Aldehydes And Ketones(12th Grade > Chemistry ) Questions and answers for exam Preparation

12th Grade > Chemistry

ALDEHYDES AND KETONES MCQs

Total Questions : 30 | Page 2 of 3 pages

Question 11. Dialkyl cadmium reacts with a compound to form a ketone. The compound is:

acid
acid chloride
ester
CO

Discuss Question

Answer: Option B. -> acid chloride
:
B

2 C H_{3} C O C l + R_{2} C d \to 2 C H_{3} - C O - R + C d C l_{2}

Question 12. The reaction given below is called,

_{_{R} ╱}^{^{R} ╲} C H O H +_{_{C H_{3}} ╱}^{^{C H_{3}} ╲} C O [(C H_{3})_{3} C O]_{3} A l - -------- \to_{_{R} ╱}^{^{R} ╲} C O +_{_{C H_{3}} ╱}^{^{C H_{3}} ╲} C H O H :

Tischenko’s reaction
Perkin’s reaction
Oppenauer oxidation
Schmidt reaction

Discuss Question

Answer: Option C. -> Oppenauer oxidation
:
C
The shown reaction is oxidation of secondary alcohol to ketones using aluminium tert. Butoxide called Oppenauer oxidation.

Question 13. The boiling points of aldehydes and ketones lie in between alkanes and alcohols of comparable masses because:

alkanes are polar
aldehydes and ketones are non-polar
alkanes are non-polar and aldehydes and ketones contain polar ╲╱C=O group and lower alcohols have H-bonding
alkanes are held together by weak van der Waals’ forces (being non-polar), aldehydes and ketones contain polar ╲╱C=O and held together by strong dipole-dipole attraction and lower alcohols have H-bonding, which is stronger than dipole-dipole attraction

Discuss Question

Answer: Option D. -> alkanes are held together by weak van der Waals’ forces (being non-polar), aldehydes and ketones contain polar ╲╱C=O and held together by strong dipole-dipole attraction and lower alcohols have H-bonding, which is stronger than dipole-dipole attraction
:
D
Alcohols have hydrogen bonding and this tendency decreases in the order

- O H > - C H O > k e t o n e s > R - H

Question 14. Benzoyl chloride is prepared from benzoic acid by

Discuss Question

Question 15. Identify X;

H_{3} C - C H_{3} | C = O C H_{3} M g I - ---- \to D r y e t h e r A H_{2} O - - \to X

CH3OH
CH3CH2OH
CH3CHOHCH3
CH3C(OH)(CH3)2

Discuss Question

Answer: Option D. -> CH3C(OH)(CH3)2
:
D

Identify X; H3C−CH3|C=OCH3MgI−−−−−→Dry etherA...

Question 16. Which of the following aldehydes on chlorination will give a product, which can be used for the synthesis of DDT?

HCHO
CH3CHO
CH3−(CH=CH)−CHO
CH3CH2CHO

Discuss Question

Answer: Option B. -> CH3CHO
:
B

Which Of The Following Aldehydes On Chlorination Will Give A...

Question 17. Cyanohydrin of which compound gives lactic acid on hydrolysis?

Acetone
Acetaldehyde
Propanal
HCHO

Discuss Question

Answer: Option B. -> Acetaldehyde
:
B

Cyanohydrin Of Which Compound Gives Lactic Acid On Hydrolysi...

Question 18. An aldehyde which undergoes Cannizzaro’s reaction and reduces Schiff’s reagent but does not reduce Fehling’s solution is:

CH3CHO
HCHO
C6H5CHO
salicylaldehyde

Discuss Question

Answer: Option C. -> C6H5CHO
:
C

C_{6} H_{5} C H O

has an aldehyde group and therefore responds to schiff’s test. Due to the absence of

α - h y d r o g e n s

it also gives a positive Cannizzaro’s test but does not reduce Fehling’s solution as the oxidizing agent is not powerful enough to oxidize benzaldehyde to benzoic acid.