- Molecular formula of benzene is:
a) C6H14
b) C6H12
c) C6H6
d) C5H6
Answer: c - Which ratio of carbon:hydrogen led to benzene’s unsaturation prediction?
a) 1:1
b) 2:1
c) 1:1.33
d) 1:1.5
Answer: c - Benzene on catalytic hydrogenation gives:
a) Cyclohexane
b) Cyclohexene
c) Cyclopentane
d) Cyclohexadiene
Answer: a - The number of π-electrons in benzene is:
a) 4
b) 6
c) 8
d) 10
Answer: b - Benzene shows fewer addition reactions than expected because of:
a) Low reactivity
b) Presence of delocalized π-electrons giving extra stability (aromatic character)
c) It is saturated
d) It has sp3 carbons
Answer: b - In Kekulé’s structure, benzene has:
a) Alternating single and double bonds in a hexagon
b) Six single bonds
c) Only π-bonds
d) No bonds
Answer: a - The modern orbital picture of benzene describes:
a) Six sp3 carbons
b) Six sp2 hybrid carbons with delocalized π-electrons above and below the plane
c) Six sp hybrid carbons
d) Ionic bonding
Answer: b - Resonance explains:
a) Only bond breaking
b) Delocalization of electrons producing equal C–C bond lengths in benzene
c) Different bond lengths
d) Single Kekulé structure dominance
Answer: b - Experimentally, all C–C bond lengths in benzene are:
a) Alternating 1.54 and 1.34 Å
b) Equal ~1.39 Å
c) All 1.20 Å
d) Different in each carbon
Answer: b - The heat of hydrogenation of benzene is:
a) Greater than three times cyclohexene
b) Less than three times cyclohexene (due to resonance stabilization)
c) Exactly three times
d) Zero
Answer: b - Hückel’s rule states aromatic compounds must have:
a) 2n electrons
b) 4n electrons
c) 4n+2 π electrons (n = 0,1,2,…)
d) Only 8 electrons
Answer: c - Benzene satisfies Huckel’s rule because it has:
a) 8 π electrons
b) 6 π electrons
c) 4 π electrons
d) 10 π electrons
Answer: b - Aromatic compounds must be:
a) Planar, conjugated, cyclic with (4n+2) π electrons
b) Non-planar
c) Open chain
d) Aliphatic
Answer: a - Resonance energy of benzene is about:
a) 36 kcal/mol
b) 120 kcal/mol
c) 152 kcal/mol
d) 0 kcal/mol
Answer: a - The high stability of benzene is due to:
a) Hyperconjugation
b) Aromatic resonance delocalization
c) Hydrogen bonding
d) Ionic bonds
Answer: b - Benzene undergoes mostly:
a) Addition reactions
b) Substitution reactions
c) Elimination reactions
d) Oxidation only
Answer: b - Nitration of benzene uses:
a) HCl + ZnCl2
b) Conc. HNO3 + conc. H2SO4
c) KMnO4
d) NaOH
Answer: b - The electrophile in nitration is:
a) NO
b) NO2+ (nitronium ion)
c) NO3-
d) NO2 radical
Answer: b - Sulphonation of benzene uses:
a) Fuming H2SO4 (oleum)
b) Conc. HNO3
c) KMnO4
d) NaOH
Answer: a - Electrophile in sulphonation is:
a) SO3
b) SO4-
c) SO2
d) S2-
Answer: a - Halogenation of benzene requires:
a) UV light
b) Lewis acid catalyst like FeCl3 or AlCl3
c) NaOH
d) Heat only
Answer: b - Electrophile in chlorination of benzene is:
a) Cl−
b) Cl2
c) Cl+ (from Cl2 + FeCl3)
d) Cl radical
Answer: c - Friedel–Crafts alkylation uses:
a) Alkyl halide + AlCl3
b) Alcohol + NaOH
c) Alkene + H2O
d) Acid + base
Answer: a - Electrophile in Friedel-Crafts alkylation is:
a) Alkyl radical
b) Alkyl cation (R+) formed in presence of AlCl3
c) Alkyl anion
d) Alkene
Answer: b - Limitation of Friedel-Crafts alkylation:
a) Carbocation rearrangement
b) Polyalkylation
c) Inactive for deactivated rings like nitrobenzene
d) All of the above
Answer: d - Friedel–Crafts acylation uses:
a) Acid chloride + AlCl3
b) Carboxylic acid + H2SO4
c) Ester + base
d) Alkyl halide + NaOH
Answer: a - Product of acylation reaction is:
a) Alcohol
b) Ketone (Ar–CO–R)
c) Aldehyde
d) Ester
Answer: b - Friedel-Crafts acylation avoids:
a) Rearrangement
b) Polyacylation (usually only monoacylation occurs)
c) Both a and b
d) None
Answer: c - Halogenation of benzene is:
a) Electrophilic
b) Nucleophilic
c) Radical
d) Free-radical substitution
Answer: a - Sulphonation is:
a) Reversible
b) Irreversible
c) Combustion
d) Oxidation
Answer: a - The function of AlCl3 in Friedel-Crafts reaction is:
a) Oxidant
b) Lewis acid catalyst to generate carbocations
c) Reducing agent
d) Base
Answer: b - Benzene reacts with CH3Cl and AlCl3 to form:
a) Toluene
b) Benzyl alcohol
c) Chlorobenzene
d) Phenol
Answer: a - Benzene reacts with CH3COCl and AlCl3 to form:
a) Acetophenone
b) Benzaldehyde
c) Toluene
d) Anisole
Answer: a - Nitration of benzene is an example of:
a) Electrophilic aromatic substitution
b) Nucleophilic substitution
c) Radical substitution
d) Elimination
Answer: a - Friedel-Crafts reaction cannot be done on:
a) Nitrobenzene
b) Toluene
c) Chlorobenzene
d) Benzene
Answer: a - Electron-donating groups (EDG) generally:
a) Activate benzene ring and direct new substituents to ortho/para positions
b) Deactivate and direct meta
c) Have no effect
d) Destroy aromaticity
Answer: a - Electron-withdrawing groups (EWG) generally:
a) Activate
b) Deactivate and direct meta
c) Deactivate and direct ortho
d) Activate and direct meta
Answer: b - –NO2 group is:
a) Activating, ortho/para directing
b) Deactivating, meta directing
c) Neutral
d) Activating, meta directing
Answer: b - –OH group is:
a) Activating, ortho/para directing
b) Deactivating, meta
c) Neutral
d) Meta directing
Answer: a - –CH3 group is:
a) Activating, ortho/para directing (inductive +H effect)
b) Deactivating, meta
c) Deactivating, para
d) Deactivating, ortho
Answer: a - –NH2 is:
a) Strong activating, ortho/para directing
b) Deactivating, meta
c) Neutral
d) Deactivating, para
Answer: a - –COOH is:
a) Activating, ortho
b) Deactivating, meta directing
c) Activating, para
d) Neutral
Answer: b - –SO3H group is:
a) Deactivating, meta
b) Activating, ortho
c) Activating, para
d) Neutral
Answer: a - –Cl on benzene is:
a) Deactivating by -I effect but ortho/para directing by lone pair resonance
b) Activating and meta
c) Deactivating and meta
d) Activating and ortho
Answer: a - –NO2 group deactivates the ring because:
a) It donates electrons
b) It withdraws electrons by -I and -M effects reducing electron density
c) It adds protons
d) It increases resonance
Answer: b - –OH activates because:
a) +M effect donates electron density to ring increasing electrophilic attack rate
b) -I withdraws electrons
c) It makes ring acidic
d) It makes it neutral
Answer: a - Orientation means:
a) Where the new group enters during electrophilic aromatic substitution
b) Solubility of benzene
c) Colour of product
d) Number of rings formed
Answer: a - Deactivating meta directors usually contain:
a) Electron withdrawing atoms/groups attached to the ring carbon
b) Alkyl groups
c) Hydroxyl groups
d) Amine groups
Answer: a - Alkyl groups are:
a) Activating ortho/para directors
b) Meta directing
c) Neutral
d) Deactivating
Answer: a - Halogens are special because:
a) Deactivate the ring by -I effect yet ortho/para direct due to lone pair resonance
b) Activate and meta
c) Activate and para
d) Deactivate and meta
Answer: a - DDT stands for:
a) Dichloro diphenyl tetraoxide
b) Dichloro diphenyl trichloroethane
c) Dimethyl diphenyl trichloroethane
d) Dinitro dichloro toluene
Answer: b - DDT is used as:
a) Herbicide
b) Insecticide
c) Fungicide
d) Preservative
Answer: b - BHC (Benzene hexachloride) is prepared by:
a) Chlorination of benzene in UV light
b) Nitration of benzene
c) Hydrogenation of benzene
d) Oxidation of benzene
Answer: a - BHC is used as:
a) Herbicide
b) Insecticide (Lindane)
c) Fertilizer
d) Preservative
Answer: b - Saccharin is:
a) Artificial sweetener (non-nutritive)
b) Pesticide
c) Analgesic
d) Antibiotic
Answer: a - Saccharin is about:
a) 2 times sweeter than sugar
b) 200–500 times sweeter than sugar
c) 10 times sweeter
d) 1000 times sweeter
Answer: b - Chloramine is used as:
a) Sweetener
b) Disinfectant/antiseptic
c) Insecticide
d) Fertilizer
Answer: b - The active species in chloramine’s disinfection is:
a) Cl2 gas
b) Nascent chlorine and hypochlorous acid
c) Ozone
d) Oxygen
Answer: b - BHC has how many Cl atoms?
a) 3
b) 4
c) 6
d) 2
Answer: c - DDT contains how many Cl atoms?
a) 2
b) 3
c) 4
d) 5
Answer: d
Hi…! Currently, I am working as an Professor at Department of Pharmaceutical Chemistry(H.O.D),The Pharmaceutical College, Barpali, Odisha. I have more than 19 years of teaching & research experience in the field of Chemistry & Pharmaceutical sciences.