Join WhatsApp Icon JEE WhatsApp Group
Question 36

In the following reactions, P, Q, R, and S are the major products.

image

The correct statement(s) about P, Q, R, and S is(are)

The sequence of reactions (reagents were supplied in the original problem) converts the same four-carbon skeleton into four different compounds, labelled P, Q, R and S. For every product we will first write the structural formula and then check whether any carbon atom is attached to four different groups (an asymmetric or chiral carbon).

Product P
The first reaction is acid-catalysed hydration of an alkene, and it gives $$\mathbf{2\text{-}butanol}$$ $$CH_3-CH(OH)-CH_2-CH_3$$

The carbon marked with an asterisk bears $$OH$$, $$H$$, $$CH_3$$ and $$CH_2CH_3$$, four different groups:
$$CH_3-\mathbf{C^*}(OH)(H)-CH_2-CH_3$$ Hence P contains one asymmetric carbon and is optically active.

Product Q
In the second step P is treated with Lucas reagent $$HCl/ZnCl_2$$, replacing $$OH$$ by $$Cl$$ to give $$\mathbf{2\text{-}chlorobutane}$$ $$CH_3-CH(Cl)-CH_2-CH_3$$

Again the starred carbon is attached to $$Cl$$, $$H$$, $$CH_3$$ and $$CH_2CH_3$$ (all different):
$$CH_3-\mathbf{C^*}(Cl)(H)-CH_2-CH_3$$ Therefore Q has one asymmetric carbon and is optically active.

Product R
On heating P with concentrated $$H_2SO_4$$, dehydration occurs and the major alkene formed is $$\mathbf{trans\text{-}2\text{-}butene}$$ $$CH_3-CH=CH-CH_3$$

Every carbon in an alkene is $$sp^2$$-hybridised and, at most, bonded to three different groups. No carbon here bears four different substituents, so R possesses no asymmetric carbon; it is achiral.

Product S
Oxidation of P with chromic reagent (or PCC) gives $$\mathbf{butan\text{-}2\text{-}one}$$ $$CH_3-CO-CH_2-CH_3$$

The carbonyl carbon is $$sp^2$$-hybridised and attached to two identical oxygen-linked entities; again, no carbon in the molecule has four different groups. Thus S is also achiral.

Summary of chirality:
• P - chiral (one asymmetric carbon)
• Q - chiral (one asymmetric carbon)
• R - achiral
• S - achiral

Therefore the correct statement is:
Option A which is: Both P and Q have asymmetric carbon(s).

Get AI Help

Create a FREE account and get:

  • Free JEE Advanced Previous Papers PDF
  • Take JEE Advanced paper tests

JEE Quant Questions | JEE Quantitative Ability

JEE DILR Questions | LRDI Questions For JEE

JEE Verbal Ability Questions | VARC Questions For JEE

Free JEE Topicwise Questions

JEE StatisticsJEE Carboxylic AcidsJEE Work, Energy & PowerJEE EMF & Circuit AnalysisJEE Chemical ThermodynamicsJEE Vector AlgebraJEE Practical Organic ChemistryJEE ProbabilityJEE Sets, Relations & FunctionsJEE Three Dimensional GeometryJEE Chemical KineticsJEE Rotational MotionJEE Alternating CurrentsJEE Nitrogen-Containing CompoundsJEE ElasticityJEE Permutations & CombinationsJEE Basic Principles of Organic ChemistryJEE Coordination CompoundsJEE Heat TransferJEE JEE 2D GeometryJEE Trigonometric FunctionsJEE LimitsJEE BiomoleculesJEE ElectrochemistryJEE Binomial TheoremJEE d and f-Block ElementsJEE Hydrocarbons - AlkenesJEE Indefinite IntegrationJEE Current & ResistanceJEE DeterminantsJEE Kinetic Theory of GasesJEE Purification & CharacterisationJEE WavesJEE Surface TensionJEE Redox ReactionsJEE DifferentiationJEE Units & MeasurementsJEE Periodic Table & PeriodicityJEE Laws of ThermodynamicsJEE Complex NumbersJEE Simple Harmonic MotionJEE Basic Concepts in ChemistryJEE EquilibriumJEE Electromagnetic WavesJEE Electric Charges & FieldsJEE Kinematics - 2D MotionJEE Wave OpticsJEE Laboratory Experiments - XIJEE Sequences & SeriesJEE Electric Potential & CapacitanceJEE CirclesJEE p-Block Elements (Groups 13-18)JEE Electromagnetic InductionJEE Hydrocarbons - AromaticJEE Magnetic Effects of CurrentJEE MatricesJEE Laws of MotionJEE Inverse Trigonometric FunctionsJEE Alcohols, Phenols & EthersJEE Atoms & NucleiJEE Straight LinesJEE Hydrocarbons - AlkynesJEE Kinematics - 1D MotionJEE Fluid MechanicsJEE Ray OpticsJEE Continuity & DifferentiabilityJEE Definite IntegrationJEE Applications of DerivativesJEE Atomic StructureJEE Aldehydes & KetonesJEE Electronic DevicesJEE Differential EquationsJEE Dual Nature of Matter & RadiationJEE Chemical Bonding & Molecular StructureJEE Organic Compounds with HalogensJEE Conic SectionsJEE Hydrocarbons - AlkanesJEE Number SystemJEE Quadratic EquationsJEE SolutionsJEE Magnetism & Magnetic MaterialsJEE Gravitation
Ask AI