Free NEET Chemistry multiple-choice questions on Isomerism. Attempt each question and reveal the answer with a full explanation.
Which of the following is the most stable conformation of n-butane? Anti Gauche Eclipsed Partially eclipsed Which method is used to separate a mixture of iodine and sand? Sublimation Distillation Chromatography Filtration The number of structural isomers possible for the molecular formula C 4H 9Cl is: 4 3 5 2 The chirality of the compound is :- E R S Z The order of stability of the following tautomeric compounds is I > II > III III > II > I II > I > III II > III > I Which of the following biphenyls is optically active? Match List-I with List-II array ll List-I & List-II (a) Benzene [ Anhyd. AlCl 3/ CuCl ] CO, HCl & (i) Hell-Volhard-Zelinsky reaction (b) R-CO-CH3 + NaOX & (ii) Gattermann-Koch reaction (c) R-CH2-OH + R'COOH , Conc. H2SO4 & (iii) Haloform reaction (d) R-CH2COOH [(ii) H2O] (i) X2/Red P & (iv) Esterification array Choose the correct answer from the options given below. (a) - (iii), (b) - (ii), (c) - (i), (d) - (iv) (a) - (i), (b) - (iv), (c) - (iii), (d) - (ii) (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i) (a) - (iv), (b) - (i), (c) - (ii), (d) - (iii) The number of structural isomers possible for the molecular formula C 3H 6O is: 9 6 3 5 Which of the following will have the highest enol content? CH 3COCH 2COCH 3 CH 3COCH 3 CH 3CHO CH 3COCH 2COOCH 3 The number of stereoisomers possible for 2,3-dichlorobutane is: 3 2 4 6 The presence of a chiral center is a condition for a molecule to be chiral. Necessary but not sufficient Necessary and sufficient Neither necessary nor sufficient Sufficient but not necessary The specific rotation of a pure enantiomer is +40 . What is the observed rotation of a mixture containing 75 % of this enantiomer and 25 % of its mirror image? +20 +10 +30 0 Which of the following is the most stable conformation of cyclohexane? Chair Boat Twist boat Half-chair Which of the following species is non-aromatic? Cyclooctatetraene Benzene Tropylium cation Cyclopentadienyl anion The specific rotation of a mixture containing 60 % of (+) enantiomer and 40 % of (-) enantiomer is (given [α] for pure (+) enantiomer is +100 ∘ ): +20 ∘ +60 ∘ +100 ∘ 0 ∘ Which of the following describes the 'Gauche' effect in 2-fluoroethanol? The gauche conformation is more stable than the anti conformation due to intramolecular hydrogen bonding. The anti conformation is more stable due to minimum steric hindrance. The eclipsed conformation is most stable due to dipole-dipole attraction. The gauche conformation is less stable due to the electronegativity of Fluorine. According to Bredt's rule, which of the following structures is highly unstable? 1-norbornene 2-norbornene Norbornane Bicyclo[2.2.2]octane The reaction of a singlet carbene with cis-2-butene gives: cis-1,2,3-trimethylcyclopropane trans-1,2,3-trimethylcyclopropane A mixture of cis and trans products Butane How many stereoisomers are possible for 2,3,4-trichloropentane? 4 2 6 8 How many optical isomers are possible for a compound with the formula CH 3CH(OH)CH(OH)CHO ? 4 2 3 8 CH3-CHCl-CH2-CH3 has a chiral centre. which one of the following represents its R-configuration? array c C2H5 | H - C - CH3 | Cl array array c C2H5 | Cl - C - CH3 | H array array c CH3 | H - C - Cl | C2H5 array array c C2H5 | H3C - C - Cl | H array Total number of possible isomers (both structural as well as stereoisomers) of cyclic ethers of molecular formula C4H8O is : 11 6 8 10 The method used for the separation of a mixture of two liquids having boiling points 350 K and 355 K is: Fractional distillation Steam distillation Distillation under reduced pressure Simple distillation The most stable conformation of n-butane is: Anti-staggered Gauche Eclipsed Partially eclipsed Which of the following is a pair of enantiomers? (R)-Lactic acid and (S)-Lactic acid Meso-tartaric acid and d-tartaric acid Acetone and Propanal Maleic acid and Fumaric acid Which type of isomerism is shown by Pentan-2-one and Pentan-3-one? Metamerism Chain isomerism Functional isomerism Geometrical isomerism The R f value in chromatography is defined as: Distance moved by substance / Distance moved by solvent Distance moved by solvent / Distance moved by substance Concentration in mobile phase / Concentration in stationary phase Velocity of substance / Velocity of light The most appropriate method for the purification of a substance which decomposes at its boiling point is: Distillation under reduced pressure Steam distillation Fractional distillation Simple distillation The number of structural isomers for a compound with the molecular formula C 3H 7Cl is: 2 3 4 1 Which type of isomerism is possible for 1-Chlorobutane and 2-Chlorobutane? Position isomerism Chain isomerism Functional isomerism Metamerism Which of the following compounds will exhibit geometrical isomerism? But-2-ene But-1-ene 2-Methylpropene Propene Identify the compound that is a 'meso' compound. meso-Tartaric acid d-Tartaric acid l-Tartaric acid Racemic tartaric acid Which of the following can show geometrical isomerism? But-2-ene Propene But-1-ene 2-Methylpropene Identify the compound that exhibits geometrical isomerism. 2-Butene 2-Methylpropene 1-Butene Propene The dihedral angle of the least stable conformation of ethane is: 0 60 120 180 The separation of a mixture of aniline and water is best carried out by: Steam distillation Fractional distillation Simple distillation Sublimation Which of the following will have the highest boiling point? n-Pentane Isopentane Neopentane n-Butane Which of the following isomers is most stable? trans-but-2-ene cis-but-2-ene but-1-ene 2-methylprop-1-ene The most suitable method for the purification of a mixture of two solids which differ in their solubilities in a particular solvent is: Fractional crystallization Distillation Steam distillation Sublimation Which of the following conformers of n-butane has the highest potential energy? Fully eclipsed Gauche Partially eclipsed Anti-staggered The purification of organic compounds by 'Sublimation' is applicable to those which: Change directly from solid to vapor on heating Are soluble in water Have very high boiling points Are liquids at room temperature The most stable conformation of cyclohexane is: Chair form Boat form Twist-boat form Half-chair form Which of the following is a pair of position isomers? Pentan-2-ol and Pentan-3-ol Pentane and Isopentane Ethanol and Dimethyl ether But-1-ene and But-2-yne What type of isomerism is shown by Diethyl ether and Methyl propyl ether? Metamerism Chain isomerism Functional isomerism Tautomerism Identify the compound that shows geometrical isomerism. But-2-ene But-1-ene 2-methylpropene Propene The dipole moment of trans-1,2-dichloroethene is: Zero 1.5 D 2.0 D Higher than the cis isomer Which of the following molecules contains only sp 2 hybridized carbon atoms? Benzene Ethane Acrylonitrile Propyne A meso compound is one which: Contains chiral centers but is optically inactive due to internal compensation. Contains no chiral centers and is optically inactive. Rotates the plane of polarized light to the left. Is a 1:1 mixture of two enantiomers. Which type of isomerism is exhibited by CH 3CH 2CH 2OH and CH 3CH(OH)CH 3 ? Position isomerism Chain isomerism Functional isomerism Metamerism The separation of a mixture of a solid and a liquid by heating where the solid turns directly into vapor is: Sublimation Distillation Crystallization Filtration Which of the following molecules has the longest C-C bond length? Ethane Ethene Ethyne Benzene The phenomenon of optical activity is shown by: Chiral molecules Acyclic molecules only All organic molecules Symmetrical molecules Which of the following methods is most suitable for the purification of benzoic acid from a mixture containing sand? Sublimation Simple distillation Fractional distillation Crystallization What is the dihedral angle in the 'Gauche' conformation of n-butane? 60° 0° 120° 180° How many chiral centers are present in 2-butanol? 1 0 2 3 The process of separating a racemic mixture into its individual enantiomers is called: Resolution Racemization Inversion Retention Which of the following statements is correct regarding the R f value in paper chromatography? It is the ratio of the distance moved by the substance to the distance moved by the solvent front. It is the ratio of the distance moved by the solvent to the distance moved by the substance. It is always greater than 1. It depends on the volume of the solvent used. Which one of the following pair represents stereo isomerism :- Linkage isomerism and Geometrical isomerism Chain isomerism and Rotational isomerism Optical isomerism and Geometrical isomerism Structural isomerism and Geometrical isomerism Which of the following is not chiral:- 2-Butanol 2,3-Dibromopentane 3-Bromopentane 2-Hydroxypropanoic acid If there is no rotation of plane polarised light by a compound in a specific solvent, though to be chiral, it may mean that the compound is certainly meso there is no compound in the solvent the compound may be a racemic mixture the compound is certainly achiral. Which of the following compounds will exhibit cis - trans (geometrical) isomerism ? 1-Butanol 2-Butene 2-Butanol 2-Butyne The correct statement regarding a carbonyl compound with a hydrogen atom on its alpha-carbon, is :- a carbonyl compound with a hydrogen atom on its alpha-carbon never equilibrates with its corresponding enol. a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as aldehyde-ketone equilibration. a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as carbonylation. a carbonyl compound with a hydrogen atom on its alpha-carbon rapidly equilibrates with its corresponding enol and this process is known as keto-enol tautomerism. The compound which shows metamerism is : C3H8O C3H6O C4H10O C5H12 Which of the following pairs are functional isomers? Ethanol and Methoxymethane Propan-1-ol and Propan-2-ol But-1-ene and But-2-ene Pentane and 2-Methylbutane Dihedral angle of least stable conformer of ethane is : 180 60 0 120 The incorrect statement regarding chirality is The product obtained by S N2 reaction of haloalkane having chirality at the reactive site shows inversion of configuration Enantiomers are superimposable mirror images on each other A racemic mixture shows zero optical rotation S N1 reaction yields 1 : 1 mixture of both enantiomers Which one of the following compounds can exist as cis-trans isomers? 1, 2-Dimethylcyclohexane Pent-1-ene 2-Methylhex-2-ene 1, 1-Dimethylcyclopropane The pair of molecules that are metamers among the following is : CH3OCH2CH2CH2CH3 and CH3CH2OCH2CH3 CH3CH2CH2OH and CH3-CH(OH)-CH3 CH3CH2CH2CH2CH3 and (CH3)2CHCH2CH3 CH3COCH3 and CH3CH2CHO In which of the following molecules all atoms are coplanar? Biphenyl Cyclohexane n-Butane Neopentane Tautomerism is not exhibited by which of the following compounds? Benzaldehyde Acetone Acetaldehyde Nitroethane Which of the following is an aromatic species according to Huckel's rule? Cycloheptatrienyl cation Cyclopentadienyl cation Cyclooctatetraene Cyclohexatriene How many chiral carbons are present in 2,3,4-trichloropentane? 2 3 1 4 Which of the following does NOT show tautomerism? Benzaldehyde Propanal Ethanol Acetone Paper chromatography is an example of: Partition chromatography Adsorption chromatography Thin layer chromatography Column chromatography What is the relationship between Maleic acid and Fumaric acid? Geometrical isomers Enantiomers Position isomers Metamers What is the relationship between the two structures of 1,2-dichloroethene ( cis and trans )? Diastereomers Enantiomers Constitutional isomers Conformers A mixture of o -nitrophenol and p -nitrophenol can be separated by: Steam distillation Crystallization Sublimation Fractional crystallization Which of the following compounds is non-aromatic? Cyclopentadiene Benzene Tropylium cation Naphthalene Which of the following conformers for ethylene glycol is most stable due to intramolecular hydrogen bonding? Gauche Anti Fully eclipsed Partially eclipsed The separation of a mixture of o -nitrophenol and p -nitrophenol is based on: Difference in volatility due to hydrogen bonding Difference in solubility in water Difference in their molecular weights Difference in their chemical reactivity What is the relationship between (2R, 3R)-2,3 -dichlorobutane and (2S, 3S)-2,3 -dichlorobutane? Enantiomers Diastereomers Meso compounds Identical The maximum number of stereoisomers possible for CH 3-CH(OH)-CH=CH-CH 3 is: 4 2 6 8 Which of the following molecules has a dipole moment equal to zero? trans-But-2-ene cis-But-2-ene Chloroform Water Which of the following is an example of an anti-aromatic species? Cyclobutadiene Benzene Cyclooctatetraene Cyclopropenyl cation The number of structural isomers possible for the molecular formula C 4H 10 O is: 7 5 6 4 Which of the following represents the most stable conformation of 1,2-dichloroethane? Anti Gauche Eclipsed Partially eclipsed The correct order of priority for the following groups according to CIP (Cahn-Ingold-Prelog) rules for R/S configuration is: -COOH > -CHO > -CH 2OH > -CH 3 -CHO > -COOH > -CH 2OH > -CH 3 -OH > -CH 2OH > -CHO > -COOH -COOH > -CH 2OH > -CHO > -CH 3 Which of the following compounds will not exhibit geometrical isomerism? 1,1-Dibromo-2-chloroethene But-2-ene 1-Bromoprop-1-ene 2-Pentene Which of the following pairs represents diastereomers? cis -but-2-ene and trans -but-2-ene D-Glucose and L-Glucose (R) -Lactic acid and (S) -Lactic acid Meso-tartaric acid and its mirror image Which of the following is a non-benzenoid aromatic compound? Azulene Naphthalene Anthracene Phenanthrene What is the maximum number of stereoisomers for 3-chlorobutan-2-ol? 4 2 3 8 The correct order of increasing bond length for C-H bonds in C 2H 6 , C 2H 4 , and C 2H 2 is: C 2H 2 < C 2H 4 < C 2H 6 C 2H 6 < C 2H 4 < C 2H 2 C 2H 4 < C 2H 2 < C 2H 6 C 2H 2 < C 2H 6 < C 2H 4 Which of the following compounds exhibits metamerism? C 4H 10 O (Ethers) C 2H 6O C 3H 8O CH 3Cl Which of the following compounds is the most stable? trans-But-2-ene cis-But-2-ene But-1-ene 2-Methylpropene The compound which is not isomeric with diethyl ether is: Butan-2-one Methyl n-propyl ether Butan-1-ol 2-Methylpropan-2-ol Which of the following compounds will exhibit geometrical isomerism? 1,2-Dibromoethene 1,1-Dibromoethene Propene 2-Methylbut-2-ene Racemic mixture is formed by mixing: Two enantiomers in equal proportions Two diastereomers Two meso compounds An enantiomer and a diastereomer Total number of chiral carbons in a glucose molecule ( C 6H 12 O 6 ) in its open-chain form is: 4 3 5 6 A mixture of benzoic acid and naphthalene can be separated by using: Hot water Cold water Ether Benzene Which of the following compounds has the highest boiling point? CH 3-CH 2-CH 2-CH 2-OH CH 3-CH 2-O-CH 2-CH 3 CH 3-CH 2-CH 2-CHO CH 3-CH 2-CH 2-CH 2-CH 3 Which of the following compounds is aromatic? Cycloheptatrienyl cation Cycloheptatriene Cyclopentadiene Cyclooctatetraene Which of the following compounds will NOT exhibit tautomerism? Benzaldehyde Acetone Acetaldehyde Cyclohexanone The total number of stereoisomers for 2,3-dichlorobutane is: 3 4 2 6 Which of the following is a pair of metamers? CH 3OCH 2CH 2CH 3 and CH 3CH 2OCH 2CH 3 CH 3CH 2CH 2OH and CH 3CH(OH)CH 3 CH 3COCH 3 and CH 3CH 2CHO CH 3CH 2CH 2CH 3 and (CH 3) 2CHCH 3 The stability of the staggered conformation of ethane over the eclipsed conformation is primarily due to: Minimum torsional strain Maximum steric hindrance Maximum torsional strain Angle strain Which of the following compounds will have the highest heat of hydrogenation? 1-Butene cis-2-Butene trans-2-Butene 2-Methylpropene The total number of stereoisomers for the compound 3-penten-2-ol is: 4 2 3 6 Which of the following compounds is the most stable alkene? 2,3-dimethylbut-2-ene But-2-ene But-1-ene Propene The dipole moment is highest for: cis-1,2-dichloroethene trans-1,2-dichloroethene 1,4-dichlorobenzene trans-2-butene What is the correct priority order of the following groups for R/S configuration? -OH, -COOH, -CHO, -CH 2OH -OH > -COOH > -CHO > -CH 2OH -COOH > -OH > -CHO > -CH 2OH -OH > -CHO > -COOH > -CH 2OH -CH 2OH > -CHO > -COOH > -OH Which of the following will not show tautomerism? Benzaldehyde Acetaldehyde Acetone Cyclohexanone Which of the following compounds will exhibit geometrical isomerism across the C=N bond? Acetaldoxime ( CH 3CH=NOH ) Acetone oxime ( (CH 3) 2C=NOH ) Formaldoxime ( CH 2=NOH ) Benzophenone oxime ( (C 6H 5) 2C=NOH ) The most stable conformation of methylcyclohexane is: Chair conformation with methyl in equatorial position Chair conformation with methyl in axial position Boat conformation Twist-boat conformation Which of the following alkanes will have the lowest heat of combustion per CH 2 group? Cyclohexane Cyclopropane Cyclobutane Cyclopentane How many structural isomers are possible for the molecular formula C 3H 6Cl 2 ? 4 3 5 2 Which of the following molecules is expected to exhibit diamagnetic behavior and follow the (4n+2)π rule for aromaticity? Cycloheptatrienyl cation Cyclopentadienyl radical Cyclooctatetraene Cyclobutadiene Which of the following compounds has the highest value of pK a ? CH 3CH 2OH CH 3COOH C 6H 5OH ClCH 2COOH Which of the following can show tautomerism? 2-Methylcyclohexanone Benzophenone Benzaldehyde Trimethylacetaldehyde