Free NEET Chemistry multiple-choice questions on Aromatic Hydrocarbons. Attempt each question and reveal the answer with a full explanation.
Which property of benzene is not explained by the Kekule structure? Resistance to addition reactions Existence of three double bonds Formation of one monosubstituted product Combustibility The major product formed by the nitration of nitrobenzene with a mixture of concentrated H 2SO 4 and HNO 3 is: m -dinitrobenzene o -dinitrobenzene p -dinitrobenzene 1,3,5-trinitrobenzene The number of chlorine atoms present in the organic products X and Y of the following reactions, respectively, are : 3 and 3 6 and 6 6 and 3 3 and 6 Predict the product 'C' in the following series of reactions: Ethyne [tube] Red hot Fe A [Anhyd. AlCl 3] CH 3Cl B [KMnO 4] OH -, Δ C Benzoic acid Benzaldehyde Toluene Benzene The ozonolysis of an aromatic compound 'X' followed by treatment with Zn/H 2O yields glyoxal, methylglyoxal, and dimethylglyoxal in a 1:1:1 molar ratio. Compound 'X' is: o-Xylene m-Xylene p-Xylene Ethylbenzene The Birch reduction of toluene using Na in liquid NH 3 and C 2H 5OH yields: 1-Methyl-1,4-cyclohexadiene Methylcyclohexane 1-Methyl-1,3-cyclohexadiene p-Xylene When benzene is treated with n-propyl chloride in the presence of anhydrous AlCl 3 , the major product formed is: Isopropylbenzene n-Propylbenzene Ethylbenzene Chlorobenzene The Birch reduction of anisole (methoxybenzene) using Na/liq. NH 3 and ethanol produces: 1-methoxycyclohexa-1,4-diene 1-methoxycyclohexa-1,3-diene Methoxycyclohexane Benzene Nitration of propane in the vapor phase at 400-500 C yields: A mixture of 1-nitropropane, 2-nitropropane, nitroethane, and nitromethane Only 2-nitropropane Only 1-nitropropane A mixture of 1-nitropropane and 2-nitropropane only Ozonolysis of o -xylene (1,2-dimethylbenzene) followed by treatment with Zn/H 2O yields a mixture of: Glyoxal, Methylglyoxal, and Dimethylglyoxal Glyoxal and Methylglyoxal only Methylglyoxal and Dimethylglyoxal only Glyoxal only What is the major product when neopentyl chloride is reacted with benzene in the presence of anhydrous AlCl 3 ? 2-Methyl-2-phenylbutane Neopentylbenzene tert-Butylbenzene Isobutylbenzene When n -butyl chloride reacts with benzene in the presence of anhydrous AlCl 3 , the major product is: sec -Butylbenzene n -Butylbenzene tert -Butylbenzene Isobutylbenzene Sodium benzoate on heating with soda lime ( NaOH + CaO ) gives: Benzene Toluene Benzoic acid Phenol When benzene is reacted with isobutyl chloride in the presence of anhydrous AlCl 3 , the major product is: t-butylbenzene isobutylbenzene n-butylbenzene sec-butylbenzene Which of the following is an aromatic annulene? [14]-Annulene [8]-Annulene [10]-Annulene (all-cis) [4]-Annulene Friedel-Crafts alkylation of aniline is generally not possible because: Aniline forms a salt with the AlCl 3 catalyst The amino group is meta-directing Aniline is too volatile The AlCl 3 catalyst is deactivated by oxygen Which of the following five-membered heterocycles is most aromatic? Thiophene Pyrrole Furan Cyclopentadiene The reaction of benzene with cyclopropane in the presence of anhydrous AlCl 3 yields: n -propylbenzene Isopropylbenzene Cyclopropylbenzene No reaction Consider the following compounds/species: i. ii. iii. iv. v. vi. vii. The number of compounds/species which obey Huckel’s rule is . 4 6 2 5 The reaction of chlorobenzene with methyl chloride in the presence of sodium and dry ether to form toluene is known as: Wurtz-Fittig reaction Fittig reaction Wurtz reaction Friedel-Crafts reaction In benzene, the C-C bond length is: Intermediate between C-C and C=C Same as in ethane Same as in ethene Longer than in ethane When 1,3,5-trimethylbenzene is formed by the polymerization of propyne, the reaction conditions are: Red hot iron tube HgSO 4 / H 2SO 4 Liquid NH 3 / NaNH 2 Anhydrous AlCl 3 The reaction of toluene with Cl 2 in the presence of FeCl 3 gives 'X', while the reaction of toluene with Cl 2 in the presence of light gives 'Y'. 'X' and 'Y' are: X = o- and p-chlorotoluene, Y = Benzyl chloride X = Benzyl chloride, Y = o- and p-chlorotoluene X = m-chlorotoluene, Y = Benzyl chloride X = o- and p-chlorotoluene, Y = m-chlorotoluene Among the following, the compound that is MOST reactive towards electrophilic nitration is: Toluene Benzene Chlorobenzene Nitrobenzene The product formed when benzene reacts with Cl 2 in the presence of ultra-violet light is: Benzene hexachloride Chlorobenzene 1,2-Dichlorobenzene Hexachlorobenzene The reaction of benzene with methyl chloride in the presence of anhydrous AlCl 3 is an example of: Electrophilic substitution Nucleophilic substitution Electrophilic addition Free radical substitution Which of the following is an electrophile in the nitration of benzene? NO 2 + NO 2 - NO 3 - NO + Which among the following is not an aromatic compound? Cyclooctatetraene Benzene Anthracene Pyridine In Friedel-Crafts reactions, anhydrous AlCl 3 acts as a Lewis acid to: Generate the electrophile by accepting a lone pair from the halogen Activate the benzene ring toward nucleophilic attack Act as a solvent for the aromatic substrate Absorb the HCl gas produced during the reaction The C-C bond order in benzene is 1.5. This implies that: All C-C bonds are identical and intermediate in length between single and double bonds Benzene contains three single and three double bonds that alternate very rapidly The carbon atoms are sp 3 hybridized The molecule is non-planar to accommodate partial double bonds The function of FeBr 3 in the bromination of benzene is to: Generate Br + electrophile Activate the benzene ring Absorb HBr formed Act as a reducing agent Benzene can be conveniently prepared from phenol by: Distillation with Zinc dust Reaction with NaNH 2 Reduction with LiAlH 4 Reaction with KMnO 4 In the nitration of toluene, the major product is a mixture of ortho and para-nitrotoluene because the methyl group is: Activating and ortho-para directing Deactivating and meta directing Activating and meta directing Deactivating and ortho-para directing Which of the following catalysts is used for the aromatization of n -hexane to benzene? Cr 2O 3/Al 2O 3 at 773 K V 2O 5 at 500 K Ni at 500 K Zn/HCl The -OCH 3 group in anisole directs the incoming electrophile to: Ortho and para positions Meta position only Ortho position only Para position only When benzene is treated with Cl 2 in the presence of anhydrous AlCl 3 , the reaction is: Electrophilic substitution Nucleophilic substitution Free radical substitution Electrophilic addition Vigorous oxidation of p -xylene (1,4-dimethylbenzene) with acidic KMnO 4 yields: Terephthalic acid Isophthalic acid Phthalic acid Benzoic acid How many sp 2 hybridized carbon atoms are present in the molecule of Naphthalene? 10 8 12 6 Which of the following groups is meta-directing in electrophilic aromatic substitution? -NO 2 -NH 2 -OH -OCH 3 The presence of which group on the benzene ring decreases the reactivity towards electrophilic substitution and directs the incoming group to the meta position? -CN -NH 2 -OCH 3 -Cl The order of decreasing reactivity towards an electrophilic reagent, for the following would be (i) benzene (ii) toluene (iii) chlorobenzene (iv) phenol (ii) > (iv) > (i) > (iii) (iv) > (iii) > (ii) > (i) (iv) > (ii) > (i) > (iii) (i) > (ii) > (iii) > (iv) Benzene reacts with CH 3Cl in the presence of anhydrous AlCl 3 to form - Xylene Toluene Chlorobenzene Benzylchloride Nitrobenzene on reaction with conc. HNO3 / H2SO4 at 80 - 100 C forms which one of the following products? 1, 2-Dinitrobenzene 1, 3-Dinitrobenzene 1, 4-Dinitrobenzene 1, 2, 4-Trinitrobenzene Some meta-directing substituents in aromatic substitution are given. Which one is most deactivating? - C N - SO3H - COOH - NO2 Which of the following compounds will not undergo Friedel-Craft's reaction easily? Cumene Xylene Nitrobenzene Toluene Amongst the following compounds the one which is most easily sulphonated is Chlorobenzene Benzene Nitro benzene Toluene Which one of the following reactions does NOT give benzene as the product? Identify the compound that will react most readily in an electrophilic substitution reaction: Phenol Nitrobenzene Benzene Toluene Which one is the most reactive towards electrophilic nitration? Toluene Benzene Nitrobenzene Benzoic acid Which species is the actual nitrating agent in the nitration of benzene with a mixture of conc. H 2SO 4 and conc. HNO 3 ? NO 2 + NO 2 NO 3 - HNO 2 Which of the following compounds is not aromatic according to Huckel's rule? Cycloheptatriene Benzene Pyrrole Cyclopentadienyl anion The product of the reaction between benzene and CH 3COCl in the presence of anhydrous AlCl 3 is: Acetophenone Benzophenone Chlorobenzene Toluene n -Hexane on heating with Cr 2O 3 at 773 K and 10-20 atm pressure gives: Benzene Cyclohexane Toluene Hexene The reaction of n -heptane with Cr 2O 3/Al 2O 3 at 773 K and 10-20 atm pressure primarily yields: Toluene Benzene Xylene Ethylbenzene Which of the following is the correct order of reactivity towards electrophilic substitution? Benzene > Nitrobenzene > Chlorobenzene Benzene > Chlorobenzene > Nitrobenzene Nitrobenzene > Chlorobenzene > Benzene Chlorobenzene > Benzene > Nitrobenzene When benzene is treated with an excess of Cl 2 in the presence of anhydrous AlCl 3 in the dark, the product is: Hexachlorobenzene Benzene hexachloride (BHC) Chlorobenzene 1,2-Dichlorobenzene Identify the aromatic species among the following: Cyclopentadienyl anion Cycloheptatrienyl cation (Tropylium ion) Benzene All of these What is the product of the reaction between toluene and CrO 2Cl 2 followed by hydrolysis? Benzaldehyde Benzoic acid Benzyl alcohol Acetophenone The reaction of benzene with Cl 2 in the presence of UV light yields: C 6H 6Cl 6 C 6Cl 6 C 6H 5Cl C 6H 4Cl 2 During the electrolysis of an aqueous solution of sodium acetate ( CH 3COONa ), the gas evolved at the anode is: Ethane and Carbon dioxide Methane and Carbon dioxide Ethane and Hydrogen Methane and Oxygen In the following reaction: C 6H 6 + Cl 2 FeCl 3 X , 'X' is: Chlorobenzene Benzene hexachloride m-Dichlorobenzene Benzyl chloride What is the product formed when benzene reacts with ozone followed by treatment with Zn/H 2O ? Glyoxal Oxalic acid Succinic acid Benzene triozonide Which of the following species is non-aromatic? Cycloheptatriene Benzene Cyclopentadienyl anion Tropylium cation The treatment of benzene with V 2O 5 at 773 K yields: Maleic anhydride Benzoic acid Phenol Cyclohexane When propyne is passed through a red-hot iron tube, the cyclic trimerization product is: Mesitylene Benzene Toluene Ethylbenzene Which of the following electrophilic aromatic substitution reactions is considered reversible? Sulfonation Nitration Chlorination Friedel-Crafts Alkylation Trans-2-butene has a higher melting point than cis-2-butene because: Trans-isomer is more symmetrical and fits better into the crystal lattice Trans-isomer has a higher dipole moment Cis-isomer is more stable Trans-isomer has higher boiling point Regarding the aromaticity of pyridine, which statement is true? It is aromatic with 6 electrons, and the lone pair on Nitrogen is not part of the aromatic system It is aromatic with 8 electrons It is non-aromatic because of the Nitrogen atom The lone pair on Nitrogen is involved in the delocalized -cloud The resonance energy of benzene is approximately: 36 kcal/mol 150.6 kJ/mol Both A and B 20 kcal/mol The electrophile involved in the Friedel-Crafts acylation of benzene is: Acylium ion Alkyl carbocation Nitronium ion Chloronium ion Which of the following reactants will not produce an alkane upon heating with soda lime? Sodium formate Sodium acetate Sodium propionate Sodium benzoate Catalytic hydrogenation of benzene in the presence of Nickel at 473-523 K gives: Cyclohexane n-Hexane Cyclohexene 1,3-Cyclohexadiene Identify the aromatic species among the following ions: Cycloheptatrienyl cation Cyclopentadienyl cation Cyclooctatetraene Cyclopropenyl anion Nitration of which of the following compounds is the most difficult? Nitrobenzene Toluene Benzene Chlorobenzene The melting point of benzene is higher than that of toluene because: Benzene has a more symmetrical structure Benzene has a higher molecular weight Toluene is more polar Benzene has more electrons Which of the following is an anti-aromatic compound? 1,3-Cyclobutadiene Benzene Cyclooctatetraene Naphthalene Which of the following will react most slowly in an electrophilic nitration reaction? Benzoic acid Benzene Toluene Phenol Aromaticity is characterized by a high resonance energy. Which of the following has the highest resonance energy per ring? Benzene Naphthalene Anthracene Phenanthrene The compound C 7H 8 on treatment with Cl 2/FeCl 3 gives 'A' and with Cl 2/heat gives 'B'. 'B' on hydrolysis gives 'C'. If 'A' is o-chlorotoluene, then 'C' is: Benzyl alcohol Benzaldehyde Benzoic acid p-Chlorobenzyl alcohol Which of the following is produced when a mixture of calcium acetate and calcium formate is dry distilled? Acetaldehyde Acetone Formaldehyde Acetic acid The compound that is anti-aromatic among the following is: 1,3-Cyclobutadiene Cyclopentadienyl anion Tropylium cation Benzene The product 'P' in the following reaction is: Ethylbenzene [2. H 3O +] 1. KMnO 4, KOH, P Benzoic acid Acetophenone Benzyl alcohol Benzaldehyde Which of the following is used as a catalyst in Friedel-Crafts reaction? Anhydrous AlCl 3 Pd/BaSO 4 V 2O 5 TiCl 4 The Tropylium cation ( C 7H 7 + ) is considered highly stable and aromatic because: It is cyclic, planar, and contains 6 electrons following Huckel's rule It contains 7 electrons in a conjugated system It is a non-planar molecule that minimizes angle strain It has 8 electrons but is anti-aromatic The rate-determining step in the electrophilic aromatic substitution of benzene is: The formation of the sigma-complex (arenium ion) The generation of the electrophile The loss of a proton from the sigma-complex The attack of the nucleophile on the electrophile How many electrons are present in the aromatic molecule Anthracene? 14 10 12 16 The Gattermann-Koch reaction is used for the synthesis of benzaldehyde from benzene using which set of reagents? CO + HCl in the presence of anhydrous AlCl 3/CuCl CO 2 + HCl in the presence of anhydrous AlCl 3 CHCl 3 + KOH CH 3Cl + AlCl 3 Which of the following electrophilic aromatic substitution reactions is notably reversible under standard laboratory conditions? Sulphonation Nitration Chlorination Friedel-Crafts Acylation Nitration of isopropylbenzene (cumene) with HNO 3/H 2SO 4 yields which major product? p-nitroisopropylbenzene o-nitroisopropylbenzene m-nitroisopropylbenzene 2,4,6-trinitroisopropylbenzene In the sulfonation of benzene, the actual electrophile that attacks the benzene ring is: SO 3 HSO 3 + SO 2 H 2SO 4 The cyclopropenyl cation is: Aromatic Anti-aromatic Non-aromatic Aliphatic Nitration of aniline in a strongly acidic medium gives a significant amount of m-nitroaniline because: In acidic medium, aniline is converted to the meta-directing anilinium ion The -NH 2 group becomes meta-directing in the presence of H 2SO 4 The nitro group preferentially attacks the meta position Aniline undergoes rearrangement during the reaction The order of reactivity of the following towards electrophilic substitution is: (I) Benzene, (II) Toluene, (III) Chlorobenzene, (IV) Nitrobenzene. II > I > III > IV I > II > III > IV II > I > IV > III IV > III > I > II The conversion of benzene to benzaldehyde by CO and HCl in the presence of anhydrous AlCl 3/CuCl is known as: Gattermann-Koch reaction Etard reaction Wurtz-Fittig reaction Friedel-Crafts acylation The Cyclopentadienyl anion ( C 5H 5 - ) is stable because it is: Aromatic with 6π electrons Non-aromatic Anti-aromatic with 4π electrons Highly substituted The oxidative ozonolysis of naphthalene followed by treatment with KMnO 4 yields: Phthalic acid Benzoic acid Glyoxal Oxalic acid The Birch reduction of benzene ( Na in liquid NH 3 and ethanol) yields: 1,4-cyclohexadiene 1,3-cyclohexadiene Cyclohexane Cyclohexene Which of the following radicals is more stable than the t -butyl radical? Benzyl radical Isopropyl radical Ethyl radical Methyl radical Which of the following compounds will exhibit the highest rate of nitration? Phenol Toluene Benzene Nitrobenzene The catalyst used in the 'Aromatization' of n -heptane to Toluene is: Cr 2O 3/Al 2O 3 V 2O 5 Pd/C Anhydrous AlCl 3 What is the product 'Y' in the following reaction sequence? Benzene + Cl 2 FeCl 3 X Na, Ether Y Biphenyl Chlorobenzene Toluene Cyclohexane Which of the following will not undergo Friedel-Crafts alkylation? Nitrobenzene Toluene Xylene Anisole The enthalpy of hydrogenation of cyclohexene is -119.5 kJ mol -1 . If resonance energy of benzene is -150.4 kJ mol -1 , its enthalpy of hydrogenation would be:- -508.9 kJ mol -1 -208.1 kJ mol -1 -269.9 kJ mol -1 -358.5 kJ mol -1 Nitrobenzene can be prepared from benzene by using a mixture of conc. HNO 3 and conc. H 2SO 4 . In the mixture, nitric acid acts as a/an - catalyst reducing agent acid base According to Huckel's rule, a cyclic, planar, fully conjugated system is aromatic if it contains how many electrons? (4n + 2) 4n (2n + 2) None of these Consider the following reaction : Phenol ->[Zn dust] X ->[CH3Cl][Anhydrous AlCl3] Y ->[Alkaline KMnO4] Z , the product Z is : Benzene Toluene Benzaldehyde Benzoic acid The radical is aromatic because it has 6 p-orbitals and 6 unpaired electrons 7 p-orbitals and 6 unpaired electrons 7 p-orbitals and 7 unpaired electrons 6 p-orbitals and 7 unpaired electrons What products are formed when the following compounds is treated with Br2 in the presence of FeBr3 ? Consider the nitration of benzene using mixed conc. H2SO4 and HNO3 . If a large amount of KHSO4 is added to the mixture, the rate of nitration will be:- faster slower unchanged doubled Identify the major products P, Q and R in the following sequence of reactions: The compound C7H8 undergoes the following reactions: C7H8 ->[3Cl2/ ] A ->[Br2/Fe] B ->[Zn/HCl] C The product 'C' is 3-bromo-2,4,6-trichlorotoluene o-bromotoluene m-bromotoluene p-bromotoluene Among the following, the reaction that proceeds through an electrophilic substitution, is: Identify compound X in the following sequence of reactions The intermediate compound 'X' in the following chemical reaction is: Which compound amongst the following is not an aromatic compound?