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 · 8 Apr · Shift 2 · Q10
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 · 8 Apr · Shift 2 · Q10

Basics of Organic Chemistry question

2024 · 8 Apr · Shift 2 · Q10

JEE MainChemistryBasics of Organic ChemistryMCQ+4 / −1
The correct sequence of acidic strength of the following aliphatic acids in their decreasing order is: CH3CH2COOH,CH3COOH,CH3CH2CH2COOH,HCOOH\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{COOH}, \mathrm{CH}_3 \mathrm{COOH}, \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}, \mathrm{HCOOH}CH3​CH2​COOH,CH3​COOH,CH3​CH2​CH2​COOH,HCOOH
  1. A
    HCOOH>CH3CH2CH2COOH>CH3CH2COOH>CH3COOH\mathrm{HCOOH}\gt \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{COOH}HCOOH>CH3​CH2​CH2​COOH>CH3​CH2​COOH>CH3​COOH
  2. B
    HCOOH>CH3COOH>CH3CH2COOH>CH3CH2CH2COOH\mathrm{HCOOH}\gt \mathrm{CH}_3 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}HCOOH>CH3​COOH>CH3​CH2​COOH>CH3​CH2​CH2​COOH
  3. C
    CH3CH2CH2COOH>CH3CH2COOH>CH3COOH>HCOOH\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{COOH}\gt \mathrm{HCOOH}CH3​CH2​CH2​COOH>CH3​CH2​COOH>CH3​COOH>HCOOH
  4. D
    CH3COOH>CH3CH2COOH>CH3CH2CH2COOH>HCOOH\mathrm{CH}_3 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{COOH}\gt \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{COOH}\gt \mathrm{HCOOH}CH3​COOH>CH3​CH2​COOH>CH3​CH2​CH2​COOH>HCOOH
View written solutionFree

Correct answer: B

  1. Principle involved

For carboxylic acids, acidic strength depends on the stability of the conjugate base, RCOO−\mathrm{RCOO^-}RCOO−.

  • Electron-donating alkyl groups show the +I+I+I effect.
  • This increases electron density on the carboxylate ion and destabilizes it.
  • Therefore, more alkyl substitution means weaker acid.

So, among aliphatic carboxylic acids:

  • Formic acid (HCOOH)(\mathrm{HCOOH})(HCOOH) is strongest because it has no alkyl group.
  • As the size of the alkyl group increases, acidity decreases.
  1. Given acids

The acids are:

  • HCOOH\mathrm{HCOOH}HCOOH = formic acid
  • CH3COOH\mathrm{CH_3COOH}CH3​COOH = acetic acid
  • CH3CH2COOH\mathrm{CH_3CH_2COOH}CH3​CH2​COOH = propionic acid
  • CH3CH2CH2COOH\mathrm{CH_3CH_2CH_2COOH}CH3​CH2​CH2​COOH = butyric acid
  1. Compare their acidic strengths

Since alkyl groups decrease acidity by the +I+I+I effect:

HCOOH>CH3COOH>CH3CH2COOH>CH3CH2CH2COOH\mathrm{HCOOH} > \mathrm{CH_3COOH} > \mathrm{CH_3CH_2COOH} > \mathrm{CH_3CH_2CH_2COOH}HCOOH>CH3​COOH>CH3​CH2​COOH>CH3​CH2​CH2​COOH
  1. Match with options
  • A: HCOOH>CH3CH2CH2COOH>CH3CH2COOH>CH3COOH\mathrm{HCOOH} > \mathrm{CH_3CH_2CH_2COOH} > \mathrm{CH_3CH_2COOH} > \mathrm{CH_3COOH}HCOOH>CH3​CH2​CH2​COOH>CH3​CH2​COOH>CH3​COOH ❌
  • B: HCOOH>CH3COOH>CH3CH2COOH>CH3CH2CH2COOH\mathrm{HCOOH} > \mathrm{CH_3COOH} > \mathrm{CH_3CH_2COOH} > \mathrm{CH_3CH_2CH_2COOH}HCOOH>CH3​COOH>CH3​CH2​COOH>CH3​CH2​CH2​COOH ✅
  • C: reverse order ❌
  • D: puts HCOOH\mathrm{HCOOH}HCOOH weakest ❌
  1. Final answer

The correct decreasing order of acidic strength is:

HCOOH>CH3COOH>CH3CH2COOH>CH3CH2CH2COOH\boxed{\mathrm{HCOOH} > \mathrm{CH_3COOH} > \mathrm{CH_3CH_2COOH} > \mathrm{CH_3CH_2CH_2COOH}}HCOOH>CH3​COOH>CH3​CH2​COOH>CH3​CH2​CH2​COOH​

Hence, the correct option is B.

PreviousNext

More from Basics of Organic Chemistry

  • IUPAC name of following hydrocarbon(X) is : Includes diagram2024 · MCQ
  • Total number of aromatic compounds among the following compounds is ​. Includes diagram2024 · Numerical
  • The number of optically active compounds from the following is ​. Includes diagram2024 · Numerical
  • Relative stability of the contributing structures is : Includes diagram2024 · MCQ
  • Correct order of basic strength of Pyrrole , Pyridine and Piperidine is : Includes diagram2024 · MCQ
  • For the given compounds, the correct order of increasing pKa​ value : Choose the correct answer from the options given below : Includes diagram2024 · MCQ
  • Methods used for purification of organic compounds are based on :2024 · MCQ
  • How many compounds among the following compounds show inductive, mesomeric as well as hyperconjugation effects? Includes diagram2024 · Numerical