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NEETChemistry

Organic Chemistry: Some Basic Principles and Techniques

24 NEET Chemistry previous year questions on Organic Chemistry: Some Basic Principles and Techniques — options free on every question; 2 include the answer & explanation free, the rest unlock with PYQ Pass.

Q1 FREE PREVIEW
PYQ
In Friedel-Crafts alkylation of aniline, one gets: [JEE Main 2022, 29 Jun (Shift 2)]
aalkylated product with ortho and para substitution.
bsecondary amine after acidic treatment
can amide product.
dPositively charged nitrogen at benzene ring.
✓ Correct answer: d) Positively charged nitrogen at benzene ring.
ExplanationThe friedel-crafts alkylation of aniline occurs as: Aniline shows an acid-base reaction with the , a lewis acid. aniline is a Lewis base, while acts as a lewis acid.
Q2 FREE PREVIEW
PYQ
With respect to the compounds , choose the incorrect statement(s).
aThe acidity of compound is due to delocalization in the conjugate base.
bThe conjugate base of compound IV is aromatic.
cCompound II becomes more acidic, when it has a substituent.
dThe acidity of compounds follows the order I
✓ Correct answer: d) The acidity of compounds follows the order I
ExplanationOption D is incorrect because the given order of acidity is not accurate.The acidity of a compound depends on the stability of its conjugate base.In compound I, the conjugate base (carbanion) is highly stabilized by resonance over three benzene rings, making it the most acidic.Compound IV forms a conjugate base that is aromatic and thus gains extra stability, so it is also relatively acidic.Next comes compound V (a terminal alkyne), where the negative charge is stabilized due to the high s-character of the sp-hybridized carbon.Compound II (benzene) is much less acidic, and compound III (an alkane) is the least acidic.Therefore, the exact order given in option D is not correctly justified, making D the incorrect statement.
Q3
PYQ
In the given structure, number of sp and hybridized carbon atoms present respectively are : [JEE Main 2025, 24 Jan (Shift 2)]
a3 and 6
b4 and 6
c3 and 5
d4 and 5
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Q4
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Methyl group attached to a positively charged carbon atom stabilizes the carbocation due to [Re-NEET 2024]
a-I-effect
belectromeric effect
chyperconjugation
dmesomeric effect
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Q5
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A steam volatile organic compound which is immiscible with water has a boiling point of \(250^\circ C\). During steam distillation, a mixture of this organic compound and water will boil

[Re-NEET 2024]

a

above \(100^\circ C\) but below \(250^\circ C\).

b

above \(250^\circ C\).

c

at \(250^\circ C\).

d

close to but below \(100^\circ C\).

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Q6
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On heating, some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as

[NEET 2024]

a

Chromatography

b

Crystallization

c

Sublimation

d

Distillation

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Q7
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Which one of the following compounds can exist as cis-trans isomers?

[NEET 2025]

a

1,1-Dimethylcyclopropane

b

1,2-Dimethylcyclohexane

c

Pent-1-ene

d

2-Methylhéx-2-ene

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Q8
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On heating, some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as

[NEET 2024]

a

Chromatography

b

Crystallization

c

Sublimation

d

Distillation

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Q9
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Methyl group attached to a positively charged carbon atom stabilizes the carbocation due to

[Re-NEET 2024]

a

- I inductive effect

b

electromeric effect

c

hyperconjugation

d

mesomeric effect

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Q10
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Methyl group attached to a positively charged carbon atom stabilizes the carbocation due to

[Re-NEET 2024]

a

-I-effect

b

electromeric effect

c

hyperconjugation

d

mesomeric effect

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Q11
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In Dumas method for the estimation of \(N _2\), the sample is heated with copper oxide and the gas evolved is passed over:

[JEE Main 2023, 31 Jan (Shift 2)]

a

\(Ni\)

b

Copper gauze

c

\(Pd\)

d

Copper oxide

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Q12
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For the separation of two immiscible liquids which method is used?

a

Chromatography

b

Fractionating column

c

Fractional distillation

d

Separating funnel

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Q13
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The compound which shows metamerism is

[NEET 2021]

a

\( \mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O} \)

b

\( \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O} \)

c

\( \mathrm{C}_{4} \mathrm{H}_{10} \mathrm{O} \)

d

\({\mathrm{C}}_{5}{\mathrm{H}}_{12}\)

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Q14
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A flask contains a mixture of isohexane and 3-methylpentane. One of the liquids boils at \(63{ }^{\circ} C\) while the other boils at \(60^{\circ} C\). What is the best way to separate the two liquids and which one will be distilled out first?

[JEE Main 2020, 8 Jan (Shift 1)]

a

Fractional distillation, 3-methylpentane

b

Simple distillation, isohexane

c

Simple distillation, 3-methylpentane

d

Fractional distillation, isohexane

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Q15
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The IUPAC name of the compound having the formula \( \mathrm{CH} \equiv \mathrm{C}-\mathrm{CH}=\mathrm{CH}_{2} \) is

a

1-butyne-3-ene

b

but-1-yne-3-ene

c

1-butene-3-yne

d

3-butene-1-yne

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Q16
PYQ

Dihedral angle (D.A.) of least stable conformer of ethane is

[NEET 2021]

a

\( 120^{\circ} \)

b

\( 180^{\circ} \)

c

\( 60^{\circ} \)

d

\( 0^{\circ} \)

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Q17
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Experimentally reducing a functional group cannot be done by which one of the following reagents?

[JEE Main 2021, 1 Sep (Shift 2)]

a

(Na /\({\mathrm{H}}_{2}\))

b

(Pt - C / \({\mathrm{H}}_{2}\))

c

(Pd - C /\({\mathrm{H}}_{2}\))

d

(Zn /\({\mathrm{H}}_{2}\mathrm{O}\))

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Q18
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Paper chromatography is an example of

[NEET 2020]

a

adsorption chromatography

b

partition chromatography

c

thin layer chromatography

d

column chromatography.

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Q19
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Which of the following compound is added to the sodium extract before addition of silver nitrate for testing of halogens?

a

Sodium hydroxide

b

Hydrochloric acid

c

Nitric acid

d

Ammonia

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Q20
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In Lassaigne's extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with \(\mathrm{Fe}^{3+}\) due to the formation of-

[NEET 2023]

a

\(\mathrm{NaSCN}\)

b

\(\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NOS}\right]^{4-}\)

c

\([\mathrm{Fe}(\mathrm{SCN})]^{2+}\)

d

\({\mathrm{Fe}}_{4}{\left[\mathrm{Fe}\left(\mathrm{CN}{)}_{6}\right)\right]}_{3}\cdot {\mathrm{xH}}_{2}\mathrm{O}\)

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Q21
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Which of the following is correct with respect to \( -I \) effect of the substituents? \( (R= \) alkyl \( ) \)

a

\( -\mathrm{NH}_{2}<-\mathrm{OR}<-\mathrm{F} \)

b

\(-{\mathrm{NR}}_{2}<-\mathrm{F}<-\mathrm{OR}\)

c

\( -\mathrm{NH}_{2}>-\mathrm{OR}>-\mathrm{F} \)

d

\( -\mathrm{N} R_{2}>-\mathrm{OR}>-\mathrm{F} \)

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Q22
PYQ

Dihedral angle of least stable conformer of ethane is

[NEET 2021]

a

\( 120^{\circ} \)

b

\( 180^{\circ} \)

c

\( 60^{\circ} \)

d

\( 0^{\circ} \)

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Q23
PYQ

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following?

[NEET 2020]

a

\( -I \) effect of \( -\mathrm{CH}_{3} \) groups

b

\( +R \) effect of \( -\mathrm{CH}_{3} \) groups

c

\( -R \) effect of \( -\mathrm{CH}_{3} \) groups

d

Hyperconjugation

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Q24
PYQ

Which of the following statements is not correct for a nucleophile?

a

Ammonia is a nucleophile.

b

Nucleophiles attack low \( e^{-} \)density sites.

c

Nucleophiles are not electron seeking.

d

Nucleophile is a Lewis acid

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