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Free download in PDF Organic Chemistry Multiple Choice Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like UPSC, NDA, SSC etc. These short solved questions or quizzes are provided by Gkseries./p>
(1)
Why in the IR spectrum of Benzoyl chloride, a weak band near 1750 cm-1 is formed?
[A]
Inductive effect
[B]
Fermi resonance between C = O band and first overtone
[C]
Conjugation effect
[D]
Hyperconjugation effect
Answer: Fermi resonance between C = O band and first overtone
(2)
Which compound having molecular formula C5H10 shows absorption at 1380 cm-1?
[A]
2-Methyl-1-butene
[B]
Cyclopentane
[C]
Pentyne
[D]
Methylcyclobutane
(3)
Why ketenes absorb in IR at a very high frequency (2150 cm-1)?
[A]
The inner C is sp hybridized
[B]
The more s character in a bond, the stronger it is
[C]
Inner C is sp2 hybridized
[D]
Inner C is sp3 hybridized
Answer: Inner C is sp2 hybridized
(4)
What is the effect of ring strain in lactone (cyclic ester) or a lactam (cyclic amide)?
[A]
Increases carbonyl stretching frequency
[B]
Decreases carbonyl stretching frequency
[C]
Increases C = C frequency
[D]
Decreases C = C frequency
Answer: Increases carbonyl stretching frequency
(5)
A compound C8 H6 decolorizes Br2 in CCl4 and gives a white precipitate with Tollen’s reagent. It has sharp band at 3300 cm-l and weak bands at 3085, 2110 cm-l. What is this compound?
[A]
Phenyl acetylene
[B]
Phenyl propylene
[C]
Phenyl ethylene
[D]
Octene
(6)
What is the relation between wave number of IR absorption and the reduced mass?
[A]
Wave number is directly proportional to reduced mass
[B]
Wave number is inversely proportional to reduced mass
[C]
Wave number is independent of the reduced mass
[D]
Wave number is directly proportional to square of reduced mass
Answer: Wave number is inversely proportional to reduced mass
(7)
What is the number of vibrational degrees of freedom in C6H5CH3?
[A]
39
[B]
15
[C]
18
[D]
40
(8)
Which of the following molecules will not show infrared spectrum?
[A]
H2
[B]
HCI
[C]
CH4
[D]
H20
(9)
The phosphorescence spectrum of the excited species is due to which transition?
[A]
Singlet to triplet transitions
[B]
Triplet to singlet transitions
[C]
Vibration modes
[D]
Electron spin transitions
Answer: Triplet to singlet transitions
(10)
Why Monomeric saturated aliphatic carboxylic acids show carbonyl stretching frequency near 1760 cm-1, while saturated aliphatic ketones near 1720 cm-1?
[A]
Mesomeric (M) effect is dominant in acids over the inductive (I) effect
[B]
I effect is dominant in carboxylic acids over the mesomeric effect
[C]
I effect on ketones is dominant over the M effect
[D]
M effect in ketones is dominant
Answer: I effect is dominant in carboxylic acids over the mesomeric effect
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