Quiz-19 Aldehydes and Ketones

Aldehydes and Ketones Quiz-19

Dear Readers,

The one subject in NEET which is candidates who can easily attain good marks is Chemistry. That's the reason, often, one doesn’t pay notice and choose to compromise it. But if one wants to rank above others, the tip is to be thorough with NEET chemistry concepts. The understanding of reactions and definite basic understanding is what requires major attention in Chemistry but once done it only gets simpler from there. The main focus on the to-do list should be on getting a hang of the NCERT syllabus of NEET chemistry. .

Q1.  Consider the reaction: RCHO + NH₂ NH₂⟶RCH = N—NH₂ What sort of reaction is it?

•  Electrophilic addition – elimination reaction
•  Free radical addition – elimination reaction
•  Electrophilic substitution – elimination reaction
•  Nucleophilic addition – elimination reaction

Solution

The reaction is nucleophilic addition-elimination reaction.

Q2.A ketone reacted with C₂ H₅ MgBr reagent followed by hydrolysis gave a product which on dehydration gives an alkene. The alkene on ozonolysis gave diethyl ketone and acetaldehyde. The ketone is:

•  Dimethyl ketone
•  Ethyl methyl ketone
•  Diethyl ketone
•  Ethyl propyl ketone

Solution

Q3.   The correct order of decreasing acid strength of trichloroacetic acid, (A), trifluoroacetic (B), acetic acid (C)and formic acid (D) is:

•  A>B>C>D
•  A>C>B>D
•  B>A>D>C
•  B>D>C>A

Solution
The presence of electron withdrawing gp. in carboxylic acid increases acidic character. Also electron withdrawing nature of F is more than Cl.

Q4. What is the product in following cross Claisen condensation?

•  
  
  
  
•  
  
  
  
•  
  
  
  
•  
  
  
  

Solution

Q5. Anhydrous CaCl₂ is used as drying agent because it:

•  Adsorbs water molecules
•  Absorbs water molecules
•  Adsorbs and absorbs water molecules
•  none of the above

Solution
 

Q6. Benzaldehyde gives a positive test with

•  Tollen’s reagent
•  Fehling’s solution
• Benedict’s solution
•  All of these

Solution

Aromatic aldehydes reduce Tollen’s reagent. Since they are less reactive they do not reduce Fehling’s solution and Benedict’s solution.

Q7.Which is more stable?

•  X
•  Y
•  Both are equally stable
•  Can’t be predicted

Solution

In carboxylic acid the oxygen attached to carboxyl carbon is more electronegative and withdraws the electrons of bond. Hence, protonation occurs at the carboxyl oxygen

Q8.Aldehyde which is formed during photosynthesis of plants is

•  Methanal
•  Acetaldehyde
•  Propanal
•  Phenylmethanal

Solution
Methanal is formed during photosynthesis of plants.

Q9.Consider the acidity of the carboxylic acids (i) PhCOOH (ii) o-NO₂ C₆ H₄COOH (iii)p-NO₂ C₆ H₄ COOH (iv)m-NO₂ C₆ H₄ COOH Which of the following order is correct?

•  (i) > (ii) > (iii) > (iv)
•  (ii) > (iv) > (iii) > (i)
•  (ii) > (iv) > (i) > (iii)
•  (ii) > (iii) > (iv) > (i)

Solution

-NO₂ group at any position shows electron withdrawing effect. Thus, acid strength is increased. But o-nitro benzoate ion is stabilised by intramolecular H-bonding like forces. Hence its acid strength is maximum. Thus, the order of acid strength is (II) > (III) > (IV) > (I).

Q10. Monocarboxylic acids show functional isomerism with :

•  Esters
•  Alcohols
•  Ethers
• Aldehydes

Solution

RCOOH and HCOOR are functional isomers having