Named Reactions MCQ Quiz in मराठी - Objective Question with Answer for Named Reactions - मोफत PDF डाउनलोड करा

The correct answer is option 2

Explanation:-

The mechanism is as follows:

• Deprotonation: The first step shows a ketone being deprotonated by a strong base, potassium hydride (KH), to form an enolate ion. The electron pair on the oxygen of the enolate then delocalizes to form a resonance-stabilized enolate with the negative charge on the carbon atom.
• Nucleophilic Attack: In the second step, this enolate ion acts as a nucleophile and attacks a nitro alkene (presumably formed in a separate reaction not shown in the image), resulting in the addition of the enolate to the beta position of the nitro alkene. This forms a new carbon-carbon bond.
• Protonation: Following the nucleophilic attack, the intermediate is protonated to form a ketone with an adjacent nitro group.
• Nucleophilic Substitution (S_N2): The nitro group positioned next to the ketone is then replaced by a nucleophile (Nu) through an S_N2 reaction. This is typically characterized by a backside attack of the nucleophile, leading to the inversion of configuration at the carbon atom, and the departure of the leaving group.
• Reduction: The final step is the reduction of the nitro group to an amine. This is achieved by treatment with zinc/ammonium chloride (Zn/Ammonium chloride), which reduces the nitro group first to a nitroso group (N=O), and subsequently to an oxime (N-OH), and finally to an amine (NH₂). The oxime may also isomerize to an imine before the final reduction to the amine.

Conclusion:-

So, the final product will be option 2.

Concept:-

Diels–Alder reaction:

• Diels–Alder reactions occur between a conjugated diene and an alkene, usually called the dienophile.
• This reaction goes in a single step simply on heating.
• Here are some examples: first an open-chain diene with a simple unsaturated aldehyde as the dienophile

Diene:

• The diene component in the Diels–Alder reaction can be open-chain or cyclic and can have many different substituents.
• There is only one limitation: The diene must have the s-cis conformation.
• Butadiene typically prefers the s-trans conformation with the two double bonds as far away from each other as possible for steric reasons. The barrier to rotation about the central σ bond is small (about 30 kJ.mol−1 at room temperature) and rotation to the less favorable but reactive s-cis conformation is rapid.

• Cyclic dienes that are permanently in the s-cis conformation are exceptionally good at Diels–Alder reactions—cyclopentadiene is a classic example—but cyclic dienes that are permanently in the s-trans conformation and cannot adopt the s-cis conformation will not do the
  Diels–Alder reaction at all.
• Dienes permanently in the s-cis conformation are excellent for Diels–Alder reactions.

• The Approach of dienophile from the below and the above of the diene plane is shown below:

Explanation:-

• The reaction pathway is shown below:

Conclusion:-

• Hence, the major product of the reaction is

Explanation:-

The Chugaev Reaction

• The reaction pathway is shown below:

• The loss of C(O)S and MeSH occur at lower ternperatures than the carboxylic ester pyrolysis and thus is rnore suitable for the preparation of sensitive alkenes.
• Heating the xanthate derived by sequential treatment of cis-2-benzylcyclopentan with sodium in toluene followed by addition of excess carbon disulfide and methyl iodide furnishes, via a syn-elimination, 3-benzylcyclopentene.

Conclusion:-

• Hence, the major product formed in the following reaction is

Concept:

• In an aldol reaction, the enolate of an aldehyde or a ketone reacts at the α-carbon atom with the carbonyl of another molecule under basic or acidic conditions to obtain a β-hydroxy carbonyl compound.
• The mechanism of the aldol reaction is shown below:

• The intramolecular aldol reaction is the condensation reaction of two aldehyde groups or ketone groups in the same molecule in presence of a base.
• An example is shown below:

Explanation:-

• The reaction pathway is shown below:

Conclusion:-

Hence, the major product formed in the following reaction is

Concept:-

 Corey–Winter reaction:

• Elimination of thionocarbonates is termed the Corey–Winter reaction.
• Attack by the phosphorus reagent on the sulfur atom is followed by fragmentation to give the alkene.

Explanation:-

• The reaction pathway is shown below
  

Conclusion:-

• Hence, option 4 is the correct answer.

Concept:-

Aldol Condensation:

• In an aldol reaction, the enolate of an aldehyde or a ketone reacts at the α-carbon atom with the carbonyl of another molecule under basic or acidic conditions to obtain a β-hydroxy carbonyl compound.
• The mechanism of the aldol reaction is shown below:
  

Explanation:-

• The mechanism of the reaction is shown below:
  
• Complete selectivity occurs for one of the two possible syn aldol products, the choice of the syn product being made by the choice of the chiral auxiliary group.
• The stereoselectivity can be rationalized by a six-membered (Zimmerman–Traxler) transition state, in which the aldehyde approaches from
  the less-hindered face.

Conclusion:-

• Hence, option 4 is the correct answer.

Explanation:-

• The Pauson–Khand reaction (or PKR or PK-type reaction) is a chemical reaction described as a [2+2+1] cycloaddition between an alkyne, an alkene, and carbon monoxide to form an α,β-cyclopentenone.
• An example is given below:

• The Payne rearrangement is the isomerization, under basic conditions, of 2,3-epoxy alcohols to isomeric 1,2-epoxy alcohols with inversion of configuration.
• An example is given below:

​

• The Paternò–Büchi reaction, named after Emanuele Paternò and George Büchi, who established its basic utility and is a photochemical reaction, specifically a [2+2] photocycloaddition, which forms four-membered oxetane rings from an excited carbonyl and reacting with an alkene.
• An example is given below:

• Thus, the given reaction is an example of the Paterno-Buchi reaction.

Conclusion:-

• Hence, it is Paterno-Buchi reaction.

Explanation:-

• The reaction pathway is shown below:

Conclusion:-

• Hence,  the product formed in the following transformations is

Explanation: -

The reaction will involve the following steps: -

Step 1: Oxidative-addition i.e. addition of organic compound on metal complex via sigma complex state with an increase in oxidation state on the metal ion.

Step 2: Transmetalation rearrangement reaction, this reaction involves the transfer of ligands from one metal to another metal complex.

Step 3: Reduction-elimination reaction, in this reaction metal, will undergo reduction by two oxidation states and two of the ligand will leave and form a single molecular species.

Conclusion: -

The reaction will produce the product preserved stereochemistry as follows: -

Hence, The correct option is - 2.

Concept:

Appel Reaction

Appel reaction remains a valuable tool for the synthesis of alkyl halides, particularly for sensitive alcohols. However, ongoing research is focused on addressing its limitations and developing more sustainable alternatives.

• The reaction typically employs triphenylphosphine (PPh₃) and tetrahalomethane (CX₄, where X = Cl, Br, or I).
• Carbon tetrachloride (CCl₄) is commonly used for synthesizing alkyl chlorides, while carbon tetrabromide (CBr₄) or bromine (Br₂) can be used for alkyl bromides, and carbon tetraiodide (CI₄) or iodine (I₂) for alkyl iodides. 

Explanation:

General Mechanism

Therefore, the correct option is 3.