Chemistry #expch001 Important Questions
Ch. 1. Basic Concepts and Isomerism #expch_006
- How many acidic hydrogen atoms are there in propyne?
•1
•3
•4
•zero
- Which of the following has +M effect? •NO2
•NH2
•CHO
•CN
- m-nitrophenol is about 100 times more acidic than phenol due to
Steric effect
Resonance effect
Solvent effect
Inductive effect
- 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′).
- No of conjugated electrons in pyridine?
Zero
6
8
5
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- 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
- Which of the following is not conjugated unsaturated system.
Allyl radical
Allyl cation
1,3-butadiene
1-penten-4-yne
- Which one is not conjugated molecule? Hint Draw structure!
Cyclohexene
Acetamide
Phenol
benzene
- which acid is strongest?
CH3COOH
ClCH2COOH
F3CCOOH
Cl3CCOOH
- 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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- 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.
- Those groups which are electron repelling and have lesser electron attracting power than hydrogen show
(+E) effect
(-E) effect
(-I) effect
(+I) effect
- Which of the following show cis trans isomerism?
1-butene
2-butene
Ethene
All of these
- 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
- which one is not isomer of butanone?
2,3-epoxybutane
ethyl vinyl ether
1,2-butanol
ter-butyl ether
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- Ethanol and acetone are
Position isomers
Chain isomers
Metamers
None of the above
Correct functional group isomers
- 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.
- How many isomeric alkanes of the molecular formula C5H12 are there?
1
2
3
4
- 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
- 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”.
- 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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