Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Basics of Organic Chemistry question

2024 · 30 Jan · Shift 2 · Q2
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Chemistry
  4. /Basics of Organic Chemistry
  5. /2024 · 30 Jan · Shift 2 · Q2

Basics of Organic Chemistry question

2024 · 30 Jan · Shift 2 · Q2

JEE MainChemistryBasics of Organic ChemistryMCQ+4 / −1
The correct stability order of carbocations is
  1. A
    (CH3)3C+>CH3−C+H2>(CH3)2C+H>C+H3\left(\mathrm{CH}_3\right)_3 \mathrm{C}^{+}\gt \mathrm{CH}_3-\stackrel{+}{\mathrm{C}} \mathrm{H}_2\gt \left(\mathrm{CH}_3\right)_2 \stackrel{+}{\mathrm{C}} \mathrm{H}\gt \stackrel{+}{\mathrm{C}} \mathrm{H}_3(CH3​)3​C+>CH3​−C+​H2​>(CH3​)2​C+​H>C+​H3​
  2. B
    (CH3)3C+>(CH3)2C+H>CH3−C+H2>C+H3\left(\mathrm{CH}_3\right)_3 \stackrel{+}{\mathrm{C}}\gt \left(\mathrm{CH}_3\right)_2 \stackrel{+}{\mathrm{C}} \mathrm{H}\gt \mathrm{CH}_3-\stackrel{+}{\mathrm{C}} \mathrm{H}_2\gt \stackrel{+}{\mathrm{C}} \mathrm{H}_3(CH3​)3​C+​>(CH3​)2​C+​H>CH3​−C+​H2​>C+​H3​
  3. C
    JEE Main 2024 (Online) 30th January Evening Shift Chemistry - Basics of Organic Chemistry Question 69 English Option 3
  4. D
    C+H3>(CH3)2C+H>CH3−C+H2>(CH3)3C+\stackrel{+}{\mathrm{C}} \mathrm{H}_3\gt \left(\mathrm{CH}_3\right)_2 \stackrel{+}{\mathrm{C}} \mathrm{H}\gt \mathrm{CH}_3-\stackrel{+}{\mathrm{C}} \mathrm{H}_2\gt \left(\mathrm{CH}_3\right)_3 \stackrel{+}{\mathrm{C}}C+​H3​>(CH3​)2​C+​H>CH3​−C+​H2​>(CH3​)3​C+​
View written solutionFree

Correct answer: B

  1. Identify the carbocations involved

The options compare the stability of:

  • Tertiary carbocation: (CH3)3C+\left(\mathrm{CH}_3\right)_3\mathrm{C}^+(CH3​)3​C+
  • Secondary carbocation: (CH3)2CH+\left(\mathrm{CH}_3\right)_2\mathrm{CH}^+(CH3​)2​CH+
  • Primary carbocation: CH3CH2+\mathrm{CH}_3\mathrm{CH}_2^+CH3​CH2+​
  • Methyl carbocation: CH3+\mathrm{CH}_3^+CH3+​
  1. Use the general stability rule for alkyl carbocations

Stability of simple alkyl carbocations depends mainly on:

  • +I+I+I effect of alkyl groups
  • Hyperconjugation

More alkyl groups attached to the positively charged carbon donate electron density and stabilize the carbocation.

Therefore, the stability order is:

3∘>2∘>1∘>methyl3^\circ > 2^\circ > 1^\circ > \text{methyl}3∘>2∘>1∘>methyl

That is,

(CH3)3C+>(CH3)2CH+>CH3CH2+>CH3+\left(\mathrm{CH}_3\right)_3\mathrm{C}^+ > \left(\mathrm{CH}_3\right)_2\mathrm{CH}^+ > \mathrm{CH}_3\mathrm{CH}_2^+ > \mathrm{CH}_3^+(CH3​)3​C+>(CH3​)2​CH+>CH3​CH2+​>CH3+​
  1. Check the options

  • Option A:

    (CH3)3C+>CH3−CH2+>(CH3)2CH+>CH3+\left(\mathrm{CH}_3\right)_3 \mathrm{C}^{+} > \mathrm{CH}_3-\mathrm{CH}_2^+ > \left(\mathrm{CH}_3\right)_2 \mathrm{CH}^+ > \mathrm{CH}_3^+(CH3​)3​C+>CH3​−CH2+​>(CH3​)2​CH+>CH3+​

    This places primary above secondary, which is incorrect.

  • Option B:

    (CH3)3C+>(CH3)2CH+>CH3CH2+>CH3+\left(\mathrm{CH}_3\right)_3\mathrm{C}^+ > \left(\mathrm{CH}_3\right)_2\mathrm{CH}^+ > \mathrm{CH}_3\mathrm{CH}_2^+ > \mathrm{CH}_3^+(CH3​)3​C+>(CH3​)2​CH+>CH3​CH2+​>CH3+​

    This is correct.

  • Option D:

    CH3+>(CH3)2CH+>CH3CH2+>(CH3)3C+\mathrm{CH}_3^+ > \left(\mathrm{CH}_3\right)_2\mathrm{CH}^+ > \mathrm{CH}_3\mathrm{CH}_2^+ > \left(\mathrm{CH}_3\right)_3\mathrm{C}^+CH3+​>(CH3​)2​CH+>CH3​CH2+​>(CH3​)3​C+

    This is the reverse trend, so incorrect.

  1. Final answer

The correct stability order is:

(CH3)3C+>(CH3)2CH+>CH3CH2+>CH3+\left(\mathrm{CH}_3\right)_3\mathrm{C}^+ > \left(\mathrm{CH}_3\right)_2\mathrm{CH}^+ > \mathrm{CH}_3\mathrm{CH}_2^+ > \mathrm{CH}_3^+(CH3​)3​C+>(CH3​)2​CH+>CH3​CH2+​>CH3+​

So, the correct option is B.

PreviousNext

More from Basics of Organic Chemistry

  • Number of geometrical isomers possible for the given structure is/are ​. Includes diagram2024 · Numerical
  • Which among the following purification methods is based on the principle of "Solubility" in two different solvents?2024 · MCQ
  • IUPAC name of following compound is : Includes diagram2024 · MCQ
  • Given below are two statements: Statement I: IUPAC name of HO−CH2​−(CH2​)3​−CH2​−COCH3​ is 7-hydroxyheptan-2-one. Statement II: 2-oxoheptan-7-ol is the correct IUPAC name for…2024 · MCQ
  • A species having carbon with sextet of electrons and can act as electrophile is called2024 · MCQ
  • Number of isomeric products formed by monochlorination of 2-methylbutane in presence of sunlight is ​.2024 · Numerical
  • Identify structure of 2,3-dibromo-1-phenylpentane.2024 · MCQ
  • The correct order of reactivity in electrophilic substitution reaction of the following compounds is : Includes diagram2024 · MCQ