Hydrocarbons

Q1 FREE PREVIEW

PYQ

Which of the following is a free radical substitution reaction? [Re-NEET 2020]

aAcetylene with

bMethane with

cPropene with

dBenzene with

✓ Correct answer: b) Methane with

ExplanationMethane + Br₂ (hv) is the classic example of free radical substitution, where light initiates the radical chain process.(a) is an addition to an alkyne, (c) is radical addition across a double bond, and (d) is electrophilic aromatic substitution.

Q2

PYQ

Given below are two statements

Statement I : The boiling point of three isomeric pentanes follows the order, n-pentane > isopentane > neopentane

Statement II : When, branching increases, the molecule attains a shape of sphere. This results in smaller surface area for contact, due to which the intermolecular forces between the spherical molecules are weak, there by lowering the boiling point.

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

[NEET 2024]

a

Statement I is incorrect but Statement II is correct.

b

Both Statement I and II are correct.

c

Both Statement I and Statement II are incorrect.

d

Statement I is correct but Statement II is incorrect

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Q3

PYQ

Baeyer's reagent is :

[Re-NEET 2024]

a

acidic potassium permanganate solution

b

acidic potassium dichromate solution

c

cold, dilute, aqueous solution of potassium permanganate

d

hot, concentrated solution of potassium permanganate

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Q4

PYQ

Baeyer's reagent is :

[Re-NEET 2024]

a

acidic potassium permanganate solution

b

acidic potassium dichromate solution

c

cold, dilute, aqueous solution of potassium permanganate

d

hot, concentrated solution of potassium permanganate

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Q5

PYQ

\( R-\mathrm{CH}_{2}-\mathrm{CCl}_{2}-R \stackrel{\text { Reagent }}{\longrightarrow} R-\mathrm{C} \equiv \mathrm{C}-R \)

The reagent is

(PYQ-1993)

a

\( \mathrm{Na} \)

b

\( \mathrm{HCl} \) in \( \mathrm{H}_{2} \mathrm{O} \)

c

\( \mathrm{KOH} \) in \( \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} \)

d

Zn in alcohol

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Q6

PYQ

\({\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{COO}}^{-}{\mathrm{Na}}^{+}\underset{\text{ heat }}{\overset{\mathrm{NaOH}+?}{⟶}}{\mathrm{CH}}_{3}{\mathrm{CH}}_{3}+{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}\text{. }\)

Consider the above reaction and identify the missing reagent/ chemical

[NEET 2021]

a

Red Phosphorus

b

\( \mathrm{CaO} \)

c

DIBAL-H

d

\( \mathrm{B}_{2} \mathrm{H}_{6} \)

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Q7

PYQ

Acetylenic hydrogens are acidic because

a

sigma electron density of C - H bond in acetylene is nearer to carbon, which has \( 50 \% \) \( s \)-character

b

acetylene has only open hydrogen in each carbon

c

acetylene contains least number of hydrogens among the possible hydrocarbons having two carbons

d

acetylene belongs to the class of alkynes with molecular formula, \( \mathrm{C}_{n} \mathrm{H}_{2 n-2} \).

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Q8

PYQ

\({\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{COO}}^{-}{\mathrm{Na}}^{+}\underset{\text{ heat }}{\overset{\mathrm{NaOH}+?}{⟶}}{\mathrm{CH}}_{3}{\mathrm{CH}}_{3}+{\mathrm{Na}}_{2}{\mathrm{CO}}_{3}\)

Consider the above reaction and identify the missing reagent/ chemical

[NEET 2021]

a

Red Phosphorus

b

\( \mathrm{CaO} \)

c

DIBAL-H

d

\( \mathrm{B}_{2} \mathrm{H}_{6} \)

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Q9

PYQ

Among the following compounds the one that is most reactive towards electrophilic nitration is

a

benzoic acid

b

nitrobenzene

c

toluene

d

benzene

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Q10

PYQ

Which one of the following can exhibit cis-trans isomerism?

a

\( \mathrm{CH}_{3}-\mathrm{CHCl}-\mathrm{COOH} \)

b

\( \mathrm{H}-\mathrm{C} \equiv \mathrm{C}-\mathrm{Cl} \)

c

\( \mathrm{ClCH}=\mathrm{CHCl} \)

d

\( \mathrm{ClCH}_{2}-\mathrm{CH}_{2} \mathrm{Cl} \)

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Q11

PYQ

The cylindrical shape of an alkyne is due to

a

two sigma \( C-C \) and one \( \pi C-C \) bonds

b

one sigma \( C-C \) and two \( \pi C-C \) bonds

c

three sigma \( C-C \) bonds

d

three \( \pi C-C \) bonds

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