Question 101: Reactions – Aromatic Substitution
Which directing group does a chloro substituent on benzene exhibit in electrophilic aromatic substitution?
A) Ortho/Para Director
B) Meta Director
C) Both Ortho and Meta Director
D) Neither Ortho nor Meta Director
Answer: A) Ortho/Para Director
Explanation:
Chlorine is an electron-withdrawing group due to its electronegativity but donates electron density through resonance. Thus, it is an Ortho/Para Director in electrophilic aromatic substitution reactions.
Question 102: Physical Properties – Solvent Effects
Which solvent is most favorable for SN2 reactions of haloalkanes?
A) Water
B) Methanol
C) Acetone
D) Toluene
Answer: C) Acetone
Explanation:
Polar aprotic solvents like acetone stabilize the cations without solvating the nucleophile, thereby enhancing the rate of SN2 reactions. Water and methanol are polar protic and can hinder SN2 by stabilizing the nucleophile, while toluene is non-polar.
Question 103: Reactions – Nucleophilic Aromatic Substitution
Which of the following haloarenes is most reactive towards nucleophilic aromatic substitution?
A) Chlorobenzene
B) 4-Chloronitrobenzene
C) 2-Chlorotoluene
D) 3-Chlorotoluene
Answer: B) 4-Chloronitrobenzene
Explanation:
Electron-withdrawing groups like nitro groups activate haloarenes towards nucleophilic substitution by stabilizing the negative charge in the intermediate. 4-Chloronitrobenzene has a nitro group para to the chlorine, making it highly reactive towards nucleophilic aromatic substitution.
Question 104: Nomenclature – Cyclic Haloalkanes
What is the IUPAC name for cyclohexyl chloride?
A) Chlorocyclohexane
B) Cyclohexane chloride
C) 1-Chlorocyclohexane
D) Both A and C
Answer: D) Both A and C
Explanation:
Both Chlorocyclohexane and 1-Chlorocyclohexane are correct IUPAC names for cyclohexyl chloride, as the chlorine substituent is understood to be at position 1 in a monosubstituted cyclohexane.
Question 105: Reactions – Dehalogenation
Which reagent is used for the dehalogenation of vicinal dihalides to form alkenes?
A) NaOH
B) KOH
C) Zn/Acetic Acid
D) KI in acetone
Answer: C) Zn/Acetic Acid
Explanation:
Zn/Acetic Acid is commonly used to remove vicinal dihalides and form alkenes through dehalogenation. It facilitates the elimination of two halogen atoms from adjacent carbons, resulting in the formation of a double bond.
Question 106: Physical Properties – Vapor Pressure
Which haloalkane has the highest vapor pressure at room temperature?
A) CH₃Cl
B) CH₃CH₂Cl
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
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