Some Basic Principles of Organic Chemistry — JEE Main PYQs

Given below are two statements :

Statement I : In $\mathrm{O_2N{-}C_6H_4{-}\overset{\oplus}{C}H{-}C_6H_4{-}OCH_3}$ [Figure: benzylic carbocation bearing a 4-nitrophenyl ring and a 4-methoxyphenyl ring], the carbocation is stabilised by +R effect of $\mathrm{-OCH_3}$ group.

Statement II : In $\mathrm{O_2N{-}C_6H_4{-}\overset{\ominus}{C}H{-}C_6H_4{-}OCH_3}$ [Figure: the corresponding benzylic carbanion], the carbanion is stabilised by $-$R effect of $\mathrm{-NO_2}$ group.

In the light of the above statements, choose the correct answer from the options given below :

Increasing order of electron withdrawing power of following functional groups is:

a. $-\mathrm{CN}$ b. $-\mathrm{COOH}$ c. $-\mathrm{NO_2}$ d. $-\mathrm{I}$

Match the LIST-I with LIST-II

List-I (Reaction)	List-II (Mechanism)
A. Williamson Synthesis	I. Electrophilic addition
B. Friedel Craft Reaction	II. Free radical substitution
C. Bromination of vinyl benzene	III. Nucleophilic substitution
D. Chlorination of toluene in light	IV. Electrophilic substitution

Choose the correct answer from the options given below:

Consider the following molecules/species:

[Figure: (x) cyclohepta-2,4,6-trien-1-one (tropone); (y) $\mathrm{(CH_3)_2C{=}O}$ (propan-2-one); (z) $\mathrm{CH_3{-}C({=}O){-}O^{(-)}}$ (acetate ion)]

The correct order of carbon – oxygen double bond length is :

The following structures are

[Figure: two wedge-dash structures of a carbon centre bearing Br (up), Cl, $\mathrm{CH_3}$ and Me, drawn as mirror images of each other — i.e. the same carbon carries both a $\mathrm{CH_3}$ and a Me group]

Given below are two statements:

Statement I: On the basis of inductive effect, the order of stability of alkyl carbanions is $\mathrm{CH_3^- > CH_3{-}CH_2^- > (CH_3)_2CH^- > (CH_3)_3C^-}$.

Statement II: Allyl and benzyl carbanions are more stabilised by inductive effect and not by resonance effect.

In the light of the above statements, choose the correct answer from the options given below

Given below are two statements:

Statement I: 2,6-diethylcyclohexanone and 6-methyl-2-n-propylcyclohexanone are metamers.

Statement II: 2,2,6,6-tetramethylcyclohexanone exhibits keto-enol tautomerism.

In the light of the above statements, choose the correct answer from the options given below

Shown below is the structure of methyl acetate with three different $\alpha$, $\beta$ and $\gamma$ carbon - oxygen bonds.

[Figure: Structure of methyl acetate $\mathrm{H_3C{-}C({=}O){-}O{-}CH_3}$ where $\alpha$ labels the $\mathrm{C{=}O}$ double bond, $\beta$ labels the acyl $\mathrm{C{-}O}$ single bond, and $\gamma$ labels the $\mathrm{O{-}CH_3}$ bond.]

The correct order of bond lengths of these bonds is :

The major product of which of the following reaction is not obtained by rearrangement reaction ?

Consider the following compound (X)

$$\mathrm{H-\overset{I}{C}\equiv C-\overset{II}{C}H_2-\overset{III}{\underset{\underset{CH_3}{|}}{C}}H-\overset{IV}{C}H_3}$$

(X)

The most stable and least stable carbon radicals, respectively, produced by homolytic cleavage of corresponding $\mathrm{C-H}$ bond are :

In 3,3-dimethylhex-1-en-4-yne, there are _____$\mathrm{sp^3}$, _____$\mathrm{sp^2}$ and _____$\mathrm{sp}$ hybridised carbon atoms respectively.

Identify the correct statements from the following.

[Figure: statements A–D show pairs of skeletal structures]

A. $\mathrm{CH_3CH_2COCH_2CH_3}$ (pentan-3-one) and $\mathrm{CH_3COCH_2CH_2CH_3}$ (pentan-2-one) are metamers B. $\mathrm{CH_3CH_2CH_2{-}CN}$ and $\mathrm{CH_3CH_2CH_2{-}NC}$ are functional isomers C. $\mathrm{CH_3CH_2CH_2CH_2CH_2OH}$ (pentan-1-ol) and $\mathrm{CH_3CH(OH)CH_2CH_2CH_3}$ (pentan-2-ol) are position isomers D. $\mathrm{CH_3CH_2CH_2CH_2NH_2}$ (butan-1-amine) and $\mathrm{CH_3CH_2{-}NH{-}CH_2CH_2CH_3}$ (N-ethylpropan-1-amine) are homologous

Choose the correct answer from the options given below:

Given below are two statements:

Statement I : Hyperconjugation is not a permanent effect.

Statement II : In general, greater the number of alkyl groups attached to a positively charged C-atom, greater is the hyperconjugation interaction and stabilization of the cation.

In the light of the above statements, choose the correct answer from the options given below

What is the correct IUPAC name of [Figure: benzene ring bearing $\mathrm{CO_2H}$, with $\mathrm{OH}$ on the carbon adjacent to $\mathrm{CO_2H}$, $\mathrm{Br}$ on the carbon adjacent to the $\mathrm{OH}$, and $\mathrm{NO_2}$ meta to $\mathrm{CO_2H}$ (positions: 1-$\mathrm{CO_2H}$, 2-$\mathrm{OH}$, 3-$\mathrm{Br}$, 5-$\mathrm{NO_2}$)] ?

In which pairs, the first ion is more stable than the second ?

[Figure: four pairs of ions — (A) cyclohexyl cation bearing an $\mathrm{-OMe}$ group on the cationic carbon & cyclohexyl cation bearing a $\mathrm{-Me}$ group on the cationic carbon; (B) cyclohexyl carbanion with an ortho-nitrophenyl group on the carbanion carbon & cyclohexyl cation with an ortho-nitrophenyl group on the cationic carbon; (C) cyclohexylmethyl cation ($\mathrm{CH_2^+}$ on a saturated cyclohexane ring) & (cyclohex-1-en-1-yl)methyl cation ($\mathrm{CH_2^+}$ attached to the ring double-bond carbon, allylic); (D) trimethyl carbocation $\mathrm{(Me)_3C^+}$ & dimethyl(methoxy) carbocation $\mathrm{Me_2C^+(OMe)}$]

The IUPAC name of the following compound is :

$$\mathrm{HC \equiv C - CH_2 - \underset{\underset{\displaystyle \mathrm{OH}}{|}}{CH} - CH_2 - CH = CH_2}$$

What is the correct IUPAC name of

[Figure: a cyclopentene ring bearing an $-\mathrm{OH}$ group on one ring carbon and an ethyl substituent on another ring carbon] ?

Match the LIST-I with LIST-II

	LIST-I		LIST-II
A.	Carbocation	I.	Species that can supply a pair of electrons.
B.	C-Free radical	II.	Species that can receive a pair of electrons.
C.	Nucleophile	III.	$\mathrm{sp^2}$ hybridized carbon with empty p-orbital.
D.	Electrophile	IV.	$\mathrm{sp^2/sp^3}$ hybridized carbon with one unpaired electron.

Choose the correct answer from the options given below:

The IUPAC name of the following compound is :

$$\mathrm{CH_3-CH(COOH)-CH_2-CH_2-CH(COOCH_3)-CH_3}$$

(COOH on the second carbon and $\mathrm{COOCH_3}$ on the fifth carbon of the hexane chain)

How many different stereoisomers are possible for the given molecule ?

$$\mathrm{CH_3-CH(OH)-CH=CH-CH_3}$$

The incorrect statements regarding geometrical isomerism are :

(A) Propene shows geometrical isomerism. (B) Trans isomer has identical atoms/groups on the opposite sides of the double bond. (C) Cis-but-2-ene has higher dipole moment than trans-but-2-ene. (D) 2-methylbut-2-ene shows two geometrical isomers. (E) Trans-isomer has lower melting point than cis isomer.

Choose the correct answer from the options given below :

The most stable carbocation from the following is :

The correct stability order of the following species/molecules is:

[Figure: three ring structures — p: cyclopropenyl anion (three-membered ring with one C=C and a negative charge), q: cyclopentadienyl anion (five-membered ring with two C=C, an H and a negative charge on the sp³ carbon), r: cyclooctatetraene (eight-membered ring with four alternating C=C)]

A compound 'X' absorbs 2 moles of hydrogen and 'X' upon oxidation with $\mathrm{KMnO_4\,|\,H^{+}}$ gives $\mathrm{CH_3{-}\overset{\overset{\textstyle O}{\|}}{C}{-}CH_3}$, $\mathrm{CH_3{-}\overset{\overset{\textstyle O}{\|}}{C}{-}OH}$ and $\mathrm{CH_3{-}\overset{\overset{\textstyle O}{\|}}{C}{-}CH_2CH_2{-}\overset{\overset{\textstyle O}{\|}}{C}{-}OH}$.

The total number of $\sigma$ bonds present in the compound 'X' is ________.

Which one of the carbocations from the following is most stable?

In the given structure, number of sp and $\mathrm{sp^2}$ hybridized carbon atoms present respectively are :

[Figure: an open-chain structure $\mathrm{CH_3-CO-CH=CH-CH_2-C{\equiv}C-CH=CH-C{\equiv}N}$ — a methyl ketone bearing a C=C, then a $\mathrm{CH_2}$, then a $\mathrm{C{\equiv}C}$ triple bond, another C=C, terminating in a nitrile $\mathrm{C{\equiv}N}$]

Identify correct statement/s :

(A) $\mathrm{-OCH_3}$ and $\mathrm{-NHCOCH_3}$ are activating group. (B) $\mathrm{-CN}$ and $\mathrm{-OH}$ are meta directing group. (C) $\mathrm{-CN}$ and $\mathrm{-SO_3H}$ are meta directing group. (D) Activating groups act as ortho- and para directing groups. (E) Halides are activating groups.

Choose the correct answer from the options given below :

The possible number of stereoisomers for 5-phenylpent-4-en-2-ol is _______.

The correct order of stability of following carbocations is :

[Figure: A = $\mathrm{Ph_3C^{\oplus}}$ (triphenylmethyl cation); B = $\mathrm{Ph_2\overset{\oplus}{C}H}$ (diphenylmethyl cation); C = tropylium (cycloheptatrienyl) cation; D = $\mathrm{H_3C{-}CH_2{-}\overset{\oplus}{C}H{-}CH_3}$ (butan-2-ylium cation)]

Given below are two statements :

Statement (I) : [Figure: a cyclopentane ring] and [Figure: an open-chain alkene, CH$_3$CH$_2$CH=CHCH$_2$CH$_3$] are isomeric compounds.

Statement (II) : [Figure: a primary amine, CH$_3$(CH$_2$)$_4$CH$_2$NH$_2$] and [Figure: a secondary amine, CH$_3$CH$_2$CH$_2$–NH–CH$_2$CH$_2$CH$_3$] are functional group isomers.

In the light of the above statements, choose the correct answer from the options given below :

What will be the decreasing order of basic strength of the following conjugate bases ?

$\mathrm{^-OH,\ R\bar{O},\ CH_3CO\bar{O},\ \bar{Cl}}$

Match List I with List II :

[Figure: List-I shows four curved-arrow mechanism steps: (A) aniline resonance — the $\mathrm{NH_2}$ lone pair delocalises into the benzene ring giving the $\mathrm{{}^+NH_2}$= iminium resonance structure with a ring carbanion; (B) cyclohexene $+ \mathrm{H^+} \rightarrow$ cyclohexyl carbocation; (C) cyclohexene $+ \mathrm{\bar{C}N} \rightarrow$ cyclohexyl carbanion bearing a CN group; (D) nitrobenzene resonance — the $\mathrm{-NO_2}$ group withdraws ring electrons giving a ring carbocation resonance structure.]

List - I (Mechanism steps)	List - II (Effect)
(A) aniline lone-pair delocalisation into ring	(I) $-$ E effect
(B) cyclohexene $+ \mathrm{H^+} \rightarrow$ carbocation	(II) $-$ R effect
(C) cyclohexene $+ \mathrm{\bar{C}N} \rightarrow$ carbanion with CN	(III) $+$ E effect
(D) nitrobenzene ring-electron withdrawal by $\mathrm{-NO_2}$	(IV) $+$ R effect

Choose the correct answer from the options given below :

Which among the following is incorrect statement ?

Correct order of stability of carbanion is -

[Figure: four cyclic carbanions — (a) cycloprop-2-en-1-yl anion (three-membered ring with one C=C, negative charge on the sp3 carbon); (b) cyclobutyl anion (four-membered saturated ring bearing a negative charge); (c) cyclopentyl anion (five-membered saturated ring bearing a negative charge); (d) cyclopentadienyl anion (five-membered ring with two C=C and a lone pair/negative charge on the fifth carbon)]

The correct nomenclature for the following compound is :

[Figure: a seven-carbon chain bearing a $-\mathrm{COOH}$ group and a $-\mathrm{CHO}$ group on C-2, an $-\mathrm{OH}$ group on C-4, and a terminal $\mathrm{CH_2{=}CH-}$ double bond at the chain end; i.e. $\mathrm{CH_2{=}CH-CH_2-CH(OH)-CH_2-CH(CHO)-COOH}$]

Match List - I with List - II.

List - I (Pair of Compounds)	List - II (Isomerism)
(A) n-propanol and Isopropanol	(I) Metamerism
(B) Methoxypropane and ethoxyethane	(II) Chain Isomerism
(C) Propanone and propanal	(III) Position Isomerism
(D) Neopentane and Isopentane	(IV) Functional Isomerism

Choose the correct answer from the options given below :

Which of the following is metamer of the given compound (X)?

[Figure: compound (X) — a benzene ring attached through NH to a carbonyl bonded to a cyclohexane ring, i.e. $\mathrm{C_6H_5{-}NH{-}CO{-}C_6H_{11}}$ (N-phenyl cyclohexanecarboxamide)]

Functional group present in sulphonic acids is :

The incorrect statement regarding the geometrical isomers of 2-butene is :

Number of carbocations from the following that are not stabilized by hyperconjugation is ________.

[Figure: seven carbocations — (1) a skeletal branched alkyl carbocation with the positive charge on a chain carbon bearing a methyl branch, (2) a $\mathrm{\overset{\oplus}{C}H}$ carbocation bonded to two tert-butyl groups, labelled (tert.-Butyl)(tert.-Butyl), (3) $\mathrm{\overset{+}{C}H_3}$, (4) cyclopentadienyl cation (five-membered ring with two double bonds and $+$ charge), (5) $\mathrm{\overset{+}{C}H_2{-}OCH_3}$, (6) tert-butyl cation (skeletal isobutyl skeleton with $+$ on central carbon), (7) $\mathrm{(CH_3)_2N{-}\overset{+}{C}H_2}$]

Given below are two statements:

Statement I: [Figure: Compound A — benzene ring bearing Cl, with one NO2 group ortho to Cl and another NO2 group para to Cl (1-chloro-2,4-dinitrobenzene skeleton)] IUPAC name of Compound A is 4-chloro-1,3-dinitrobenzene.

Statement II: [Figure: Compound B — benzene ring bearing NH2, with a CH3 group ortho to NH2 and a C2H5 group para to NH2] IUPAC name of Compound B is 4-ethyl-2-methylaniline.

In the light of the above statements, choose the most appropriate answer from the options given below:

In the given compound, the number of 2° carbon atom/s is __________.

$$\mathrm{CH_3-\underset{\underset{\mathrm{H}}{|}}{C}(CH_3)-\underset{\underset{\mathrm{H}}{|}}{C}H-\underset{\underset{\mathrm{H}}{|}}{C}(CH_3)-CH_3}$$

The number of optical isomers in following compound is:_________

[Figure: three linearly fused six-membered rings (perhydroanthracene skeleton); Br on a ring-fusion carbon of the left ring and CH3 on a carbon of the right ring]

The shape of carbocation is :

IUPAC name of following hydrocarbon (X) is :

$$\underset{\underset{\mathrm{CH_3}}{|}}{\mathrm{CH_3-CH}}-\mathrm{CH_2-CH_2}-\underset{\underset{\mathrm{CH_3}}{|}}{\mathrm{CH}}-\underset{\underset{\mathrm{CH_3}}{|}}{\mathrm{CH}}-\mathrm{CH_2-CH_3}$$

(X)

Total number of optically active compounds from the following is __________.

[Figure: structures — (1) 2,3-dimethylbutane-2,3-diol shown as a Fischer-type projection ($\mathrm{CH_3-C(OH)(H)}$ over $\mathrm{C(OH)(H)-CH_3}$; both carbons bear H and OH), (2) hexane-2,3,4-triol skeletal structure with OH at C2, C3, C4]

and the condensed formulas: $\mathrm{CH_3-CH_2-CH_2-CH_2-OH}$, $\mathrm{CH_3-CH_2-\underset{\underset{\mathrm{Cl}}{|}}{CH}-CH_3}$, $\mathrm{CH_3-CH_2-CH_2-CH_2-Cl}$, $\mathrm{(CH_3)_2CH-CH_2-CH_2-Cl}$

Relative stability of the contributing structures is :

$$\mathrm{CH_2{=}CH{-}CH{=}O\ \,(I)\ \longleftrightarrow\ \overset{+}{C}H_2{-}CH{=}CH{-}\overset{-}{O}\ \,(II)\ \longleftrightarrow\ \overset{-}{C}H_2{-}CH{=}CH{-}\overset{+}{O}\ \,(III)}$$

(Resonance structures of prop-2-enal: (I) neutral structure with $\mathrm{C{=}O}$; (II) positive charge on terminal $\mathrm{CH_2}$ carbon and negative charge on oxygen; (III) negative charge on terminal $\mathrm{CH_2}$ carbon and positive charge on oxygen)

How many compounds among the following compounds show inductive, mesomeric as well as hyperconjugation effects ?

[Figure: eight structures — anisole ($\mathrm{C_6H_5OCH_3}$); $\mathrm{(CH_3)_2CH{-}CH{=}CH{-}CO{-}CH_3}$ (5-methylhex-3-en-2-one); benzene; chlorocyclohexane; 1-isopropyl-2-nitrobenzene; 1-(but-3-en-2-yl)-2-nitrobenzene; 1,3-dimethylbenzene (m-xylene); 1-acetyl-2-methylcyclohexene ($\mathrm{COCH_3}$ and $\mathrm{CH_3}$ on the double-bond carbons of cyclohexene)]

The correct stability order of the following resonance structures of $\mathrm{CH_3-CH=CH-CHO}$ is

[Figure: three resonance structures — I: $\mathrm{CH_3-\overset{\ominus}{C}H-CH=CH-\overset{\oplus}{O}}$ (carbanion on the carbon next to $\mathrm{CH_3}$, positively charged oxygen); II: $\mathrm{CH_3-\overset{\oplus}{C}H-CH=CH-\overset{\ominus}{O}}$ (carbocation on the carbon next to $\mathrm{CH_3}$, negatively charged oxygen); III: $\mathrm{CH_3-CH=CH-CH=O}$ (neutral structure)]

Total number of stereo isomers possible for the given structure :

[Figure: $\mathrm{CH_3-C(Br)=CH-CH_2-CH(Br)-C(CH_3)=C(Br)-CH_3}$ (a diene with Br on both double bonds and on the sp$^3$ carbon between them)]

Ionic reactions with organic compounds proceed through :

(A) homolytic bond cleavage

(B) heterolytic bond cleavage

(C) free radical formation

(D) primary free radical

(E) secondary free radical

Choose the correct answer from the options given below :

Which of the following compound will most easily be attacked by an electrophile ?

Total number of deactivating groups in aromatic electrophilic substitution reaction among the following is ________.

$\mathrm{-\overset{\displaystyle O}{\overset{\|}{C}}-OCH_3}$ , $\mathrm{-\underset{\displaystyle H}{N}-\overset{\displaystyle O}{\overset{\|}{C}}-CH_3}$ , $\mathrm{-\underset{\displaystyle H}{N}-CH_3}$ , $\mathrm{-C{\equiv}N}$ , $\mathrm{-OCH_3}$

Number of optical isomers possible for 2-chlorobutane ________.

The functional group that shows negative resonance effect is :

The set of meta directing functional groups from the following sets is :

IUPAC name of following compound (P) is :

[Figure: cyclohexane ring bearing two methyl groups on the same carbon (gem-dimethyl) and an ethyl group on the carbon two positions away]

Cyclohexene [Figure: cyclohexene ring structure] is ________ type of an organic compound.

Among the following, total number of meta directing functional groups is ________. (Integer based)

$\mathrm{-OCH_3,\ -NO_2,\ -CN,\ -CH_3,\ -NHCOCH_3,\ -COR,\ -OH,\ -COOH,\ -Cl}$

Among the given organic compounds, the total number of aromatic compounds is ________.

(A) [Structure: two fused six-membered rings, each ring containing two C=C double bonds with sp3 ring-fusion carbons (4a,8a-dihydronaphthalene)]

(B) [Structure: benzene ring connected through a $\mathrm{CH_2}$ group to a cyclohexene ring]

(C) [Structure: benzene ring fused to a five-membered ring whose apex carbon bears a lone pair (carbanion-type centre)]

(D) [Structure: two benzene rings fused to a central five-membered ring whose carbon bears a negative charge (fluorenyl anion)]

3-Methylhex-2-ene on reaction with HBr in presence of peroxide forms an addition product (A). The number of possible stereoisomers for 'A' is ________.

The interaction between $\pi$ bond and lone pair of electrons present on an adjacent atom is responsible for

The difference in energy between the actual structure and the lowest energy resonance structure for the given compound is

Number of compounds among the following which contain sulphur as heteroatom is ________.

Furan, Thiophene, Pyridine, Pyrrole, Cysteine, Tyrosine

Structure of 4-Methylpent-2-enal is :

Which of the following molecule/species is most stable ?

The correct stability order of carbocations is

IUPAC name of following compound is :

$$\mathrm{CH_3 - \underset{\underset{NH_2}{|}}{CH} - CH_2 - CN}$$

Number. of geometrical isomers possible for the given structure is/are _________.

[Figure: an open-chain triene skeleton drawn with three carbon-carbon double bonds; the two terminal alkene carbons each bear one H and one D, and a central carbon of the chain carries a methyl branch as well as an exocyclic C=C to a CH(D)(CH3)-type terminus]

A species having carbon with sextet of electrons and can act as electrophile is called

Given below are two statements: Statement I: IUPAC name of $\mathrm{HO-CH_2-(CH_2)_3-CH_2-COCH_3}$ is 7-hydroxyheptan-2-one. Statement II: 2-oxoheptan-7-ol is the correct IUPAC name for above compound. In the light of the above statements, choose the most appropriate answer from the options given below: