Chemistry #expch001 Important Questions
Ch. 1. Basic Concepts and Isomerism #expch_006

1. How many acidic hydrogen atoms are there in propyne?

•1

•3

•4

•zero

2. Which of the following has +M effect? •NO2

•NH2

•CHO

•CN

3. m-nitrophenol is about 100 times more acidic than phenol due to

Steric effect

Resonance effect

Solvent effect

Inductive effect

4. Which isomerism is not exhibited in alkene?

•Geometrical

•Metamerism

•Chain isomerism

•Position isomerism

Hint

Alkenes can show chain isomerism (different longest chain but same formula), position isomerism (substituents at different places) and geometrical isomerism (cis-trans) but not metamerism, because it does not contain any functional group like two alkyl groups on either side (R−O−R′).

5. No of conjugated electrons in pyridine?

Zero

6

8

5

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6. Which of the following is most basic

NH3

H20

CH3NH2

CH3OH

Hint

Methyl amine is a stronger base effect of methyl group increases it more basic than NHX3. than ammonia because +I electron density on N making

7. Which of the following is not conjugated unsaturated system.

Allyl radical

Allyl cation

1,3-butadiene

1-penten-4-yne

8. Which one is not conjugated molecule? Hint Draw structure!

Cyclohexene

Acetamide

Phenol

benzene

9. which acid is strongest?

CH3COOH

ClCH2COOH

F3CCOOH

Cl3CCOOH

10. Which of the following is a temporary effect brought into play at the requirement of attacking reagent?

Inductive effect

Mesomeric effect

Electromeric effect

Inductomeric effect

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11. Select the correct statement from the following option.

Conjugate effect is stronger than (-I) effect

Conjugate effect is weaker than (-I) effect

Conjugate effect is same as (-I) effect

None of the mentioned

Hint

Conjugate effect is stronger than (-I) effect. Conjugate effect (or delocalization) is an effect in which molecular orbitals (MOs) are conjugated to new molecular orbitals that are more delocalized and therefore generally lower in energy.

When the substituents like -OH have an unshared pair of electrons, the resonance effect is stronger than the inductive effect which make these substituents stronger activators, since this resonan effect direct the electron toward the ring.

12. Those groups which are electron repelling and have lesser electron attracting power than hydrogen show

(+E) effect

(-E) effect

(-I) effect

(+I) effect

13. Which of the following show cis trans isomerism?

1-butene

2-butene

Ethene

All of these

14. if position of functional group varies in each of its isomers then it is

Position isomerism

Functional group isomerism

Chain isomerism

None of the above

15. which one is not isomer of butanone?

2,3-epoxybutane

ethyl vinyl ether

1,2-butanol

ter-butyl ether

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16. Ethanol and acetone are

Position isomers

Chain isomers

Metamers

None of the above

Correct functional group isomers

17. Which of the following is a tautomer of phenol?

18.In keto-enol from presence of which type of hydrogen is must?

Alpha

Beta

Gamma

Any position of hydrogen

Hint

For Keto-Enol tautomerism, keto form should have α-hydrogen, as shown in below example.

19. How many isomeric alkanes of the molecular formula C5H12 are there?

1

2

3

4

20. How many alcohols are structural isomers with the formula: C5H11OH?

5

6

7

8

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21.Which of the following does NOT exhibit geometric isomerism? (Hint: draw them!)

4-octene

2-pentene

3-hexene

1-hexene

22.Hyperconjugation involves the delocalisation of __

σ bond orbital

π bond orbital

Both σ and π bond orbital

None of the mentioned

Hint

Hyperconjugation involves the delocalisation of σ bond orbital. It is the stabilising interaction that results from the interaction of the electrons in a σ-bond (usually C-H or C-C) with an adjacent empty or partially filled p-orbital or a π orbital to give an extended molecular orbital that increases the stability of the system.

23.larger the number of hyperconjugation structures, the stability of free radicals will __

Increase

Decrease

Remains same

None of the mentioned

24. When the contributing structure contains the same number of two-electron bonds as the normal lewis formula, it will be __

Heterovalent hyperconjugation

Sacrificial hyperconjugation

isovalent hyperconjugation

All of the mentioned

What is Isovalent Hyperconjugation? Isovalent hyperconjugation refers to the hyperconjugation that occurs in free radicals and carbocations where the canonical form displays no charge separation, but the main form has a charge separation

Sacrificial hyperconjugation refers to the hyperconjugation where canonical form involves no bond resonance but in the main form involves no charge distribution. This type of hyperconjugation is also known as “no bond hyperconjugation”.

25. Ethene is devoid of any alpha hydrogen so hyperconjugation is not possible.

True

False

not known

both

Hint

Ethene is devoid of any alpha hydrogen so hyperconjugation is not possible because the presence of alpha hydrogen is the necessary condition for hyperconjugation.

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