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JEE Main 20265 AprilMorning Shift
Exam
JEE Main
Year
2026
Date
5 April
Shift
Morning Shift
Subject
Chemistry
Chapter
Alcohols Phenols and Ethers

JEE Main 2026 · 5 April · Morning Shift · Chemistry · Alcohols Phenols and Ethers

Consider compounds A, B and C with following structural formulae A...

Consider compounds A, B and C with following structural formulae
A=A = CH3_3 - CH2_2 - CH2_2 - CH2_2 - CH2_2 - OH
B=B = CH2=_2 = CH - CH2_2 - CH2_2 - CH3_3
C=C = HO - CH2_2 - CH2_2 - CH(OH) - CH3_3
For the conversion of B from A, reagent (D) required is _________ and structural formula of product (E) obtained when C undergoes same reaction using excess reagent (D) is _________.

Options

  1. A
    DE
    Conc. H2_2SO4_4CH2=_2 = CH −- CH(OH)CH3_3
  2. B
    DE
    PCCHO −- CH2_2 −- CH2_2 −- CH = CH2_2
  3. C
    DE
    PCCCH2=_2 = CH −- CH = CH2_2
  4. D
    DE
    Conc. H2_2SO4_4 or H3_3PO4_4CH2=_2 = CH −- CH = CH2_2

Correct answer

D.

DE
Conc. H2_2SO4_4 or H3_3PO4_4CH2=_2 = CH −- CH = CH2_2

Step-by-step solution

Compound A is pen\tan^{-1}-ol (CH3−CH2−CH2−CH2−CH2−OHCH_3-CH_2-CH_2-CH_2-CH_2-OH) and Compound B is pent-1-ene (CH2=CH−CH2−CH2−CH3CH_2=CH-CH_2-CH_2-CH_3).

The conversion of an alcohol to an alkene is a dehydration reaction, which requires an acidic dehydrating agent such as concentrated H2SO4H_2SO_4 or H3PO4H_3PO_4. Thus, reagent D is concentrated H2SO4H_2SO_4 or H3PO4H_3PO_4.

Compound C is butane-1,3-diol (HO−CH2−CH2−CH(OH)−CH3HO-CH_2-CH_2-CH(OH)-CH_3).

When C is treated with excess dehydrating agent (reagent D), both hydroxyl groups undergo elimination (dehydration). The elimination of two water molecules yields a conjugated diene, which is highly stable due to resonance.

The product E formed is 1,3-butadiene (CH2=CH−CH=CH2CH_2=CH-CH=CH_2).

Answer:
DE
Conc. H2_2SO4_4 or H3_3PO4_4CH2=_2 = CH −- CH = CH2_2
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