Top organic chemistry questions for PGT Preparation. Read these 20 Questions

1. Uric acid on oxidation with alkaline KMnO4 forms :
(a) Urea
(b) Barbituric acid
(c) Allantoin
(d) Caffeine

Ans- C

2. Diethyl malonate reacts with urea in the presence of sodium ethoxide to form
(a) Uric acid
(b) Barbituric acid
(c) Phenobarbital
(d) Barbital

Answer. (b)

3. All chiral D-sugars rotate plane-polarized light :
(a) clockwise
(b) counterclockwise
(c) +20.0°
(d) in a direction that cannot be predicted but must be determined experimentally

Answer. (d)

4. How many stereoisomers are possible for a 2-ketohexose?
(a) 2
(b) 4
(c) 8
(d) 16

Answer. (c)

5. An aqueous solution of glucose behaves as an aldehyde because
(a) it is hydrolyzed by water to the free aldehyde
(b) it is a ketone, but is in equilibrium with the aldehyde form
(c) glucose is actually a cyclic aldehyde
(d) its cyclic hemiacetal, the predominant form, is in equilibrium with the free
aldehyde form


Answer. (d)


6. Which of the following statements best describes the meaning of
“mutarotation”?
(a) a rapid exchange between the α and β forms of diastereomeric sugars
(b) a rapid exchange between the D and Lforms
(c) a slow exchange between hydrogen and deuterated hydrogen
(d) a slow change in optical rotation to reach an equilibrium value

Answer. (d)

7. α-D-Glucopyranose is a(n) :
(a) hemiacetal
(b) hemiketal
(c) acetal
(d) ketal

Answer. (a)

8. Which of the following carbohydrates is sweeter than sucrose?
(a) Glucose
(b) Fructose
(c) Lactose

Ans – (b) Fructose

9.By approximately what factor is the sweetness of saccharin greater than that
of sugar?
(a) 5
(b) 50
(c) 500
(d) 1000

Ans- (c) 500

10. The reagent that can be used to differentiate an aldose and a ketose is :
(a) Bromine water
(b) Fehling’s solution
(c) Tollens’ reagent
(d) None of these

Ans- (a)

11. Coal-tar is the main source of :
(a) Aromatic compounds
(b) Aliphatic compounds
(c) Heterocyclic compounds
(d) None of these

Answer. (a)

12. What is the term used for isomers that are in rapid equilibrium?
(a) keto-enol tautomers
(b) constitutional isomers
(c) conformational isomers
(d) cis-trans isomers

Answer. (a)

13. Which of the following is not a correct statement about the electrophilic
substitution mechanism of benzene?
(a) Benzene functions as a nucleophile.
(b) Formation of a carbocation intermediate is the rate-determining step.
(c) The carbocation intermediate contains an sp3 hybridized carbon in the ring.
(d) The addition product is a frequently observed minor product.

Answer. (d)

14. Which of the following agents is used in order to make benzene react with
bromine to give bromobenzene?
(a) Ultraviolet light
(b) Fe catalyst
(c) Nickel catalyst
(d) Al2O3 catalyst

Answer. (b)

15. In sulfonation of benzene, the attacking species is
(a) H+
(b) SO2
(c) SO3 (d) HSO3

Ans- (c) SO3.

16. Ozonolysis of benzene gives
(a) Formic acid
(b) Glyoxal
(c) Formaldehyde
(d) Glycine

Answer. (b)

16. DDT is prepared by the reaction of chlorobenzene with (in the presence of
conc. H2SO4)
(a) Chloral
(b) Chlorine
(c) Chloroform
(d) Carbon tetrachloride

Ans- (a) Chloral

17. Benzamide reacts with Br2 and KOH to give
(a) Benzene
(b) Benzylamine
(c) Aniline
(d) Benzonitrile

Answer. (b)

18. Aniline undergoes oxidation with Na2Cr2O7/H2SO4 to give
(a) Schiff’s base
(b) p-Benzoquinone
(c) Phenol
(d) Benzoic acid

Answer. (b)

19. Which of the following compounds will be most soluble in water at room
temperature?
(a) Phenol
(b) Phenylammonium chloride
(c) Benzoic acid
(d) Benzylamine

Answer. (b)

20. Benzenediazonium chloride reacts with warm water to give
(a) Aniline
(b) Phenol
(c) Benzene
(d) Chlorobenzene

Answer. (b)

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