All Exams  >   NEET  >   1 Year Dropper Course for NEET  >   All Questions

All questions of Aldehydes, Ketones and Carboxylic Acids for NEET Exam

The IUPAC name of CH3CHO is:
  • a)
    Acetaldehyde
  • b)
    Ethanal
  • c)
    Formaldehyde
  • d)
    Methanal
Correct answer is option 'A'. Can you explain this answer?

  • The functional group is an aldehyde; −CHO and the given compound has two carbon atoms.
  • Thus, the IUPAC name of the compound is ethanal.

 Which of the following statements are correct in case of the carbonyl bond between carbon and oxygen?
  • a)
    Carbon is the nucleophilic centre and Oxygen is the electrophilic centre.
  • b)
    Oxygen is the nucleophilic centre and Carbon is the electrophilic centre.
  • c)
    Carbon and Oxygen double bond is polarised.
  • d)
    Both ‘b’ and ‘c’ are correct
Correct answer is option 'C'. Can you explain this answer?

Nandini Patel answered
The double bonds in alkenes and double bonds in carbonyl groups are VERY different in terms of reactivity. The C=C is less reactive due to C=O electronegativity attributed to the oxygen and its two lone pairs of electrons.  One pair of the oxygen lone pairs are located in 2s while the other pair are in 2p orbital where its axis is directed perpendicular to the direction of the pi orbitals.  The Carbonyl groups properties are directly tied to its electronic structure as well as geometric positioning.  For example, the electronegativity of oxygen also polarizes the pi bond allowing the single bonded substituent connected to become electron withdrawing.

 Which of the following statement about C=O and C=C is correct?
  • a)
    Both consist of a sigma and pi bond
  • b)
    C=O is polar but C=C is non-polar
  • c)
    Both a and b are correct
  • d)
    Both C=O and C=C undergo nucleophilic addition reactions
Correct answer is option 'C'. Can you explain this answer?

Knowledge Hub answered
  • The first bond formed is a sigma bind and the second one is a pi bond.
  • O has a higher electronegativity than C and hence the electron cloud will be shifted towards the O atom, making the compound polar.
  • This is not possible in C=C.

Propanone and prop-2-en-1-ol are examples of which type of isomerism?
  • a)
    Functional isomers
  • b)
    Chain isomers
  • c)
    Tautomers
  • d)
    Position isomers
Correct answer is option 'A'. Can you explain this answer?

Functional isomers

Explanation: Propanone (CH3COCH3) and prop-2-en-1-ol (CH2=CHCH2OH) are examples of functional isomers because they have the same molecular formula (C3H6O) but different functional groups. Propanone has a carbonyl group (C=O) while prop-2-en-1-ol has an alcohol group (OH) and a carbon-carbon double bond (C=C).

What is the common name of 2-methyl-propanal?
  • a)
    formaldehyde
  • b)
    Isobutyraldehyde
  • c)
    carbaldehyde
  • d)
    acetaldehyde
Correct answer is 'B'. Can you explain this answer?

Nikita Singh answered
  • Isobutyraldehyde is the chemical compound with the formula (CH₃)₂CHCHO.
  • It is an aldehyde, isomeric with n-butyraldehyde.
  • Isobutyraldehyde is manufactured, often as a side-product, by the hydroformylation of propene. Its odour is described as that of wet cereal or straw.

CH3CHO and C6H5CH2CHO can be distinguished chemically by: [2012]
  • a)
    Benedict test
  • b)
    Iodoform test
  • c)
    Tollen’s reagent test
  • d)
    Fehling solution test
Correct answer is option 'B'. Can you explain this answer?

CH3CHO and C6H5CH2CHO both are aldehydes so they can give the test of Tollen’s reagent, Fehling's solution and Benedict’s solution.
The carbonyl compounds with the structure R-CO-CH3 can only give the Iodoform test.
CH3CHO is the only aldehyde which reacts with NaOH and I2 to give yellow crystals of Iodoform while C6H5CH2CHO doesn’t react with it. 
So, the iodoform test is used to distinguish between CH3CHO and C6H5CH2CHO compounds. 
CH3CHO + 3I+ 4NaOH ⟶ CHI+ HCOONa + 3NaI +3H2O
C6H5CH2CHO + I+ 4NaOH⟶ No reaction.

Propionic acid with Br2|P yields a dibromo product. Its structure would be: [2009]
  • a)
  • b)
    CH2Br – CH2 – COBr
  • c)
  • d)
    CH2 Br – CHBr – COOH
Correct answer is option 'C'. Can you explain this answer?

Anand Jain answered
This reaction is an example of Hell - Volhard
Zelinsky reaction. In this reaction acids
containing α– H on treatment with X2 /P
give di-halo substituted acid.

Arrange the following compounds in decreasing order of their acid strength: i) trichloroacetic acid ii) trifluoroacetic acid iii) acetic acid and iv) formic acid
  • a)
    trifluoroacetic acid, trichloroacetic acid, formic acid and acetic acid
  • b)
    formic acid., trifluoroacetic acid, trichloroacetic acid, and acetic acid
  • c)
    trichloroacetic acid, trifluoroacetic acid, acetic acid and formic acid.
  • d)
    trifluoroacetic acid, formic acid acetic acid and Propan – 1 – ol, 4 – methylphenol
Correct answer is option 'A'. Can you explain this answer?

Tanuja Kapoor answered
Acidic strength of carboxylic acid -
–  More acidic than phenols or alcohols.
–  Acidity increase with the presence of a group with  -I effect in the alkyl group.Whereas it decreases with the presence of  +I group.
–  Acidity increases with increase in the number of halogen atoms on  - position.
–  It decreases with increasing distance of halogen from   
–  It increases with increase in the electronegativity of halogen.
- CF3COOH > CCl3COOH > HCOOH > CH3 COOH

A strong base can abstract an α – hydrogen from
  • a)
    Alkane.
  • b)
    Amine
  • c)
    Ketone
  • d)
    Alkene
Correct answer is option 'C'. Can you explain this answer?

Vijay Bansal answered
After deprotonation the negative charge will be in conjugation with the pi orbital of carbonyl..so base will prefer to abstract alpha hydrogen from ketone.

In which of the following reactions, ketone is formed as the major organic product?
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'A,C'. Can you explain this answer?

If acid derivatives like nitrile, acid chlorid e or ester is taken in excess in Grignard synthesis, second addition of Grignard’s reagent on carbonyl product does not succeed and carbonyls are obtained as major products.
In option (b), carboxylic acids and in option (d), an aldehyde is formed.

Which one of the following compounds will be most readily dehydrated?       [2010]
  • a)
  • b)
  • c)
  • d)
Correct answer is option 'D'. Can you explain this answer?

Raghav Khanna answered
The intermediate is carbocation which is
destabilised by C = O group (present on ��-
carbon to the –OH group) in the first three
cases. In (d), α–hydrogen is more acidic which
can be removed as water. Moreover, the
positive charge on the intermediate carbocation
is relatively away from the C = O group.
∴ Correct choice : (d)

Clemmensen reduction of a ketone is carried outin the presence of which of the following ? [2011]
  • a)
    Glycol with KOH
  • b)
    Zn-Hg with HCl
  • c)
    Li Al H4
  • d)
    H2 and Pt as catalyst
Correct answer is option 'B'. Can you explain this answer?



Clemmensen Reduction and Its Mechanism:

The Clemmensen reduction is a chemical reaction that involves the conversion of a carbonyl group in a ketone to a methylene group using zinc amalgam and hydrochloric acid. This process is particularly effective for reducing ketones to alkanes.

Role of Zn-Hg with HCl:

- In the Clemmensen reduction, zinc amalgam (Zn-Hg) serves as the reducing agent while hydrochloric acid (HCl) acts as a catalyst.
- The reaction occurs at high temperatures, typically refluxing conditions, to facilitate the reduction of the carbonyl group.
- The zinc amalgam reacts with the carbonyl group in the ketone, leading to the formation of an alkyl zinc intermediate.
- The alkyl zinc intermediate is unstable and undergoes protonation by HCl to form the corresponding alkane.

Comparison with Other Reagents:

- Glycol with KOH is commonly used for cleaving ethers, not for the Clemmensen reduction of ketones.
- LiAlH4 is a powerful reducing agent that can reduce ketones to alcohols, but it is not typically used in the Clemmensen reduction.
- H2 and Pt as a catalyst are commonly used for hydrogenation reactions, not for the Clemmensen reduction.

In conclusion, the Clemmensen reduction of a ketone is carried out in the presence of zinc amalgam and hydrochloric acid. These reagents work together to reduce the carbonyl group in the ketone to a methylene group, producing the desired alkane product.

Which of the following represents the correctorder of the acidity in the given compounds?          [2007]
  • a)
    FCH2COOH > CH3COOH > BrCH2COOH >ClCH2COOH
  • b)
    BrCH2COOH > ClCH2COOH > FCH2COOH> CH3COOH
  • c)
    FCH2COOH > ClCH2COOH > BrCH2COOH> CH3COOH
  • d)
    CH3 COOH > BrCH2COOH > ClCH2COOH >FCH2COOH
Correct answer is option 'C'. Can you explain this answer?

Sneha Basak answered
Electron withdrawing substituent (like
halogen, —NO2, C6H5 etc.) would disperse
the negative charge and hence stabilise the
carboxylate ion and thus increase acidity
of the parent acid. On the other hand,
electron-releasing substituents would
intensify the negative charge, destabilise
the carboxylate ion and thus decrease
acidity of the parent acid.
Electronegativity decreases in order
F > Cl > Br
and hence –I effect also decreases in the
same order, therefore the correct option is
FCH2COOH > ClCH2COOH > BrCH2COOH> CH3COOH

Chapter doubts & questions for Aldehydes, Ketones and Carboxylic Acids - 1 Year Dropper Course for NEET 2025 is part of NEET exam preparation. The chapters have been prepared according to the NEET exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for NEET 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.

Chapter doubts & questions of Aldehydes, Ketones and Carboxylic Acids - 1 Year Dropper Course for NEET in English & Hindi are available as part of NEET exam. Download more important topics, notes, lectures and mock test series for NEET Exam by signing up for free.

1 Year Dropper Course for NEET

503 videos|1698 docs|628 tests

Top Courses NEET

Related NEET Content