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NEET Chemistry MCQ
Isomerism And Steroisomerism Mcq Neet Chemistry
Quiz 3
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Q.1
If there is no rotation of plane polarized light by a compound in a specific solvent thought to be chiral. it may mean that .. [ AIPMT 2007]
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a) the compound may be a racemic mixture
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b) compound is certainly a chiral
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c) the compound is certainly meso
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d) there is no compound in the solvent
Explanation
given that compound is chiral but no optical rotation, it must be mesocompound Answer:(c)
Q.2
ion Q62) The following two compounds are
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a) Enantiomers
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b) Diasteromers
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c) Identical
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d) Epimers
Explanation
The two compounds are mirror non- superimposable mirror image of each other and hnece are enantiomers Answer:(a)
Q.3
RNA and DNA are chiral molecules their cllirality is due to
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a) D-sugar component
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b) L-sugar component
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c) Chiral bases
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d) Chiral phosphate ester groups
Explanation
DNA and RNA are chiral due to chirality of the sugar component(D-2deoxy ribose and D-ribose) Answer:(a)
Q.4
ion Q64) The consider the following organic compound, To make it a chiral compound, the attack should be on carbon ...[ DEC2001]
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a) 1
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b) 3
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c) 4
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d) 7
Explanation
Answer:(b)
Q.5
Which one of the following can exhibit cis-trans isomerism? .. [CBSE PMT 1989]
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a) CH3 - CHCl - COOH
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b) H-C ≡ C-Cl
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c) ClCH = CHCl
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d) ClCH2-CH2Cl
Explanation
Answer:(c)
Q.6
hich one of the following does not exhibit thephenomenon of mutarotation? [ AIPMT 2010]
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a) (+) Sucrose
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b) (+) Lactose
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c) (+) Maltose
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d) (–) Fructose
Explanation
Mutarotation is the change in the optical rotation because of the change in the equilibrium between two anomers, (+) sucrose is not a reducing sugar and does not exhibit mutarotation because the glycosidic bond is between the anomeric carbon of glucose and the anomeric carbon of fructose Answer:(a)
Q.7
The numberof possible open chain (acyclic) isomeric compounds for molecular formula C5H10 would be ..[ AMU 1997]
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a) 8
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b) 7
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c) 6
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d) 5
Explanation
CH3CH2CH2CH = CH2 (1-pentene) Answer:(c)
Q.8
An organic compound will show optical isomerism if ... [ MPPMT 1999]
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a) four groupos attached to C atom are different
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b) three groups attached to C atoms are different
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c) two group attached to C atoms are different
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d) all the groups attached to C atom are same
Explanation
Answer:(a)
Q.9
In the following the most stable conformation of n-butane is: [ AIPMT 2010]
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a)
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b)
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c)
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d)
Explanation
Answer:(b)
Q.10
Which organicstructure among the following is not an isomer of the compound CH3 - CO -CH2-CH2CH2-CH3
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a) CH3CH2OCH = CHCH2CH3
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b) CH3CH = CHCH2CH2CHO
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c) (CH3)2CH - CO- CH2CH3
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d) CH3CH2COCH2CH2CH3
Explanation
Molecular formula of 'b' is C6H10O while others have C6H12O Answer:(b)
Q.11
ion Q71) Given Which of the given compounds can exhibit tautormerism ?
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a) I, II and III
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b) I and II
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c) I and III
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d) II and III
Explanation
Answer:(a)
Q.12
The prefixes and anti areused to denote ..[ DPMT 2002]
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a) Structural isomers
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b) Conformatonal isomers
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c) Geometrical isomers
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d) Optical isomers
Explanation
Answer:(c)
Q.13
Which of the following compounds is isomeric with 2,2,4,4-tetramethylhexane ..[ AMU 1997]
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a) 3-Ethyl-2,2-dimethylpentane
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b) 4-Isopropylheptane
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c) 4-Ethyl-3-methyl-4-n-propyloctane
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d) 4,4-Diethyl-3-methylheptane
Explanation
Molecular formula of 4-isopropylheptane is also C10H22 Answer:(b)
Q.14
ion Q74) Given Which of the given compounds can exhibit tautormerism ? [ AIPMT 2015]
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a) I, II and III
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b) I and II
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c) I and III
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d) II and III
Explanation
tautomerism, arises due to 1,3-migration of a proton from one polyvalent atom to other within same molecule. or a double bond is able to ‘extend’ the mesomeric properties of a carbonyl compound across two additional atoms. Answer:(a)
Q.15
An organic molecule necessarilyshows optical acrivity if it ,,, [ Roorkee 1993]
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a) contains asymmetric carbon atoms
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b) is non-polar
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c) is non-superimposable on its mirror image
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d) is superimposable on its mirror image
Explanation
Answer:(c)
Q.16
An enantiometricallypure acidis treatedwith mixture of an alcohol havingone chiral carbon. Theester formed will be ..[ IIT 2003]
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a) Optically active mixture
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b) Pureenantiomer
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c) Meso compound
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d) Racemicmixture
Explanation
Answer:(a)
Q.17
The optically active tartaric acid is named as D-(+)- tartaric acid because it has a positive..[ IIT1999]
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a) Optical rotation and is derived from D-glucose
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b) pH in organic solvent
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c) Optical rotation and is derived from D-(+)-glyceraldehyde
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d) optical rotation only when substituted by deduterium
Explanation
The configuration of the penultimate carbon of many optically active compound is always corelated with D-(+)-glyceraldehyde. Answer:(c)
Q.18
The correct statement regarding the comparison of staggered and eclipsed conformation of ethane, is :- [ NEET 2016]
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a) The staggered conformation of ethane is less stable than eclipsed conformation, because staggered conformation has torsional strain
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b) The eclipsed conformation of ethane is more stable than staggered conformation, because eclipsed conformation has no torsional strain
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c) The eclipsed conformation of ethane is more stable than staggered conformation even through the eclipsed conformation has torsional strain
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d) The staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain
Explanation
Answer:(d)
Q.19
ion Q79) The correct corresponding order names of four aldoses with configuration given below respectively, is :-
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a) L-erythrose, L-threose, D-erythrose, D-threose
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b) D-erythrose, D-threose, L-erythrose, L-threose
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c) L-erythrose, L-threose, L-erythrose, D-threose
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d) D-threose, D-erythrose, L-threose, L-erythrose
Explanation
configuration with –OH group at right side was given D-configuration where as the configuration with –OH group at left side was given L-configuration. the configuration of stereocentre farthest from carbonyl group is compared with glyceraldehydes Answer:(b)
Q.20
The most stable conformation of ethylene glycol is ..[ JIPMER 2001]
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a) Anti
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b) Gauche
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c) Partially eclipsed
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d) Fully eclipsed
Explanation
Answer:(b)
Q.21
With respect to the conformers of ethane, which of the following statements is true ?
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a) Bond angle changes but bond length remains same
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b) Both bond angle and bond length change
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c) Both bond angles and bond length remains same
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d) Bond angle remains same but bond length changes
Explanation
In conformation bond angle and bond length emain same. Answer:(c)
Q.22
The (R)- and (S)- enantiomers of an optically active compound differ in ...[ CBSE PMT 2000 ]
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a) their reactivity with achiral reagents
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b) their optical rotation of plane polarized light
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c) their melting points
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d) their solubility in achiral reagent
Explanation
Answer:(b)
Q.23
How many optically active stereoisomers are posible for butane-2,3-diol? [ IIT 1997]
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a) 1
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b) 2
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c) 3
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d) 4
Explanation
Butane-2,3-diol has two similar chiral carbon atoms. there has three steroisomeric forms (d-, l- and meeso). Out of which only two(d- and l-) are optically active Answer:(b)
Q.24
The letter 'D' in D-glucose signifies ..[ NEET Guj 2017]
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a) Configuration at all chiral carbons
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b) Dextrorotatory
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c) That it is a monosaccharide
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d) Configuration at a particular chiral carbon
Explanation
Answer:(d)
Q.25
A compound which is not isomeric with diethylether is ...[ CPMT 1989]
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a) n-Propyl methyl ether
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b) 1-butanol
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c) 2-methyl-2propanol
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d) butanone
Explanation
Answer:(d)
Q.26
The correct statement regarding ethane conformationis : [NEET Guj 2017 ]
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a) Rotation around carbon-carbon bond in ethane molecule is not possible, because ethane molecule contains a pi (π) bond between the carbon and carbon and ethane has very low melting Point.
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b) Rotation atound carbon-carbon bond in ethane molecule is not possible, because ethane molecule contains both srgma (σ) bond and pi (π) bond between the carbon and carbon.
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c) Rotation around carbon-carbon bond in ethane molecule is possible because of cylindrical symmetry of sigma (σ) bond between carbon-carbon a toms.
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d) Rotation around carbon-carbon bond in ethane molecule is not possible, because ethane molecule contains hoth sigma (σ)bond and pi (π) bond between the carbon and carbon and ethane has very high bo ing point
Explanation
Answer:(c)
Q.27
The most stable conformation of n-butane is ...[ CBSE PMT 1997]
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a) skew-boat
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b) eclipsed
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c) Gauche
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d) Staggered-antil.
Explanation
Answer:(d)
Q.28
The Baeyer's angle strain is expected to be maximum in ...
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a) Cyclodecane
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b) Cyclopentane
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c) Cyclohexane
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d) Cyclooctane
Explanation
Structures are planner and SP3 hybridized thus bond angle expected 109° As the size of the ring increases, the internal angle increases accordingly. As a result,the Cyclodecane have maximum strain Answer:(a)
Q.29
ionMore than one correct answer Q89) The correct statement(s) for the following addition reactions is(are) [IIT Advance2017]
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a) (M and O) and (N and P) are two pairs of diastereomers
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b) Bromination proceeds through trans-addition in both the reactions
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c) O and P are identical molecules
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d) (M and O) and (N and P) are two pairs of enantiomers
Explanation
(i) reaction of trans-butane is Thus M nad N are identical meso compounds (ii) Reaction of cis-butane O and P are (O) and (P) are enantiomers Thus (M and O) and (N and P) are two pairs of diastereomers option(a) is true Addition of Br2 on alkene follows non-classical carbocation mechanism. It is anti or trans addition. option(b) is true ((O) and (P) are enantiomers option(c) is false (M) and (N) are identical and (O) and (P) are enantiomers. (M and O) are distereomers and (N and P) are distereomers.option(d) is false Answer:(a, b)
Q.30
Fischer projection indicates
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a) Horizontal substituents above the plane
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b) Vertical substituents above the plane
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c) Both horizontal and vertical substituents below the plane
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d) Both horizontal and vertical substituents above the plane
Explanation
Answer:(a)
0 h : 0 m : 1 s
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