Phenol MCQ

Electrophilic Substitution Reactions of Benzene

Aromatic, Anti-aromatic and Non-aromatic MCQ

 

The stability of a Carbocation

 The stability of a carbocation  (a positively charged carbon atom with only six electrons in its valence shell) is influenced by several factors. 

Carbocations are generally unstable due to the lack of a full octet. However, their stability can vary depending on the following factors:
 

1. Alkyl Substitution (Inductive Effect):

 -Tertiary carbocations (3°) are more stable than secondary (2°), which are more stable than primary (1°), and methyl carbocations are the least stable.

     - Tertiary > Secondary > Primary > Methyl

   - This trend arises because alkyl groups donate electron density through the inductive effect, helping to stabilize the positive charge on the carbocation.
 

2. Resonance Stabilization:

 
   - Resonance can significantly stabilize carbocations. If the positive charge is adjacent to a double bond or an aromatic ring (as in allylic or benzylic carbocations), the charge can be delocalized, making the carbocation more stable.
     - Allylic and benzylic carbocations are more stable due to the delocalization of the positive charge through resonance structures.

3. Hyperconjugation:

 
   - Hyperconjugation refers to the overlap of σ-bonds (typically from C-H or C-C bonds) with the empty p-orbital of the carbocation, providing additional stabilization.
   - More alkyl groups (and thus more hyperconjugation) lead to increased carbocation stability.
 

4. Electronegativity of Neighboring Atoms:

 
   - A carbocation near an electronegative atom, such as oxygen or nitrogen, can be destabilized because electronegative atoms withdraw electron density, making the positive charge more pronounced.
   - However, in some cases, neighboring atoms with lone pairs can stabilize the carbocation by donating electron density through π-donation or backbonding.
 

5. Hybridization of the Carbocation:

   - A carbocation in an sp²-hybridized orbital (as in an alkyl carbocation) is more stable than a carbocation in an sp-hybridized orbital (as in a vinyl carbocation).
   - Vinylic carbocations (where the positive charge is on a carbon of a C=C bond) and aryl carbocations (where the positive charge is on a carbon of a benzene ring) are highly unstable due to a lack of resonance stabilization and poor hyperconjugation.
 

6. Solvent Effects:

   - In polar solvents, carbocations are generally more stable as the solvent molecules can stabilize the positive charge through solvation.
 

Stability Trend Summary:
   - Tertiary (3°) carbocations (most stable)
   - Secondary (2°) carbocations
   - Primary (1°) carbocations
   - Methyl carbocation (least stable)
   - Resonance-stabilized carbocations, such as allylic and benzylic, can be more stable than tertiary carbocations. 

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Online Quiz PROCESS CHEMISTRY

 

MCQ Benzoic Acid

1. What is the relation between the acidic strength of A and B? 

A. A=B

B. A>B

C. A<B

D. A>>B
 

2.  It is given that the following compound has a higher pKa value than benzoic acid. Which is the most probable substituent group X of the compound? 

A. -OH

B. -Cl

C. -CN

D. -NO2

3. Which of the following is the most acidic?  

A. Benzoic acid

B. o-Toluic acid 

C. m-Toluic acid

D. p-Toluic acid

 4. Which of the following has a higher acidic character than benzoic acid? 

A. Acetic acid

B. p-Methoxybenzoic acid

C. p-Bromobenzoic acid

D. p-Aminobenzoic acid 

5. Benzoic acid reacts with alcohols in the presence of concentrated sulfuric
acid to form-

A. Amide

B. Acid

C. Ether

D. Ester

 

 

 

MCQ Benzoic Acid

Unit-I Benzene and Its Derivative

Unit-I Benzene and Its Derivative

Electrophilic Aromatic Substitution Reactions MCQ

MCQ on Basics of Aromaticity

To be a Aromatic Compound molecule must

Molecule must fulfill following condition to be Aromatic.

• Compound must be cyclic
• 
  

• The molecule must be Planner. [ Possible when carbon in SP2 and SP ]
• 
  

• Every atom of cyclic chain must have an available p-orbital.
• 
  

• Should satisfy Huckel`s Rule [4n+2] pi electrons where, the number of electrons in the pi system must be 2, 6, 10, 14, 18, or a higher number i.e. integer value.
• 
  

Distinguishing the Aromatic and non Aromatic compounds?

Aromatic compounds

• Are Cyclic Structure
• Planar [ all atoms of cyclic ring in SP2 or SP Hybridization ]
• Satisfy Huckle`s rule [ 4n + 2  = pi ]
• Resonance stabilized
• Negative Bromine test [ Test for Unsaturation ]
• Dry Heating test burn with sooty flame

e.g.- Benzene, Phenol, Aniline, Naphthalene etc

Non Aromatic compounds

• May or may not Cyclic Structure
• May or may not Planar 
• Not Satisfy Huckle`s rule [ 4n + 2  = pi ]
• May or may not Resonance stabilized
• May or may not Positive Bromine test [ Test for Unsaturation ]
• Dry Heating test burn with non sooty flame

e.g.- Cyclopentane, Cyclobutene, Hexane etc

Stereoselective and Stereospecific Reaction

Stereoselective and Stereospecific Reaction

MCQ Multiple Choice Question Atomic Structure

Atomic Orbital

A. The Aufbau Principle states that?

1. Only two electrons can occupy an orbita

2. Electrons enter the lowest available energy level

3. Orbitals are regions in space around nucleus where one is likely to find an electron

4. Electrons remain unpaired if possible

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B. Which one of the following statements about orbitals is incorrect ?

1. Orbitals can hold two electrons provided they are spinning in the same direction

2. Orbitals are regions in space around nucleus where probability of finding of an electron is more

3. s, p, d and f orbitals are possible

4. Orbitals can hold up to two electrons

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C. Hund's Rule states that

1. Electrons enter the lowest available energy level

2. An orbital can hold up to two electrons

3. Electrons in similar energy orbitals remain unpaired as far as possible

4. Electrons enter the lowest available energy level

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D. Which of the following atoms has two unpaired electrons?

1. B

2. C

3. N

4. O

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E. Which one of the following statements about s orbitals is incorrect ?

1. They are found in all principal energy levels

2. They can only hold only one electron

3. They are spherical in shape

4. The maximum number of s orbitals in any principal level is 1

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F. Which one of the following statements about p orbitals is incorrect?

1. They are found in all principal energy levels

2. They have a dumb-bell shape

3. There are three types of p orbital

4. Each p orbital can hold up to two electrons

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G. Which one of the following statements about d orbitals is incorrect?

1. They are not found in the first two principal energy levels

2. They are associated with transition elements

3. There are 5 types of d orbital

4. d orbitals are filled before p orbitals in the same principal energy level

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H. Which one of the following statements is correct?

1. The 3d sub level is filled before the 4s sub level

2. The 3rd principal energy level only contains 8 electrons

3. Principal energy levels get closer together as they get further from the nucleus

4. Orbitals are always filled in numerical order

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I. The order of filling orbitals is

1. 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p

2. 1s, 2s, 2p, 3s, 3p, 3d, 4p, 3d

3. 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p

4. 4p, 4s, 3d, 3p, 3s, 2p, 2s, 1s

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J. Electrons enter the 4s sub-level before the 3d sub-level because

1. The 4s orbital has a lower energy

2. The 3d orbitals have a lower energy

3. The 4s orbital is spherical

4. There is only one 4s orbital and there are five 3d orbitals

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K. Which statement about chromium is incorrect?

1. Chromium is a transition metal

2. Chromium has an atomic number of 24

3. The electronic configuration of chromium atoms is 1s22s22p63s23p64s23d4

4. The electronic configuration of chromium atoms is 1s22s22p63s23p64s13d5

Willgerodt rearrangement

MCQ Multiple Choice Question on Polycyclic Aromatic Hydrocarbon

Polycyclic Aromatic Hydrocarbon

1.  Which is the most probable main product of the following reaction ?

   

 Answer:- b.

Electrophilic substitution on naphthalene occurs preferentially at C1/ α carbon.

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2. Which is the most probable main product of the following electrophilic substitution reaction of napphthalene?

Answer:-a. 

The most reactive site of naphthalene is C1 and remember that amino NH2 group is an activating, o,p-directing group in aromatic electrophilic substitution reaction; consequently, nitration occurs predominantly at C4 in this reaction.

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3. Which is the most probable main product of the following reaction?

Answer:- d.

Electrophilic substitution on anthracene occurs preferentially at C 9 carbon.
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4.  Which is impossible as a resonance contributor of anthracene.

 

Answer:- b.

In this structure two carbon atoms with five valencies.

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5. Which of following is the most important resonance contributing structure of the naphthalenium ion intermediate in an electrophilic substitution reaction of naphthalene?

 

Answer:- a.

In this one of the benzene ring having benzenoid i.e sexted state, rest of structure not.

Thank you. 

 

Isomerism and its type

Structural Isomerism or Constitutional Isomerism

Structural Isomerism or Constitutional Isomerism

Stereoisomerism and its type

 

 

Conformation Isomerism and Conformation of n-butane

Point to be covered

• Conformation Isomerism 
• Conformation of n-butane
• Projection of conformers