Question 21: Nomenclature
What is the IUPAC name for CH₃-CH(Br)-CH₂-CH₃?
A) 1-Bromobutane
B) 2-Bromobutane
C) 3-Bromobutane
D) Bromobutane
Answer: B) 2-Bromobutane
Explanation:
Number the longest chain to give the substituent the lowest possible number. The bromine is on the second carbon, so the name is 2-Bromobutane.
Question 22: Physical Properties – Density
Which haloalkane has a density greater than water?
A) CH₃Cl
B) C₂H₅Cl
C) C₃H₇Cl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
Haloalkanes generally have densities greater than water due to the presence of heavy halogen atoms. CH₃Cl (methyl chloride) has a density greater than water.
Question 23: Reactions – Dehydrohalogenation
What is the major product when 2-chloro-2-methylpropane is treated with a strong base?
A) 2-Methylpropene
B) 1-Methylpropene
C) 2,2-Dimethylpropane
D) 1,2-Dimethylpropene
Answer: A) 2-Methylpropene
Explanation:
Treatment with a strong base leads to elimination. 2-Chloro-2-methylpropane forms 2-Methylpropene as the major product due to the formation of the more stable tertiary alkene.
Question 24: Properties – Reactivity
Which of the following factors does NOT affect the reactivity of haloalkanes in nucleophilic substitution reactions?
A) Nature of the carbon atom bonded to the halogen
B) Strength of the C-X bond
C) Solvent used
D) Color of the haloalkane
Answer: D) Color of the haloalkane
Explanation:
Reactivity in SN reactions is influenced by the carbon’s substitution (primary, secondary, tertiary), the C-X bond strength, and the solvent type. Color has no effect on reactivity.
Question 25: Nomenclature – Multiple Halogens
What is the IUPAC name for CH₃-CHCl-CHCl-CH₃?
A) 2,3-Dichlorobutane
B) 2,2-Dichlorobutane
C) 1,3-Dichlorobutane
D) 1,2-Dichlorobutane
Answer: A) 2,3-Dichlorobutane
Explanation:
Number the chain to assign the lowest numbers to the substituents. Chlorines are on the 2nd and 3rd carbons, hence 2,3-Dichlorobutane.
Question 26: Reactions – Radical Halogenation
Which haloalkane is formed predominantly when methane undergoes bromination?
A) Chloromethane
B) Bromomethane
C) Methyl chloride
D) No reaction occurs
Answer: B) Bromomethane
Explanation:
When methane undergoes bromination (a radical substitution), bromomethane (CH₃Br) is formed.
Question 27: Physical Properties – Intermolecular Forces
Which haloalkane exhibits hydrogen bonding?
A) CH₃Cl
B) CH₃CH₂Br
C) (CH₃)₂CHCl
D) (CH₃)₃CCl
Answer: A) CH₃Cl
Explanation:
Hydrogen bonding occurs when hydrogen is bonded to highly electronegative atoms like chlorine. CH₃Cl can engage in hydrogen bonding due to the C-Cl bond.
Question 28: Reactions – Substitution Specificity
Which haloalkane is least likely to undergo nucleophilic substitution under standard conditions?
A) CH₃Br
B) CH₃CH₂Br
C) (CH₃)₂CHBr
D) (CH₃)₃CBr
Answer: D) (CH₃)₃CBr
Explanation:
(CH₃)₃CBr (tert-Butyl bromide) is a tertiary haloalkane that favors elimination over substitution due to steric hindrance, making it least likely to undergo nucleophilic substitution.
Question 29: Nomenclature – Aromatic Substituents
What is the IUPAC name for a benzene ring substituted with two bromine atoms at the 1st and 3rd positions?
A) 1,2-Dibromobenzene
B) 1,3-Dibromobenzene
C) 1,4-Dibromobenzene
D) 2,3-Dibromobenzene
Answer: B) 1,3-Dibromobenzene
Explanation:
Two substituents at positions 1 and 3 on a benzene ring are referred to as 1,3-Dibromobenzene.
Question 30: Reactions – Electrophilic Substitution
Which of the following is a product when chlorobenzene undergoes nitration?
A) Nitrochlorobenzene
B) Chloronitromethane
C) 1,4-Dichlorobenzene
D) 1,3-Dinitrobenzene
Answer: A) Nitrochlorobenzene
Explanation:
Nitration of chlorobenzene introduces a nitro group to form Nitrochlorobenzene through electrophilic aromatic substitution.
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