Organic Molecules MCQs [Organic Chemistry]

By: Prof. Dr. Fazal Rehman | Last updated: February 3, 2024

 

MCQs are based on questions and answers on Structural Concepts and Bonding in Organic Molecules in organic chemistry.

Which of the mentioned is the true order of bond length?

1. C-CC=CC=C
2. C-C>C=CC=C
3. C=C>C-C>C=C
4. C C<C-C>C=C

Question’s Answer: C-C>C=CC=C

 

Which, statement is true?

1. Resonance hybrids are inherently unstable
2. Resonance hybrids are averages of all resonance forms resembling the more stable forms
3. Resonance hybrids are average of all resonance forms resembling the less stable forms
4. Resonance hybrids are more stable than any individual resonance form

Question’s Answer: Resonance hybrids are averages of all resonance forms resembling the more stable forms

 

Which of the mentioned statement is false about resonance?

1. It increases the stability of a molecule
2. It decreases the reactivity of the molecule
3. It increases the reactivity of the molecule
4. It leads to similar type of bonds

Question’s Answer: It leads to similar type of bonds

 

The greater stability of benzyl carbonium ion as compared to t-butyl carbonium ion is due to

1. Inductive effect
2. Electrometric effect
3. Resonance effect
4. Steric effect

Question’s Answer: Resonance effect

 

Compounds in which carbons use only sp³ hybrid orbital for bond formation is

1. CH₃CH₂CH₃
2. HC=CH
3. CH₃ – CH = CH₂
4. CH=CH-CH₂-CH₃

Question’s Answer: CH₃CH₂CH₃

 

What is the bond angle between hybrid orbitals in methane?

115. 115.5°
116. 105.7°
117. 109.5°
118. 180°

Question’s Answer: 109.5°

 

In hydrogen bonding a hydrogen atom is bonded to which of the highly electronegative atoms?

1. N, O, F
2. O
3. F
4. N

Question’s Answer: N, O, F

 

Which of the mentioned statements is not true regarding applications of H- bonding?

1. It has strong influence on the configuration of certain molecules
2. It explains the solubility of certain organic compounds in hydroxylic solvents
3. It explains the lack of ideal behavior in gases and solutions
4. It explains the usual b.p. and m.p. of certain class of compounds

Question’s Answer: It explains the usual b.p. and m.p. of certain class of compounds

 

The compounds whose formation require a host compound and a guest compound are known as _______.

1. Exclusion compounds
2. Crystal compounds
3. Inclusion compounds
4. Stoichiometric compounds

Question’s Answer: Inclusion compounds

 

What is the common host compound for the formation of inclusion compound?

1. Cholic acid
2. Thiourea
3. Urea
4. All A, B, and C

Question’s Answer: All A, B, and C

 

Which of the mentioned order of bond angles is not true?

1. H₂O < NH₃ < CH₄
2. H₂S < H₂O< NH₃
3. H₂O < CH₄ <H₂S
4. PH₃<NH₃<CH₄

Question’s Answer: H₂O < CH₄ <H₂S

 

Which of the mentioned is the true order of bond dipole moment?

1. C-CI < C-1 < -Br
2. C-CI > C-Br > C-1
3. C-Br < C-1 < C-Cl
4. C-I > C-Br > C-CI

Question’s Answer: C-CI > C-Br > C-1

 

Which of the mentioned molecule has more dipole moment?

1. Methane
2. Chloroform
3. Nitro phenol
4. Toluene

Question’s Answer: Nitro phenol

 

An induction of dipole or polarity in non- polar bond, and consequent electron shifting along a chain of atoms is known as

1. Resonance effect
2. Inductive effect
3. Hyper conjugation
4. Stark effect.

Question’s Answer: Inductive effect

 

The chemistry of carbon compounds and its derivatives is known as _______.

1. Physical chemistry
2. Analytical chemistry
3. Applied chemistry
4. Organic chemistry

Question’s Answer: Organic chemistry

 

Molecular orbital theory was developed by Which of the mentioned scientist?

1. Mulliken, Hund and Huckel
2. Pauling
3. Heitler, London and Pauling
4. E. Schrodinger

Question’s Answer: Mulliken, Hund and Huckel

 

Which of the mentioned bonds has least bond energy?

1. Ionic bond
2. Covalent bond
3. H-bond
4. Coordinate bond

Question’s Answer: H-bond

 

The complete transfer of a shared pair of electrons to one of the atoms joined by a double or triple bond at the requirement of an attacking reagent is known as

1. Electromeric effect
2. Resonance effect
3. Hyperconjugation
4. Inductive effect

Question’s Answer: Electromeric effect

 

Which of the mentioned statements is not true regarding electrometric effect?

1. It precedes a polar addition reaction
2. It is brought into play instantaneously at the demand of attacking reagent
3. It is permanent effect
4. The original electronic condition is restored after the removal of attacking reagent

Question’s Answer: It is permanent effect

 

The decrease in electron density at one position accompanied by a corresponding increase at other position is known as _______.

1. Resonance effect
2. Asymmetric effect
3. Electromeric effect
4. Inductive effect

Question’s Answer: Resonance effect

 

Which of the mentioned statements is not true regarding resonance?

1. All limiting structures must contribute equally
2. The limiting structures must have same number of paired and unpaired electrons
3. The energy of the various limiting structures must be same
4. The position of atomic nuclei must be same

Question’s Answer: All limiting structures must contribute equally

 

Which of the mentioned statements is not true regarding the important characteristics of aromatic compounds?

1. They are usually cyclic compounds
2. They are resistant to usual addition reactions
3. They are less stable
4. They usually undergo substitution reactions

Question’s Answer: They are less stable

 

Inductive effect can be used to explain

1. Dipole moment of chemical bonds
2. Strength of bases
3. Strength of acids
4. All A, B, and C

Question’s Answer: All A, B, and C

 

True order of increasing-I effect of groups is

1. –CN > -NO₂ > -COOH > -F

B.–NO₂ > -CN > -COOH > -F

1. –F > -COOH > -CN > -NO₂
2. –F > -CN > -NO₂ >- COOH

Question’s Answer: –NO₂ > -CN > -COOH > -F

 

Which of the mentioned case of acid or base strength is not explained by inductive effect?

1. Dimethyl amine > trimethyl amine
2. Formic acid > acetic acid
3. Dimethyl amine > methyl amine
4. Chloroacetic acid > acetic acid

Question’s Answer: Dimethyl amine > trimethyl amine

 

Which of the mentioned class of compounds follow the criteria of aromaticity?

1. The compounds must have high degree of unsaturation
2. They must have the property to undergo addition reactions
3. They must have cyclic clouds of delocalized (4n + 2)π electrons
4. They must have the property to undergo substitution reactions

Question’s Answer: They must have the property to undergo addition reactions

 

How many electrons are present in benzene, naphthalene and anthracene?

1. 10, 6, 14
2. 6, 10, 14
3. 2, 6, 14
4. 2, 4, 6

Question’s Answer: 6, 10, 14

 

Which of the mentioned organic molecule is not aromatic?

1. Cyclo-octatetraene
2. Naphthalene
3. Anthracene
4. Benzene

Question’s Answer: Cyclo-octatetraene

 

Cyclic polymers of ethylene glycol formed by condensation are known as _______.

1. Cryptates
2. Brown ether
3. Crown ether
4. Both A and C

Question’s Answer: Both A and C

 

Compounds consisting of two or more interlocked rings are known as _______.

1. Inclusion compounds.
2. Catenanes
3. Cage compounds
4. Crown ether

Question’s Answer: Catenanes

 

The most stable carbonium ion is

1. See butyl
2. Tert butyl
3. n-butyl
4. Isobutyl

Question’s Answer: Tert butyl

 

Each of the following group exerts a +I effect except

1. CH⁺₃
2. CH₃
3. OH^–
4. (CH₃)₃ C^–

Question’s Answer: CH⁺₃

 

Which of the mentioned compounds has highest dipole moment?

1. Chloromethane
2. Chloroform
3. Dichloromethane
4. Carbon tetrachloride

Question’s Answer: Dichloromethane

 

The delocalization involving C-H sigma bond electrons is known as

1. Conjugation
2. Mesomerism
3. Resonance
4. Hyperconjugation

Question’s Answer: Mesomerism

 

 

Which of the mentioned group will have hyperconjugation effect when attached to benzene?

1. -CH(CH₃)₂
2. CH

C.-C(CH₃)₃

1. -CH₃

Question’s Answer: -CH₃

 

Which of the mentioned is most basic?

1. N-methylaniline
2. Benzylamine
3. Diphenylamine
4. Aniline

Question’s Answer: N-methylaniline

 

The hybridization of C-atoms in 1, 2- butadiene is

1. sp
2. sp²
3. sp, sp², sp³
4. sp³

Question’s Answer: sp, sp², sp³

 

Which of the mentioned hybridization results in a linear organic molecules?

1. sp²
2. sp
3. sp³
4. sp³d

Question’s Answer: sp

 

Which of the mentioned molecules has shortest C-C bond length?

1. CH₃ – CH₂ – CH₃
2. CH₃CH=CH₂
3. CH₃C = CH
4. CH₂=CH-CH₂-CH₃

Question’s Answer: CH₃C = CH

 

Which of the mentioned is most acidic?

1. p-nitrophenol
2. Phenol
3. o-Nitrophenol
4. m-nitrophenol

Question’s Answer: p-nitrophenol

 

Which of the mentioned effects best explains that o-nitrophenol is insoluble in water?

1. Inductive effect
2. Resonance effect
3. Intramolecular H-bonding.
4. Intermolecular H-bonding

Question’s Answer: Intramolecular H-bonding

 

Trimethylamine is a weaker base than dimethylamine is explained by

1. Resonance effect
2. Steric effect
3. Inductive effect
4. Electromeric effect

Question’s Answer: Steric effect

 

All bond lengths in benzene are identical due to

1. Hyperconjugation
2. Inductomeric effect
3. Electromeric effect
4. Resonance effect

Question’s Answer: Resonance effect

 

 

What is the bond length of C=C ?

1. 1.20A°
2. 1.68A°
3. 1.54A°
4. 1.34A°

Question’s Answer: 1.68A°

 

Which of the mentioned hydrocarbons has the shortest C-C bond length?

1. HC=CH
2. CH₂=CH₂
3. CH₃CH₃
4. Benzene

Question’s Answer: HC=CH

The carbon-carbon bond strength is maximum in __________.

1. CH₃CH₃
2. CH₂=CH₂
3. HC=CH
4. Benzene

Question’s Answer: CH₃CH₃

 

The criteria for aromaticity is presence of

1. Presence of 4nπ electrons
2. Cyclic structure
3. Unsaturation’s
4. Presence of 4n + 2π electrons

Question’s Answer: Presence of 4n + 2π electrons

 

C-O bond lengths in carboxylate anion are equal because of ___.

1. Resonance effect
2. Resonance of identical contributing structures
3. H-bonding
4. Inductive effect

Question’s Answer: Resonance of identical contributing structures

 

Chlorine when attached to benzene has

1. +I and +R effect
2. -I and -R effect
3. +1 and -R effect
4. -1 and +R effect

Question’s Answer: -1 and +R effect

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