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Aldehydes Ketones and Carboxylic Acids question

2021 · 1 Sep · Shift 2 · Q4
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Aldehydes Ketones and Carboxylic Acids question

2021 · 1 Sep · Shift 2 · Q4

JEE MainChemistryAldehydes Ketones and Carboxylic AcidsMCQ+4 / −1
In the following sequence of reactions a compound A, (molecular formula C6H12O2C_6H_{12}O_2C6​H12​O2​) with a straight chain structure gives a C4C_4C4​ carboxylic acid. A is : JEE Main 2021 (Online) 1st September Evening Shift Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 118 English
  1. A
    CH3−CH2−COO−CH2−CH2−CH3C{H_3} - C{H_2} - COO - C{H_2} - C{H_2} - C{H_3}CH3​−CH2​−COO−CH2​−CH2​−CH3​
  2. B
    JEE Main 2021 (Online) 1st September Evening Shift Chemistry - Aldehydes, Ketones and Carboxylic Acids Question 118 English Option 2
  3. C
    CH3−CH2−CH2−COO−CH2−CH3C{H_3} - C{H_2} - C{H_2} - COO - C{H_2} - C{H_3}CH3​−CH2​−CH2​−COO−CH2​−CH3​
  4. D
    CH3−CH2−CH2−O−CH=CH−CH2−OHC{H_3} - C{H_2} - C{H_2} - O - CH = CH - C{H_2} - OHCH3​−CH2​−CH2​−O−CH=CH−CH2​−OH
View written solutionFree

Correct answer: C

  1. Identify the functional type from molecular formula

Given AAA has molecular formula C6H12O2C_6H_{12}O_2C6​H12​O2​ and a straight chain structure.

The options shown are mainly esters/unsaturated alcohol ether types. We are told that in the reaction sequence, AAA gives a C4C_4C4​ carboxylic acid.

For such questions, the usual key idea is:

  • On hydrolysis of an ester RCOOR′RCOOR'RCOOR′, the acid part becomes the carboxylic acid RCOOHRCOOHRCOOH.
  • Therefore, to obtain a C4C_4C4​ carboxylic acid, the acyl part must contain 4 carbons total including the carbonyl carbon.

So we inspect each ester option.

  1. Check option A

Option A is:

CH3−CH2−COO−CH2−CH2−CH3CH_3-CH_2-COO-CH_2-CH_2-CH_3CH3​−CH2​−COO−CH2​−CH2​−CH3​

This is propyl propanoate.

Acid part = CH3CH2CO−CH_3CH_2CO-CH3​CH2​CO−, which gives on hydrolysis:

CH3CH2COOHCH_3CH_2COOHCH3​CH2​COOH

This is propanoic acid, a C3C_3C3​ carboxylic acid, not C4C_4C4​.

So, A is incorrect.

  1. Check option C

Option C is:

CH3−CH2−CH2−COO−CH2−CH3CH_3-CH_2-CH_2-COO-CH_2-CH_3CH3​−CH2​−CH2​−COO−CH2​−CH3​

This is ethyl butanoate.

Acid part = CH3CH2CH2CO−CH_3CH_2CH_2CO-CH3​CH2​CH2​CO−, which gives on hydrolysis:

CH3CH2CH2COOHCH_3CH_2CH_2COOHCH3​CH2​CH2​COOH

This is butanoic acid, a C4C_4C4​ carboxylic acid.

Hence this matches the condition.

So, C is correct.

  1. Check option D

Option D is:

CH3−CH2−CH2−O−CH=CH−CH2−OHCH_3-CH_2-CH_2-O-CH=CH-CH_2-OHCH3​−CH2​−CH2​−O−CH=CH−CH2​−OH

This is not an ester. It would not directly yield a C4C_4C4​ carboxylic acid by ordinary ester hydrolysis logic.

So, D is incorrect.

  1. Conclusion

The only straight-chain compound with formula C6H12O2C_6H_{12}O_2C6​H12​O2​ that gives a C4C_4C4​ carboxylic acid is:

CH3−CH2−CH2−COO−CH2−CH3CH_3-CH_2-CH_2-COO-CH_2-CH_3CH3​−CH2​−CH2​−COO−CH2​−CH3​

Therefore, the correct option is C.

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