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Multiple Choice Questions
1. The IUPAC name of $\text{C}_6\text{H}_5\text{COCl}$ is [JEE 2006]
(a) Benzoyl chloride
(b) Benzene chloro ketone
(c) Benzene carbonyl chloride
(d) Chloro phenyl ketone
Answer: (c)
Explanation: The IUPAC name of $\text{C}_6\text{H}_5\text{COCl}$ is Benzene carbonyl chloride.
2. The number of structural isomers for $\text{C}_6\text{H}_{14}$ is [JEE 2007 P-I]
(a) 3
(b) 4
(c) 5
(d) 6
Answer: (c)
Explanation: $\text{C}_6\text{H}_{14}$ has 5 structural isomers:
1. $\text{H}_3\text{C}-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CH}_3$
2. $\text{H}_3\text{C}-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}_2-\text{CH}_3$
3. $\text{H}_3\text{C}-\text{CH}_2-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}_3$
4. $\text{H}_3\text{C}-\text{CH}(\text{CH}_3)-\text{CH}(\text{CH}_3)-\text{CH}_3$
5. $\text{H}_3\text{C}-\text{C}(\text{CH}_3)_2-\text{CH}_2-\text{CH}_3$
Hence (c) is correct.
3. The number of stereoisomers obtained by bromination of trans-2-butene is [JEE 2007 P-II]
(a) 1
(b) 2
(c) 3
(d) 4
Answer: (a)
Explanation: Anti-addition of $\text{Br}_2$ to trans-2-butene yields a meso product (single meso compound). Hence (a) is correct.
4. The correct statement(s) about the compound given below is (are) [JEE 2008 P-I]
(a) The compound is optically active
(b) The compound possesses centre of symmetry
(c) The compound possesses plane of symmetry
(d) The compound possesses axis of symmetry
Answer: (a, d)
Explanation: Rotating carbon 1 by $180^\circ$ shows that the molecule is optically active and possesses an axis of symmetry ($C_2$) perpendicular to the $\text{C}-\text{C}$ bond.
5. The correct statement (s) concerning the structures E, F and G is (are) [JEE 2008 P-I]
(a) E, F and G are resonance structures
(b) E, F and E, G are tautomers
(c) F and G are geometrical isomers
(d) F and G are diastereomers
Answer: (b, c, d)
Explanation: E and F, and E and G are tautomers (keto-enol forms). F and G are cis-trans geometrical isomers, which are non-mirror image stereoisomers (diastereomers).
6. The IUPAC name of $[\text{Ni}(\text{NH}_3)_4][\text{NiCl}_4]$ is [JEE 2008 P-II]
(a) Tetrachloronickel (II) – tetraamminenickel (II)
(b) Tetraamminenickel (II) – tetrachloronickel (II)
(c) Tetraamminenickel (II) – tetrachloronickelate (II)
(d) Tetrachloronickel (II) – tetraamminenickelate (II)
Answer: (c)
Explanation: IUPAC name is tetraamminenickel (II) – tetrachloronickelate (II).
7. The correct statement(s) about the compound $\text{H}_3\text{C}(\text{HO})\text{HC}-\text{CH}=\text{CH}-\text{CH}(\text{OH})\text{CH}_3$ (X) is(are) [JEE 2009 P-I]
(a) The total number of stereoisomers possible for X is 6
(b) The total number of diastereomers possible for X is 3
(c) If the stereochemistry about the double bond in X is trans, the number of enantiomers possible for X is 4
(d) If the stereochemistry about the double bond in X is cis, the number of enantiomers possible for X is 2
Answer: (a, d)
Explanation: Total number of stereoisomers possible for X is 6. If the stereochemistry about the double bond in X is cis, 2 enantiomers are possible.
8. The IUPAC name of the following compound is [JEE 2009 P-I]
(a) 4-Bromo-3-cyanophenol
(b) 2-Bromo-5-hydroxybenzonitrile
(c) 2-Cyano-4-hydroxybromobenzene
(d) 6-Bromo-3-hydroxybenzonitrile
Answer: (b)
Explanation: Priority of $-\text{CN}$ is highest, so the benzonitrile ring gets position 1 at $-\text{CN}$, making it 2-Bromo-5-hydroxybenzonitrile.
9. In the Newman projection for 2, 2-dimethyl butane X and Y can respectively be [JEE 2010 P-I]
(a) $\text{H}$ and $\text{H}$
(b) $\text{H}$ and $\text{C}_2\text{H}_5$
(c) $\text{C}_2\text{H}_5$ and $\text{H}$
(d) $\text{CH}_3$ and $\text{CH}_3$
Answer: (b, d)
Explanation: On $\text{C}_2-\text{C}_3$ bond axis $\text{X} = \text{CH}_3, \text{Y} = \text{CH}_3$. On $\text{C}_1-\text{C}_2$ bond axis $\text{X} = \text{H}, \text{Y} = \text{C}_2\text{H}_5$.
10. Amongst the given options, the compound(s) in which all the atoms are in one plane in all the possible conformations (if any), is (are) [JEE 2011 P-I]
(a) $\text{H}_2\text{C}=\text{C}=\text{O}$
(b) $\text{H}_2\text{C}=\text{C}=\text{CH}_2$
(c) $\text{H}_2\text{C}=\text{CH}-\text{CH}=\text{CH}_2$
(d) $\text{H}_2\text{C}=\text{C}=\text{C}=\text{CH}_2$
Answer: (b, c)
Explanation: Molecules (b) and (c) have planar atom arrangements across their conformations.
11. As per IUPAC nomenclature, the name of the complex $[\text{Co}(\text{H}_2\text{O})_4(\text{NH}_3)_2]\text{Cl}_3$ is [JEE 2012 P-I]
(a) Tetraaquadiaminecobalt (III) chloride
(b) Tetraaquadiaminecobalt (III) chloride
(c) Diaminetetraaquacobalt (III) chloride
(d) Diamminetetraaquacobalt (III) chloride
Answer: (d)
Explanation: $[\text{Co}(\text{H}_2\text{O})_4(\text{NH}_3)_2]\text{Cl}_3$ is named Diamminetetraaquacobalt (III) chloride.
12. The carboxyl functional group ($-\text{COOH}$) is present in [JEE 2012 P-I]
(a) picric acid
(b) barbituric acid
(c) ascorbic acid
(d) aspirin
Answer: (d)
Explanation: Aspirin contains 2-acetoxybenzoic acid which has a carboxylic group ($-\text{COOH}$).
13. Which of the given statement(s) about N, O, P and Q with respect to M is (are) correct? [JEE 2012 P-II]
(a) M and N are non mirror image stereoisomers
(b) M and O are identical
(c) M and P are enantiomers
(d) M and Q are identical
Answer: (a, b, c)
Explanation: M and N are diastereomers (non-mirror image stereoisomers). M and O represent identical configurations upon rotation. M and P are non-superimposable mirror images (enantiomers).
14. A solution of (–)-1-chloro-1-phenylethane in toluene racemises slowly in the presence of a small amount of $\text{SbCl}_5$ due to the formation of [JEE Main 2013]
(a) carbanion
(b) carbene
(c) carbocation
(d) free radical
Answer: (c)
Explanation: Racemises slowly due to formation of intermediate planar carbocation.
15. The correct combination of names for isomeric alcohols with molecular formula $\text{C}_4\text{H}_{10}\text{O}$ is/are [JEE Adv. 2014 P-I]
(a) tert-butanol and 2-methylpropan-2-ol
(b) tert-butanol and 1,1-dimethylethan-1-ol
(c) n-butanol and butan-1-ol
(d) isobutyl alcohol and 2-methylpropan-1-ol
Answer: (a, c, d)
Explanation: Isomeric alcohols of $\text{C}_4\text{H}_{10}\text{O}$ are:
$\text{H}_3\text{C}-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{OH}$ (n-butanol or butan-1-ol)
$\text{H}_3\text{C}-\text{CH}_2-\text{CH}(\text{OH})-\text{CH}_3$ (sec-butyl alcohol or butan-2-ol)
$\text{H}_3\text{C}-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{OH}$ (2-methylpropan-1-ol or isobutyl alcohol)
$\text{H}_3\text{C}-\text{C}(\text{CH}_3)_2-\text{OH}$ (tert-butanol or 2-methylpropan-2-ol)
16. Which of the following compounds will exhibit geometrical isomerism? [JEE Main 2015]
(a) 1-Phenyl-2-butene
(b) 3-Phenyl-1-butene
(c) 2-Phenyl-1-butene
(d) 1,1-Diphenyl-2-propane
Answer: (a)
Explanation: 1-Phenyl-2-butene ($\text{Ph}-\text{CH}_2-\text{CH}=\text{CH}-\text{CH}_3$) has different groups on both double-bonded carbons, exhibiting cis-trans geometrical isomerism.
17. Compound(s) that on hydrogenation produce(s) optically inactive compound(s) is (are) [JEE Adv. 2015 P-I]
(a) Compound (1)
(b) Compound (2)
(c) Compound (3)
(d) Compound (4)
Answer: (b, d)
Explanation:
(1) $\text{H}_3\text{C}-\text{CH}=\text{CH}-\text{CH}(\text{Br})\text{CH}_3 \xrightarrow{\text{H}_2/\text{Pt}} \text{H}_3\text{C}-\text{CH}_2-\text{CH}_2-\text{CH}(\text{Br})\text{CH}_3$ (Optically active)
(2) $\text{H}_3\text{C}-\text{CH}=\text{C}(\text{Br})-\text{CH}_2-\text{CH}_3 \xrightarrow{\text{H}_2/\text{Pt}} \text{H}_3\text{C}-\text{CH}_2-\text{CH}(\text{Br})-\text{CH}_2-\text{CH}_3$ (Optically inactive)
(3) $\text{H}_2\text{C}=\text{C}(\text{CH}_3)-\text{CH}(\text{Br})\text{CH}_3 \xrightarrow{\text{H}_2/\text{Pt}} \text{H}_3\text{C}-\text{CH}(\text{CH}_3)-\text{CH}(\text{Br})\text{CH}_3$ (Optically active)
(4) $\text{H}_2\text{C}=\text{CH}-\text{CH}(\text{Br})-\text{CH}_2-\text{CH}_3 \xrightarrow{\text{H}_2/\text{Pt}} \text{H}_3\text{C}-\text{CH}_2-\text{CH}(\text{Br})-\text{CH}_2-\text{CH}_3$ (Optically inactive)
18. The IUPAC name(s) of the following compound is (are) [JEE Adv. 2015 P-I]
(a) 1-chloro-4-methylbenzene
(b) 4-chlorotoluene
(c) 1-methyl-4-chlorobenzene
(d) 4-methylchlorobenzene
Answer: (a, b)
Explanation: Both 1-chloro-4-methylbenzene and 4-chlorotoluene are accepted IUPAC names for the given compound.
19. The absolute configuration of the given compound is: [JEE Main 2016]
(a) (2R, 3S)
(b) (2S, 3R)
(c) (2S, 3S)
(d) (2R, 3R)
Answer: (b)
Explanation: Assigning priorities according to CIP rules gives (2S, 3R).
20. Consider the following reaction and statements
$$[\text{Co}(\text{NH}_3)_4\text{Br}_2]^+ + \text{Br}^- \longrightarrow [\text{Co}(\text{NH}_3)_3\text{Br}_3] + \text{NH}_3$$
(i) Two isomers are produced if the reactant complex ion is a cis-isomer
(ii) Two isomers are produced if the reactant complex ion is a trans-isomer
(iii) Only one isomer is produced if the reactant complex ion is a trans-isomer
(iv) Only one isomer is produced if the reactant complex ion is a cis-isomer [JEE Main 2019]
(a) (II) and (IV)
(b) (I) and (II)
(c) (I) and (III)
(d) (III) and (IV)
Answer: (d)
Explanation: Cis-isomer gives only one isomer (fac), and trans-isomer gives only one isomer (mer). Thus, statements (III) and (IV) are correct.
21. The IUPAC name of the following compound is : [JEE Main 2019]
$\text{H}_3\text{C}-\text{CH}(\text{CH}_3)-\text{CH}(\text{OH})-\text{CH}_2-\text{COOH}$
(a) 2-Methyl-3-hydroxypentan-5-oic acid
(b) 4,4-Dimethyl-3-hydroxy butanoic acid
(c) 3-Hydroxy-4-methylpentanoic acid
(d) 4-Methyl-3-hydroxypentanoic acid
Answer: (c)
Explanation: $-\text{COOH}$ gets position 1. Main chain has 5 carbons with $-\text{OH}$ at C-3 and $-\text{CH}_3$ at C-4, so 3-Hydroxy-4-methylpentanoic acid.
22. The IUPAC symbol for the element with atomic number 119 would be : [JEE Main 2019]
(a) unh
(b) uun
(c) une
(d) uue
Answer: (d)
Explanation: 1 = un, 1 = un, 9 = enn $\implies$ uue (Ununennium).
23. The total number of isomers for a square planar complex $[\text{M}(\text{F})(\text{Cl})(\text{SCN})(\text{NO}_2)]$ is : [JEE Main 2019]
(a) 12
(b) 8
(c) 16
(d) 4
Answer: (a)
Explanation: For $[\text{M}(a)(b)(c)(d)]$, 3 geometrical isomers exist. Because $\text{SCN}^-$ and $\text{NO}_2^-$ are ambidentate ligands (2 modes each: $\text{SCN}/\text{NCS}$ and $\text{NO}_2/\text{ONO}$), total isomers = $3 \times 2 \times 2 = 12$.
24. A reaction of cobalt(III) chloride and ethylenediamine in a 1 : 2 mole ratio generates two isomeric products A (violet coloured) B (green coloured). A can show optical activity, B is optically inactive. What type of isomers does A and B represent ? [JEE Main 2019]
(a) Geometrical isomers
(b) Ionisation isomers
(c) Coordination isomers
(d) Linkage isomers
Answer: (a)
Explanation: A is cis-$[\text{Co}(\text{en})_2\text{Cl}_2]^+$ (violet, optically active) and B is trans-$[\text{Co}(\text{en})_2\text{Cl}_2]^+$ (green, optically inactive). They are geometrical isomers.
25. What is the IUPAC name of the following compound? [JEE Main 2019]
(a) 3-Bromo-1, 2-dimethylbut-1-ene
(b) 4-Bromo-3-methylpent-2-ene
(c) 2-Bromo-3-methylpent-3-ene
(d) 3-Bromo-3-methyl-1, 2-dimethylprop-1-ene
Answer: (b)
Explanation: Longest chain with double bond gives 4-Bromo-3-methylpent-2-ene.
Statement/Assertion and Reason
26. Statement-I: Molecules that are not superimposable on their mirror images are chiral.
Because
Statement-II: All chiral molecules have chiral centres. [JEE 2007 P-II]
(a) Statement-I is True, Statement-II is True; Statement-II is a correct explanation for Statement-I
(b) Statement-I is True, Statement-II is True; Statement-II is not a correct explanation for Statement-I
(c) Statement-I is True, Statement-II is False
(d) Statement-I is False, Statement-II is True
Answer: (c)
Explanation: Statement-I is true. Statement-II is false because some chiral molecules (e.g. substituted allenes, biphenyls) do not contain chiral carbon centres.
27. Statement-I: The geometrical isomers of the complex $[\text{M}(\text{NH}_3)_4\text{Cl}_2]$ are optically inactive.
and
Statement-II: Both geometrical isomers of the complex $[\text{M}(\text{NH}_3)_4\text{Cl}_2]$ possess axis of symmetry. [JEE 2008 P-II]
(a) Statement-I is True, Statement-II is True; Statement-II is a correct explanation for Statement-I
(b) Statement-I is True, Statement-II is True; Statement-II is not a correct explanation for Statement-I
(c) Statement-I is True, Statement-II is False
(d) Statement-I is False, Statement-II is True
Answer: (b)
Explanation: Both statements are true. Optical inactivity is due to the presence of a plane of symmetry ($\sigma$) or centre of inversion ($i$), not merely an axis of symmetry ($C_n$).
Paragraph
Paragraph for Question Nos. 28 to 29
P and Q are isomers of dicarboxylic acid $\text{C}_4\text{H}_4\text{O}_4$. Both decolorize $\text{Br}_2 / \text{H}_2\text{O}$. On heating, P forms the cyclic anhydride. Upon treatment with dilute alkaline $\text{KMnO}_4$, P as well as Q could produce one or more than one from S, T & U. [JEE Adv. 2013 P-II]
28. Compounds formed from P and Q are, respectively
(a) Optically active S and optically active pair (T, U)
(b) Optically inactive S and optically inactive pair (T, U)
(c) Optically active pair (T, U) and optically active S
(d) Optically inactive pair (T, U) and optically inactive S
Answer: (b)
Explanation: P is maleic acid (cis-isomer) which gives meso-tartaric acid (S, optically inactive) on syn-hydroxylation with alkaline $\text{KMnO}_4$. Q is fumaric acid (trans-isomer) which gives racemic mixture of (T, U) (optically inactive pair).
29. In the following reaction sequences V and W are, respectively
$$\text{Q} \xrightarrow{\text{H}_2/\text{Ni}, \Delta} \text{V} \xrightarrow{\text{AlCl}_3 \text{ (anhydrous)}} \xrightarrow{\text{1. Zn-Hg/HCl}, \text{ 2. H}_3\text{PO}_4} \text{W}$$
(a) V is Succinic anhydride / Cyclic derivative and W is 1-tetralone derivative
(b) V and W as depicted in option (a)
(c) Option c
(d) Option d
Answer: (a)
Explanation: Reduction of fumaric acid gives succinic acid, which undergoes cyclization to form succinic anhydride (V) and subsequent Friedel-Crafts reaction to give (W).
Integer and Subjective
30. The total number of cyclic structural as well as stereo isomers possible for a compound with the molecular formula $\text{C}_5\text{H}_{10}$ is…………… [JEE 2009 P-II]
Answer: 7
Explanation: For $\text{C}_5\text{H}_{10}$, cyclic structures include cyclopentane (1), methylcyclobutane (1), 1,2-dimethylcyclopropane (cis/trans and optical: 3), 1,1-dimethylcyclopropane (1), and ethylcyclopropane (1). Total = 7 isomers.
31. The total number of cyclic isomers possible for a hydrocarbon with the molecular formula $\text{C}_4\text{H}_6$ is [JEE 2010 P-I]
Answer: 5
Explanation: The possible cyclic isomers for $\text{C}_4\text{H}_6$ are 5 (cyclobutene, 1-methylcyclopropene, 3-methylcyclopropene, methylenecyclopropane, and bicyclo[1.1.0]butane).
32. The maximum number of isomers (including stereoisomers) that are possible on monochlorination of the following compound is…….. [JEE 2011 P-II]
$\text{CH}_3-\text{CH}_2-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}_3$
Answer: 8
Explanation: Monochlorination yields enantiomeric pairs and structural isomers: 2 enantiomeric pairs + 4 singlet isomers = 8 total isomers.
33. The total number(s) of stable conformers with non-zero dipole moment for the following compound is (are)……. [JEE Adv. 2014 P-I]
Answer: 3
Explanation: Stable gauche conformers have non-zero dipole moments. Total number = 3.
34. Where $\mu_1$ is the dipole moment of stable conformer and $x_i$ is the mole fraction of that conformer:
(a) Write stable conformer for $\text{Z}-\text{CH}_2-\text{CH}_2-\text{Z}$ in Newman's projection. If $\mu_{\text{solution}} = 1.0\text{ D}$ and mole fraction of anti form = 0.82, find $\mu_{\text{gauche}}$.
(b) Write most stable meso conformer of $\text{CHDY}-\text{CHDY}$. [JEE 2015]
Answer: 2.35 D
Explanation: $\mu_{\text{obs}} = \sum \mu_i x_i$. Mole fraction of Gauche form $= 1 - 0.82 = 0.18$. $\mu_{\text{anti}} = 0$. $1.0 = \mu_{\text{gauche}} \times 0.18 \implies \mu_{\text{gauche}} = 2.35\text{ D}$.
35. For the given compound X, the total number of optically active stereoisomers is _________.[JEE Adv. 2018 P-II]
Answer: 7
Explanation: Total stereocentres = 3. Total isomers = $2^3 = 8$. But 1 isomer is meso (optically inactive). So, total optically active stereoisomers = 7.
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