Hydrocarbons — JEE Main PYQs

The compound (X) on

(i) on heating in the presence of anhydrous $\mathrm{AlCl_3}$ and HCl gas gives 2,4-dimethyl pentane

(ii) aromatization gives toluene and

(iii) cyclisation gives methyl cyclohexane

The correct name of compound (X) is :

An alkene (X) on ozonolysis followed by reduction gives following products.

$\mathrm{H{-}CHO}$ (2 moles), $\mathrm{OHC{-}CO{-}CHO}$, $\mathrm{CH_3{-}CO{-}CO{-}CO{-}CH_3}$

[Figure: the three carbonyl products drawn as structural formulae — formaldehyde (2 moles), a 1,2,3-tricarbonyl dialdehyde, and a 1,2,3-tricarbonyl with terminal methyl ketones]

The alkene (X) is:

[Figure: styrene (vinylbenzene, $\mathrm{C_6H_5{-}CH{=}CH_2}$), labelled (X)]

$\mathrm{(X)} \xrightarrow[\begin{array}{l}\text{(ii) } \mathrm{NaNH_2} \text{ excess} \\ \text{(iii) } \mathrm{CH_3I} \\ \text{(iv) } \mathrm{H_2,\ Na/NH_3}\ (l)\end{array}]{\text{(i) } \mathrm{Br_2\,/\,CHCl_3}}$ Major Product (Y)

Compound (X) is subjected to the sequence of reactions as shown above. Molar mass of the major product (Y) formed is ______________ $\mathrm{g\ mol^{-1}}$.

(Given molar mass in $\mathrm{g\ mol^{-1}}$ C: 12, H: 1, O: 16)

"P" is a hydrocarbon of molecular formula:- $\mathrm{C_8H_{14}}$. On ozonolysis, "P" forms "Q". "Q" on treatment with alkali under reflux condition produces "R", which on treatment with $\mathrm{I_2}$/NaOH gives a yellow precipitate. Acidification of the solution gives "S". The structure of "S" is given below:-

[Figure: cyclopentene ring with $\mathrm{-CH_3}$ on one doubly-bonded carbon and $\mathrm{-COOH}$ on the other, i.e. 2-methylcyclopent-1-ene-1-carboxylic acid]

The correct structure of "P" is

For the following Friedel Craft's alkylation reaction, which of the statements are correct?

[Figure: benzene + 1-chloropropane $\xrightarrow{\text{Anhydrous } \mathrm{AlCl_3}}$ Alkylbenzene]

$\mathrm{C_6H_6 + CH_3CH_2CH_2Cl \xrightarrow[\text{Anhydrous}]{\mathrm{AlCl_3}} Alkylbenzene}$

A. Major product is n-propyl benzene. B. iso-propyl carbocation intermediate is also generated. C. Multiple substitution is inevitable. D. Introducing electron-donating substituent on benzene will not produce any alkyl benzene.

Choose the correct answer from the options given below:

IUPAC name of the some alkenes are given below.

Find out the correct stability order.

A. 2-Methylbut-2-ene

B. cis-But-2-ene

C. 2,3-Dimethylbut-2-ene

D. Prop-1-ene

Choose the correct answer from the options given below :

Identify the correct IUPAC name of hydrocarbon ($x$) containing three primary carbon atoms and with molar mass 72 $\mathrm{g\ mol^{-1}}$.

Given below are two statements:

Statement I: Methane can be prepared by decarboxylation of sodium ethanoate, Kolbe's electrolysis of sodium acetate and reaction of $\mathrm{CH_3MgBr}$ with water.

Statement II: Methane cannot be prepared from unsaturated hydrocarbons and by Wurtz reaction.

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

An alkane (Y) requires 8 moles of oxygen for complete combustion and on chlorination with $\mathrm{Cl_2}/h\nu$, (Y) gives only one monochlorinated product (Z). The total number of primary carbon atoms in (Y) is ________.

The total number of aromatic compounds/species from the following is

[Figure: six structures — (1) cyclohexa-2,5-diene-1,4-dione (p-benzoquinone), (2) tropylium cation (cycloheptatrienyl cation, $\mathrm{C_7H_7^+}$), (3) phenanthrene, (4) 1,2-dihydronaphthalene, (5) cyclobutadienyl dication ($\mathrm{C_4H_4^{2+}}$), (6) cyclohexadienyl anion ($\mathrm{C_6H_7^-}$)]

Designate whether each of the following compounds is aromatic or not aromatic.

[Figure: eight ring structures — (a) cyclopentadienyl anion; (b) cyclopentadienyl cation; (c) cyclobutadienyl dication (four-membered ring with two + charges); (d) cyclobutadienyl dianion (four-membered ring with two − charges); (e) cycloheptatrienyl (tropylium) cation; (f) cyclooctatetraene; (g) cyclobutadiene; (h) cyclopropenyl cation]

Given below are two statements :

Statement (I) : Neopentane forms only one monosubstituted derivative.

Statement (II) : Melting point of neopentane is higher than n-pentane.

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

Which compound would give 3-methyl-6-oxoheptanal upon ozonolysis?

In the following series of reactions identify the major products A & B respectively

$$\text{Bromobenzene} \xrightarrow[\mathrm{H_2SO_4}]{\mathrm{SO_3}} \underset{\text{Major product}}{\mathrm{A}} \xrightarrow{\mathrm{Br_2,\ Fe}} \underset{\text{Major product}}{\mathrm{B}}$$

[Figure: bromobenzene structure shown; the options are drawn structures]

The total number of structural isomers possible for the substituted benzene derivatives with the molecular formula $\mathrm{C_9H_{12}}$ is __________.

Consider the following molecule (X).

The structure of X is

[Figure: a tricyclic hydrocarbon (X) made of two fused six-membered rings and one fused five-membered ring, containing three C=C double bonds — a conjugated diene across the two six-membered rings and one double bond at the ring fusion of the five-membered ring]

The major product formed when the given molecule (X) is treated with HBr (1 eq) is :

The reactions which cannot be applied to prepare an alkene by elimination, are

A. [Figure: 1-bromo-2-methylcyclohexane] $\xrightarrow{\text{NaOEt}}$

B. $\mathrm{CH_3{-}CH_2{-}\underset{\underset{\mathrm{Br}}{|}}{CH}{-}CH_3} \xrightarrow{\text{KOH (aq)}}$

C. $\mathrm{(CH_3)_3C{-}Br} \xrightarrow{\text{NaOMe}}$

D. [Figure: phenol] $\xrightarrow[\mathrm{H_2SO_4}]{\mathrm{Na_2Cr_2O_7}}$

E. $\mathrm{(CH_3)_3C{-}OH} \xrightarrow[573\ \mathrm{K}]{\text{Cu}}$

Choose the correct answer from the options given below:

Given below are two statements:

Statement I: Ozonolysis followed by treatment with Zn, $\mathrm{H_2O}$ of cis-2-butene gives ethanal.

Statement II: The product obtained by ozonolysis followed by treatment with Zn, $\mathrm{H_2O}$ of 3, 6-dimethyloct-4-ene has no chiral carbon atom.

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

The number of optically active products obtained from the complete ozonolysis of the given compound is :

[Figure: $\mathrm{H_3C-CH=CH-C^*(CH_3)(H)-CH=CH-C^*(H)(CH_3)-CH=CH-CH_3}$, a triene with two stereocentres (the first bearing wedge-CH$_3$/hash-H, the second bearing wedge-H/hash-CH$_3$)]

1,2-dibromocyclooctane $\xrightarrow{\text{(i) KOH (alc.) (ii) } \mathrm{NaNH_2} \text{ (iii) } \mathrm{Hg^{2+}/H^+} \text{ (iv) } \mathrm{Zn{-}Hg/H^+}}$ P (major product)

'P' is

Given below are two statements :

Statement I : One mole of propyne reacts with excess of sodium to liberate half a mole of $\mathrm{H_2}$ gas.

Statement II : Four g of propyne reacts with $\mathrm{NaNH_2}$ to liberate $\mathrm{NH_3}$ gas which occupies 224 mL at STP.

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

When sec-butyl cyclohexane reacts with bromine in the presence of sunlight, the major product is :

The alkane from below having two secondary hydrogens is :

The compound with molecular formula $\mathrm{C_6H_6}$, which gives only one monobromo derivative and takes up four moles of hydrogen per mole for complete hydrogenation has __________ $\pi$ electrons.

Match List-I (Isomers of $\mathrm{C_{10}H_{14}}$) with List-II (Ozonolysis product).

[Figure: List-I shows four bicyclic hydrocarbon structures (methyl-substituted hydrindane/indane-type fused 6- and 5-membered rings, each with one ring double bond) labelled (A), (B), (C), (D); List-II shows four open-chain poly-carbonyl ozonolysis products labelled (I)-(IV).]

• (A) 2-methyl bicyclic isomer with double bond in the six-membered ring
• (B) 2-methyl isomer with double bond at the ring fusion / five-membered ring
• (C) 6-methyl isomer with double bond in the six-membered ring
• (D) 1-methyl isomer with the double bond conjugated to the ring junction

List-II products:

• (I) $\mathrm{H{-}CO{-}CH(CH_3){-}CH_2{-}CO{-}(CH_2)_3{-}CO{-}CHO}$ type dialdehyde/diketone with a branch methyl
• (II) $\mathrm{CH_3{-}CO{-}CO{-}(CH_2)_4{-}CO{-}CHO}$ type
• (III) $\mathrm{H{-}CO{-}CH_2CH_2{-}CO{-}CH(CH_3){-}CO{-}CHO}$ type (two terminal CHO, a mid ketone and a branch methyl)
• (IV) $\mathrm{H{-}CO{-}CO{-}(CH_2)_4{-}CO{-}CO{-}CH_3}$ type

Choose the correct answer from the options given below :

Following are the four molecules "P", "Q", "R" and "S". Which one among the four molecules will react with $\mathrm{H{-}Br_{(aq)}}$ at the fastest rate?

[Figure: P = 3,6-dihydro-2H-pyran (six-membered ring with O, C=C not adjacent to O); Q = 3,4-dihydro-2H-pyran (six-membered ring with O, C=C adjacent to O); R = 1-methylcyclohexene; S = 1,2-dimethylcyclohexene]

The hydrocarbon (X) with molar mass $80\ \mathrm{g\ mol^{-1}}$ and 90% carbon has _______ degree of unsaturation.

Identify product [A], [B] and [C] in the following reaction sequence.

\mathrm{CH_3 - C \equiv CH} \xrightarrow[\mathrm{H_2}]{\mathrm{Pd/C}} [A] \xrightarrow[\text{(ii) Zn, H_2O}]{\text{(i) O_3}} [B] + [C]

The total number of compounds from below when treated with hot $\mathrm{KMnO_4}$ giving benzoic acid is :

[Figure: eight compounds — toluene, ethylbenzene, isopropylbenzene (cumene), tert-butylbenzene, isobutylbenzene, 2-phenylpropan-2-ol, n-propylbenzene, 4,4'-dimethylbiphenyl]

The number of different chain isomers for $\mathrm{C_7H_{16}}$ is ________.

[Figure: reaction sequence — 1-methylcyclohex-1-ene $\xrightarrow{\text{"A"}}$ open-chain keto aldehyde $\mathrm{CH_3CO(CH_2)_4CHO}$ (6-oxoheptanal) $\xrightarrow{\text{"B"}}$ sodium carboxylate $\mathrm{NaOOC(CH_2)_4CHO}$ (sodium 6-oxohexanoate)]

In the above chemical reaction sequence "A" and "B" respectively are

Given below are two statements :

Statement I : Nitration of benzene involves the following step -

$$\mathrm{H{-}\overset{\oplus}{O}(H){-}NO_2 \rightleftharpoons H_2O + \overset{\oplus}{N}O_2}$$

Statement II : Use of Lewis base promotes the electrophilic substitution of benzene.

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

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : Cis form of alkene is found to be more polar than the trans form.

Reason (R) : Dipole moment of trans isomer of 2-butene is zero.

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

Consider the given chemical reaction :

[Figure: cyclohexene $\xrightarrow[\text{Heat}]{\mathrm{KMnO_4 - H_2SO_4}}$ Product "A"]

Product "A" is :

The product $\mathrm{(C)}$ in the following sequence of reactions has ________ $\pi$ bonds.

[Figure: propylbenzene ($\mathrm{C_6H_5{-}CH_2CH_2CH_3}$) $\xrightarrow[\Delta]{\mathrm{KMnO_4 - KOH}}$ (A) $\xrightarrow{\mathrm{H_3O^+}}$ (B) $\xrightarrow[\mathrm{FeBr_3}]{\mathrm{Br_2}}$ (C)]

The major product of the following reaction is P.

$$\mathrm{CH_3C \equiv C{-}CH_3} \xrightarrow[\substack{\text{(ii) dil. } \mathrm{KMnO_4} \\ 273\ \mathrm{K}}]{\text{(i) Na/liq. } \mathrm{NH_3}} \text{'P'}$$

Number of oxygen atoms present in product 'P' is ________. (nearest integer)

The major products from the following reaction sequence are product A and product B.

[Figure: cyclohexene at the centre undergoing two separate reaction sequences — to the right: (i) $\mathrm{Br_2}$, (ii) $\mathrm{HC{\equiv}C{-}CH_2{-}O^-Na^+}$ (1.0 eq.) giving A; to the left: (i) $\mathrm{Br_2}$, (ii) alc. KOH (3 eq.) giving B]

The total sum of $\pi$ electrons in product A and product B are _________ (nearest integer)

[Figure: four benzene rings — (I) with $\mathrm{CH_3}$ substituent (toluene), (II) unsubstituted (benzene), (III) with $\mathrm{OCH_3}$ substituent (anisole), (IV) with $\mathrm{CF_3}$ substituent]

The correct arrangement for decreasing order of electrophilic substitution for above compounds is :

Which of the following are aromatic?

A. [Figure: naphthalene — two fused six-membered rings, fully conjugated]

B. [Figure: styrene — benzene ring with a vinyl ($\mathrm{CH{=}CH_2}$) substituent]

C. [Figure: ten-membered monocyclic ring with five alternating double bonds ([10]annulene)]

D. [Figure: sixteen-membered monocyclic ring with eight alternating double bonds ([16]annulene)]

Major product B of the following reaction has ________ $\pi$-bond.

[Figure: ethylbenzene — benzene ring bearing a CH2CH3 group]

$$\mathrm{C_6H_5CH_2CH_3 \xrightarrow[\Delta]{KMnO_4-KOH} (A) \xrightarrow{HNO_3/H_2SO_4} (B)}$$

Total number of aromatic compounds among the following compounds is ________.

[Figure: six ring structures — (1) a bicyclic decalin-like ring system with non-conjugated double bonds (isomer of naphthalene with broken conjugation), (2) two cyclopentadiene rings joined by an exocyclic C=C double bond (fulvalene-type), (3) cyclopentadienyl cation (five-membered ring with positive charge), (4) cyclooctatetraene, (5) pyridine (six-membered ring with N lone pair), (6) cycloheptatriene]

The incorrect statement regarding ethyne is

Number of compounds from the following which cannot undergo Friedel-Crafts reactions is: ________

toluene, nitrobenzene, xylene, cumene, aniline, chlorobenzene, m-nitroaniline, m-dinitrobenzene

In the given reactions identify A and B

$\mathrm{H_2 + A \xrightarrow{Pd/C}}$ [Figure: cis-alkene with $\mathrm{CH_3}$ and H on one doubly-bonded carbon and $\mathrm{C_2H_5}$ and H on the other, i.e. cis-pent-2-ene]

$\mathrm{CH_3-C\equiv C-CH_3 + H_2 \xrightarrow{\text{Na/Liquid } NH_3}}$ "B"

Total number of isomeric compounds (including stereoisomers) formed by monochlorination of 2-methylbutane is ________.

Identify product A and product B :

[Figure: a cyclohexadiene ring + $\mathrm{Cl_2}$; upper path with $h\nu$ gives Product A, lower path in $\mathrm{CCl_4}$ gives Product B]

Compound A formed in the following reaction reacts with B gives the product C. Find out A and B.

$$\mathrm{CH_3{-}C{\equiv}CH + Na \longrightarrow A \xrightarrow{B} \underset{(C)}{CH_3{-}C{\equiv}C{-}CH_2{-}CH_2{-}CH_3} + NaBr}$$

Products A and B formed in the following set of reactions are

[Figure: reaction scheme — 1-methylcyclohexene at the centre; arrow to the right labelled $\mathrm{H^+/H_2O}$ gives A; arrow to the left labelled $\mathrm{B_2H_6}$ (above) and $\mathrm{H_2O_2}$, NaOH(aq) (below) gives B]

Number of alkanes obtained on electrolysis of a mixture of $\mathrm{CH_3COONa}$ and $\mathrm{C_2H_5COONa}$ is ________.

The correct order of reactivity in electrophilic substitution reaction of the following compounds is :

[Figure: four benzene-ring structures — A: benzene, B: toluene ($\mathrm{C_6H_5CH_3}$), C: chlorobenzene ($\mathrm{C_6H_5Cl}$), D: nitrobenzene ($\mathrm{C_6H_5NO_2}$)]

Major product of the following reaction is -

[Figure: 1-methylcyclopent-1-ene treated with $\mathrm{D-Cl}$]

$$\text{1-methylcyclopentene} \xrightarrow{\mathrm{D-Cl}} ?$$

Identify major product 'P' formed in the following reaction.

$$\mathrm{C_6H_6} + \mathrm{C_6H_5COCl} \xrightarrow{\text{Anhydrous } \mathrm{AlCl_3}} \text{'P' (Major Product)}$$

[Figure: benzene plus benzoyl chloride reaction scheme]