 5 carbon atoms, hence the base name is pentane. The -OH group is attached to the second carbon, so the compound is named as pentan-2-ol according to IUPAC rules.
2. Which of the following represents a pair of functional isomers?
A. C₂H₅OH and CH₃OCH₃
B. C₆H₆ and C₆H₁₂
C. C₂H₆O and CH₃COOH
D. CH₃CH₂CH₂OH and CH₃CH₂CH₂CH₃
Answer: A. C₂H₅OH and CH₃OCH₃
Explanation:
Functional isomers have the same molecular formula but different functional groups. C₂H₅OH is ethanol (alcohol) and CH₃OCH₃ is dimethyl ether (ether). Both have the same molecular formula (C₂H₆O) but different functional groups (alcohol and ether).
3. Which of the following represents geometrical isomerism?
A. But-2-ene
B. 1-Butene
C. Propene
D. 2-Methylpropene
Answer: A. But-2-ene
Explanation:
Geometrical isomerism occurs due to the restricted rotation around a double bond and the presence of different groups attached to the double-bonded carbons. In but-2-ene, there is a possibility of cis and trans isomers because of the presence of two different groups on each carbon of the double bond.
4. Which of the following reactions follows the SN1 mechanism?
A. CH₃Cl + OH⁻
B. (CH₃)₃CCl + OH⁻
C. CH₃CH₂Cl + OH⁻
D. C₆H₅CH₂Cl + OH⁻
Answer: B. (CH₃)₃CCl + OH⁻
Explanation:
SN1 mechanism involves a two-step process where the rate-determining step is the formation of a carbocation. Tertiary alkyl halides like (CH₃)₃CCl form stable carbocations and hence undergo substitution via the SN1 mechanism.
5. Which one of the following pairs can exhibit tautomerism?
A. Acetone and Propanol
B. Ethanol and Methanal
C. Acetaldehyde and Acetic acid
D. Acetone and Acetaldehyde
Answer: D. Acetone and Acetaldehyde
Explanation:
Tautomerism is a phenomenon where compounds exist in equilibrium between two structural forms, usually keto and enol forms. Both acetone (a ketone) and acetaldehyde (an aldehyde) can show keto-enol tautomerism.
6. Which of the following reactions involves an electrophilic substitution mechanism?
A. Halogenation of alkanes
B. Nitration of benzene
C. Hydrolysis of esters
D. Dehydration of alcohols
Answer: B. Nitration of benzene
Explanation:
Electrophilic substitution reactions typically occur in aromatic compounds like benzene. In the nitration of benzene, a nitronium ion (NO₂⁺) acts as the electrophile and substitutes a hydrogen atom in the benzene ring.
7. Which of the following compounds exhibits optical isomerism?
A. 2-Butanol
B. Propan-2-ol
C. 1-Butanol
D. 2-Methylpropane
Answer: A. 2-Butanol
Explanation:
Optical isomerism arises when a compound contains a chiral center, i.e., a carbon atom bonded to four different groups. In 2-butanol, the second carbon is attached to four different groups, making it optically active.
8. In the reaction mechanism of nucleophilic substitution, the rate of reaction for SN2 depends on:
A. Concentration of the nucleophile only
B. Concentration of alkyl halide only
C. Both nucleophile and alkyl halide concentrations
D. None of the above
Answer: C. Both nucleophile and alkyl halide concentrations
Explanation:
In the SN2 mechanism, the reaction occurs in a single step where the nucleophile attacks the substrate, leading to the simultaneous breaking of the carbon-halogen bond. The rate of reaction depends on both the nucleophile and the substrate concentrations.
9. Which of the following is an example of a Markovnikov addition?
A. Addition of HBr to propene
B. Addition of HBr to 1-butene in the presence of peroxide
C. Hydration of ethyne
D. Oxidation of ethene with KMnO₄
Answer: A. Addition of HBr to propene
Explanation:
According to Markovnikov’s rule, in the addition of HX (where X is a halogen) to an alkene, the hydrogen atom attaches to the carbon with the greater number of hydrogen atoms (the less substituted carbon), while the halogen attaches to the more substituted carbon. This is seen in the addition of HBr to propene.
10. Which of the following is an anti-Markovnikov addition reaction?
A. Addition of HBr to 1-butene in the presence of peroxide
B. Addition of H₂O to ethene
C. Nitration of benzene
D. Sulphonation of benzene
Answer: A. Addition of HBr to 1-butene in the presence of peroxide
Explanation:
The presence of peroxides leads to an anti-Markovnikov addition of HBr, where the bromine attaches to the less substituted carbon. This reaction is also known as the peroxide effect or Kharasch effect.
11. Which of the following compounds exhibits position isomerism?
A. Butan-1-ol and Butan-2-ol
B. Ethanol and Dimethyl ether
C. Propanal and Propanone
D. Ethanoic acid and Methyl methanoate
Answer: A. Butan-1-ol and Butan-2-ol
Explanation:
Position isomerism occurs when the functional group occupies different positions on the same carbon chain. In Butan-1-ol and Butan-2-ol, the hydroxyl (-OH) group is at different positions in the carbon chain.
12. Which of the following is the most reactive towards nucleophilic substitution via the SN2 mechanism?
A. CH₃Cl
B. CH₃CH₂Cl
C. (CH₃)₃CCl
D. C₆H₅CH₂Cl
Answer: A. CH₃Cl
Explanation:
In the SN2 mechanism, reactivity increases as the steric hindrance decreases. Methyl halides like CH₃Cl have the least steric hindrance, making them the most reactive toward SN2 reactions.
13. Which one of the following is a pair of chain isomers?
A. Pentane and 2-Methylbutane
B. Pentan-2-one and Pentan-3-one
C. Ethanol and Ethanoic acid
D. Propan-1-ol and Propan-2-ol
Answer: A. Pentane and 2-Methylbutane
Explanation:
Chain isomerism occurs when the carbon skeleton of a molecule is arranged differently. Pentane and 2-Methylbutane are chain isomers because they differ in the branching of their carbon chain.
14. Which of the following reactions involves a free radical mechanism?
A. Bromination of benzene
B. Halogenation of methane
C. Esterification of carboxylic acids
D. Hydrolysis of alkyl halides
Answer: B. Halogenation of methane
Explanation:
The halogenation of alkanes, such as methane, proceeds via a free radical mechanism, involving initiation, propagation, and termination steps where free radicals are formed and consumed.
15. Which of the following compounds exhibits geometrical isomerism?
A. 1-Butene
B. But-2-yne
C. But-2-ene
D. 2-Methylpropene
Answer: C. But-2-ene
Explanation:
Geometrical isomerism occurs due to restricted rotation around a double bond, where different groups are attached to the double-bonded carbons. But-2-ene has cis and trans isomers due to the arrangement of substituents around the double bond.
16. Which of the following reactions will proceed via an SN1 mechanism?
A. 2-Bromo-2-methylpropane with OH⁻
B. Methyl bromide with OH⁻
C. Chloromethane with CN⁻
D. Bromoethane with OH⁻
Answer: A. 2-Bromo-2-methylpropane with OH⁻
Explanation:
Tertiary alkyl halides, like 2-Bromo-2-methylpropane, undergo nucleophilic substitution through the SN1 mechanism due to the stability of the tertiary carbocation formed during the reaction.
17. The IUPAC name of the compound CH₃CH₂COCH₃ is:
A. Propan-2-one
B. Butan-2-one
C. Butanone
D. Butanal
Answer: B. Butan-2-one
Explanation:
The compound contains four carbon atoms, with a ketone group (-CO) attached to the second carbon atom. Thus, the correct name is butan-2-one.
18. Which of the following compounds exhibits optical isomerism?
A. 2-Butanol
B. 2-Methylpropane
C. But-2-ene
D. 1-Butanol
Answer: A. 2-Butanol
Explanation:
Optical isomerism occurs when a molecule contains a chiral center, a carbon atom attached to four different groups. In 2-butanol, the second carbon is chiral, making the molecule optically active.
19. Which of the following pairs can be classified as tautomers?
A. Acetone and Propan-2-ol
B. Ethanol and Acetic acid
C. Acetone and Propanal
D. Acetone and Enol
Answer: D. Acetone and Enol
Explanation:
Tautomers are isomers of a compound that differ in the position of a proton and the connectivity of atoms. Acetone (keto form) and enol are keto-enol tautomers.
20. Which of the following will undergo electrophilic aromatic substitution most readily?
A. Nitrobenzene
B. Benzene
C. Toluene
D. Chlorobenzene
Answer: C. Toluene
Explanation:
Toluene has a methyl group (-CH₃), which is an electron-donating group. This activates the benzene ring towards electrophilic substitution, making toluene more reactive than benzene and other substituted benzene rings with electron-withdrawing groups.
21. Which of the following reactions is an example of an electrophilic addition?
A. Addition of HBr to propene
B. Nitration of benzene
C. Dehydration of alcohols
D. Esterification of carboxylic acids
Answer: A. Addition of HBr to propene
Explanation:
In the addition of HBr to propene, an electrophile (H⁺) adds to the carbon-carbon double bond, followed by nucleophilic attack by Br⁻. This is an example of electrophilic addition.
22. Which one of the following molecules can exhibit optical activity?
A. 2-Chloropropane
B. 2-Chlorobutane
C. 2-Chlorobutene
D. 1-Chlorobutane
Answer: B. 2-Chlorobutane
Explanation:
2-Chlorobutane has a chiral carbon (the second carbon), which is attached to four different groups, making it optically active.
23. Which one of the following reactions proceeds through a carbocation intermediate?
A. SN1 reaction
B. SN2 reaction
C. E2 reaction
D. Free radical substitution
Answer: A. SN1 reaction
Explanation:
The SN1 mechanism involves the formation of a carbocation intermediate in the rate-determining step.
24. In the reaction: CH₃CH₂CH₂Br + NaCN → CH₃CH₂CH₂CN, the mechanism followed is:
A. SN1
B. SN2
C. E1
D. E2
Answer: B. SN2
Explanation:
Primary alkyl halides, such as CH₃CH₂CH₂Br, typically undergo nucleophilic substitution via the SN2 mechanism, where the nucleophile (CN⁻) attacks the carbon bearing the leaving group from the opposite side.
25. Which of the following compounds will undergo nucleophilic substitution via an SN2 mechanism the slowest?
A. Methyl bromide
B. Ethyl bromide
C. Isopropyl bromide
D. Tert-butyl bromide
Answer: D. Tert-butyl bromide
Explanation:
The SN2 mechanism requires backside attack by the nucleophile, which is hindered in tertiary alkyl halides like tert-butyl bromide due to steric hindrance. Therefore, tert-butyl bromide reacts the slowest via the SN2 mechanism.
26. Which of the following reactions represents a nucleophilic addition mechanism?
A. Addition of HBr to ethene
B. Addition of CN⁻ to acetone
C. Bromination of benzene
D. Nitration of benzene
Answer: B. Addition of CN⁻ to acetone
Explanation:
Nucleophilic addition occurs in carbonyl compounds like acetone, where a nucleophile (CN⁻) adds to the electrophilic carbon of the carbonyl group.
27. Which of the following exhibits both geometrical and optical isomerism?
A. 2-Butanol
B. 2-Butene
C. 2-Chlorobutane
D. 3-Methylpent-2-ene
Answer: D. 3-Methylpent-2-ene
Explanation:
3-Methylpent-2-ene exhibits geometrical isomerism due to restricted rotation around the double bond, and optical isomerism due to the presence of a chiral center at the third carbon.
28. Which of the following is the major product when 2-bromopropane reacts with KOH in ethanol?
A. Propene
B. 1-Propanol
C. 2-Propanol
D. 2-Bromo-1-propene
Answer: A. Propene
Explanation:
In the presence of KOH in ethanol, elimination occurs via the E2 mechanism, and the major product is propene.
29. Which of the following represents an electrophile?
A. OH⁻
B. H₂O
C. NO₂⁺
D. CH₃O⁻
Answer: C. NO₂⁺
Explanation:
An electrophile is an electron-deficient species that can accept a pair of electrons. NO₂⁺ (nitronium ion) is an example of an electrophile as it is positively charged and electron-deficient.
30. Which of the following pairs of compounds are functional isomers?
A. Ethanol and Dimethyl ether
B. Propanal and Propanone
C. Butanal and Butanone
D. Ethanoic acid and Methyl methanoate
Answer: A. Ethanol and Dimethyl ether
Explanation:
Functional isomers have the same molecular formula but different functional groups. Ethanol (an alcohol) and dimethyl ether (an ether) have the same molecular formula (C₂H₆O) but different functional groups.
31. Which of the following is an example of optical isomerism?
A. 2-Butanol
B. But-2-ene
C. Propan-2-ol
D. 1-Butanol
Answer: A. 2-Butanol
Explanation:
Optical isomerism occurs when a molecule contains a chiral center, i.e., a carbon atom attached to four different groups. In 2-butanol, the second carbon is chiral, making it optically active.
32. Which one of the following reactions is an example of a Markovnikov addition?
A. Addition of HBr to propene
B. Addition of HBr to 1-butene in the presence of peroxide
C. Hydrogenation of ethyne
D. Oxidation of ethene with KMnO₄
Answer: A. Addition of HBr to propene
Explanation:
According to Markovnikov’s rule, in the addition of HX to an unsymmetrical alkene, the hydrogen atom bonds to the carbon with more hydrogen atoms (less substituted), and the halogen bonds to the more substituted carbon. This occurs in the addition of HBr to propene.
33. Which of the following compounds shows geometrical isomerism?
A. 1-Pentene
B. But-2-yne
C. 2-Methylpropene
D. But-2-ene
Answer: D. But-2-ene
Explanation:
Geometrical isomerism occurs due to restricted rotation around a double bond, and But-2-ene has cis and trans isomers based on the relative positions of the substituents around the double bond.
34. The major product in the dehydration of 2-methyl-2-butanol using concentrated H₂SO₄ is:
A. 2-Methyl-1-butene
B. 2-Methyl-2-butene
C. 3-Methyl-1-butene
D. 2-Butene
Answer: B. 2-Methyl-2-butene
Explanation:
Dehydration of alcohols in the presence of strong acids like H₂SO₄ proceeds via an E1 mechanism. According to Zaitsev’s rule, the more substituted alkene is the major product, which in this case is 2-Methyl-2-butene.
35. Which of the following undergoes nucleophilic substitution by an SN1 mechanism?
A. Methyl chloride
B. Ethyl chloride
C. Tert-butyl chloride
D. Propyl chloride
Answer: C. Tert-butyl chloride
Explanation:
Tertiary alkyl halides like tert-butyl chloride form stable carbocations and undergo nucleophilic substitution via the SN1 mechanism.
36. Which of the following pairs of compounds are chain isomers?
A. Propanol and Propanone
B. Butanal and 2-Methylpropanal
C. Butane and 2-Methylpropane
D. 2-Butene and 1-Butene
Answer: C. Butane and 2-Methylpropane
Explanation:
Chain isomers have the same molecular formula but differ in the arrangement of the carbon chain. Butane and 2-Methylpropane have the same molecular formula (C₄H₁₀) but different carbon chain structures.
37. Which of the following will undergo electrophilic aromatic substitution fastest?
A. Nitrobenzene
B. Benzene
C. Toluene
D. Chlorobenzene
Answer: C. Toluene
Explanation:
Toluene contains a methyl group, which is electron-donating and activates the benzene ring towards electrophilic substitution, making toluene more reactive than benzene and the other compounds.
38. Which of the following reactions is an example of an anti-Markovnikov addition?
A. Addition of HBr to propene in the presence of peroxide
B. Addition of HBr to propene
C. Nitration of benzene
D. Dehydration of alcohols
Answer: A. Addition of HBr to propene in the presence of peroxide
Explanation:
In the presence of peroxides, HBr adds to alkenes via the anti-Markovnikov rule (peroxide effect), where the bromine attaches to the less substituted carbon of the double bond.
39. The IUPAC name of the compound CH₃CH₂CH₂COOH is:
A. Propanoic acid
B. Butanoic acid
C. Pentanoic acid
D. 2-Butanoic acid
Answer: B. Butanoic acid
Explanation:
The compound contains a carboxylic acid group (-COOH) attached to a four-carbon chain, making the correct name butanoic acid.
40. Which of the following compounds shows both geometrical and optical isomerism?
A. 2-Butene
B. 2-Butanol
C. 3-Methylpent-2-ene
D. Butanal
Answer: C. 3-Methylpent-2-ene
Explanation:
3-Methylpent-2-ene exhibits geometrical isomerism due to the double bond and optical isomerism due to the presence of a chiral center at carbon 3.
41. Which of the following reactions occurs via a free radical mechanism?
A. Halogenation of alkanes
B. Addition of HBr to propene
C. Nitration of benzene
D. Esterification of alcohols
Answer: A. Halogenation of alkanes
Explanation:
The halogenation of alkanes proceeds via a free radical mechanism involving the generation of halogen radicals and their propagation through the reaction.
42. Which of the following is the correct order of reactivity towards nucleophilic substitution (SN1)?
A. Methyl > Ethyl > Isopropyl > Tert-butyl
B. Tert-butyl > Isopropyl > Ethyl > Methyl
C. Ethyl > Methyl > Tert-butyl > Isopropyl
D. Methyl > Tert-butyl > Isopropyl > Ethyl
Answer: B. Tert-butyl > Isopropyl > Ethyl > Methyl
Explanation:
The stability of the carbocation formed determines the reactivity in the SN1 mechanism. Tertiary carbocations are more stable than secondary, followed by primary and methyl carbocations.
43. Which of the following undergoes nucleophilic addition?
A. Benzene
B. Propanal
C. Ethene
D. 1-Butyne
Answer: B. Propanal
Explanation:
Carbonyl compounds like aldehydes (propanal) undergo nucleophilic addition reactions because the carbonyl carbon is electrophilic and susceptible to nucleophilic attack.
44. Which of the following reactions is an example of a condensation reaction?
A. Dehydration of alcohols
B. Hydrolysis of esters
C. Aldol reaction
D. Hydrogenation of alkenes
Answer: C. Aldol reaction
Explanation:
The Aldol reaction is a condensation reaction where two aldehydes or ketones combine, with the elimination of a small molecule, often water.
45. Which of the following exhibits tautomerism?
A. Propanal
B. Propanone
C. Butanal
D. 2-Pentanone
Answer: B. Propanone
Explanation:
Keto-enol tautomerism occurs in carbonyl compounds, including ketones like propanone, where the keto form is in equilibrium with the enol form.
46. Which of the following compounds exhibits meso isomerism?
A. 2,3-Dibromobutane
B. 2,3-Dichloropentane
C. 2-Butene
D. Propanoic acid
Answer: A. 2,3-Dibromobutane
Explanation:
Meso compounds have a plane of symmetry and are optically inactive despite having chiral centers. 2,3-Dibromobutane has two chiral centers but a plane of symmetry, making it a meso compound.
47. Which of the following is the most stable carbocation?
A. Methyl carbocation (CH₃⁺)
B. Ethyl carbocation (CH₃CH₂⁺)
C. Isopropyl carbocation (CH₃CH⁺CH₃)
D. Tert-butyl carbocation [(CH₃)₃C⁺]
Answer: D. Tert-butyl carbocation [(CH₃)₃C⁺]
Explanation:
The stability of carbocations increases with the number of alkyl groups attached to the positively charged carbon atom due to hyperconjugation and the inductive effect. The tertiary carbocation (tert-butyl) is the most stable.
48. Which of the following reactions proceeds via a carbocation intermediate?
A. SN1 reaction
B. SN2 reaction
C. E2 reaction
D. Free radical halogenation
Answer: A. SN1 reaction
Explanation:
The SN1 mechanism involves a two-step process where the first step is the formation of a carbocation intermediate, followed by nucleophilic attack.
49. Which of the following compounds undergoes nucleophilic substitution the fastest via the SN2 mechanism?
A. Methyl bromide
B. Ethyl bromide
C. Isopropyl bromide
D. Tert-butyl bromide
Answer: A. Methyl bromide
Explanation:
The SN2 mechanism is favored by less steric hindrance. Methyl bromide, with no bulky groups attached to the carbon bearing the leaving group, undergoes SN2 substitution the fastest.
50. Which of the following reactions follows anti-Markovnikov’s rule?
A. Addition of HBr to propene in the presence of peroxide
B. Addition of HCl to ethene
C. Hydration of propene
D. Addition of HBr to ethene
Answer: A. Addition of HBr to propene in the presence of peroxide
Explanation:
According to the anti-Markovnikov rule, in the presence of peroxides, HBr adds to an alkene in such a way that the bromine atom attaches to the less substituted carbon.
51. Which of the following is the correct IUPAC name for CH₃CH₂COOCH₃?
A. Methyl ethanoate
B. Methyl propanoate
C. Ethyl methanoate
D. Propyl methanoate
Answer: B. Methyl propanoate
Explanation:
The compound is an ester where the alkyl group attached to the oxygen is methyl, and the acid part is propanoic acid, making the name methyl propanoate.
52. Which of the following compounds exhibits cis-trans isomerism?
A. 2-Butene
B. Butane
C. Ethyne
D. 1-Butene
Answer: A. 2-Butene
Explanation:
Cis-trans (geometrical) isomerism occurs due to restricted rotation around a double bond, with different groups attached to the double-bonded carbons. 2-Butene has both cis and trans forms.
53. Which of the following is an example of a nucleophilic substitution reaction?
A. Reaction of methyl chloride with NaOH
B. Hydrogenation of alkenes
C. Nitration of benzene
D. Addition of HCl to ethene
Answer: A. Reaction of methyl chloride with NaOH
Explanation:
The reaction of methyl chloride (CH₃Cl) with NaOH involves the substitution of the chloride ion with a hydroxide ion (OH⁻), a nucleophile, making it a nucleophilic substitution reaction.
54. Which of the following exhibits keto-enol tautomerism?
A. Acetone
B. Benzene
C. Ethanol
D. Methane
Answer: A. Acetone
Explanation:
Keto-enol tautomerism occurs when a compound containing a carbonyl group (such as acetone) is in equilibrium with its enol form, where a hydrogen atom shifts from the alpha carbon to the oxygen.
55. Which of the following is an example of a dehydration reaction?
A. Conversion of ethanol to ethene
B. Hydrolysis of esters
C. Oxidation of alcohols
D. Hydrogenation of alkenes
Answer: A. Conversion of ethanol to ethene
Explanation:
Dehydration is the removal of water (H₂O) from a compound. When ethanol is heated with an acid catalyst, it undergoes dehydration to form ethene and water.
56. Which of the following will undergo nucleophilic substitution the slowest via an SN2 mechanism?
A. Methyl chloride
B. Ethyl chloride
C. Isopropyl chloride
D. Tert-butyl chloride
Answer: D. Tert-butyl chloride
Explanation:
The SN2 mechanism requires backside attack by the nucleophile. Tert-butyl chloride has significant steric hindrance due to three bulky methyl groups, making it the slowest to undergo SN2 substitution.
57. The correct order of reactivity of the following compounds in the SN1 mechanism is:
A. Methyl chloride > Ethyl chloride > Isopropyl chloride > Tert-butyl chloride
B. Tert-butyl chloride > Isopropyl chloride > Ethyl chloride > Methyl chloride
C. Isopropyl chloride > Methyl chloride > Ethyl chloride > Tert-butyl chloride
D. Ethyl chloride > Methyl chloride > Tert-butyl chloride > Isopropyl chloride
Answer: B. Tert-butyl chloride > Isopropyl chloride > Ethyl chloride > Methyl chloride
Explanation:
In the SN1 mechanism, the reactivity is determined by the stability of the carbocation formed. Tertiary carbocations are the most stable, followed by secondary, primary, and methyl carbocations.
58. Which of the following is an example of an electrophilic addition reaction?
A. Addition of HCl to ethene
B. Reaction of methyl chloride with KCN
C. Nitration of benzene
D. Hydrolysis of esters
Answer: A. Addition of HCl to ethene
Explanation:
Electrophilic addition involves the attack of an electrophile on an electron-rich species like an alkene. In the addition of HCl to ethene, the H⁺ (electrophile) adds to the double bond, followed by the chloride ion.
59. Which of the following compounds is optically active?
A. 2-Chlorobutane
B. 1-Chlorobutane
C. 2-Methylpropane
D. 2-Butene
Answer: A. 2-Chlorobutane
Explanation:
Optical activity is exhibited by compounds with a chiral center. 2-Chlorobutane has a carbon atom attached to four different groups, making it chiral and optically active.
60. Which of the following is the major product in the dehydration of 2-methylpropan-2-ol?
A. 2-Methylpropene
B. 1-Butene
C. 2-Butene
D. But-1-yne
Answer: A. 2-Methylpropene
Explanation:
Dehydration of alcohols proceeds via an elimination reaction. According to Zaitsev’s rule, the more substituted alkene is formed as the major product, which in this case is 2-Methylpropene.
61. Which of the following is an example of a free radical substitution reaction?
A. Chlorination of methane
B. Nitration of benzene
C. Addition of HCl to propene
D. Reduction of alkenes
Answer: A. Chlorination of methane
Explanation:
In the chlorination of methane, chlorine radicals are generated, which substitute hydrogen atoms in methane to form chloromethane. This reaction proceeds via a free radical mechanism.
62. Which of the following is a nucleophile?
A. H⁺
B. NO₂⁺
C. OH⁻
D. BF₃
Answer: C. OH⁻
Explanation:
A nucleophile is a species that donates a pair of electrons to form a new covalent bond. OH⁻ (hydroxide ion) is a nucleophile because it has a lone pair of electrons.
63. Which of the following compounds undergoes electrophilic substitution easily?
A. Nitrobenzene
B. Benzene
C. Phenol
D. Chlorobenzene
Answer: C. Phenol
Explanation:
Phenol undergoes electrophilic substitution more easily than benzene because the hydroxyl group (-OH) is electron-donating and activates the ring, making it more reactive toward electrophiles.
64. Which of the following is an example of a rearrangement reaction?
A. Wagner-Meerwein rearrangement
B. Hydrolysis of esters
C. Nitration of benzene
D. Addition of HBr to ethene
Answer: A. Wagner-Meerwein rearrangement
Explanation:
The Wagner-Meerwein rearrangement involves the migration of an alkyl group to stabilize a carbocation intermediate during a reaction, making it a rearrangement reaction.
65. Which of the following is the most reactive in an SN2 reaction?
A. Methyl iodide
B. Ethyl iodide
C. Isopropyl iodide
D. Tert-butyl iodide
Answer: A. Methyl iodide
Explanation:
The SN2 reaction is favored by minimal steric hindrance. Methyl iodide, being the least sterically hindered, reacts the fastest in an SN2 mechanism.
66. Which of the following is an example of geometrical isomerism?
A. But-2-ene
B. Butane
C. Ethyne
D. 2-Butanol
Answer: A. But-2-ene
Explanation:
Geometrical isomerism occurs due to restricted rotation around a double bond. In but-2-ene, the position of the substituents around the double bond gives rise to cis and trans isomers.
67. Which of the following undergoes nucleophilic addition reactions?
A. Aldehydes
B. Benzene
C. Ethene
D. Acetylene
Answer: A. Aldehydes
Explanation:
Aldehydes undergo nucleophilic addition reactions because the carbonyl carbon is electrophilic and can be attacked by nucleophiles.
68. Which of the following compounds shows optical isomerism?
A. 2-Chloropropane
B. 2-Bromobutane
C. 2-Butene
D. Cyclohexane
Answer: B. 2-Bromobutane
Explanation:
Optical isomerism occurs when a molecule has a chiral center. 2-Bromobutane has a chiral carbon attached to four different groups, making it optically active.
69. Which of the following is the correct order of stability of carbocations?
A. Methyl < Ethyl < Isopropyl < Tert-butyl
B. Tert-butyl < Isopropyl < Ethyl < Methyl
C. Methyl < Tert-butyl < Ethyl < Isopropyl
D. Isopropyl < Methyl < Ethyl < Tert-butyl
Answer: A. Methyl < Ethyl < Isopropyl < Tert-butyl
Explanation:
Carbocation stability increases with the number of alkyl groups attached to the positively charged carbon. Tertiary (tert-butyl) carbocations are more stable than secondary (isopropyl), primary (ethyl), and methyl carbocations.
70. Which of the following reactions is an example of Markovnikov’s rule?
A. Addition of HCl to propene
B. Addition of HBr to propene in the presence of peroxide
C. Free radical halogenation
D. Oxidation of alkenes
Answer: A. Addition of HCl to propene
Explanation:
Markovnikov’s rule states that in the addition of HX to an unsymmetrical alkene, the hydrogen atom bonds to the carbon with more hydrogen atoms (the less substituted carbon), and the halide bonds to the more substituted carbon.
71. Which of the following compounds will undergo nucleophilic substitution most easily?
A. Methyl bromide
B. Ethyl bromide
C. Isopropyl bromide
D. Tert-butyl bromide
Answer: A. Methyl bromide
Explanation:
In the SN2 mechanism, nucleophilic substitution occurs more easily with less steric hindrance. Methyl bromide, being the least sterically hindered, undergoes substitution most easily.
72. Which of the following is an example of a condensation reaction?
A. Aldol reaction
B. Hydrogenation of alkenes
C. Nitration of benzene
D. Oxidation of alcohols
Answer: A. Aldol reaction
Explanation:
In the Aldol reaction, two carbonyl compounds combine to form a β-hydroxy ketone or aldehyde, with the elimination of water, making it a condensation reaction.
73. Which of the following is the major product in the reaction of propene with HBr in the absence of peroxides?
A. 1-Bromopropane
B. 2-Bromopropane
C. Propanol
D. 2-Bromobutane
Answer: B. 2-Bromopropane
Explanation:
According to Markovnikov’s rule, in the absence of peroxides, the bromine atom will add to the more substituted carbon (the carbon with fewer hydrogen atoms), forming 2-bromopropane.
74. Which of the following undergoes an E2 elimination reaction?
A. 2-Bromopropane with KOH in ethanol
B. Ethyl chloride with NaOH in water
C. Benzyl chloride with NaCN
D. Chloromethane with NH₃
Answer: A. 2-Bromopropane with KOH in ethanol
Explanation:
The reaction of 2-bromopropane with KOH in ethanol undergoes an E2 elimination mechanism, resulting in the formation of propene.
75. Which of the following is an electrophilic addition reaction?
A. Addition of HCl to ethene
B. Nitration of benzene
C. Reduction of alkenes
D. Free radical chlorination
Answer: A. Addition of HCl to ethene
Explanation:
In the addition of HCl to ethene, the electrophilic hydrogen ion (H⁺) adds to the double bond, followed by the nucleophilic attack of chloride ion (Cl⁻), making it an electrophilic addition reaction.
76. Which of the following compounds exhibits geometrical isomerism?
A. 2-Butene
B. Ethane
C. 1-Butanol
D. Benzene
Answer: A. 2-Butene
Explanation:
Geometrical isomerism arises due to restricted rotation around a double bond. In 2-butene, the arrangement of the substituents around the double bond leads to cis and trans isomers.
77. Which of the following compounds is the most acidic?
A. Acetic acid
B. Ethanol
C. Methane
D. Ethene
Answer: A. Acetic acid
Explanation:
Acetic acid is a carboxylic acid, and the -COOH group donates a proton (H⁺), making it more acidic than alcohols (ethanol), hydrocarbons (methane), or alkenes (ethene).
78. Which of the following will undergo SN1 reaction most readily?
A. Methyl bromide
B. Ethyl bromide
C. Isopropyl bromide
D. Tert-butyl bromide
Answer: D. Tert-butyl bromide
Explanation:
The SN1 reaction mechanism proceeds via the formation of a carbocation intermediate. Tert-butyl bromide forms a stable tertiary carbocation, making it the most reactive in SN1 reactions.
79. Which of the following is the most basic compound?
A. Aniline
B. Ammonia
C. Methylamine
D. Dimethylamine
Answer: D. Dimethylamine
Explanation:
Basicity in amines increases with the electron-donating effects of alkyl groups. Dimethylamine, having two methyl groups, is more basic than ammonia, methylamine, and aniline.
80. Which of the following compounds exhibits both geometrical and optical isomerism?
A. 2-Butene
B. 2-Chlorobutane
C. 1,2-Dichlorocyclopropane
D. 1,3-Butadiene
Answer: C. 1,2-Dichlorocyclopropane
Explanation:
1,2-Dichlorocyclopropane exhibits both geometrical isomerism (cis-trans) due to restricted rotation in the ring and optical isomerism if the compound has non-superimposable mirror images.
81. Which of the following undergoes nucleophilic substitution via the SN2 mechanism most easily?
A. Tert-butyl chloride
B. Isopropyl chloride
C. Ethyl chloride
D. Methyl chloride
Answer: D. Methyl chloride
Explanation:
The SN2 mechanism requires a backside attack by a nucleophile, which is easier when steric hindrance is minimal. Methyl chloride, having no bulky groups, undergoes SN2 substitution most easily.
82. Which of the following is a major product in the oxidation of 2-propanol?
A. Propanal
B. Acetone
C. Propanoic acid
D. Methane
Answer: B. Acetone
Explanation:
The oxidation of a secondary alcohol, such as 2-propanol, produces a ketone. In this case, acetone is formed as the major product.
83. Which of the following is an electrophile in the nitration of benzene?
A. H₂SO₄
B. NO₂⁺
C. HNO₃
D. SO₃
Answer: B. NO₂⁺
Explanation:
In the nitration of benzene, the nitronium ion (NO₂⁺) acts as the electrophile, attacking the electron-rich benzene ring to form nitrobenzene.
84. Which of the following reactions is an example of an elimination reaction?
A. Dehydration of ethanol to ethene
B. Hydrogenation of alkenes
C. Nitration of benzene
D. Hydrolysis of esters
Answer: A. Dehydration of ethanol to ethene
Explanation:
Elimination reactions involve the removal of atoms or groups from adjacent carbon atoms, forming a double bond. Dehydration of ethanol leads to the formation of ethene and water, making it an elimination reaction.
85. Which of the following is an optically active compound?
A. 2-Chlorobutane
B. 1-Chlorobutane
C. 2-Butene
D. Benzene
Answer: A. 2-Chlorobutane
Explanation:
Optical activity arises from chirality, where a compound has a carbon atom attached to four different groups. 2-Chlorobutane has such a chiral carbon, making it optically active.
86. Which of the following reagents is used for the oxidation of a primary alcohol to an aldehyde?
A. PCC (Pyridinium chlorochromate)
B. KMnO₄
C. H₂SO₄
D. NaBH₄
Answer: A. PCC (Pyridinium chlorochromate)
Explanation:
PCC is a selective oxidizing agent that oxidizes primary alcohols to aldehydes without further oxidation to carboxylic acids.
87. Which of the following undergoes nucleophilic addition reactions most readily?
A. Benzene
B. Ethene
C. Formaldehyde
D. Methane
Answer: C. Formaldehyde
Explanation:
Aldehydes, especially formaldehyde, undergo nucleophilic addition reactions readily due to the partial positive charge on the carbonyl carbon, making it susceptible to attack by nucleophiles.
88. Which of the following exhibits cis-trans isomerism?
A. 2-Butene
B. Propane
C. 2-Propanol
D. 1-Chloropropane
Answer: A. 2-Butene
Explanation:
Cis-trans (geometrical) isomerism occurs in alkenes with restricted rotation around a double bond. 2-Butene has both cis and trans forms due to the arrangement of groups around the double bond.
89. Which of the following is the correct IUPAC name for CH₃CH₂COCH₃?
A. Propanone
B. Butanone
C. 2-Propanol
D. 3-Butanol
Answer: B. Butanone
Explanation:
The compound is a four-carbon ketone where the carbonyl group is located on the second carbon. The correct IUPAC name is butanone.
90. Which of the following compounds undergoes free radical halogenation most easily?
A. Methane
B. Ethane
C. Propane
D. Isobutane
Answer: D. Isobutane
Explanation:
Free radical halogenation proceeds more readily with alkanes that can form stable radicals. Isobutane forms a tertiary radical, which is more stable than the radicals formed by methane, ethane, or propane.
91. Which of the following reactions is an example of a reduction reaction?
A. Hydrogenation of ethene to ethane
B. Dehydration of ethanol to ethene
C. Oxidation of ethanol to acetic acid
D. Hydrolysis of esters
Answer: A. Hydrogenation of ethene to ethane
Explanation:
Reduction reactions involve the gain of electrons or hydrogen atoms. In the hydrogenation of ethene, hydrogen is added to the double bond, reducing it to ethane.
92. Which of the following is the major product of the reaction of but-1-ene with HCl?
A. 1-Chlorobutane
B. 2-Chlorobutane
C. Butanol
D. 1,2-Dichlorobutane
Answer: B. 2-Chlorobutane
Explanation:
According to Markovnikov’s rule, the hydrogen atom adds to the carbon with more hydrogen atoms, and the chlorine adds to the more substituted carbon, forming 2-chlorobutane.
93. Which of the following compounds shows optical isomerism?
A. 2-Bromobutane
B. 1-Bromobutane
C. 2-Butene
D. Cyclohexane
Answer: A. 2-Bromobutane
Explanation:
Optical isomerism occurs when a molecule has a chiral center. 2-Bromobutane has a chiral carbon atom attached to four different groups, leading to optical isomerism
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