The INCORRECT statement(s) among the following is/are:a)[4π + 2π] cycloaddition reactions are carried out in presence of light.b)[2π + 2π] cycloaddition reaction between a keto group and all alkene is photochemically allowedc)[4π + 2π] cycloaddition reactions are thermally allowedd)Transold dienes undergo Diels- Alder reactionsCorrect answer is option 'A,D'. Can you explain this answer?

Question

The INCORRECT statement(s) among the following is/are:a)[4&#960; + 2&#960;] cycloaddition reactions are carried out in presence of light.b)[2&#960; + 2&#960;] cycloaddition reaction between a keto group and all alkene is photochemically allowedc)[4&#960; + 2&#960;] cycloaddition reactions are thermally allowedd)Transold dienes undergo Diels- Alder reactionsCorrect answer is option 'A,D'. Can you explain this answer?

Answer

[4 2] Cycloaddition reactions are carried out in presence of light and transold dienes undergo Diels-Alder reactions are the incorrect statements among the given options. Let's understand why.

[4 2] Cycloaddition reactions are thermally allowed:
The [4 + 2] cycloaddition reaction is a type of pericyclic reaction that involves the reaction of a diene and a dienophile to form a cyclohexene ring. This reaction is thermally allowed, meaning it can proceed at normal temperatures without the need for light or other external stimuli. In fact, some [4 + 2] cycloaddition reactions are known to proceed faster at higher temperatures.

[2 2] Cycloaddition reaction between a keto group and all alkene is photochemically allowed:
The [2 + 2] cycloaddition reaction is another type of pericyclic reaction that involves the reaction of two alkenes to form a cyclobutane ring. This reaction is photochemically allowed, meaning it requires the presence of light to proceed. However, the statement that this reaction occurs between a keto group and all alkene is incorrect. The reaction only occurs between two alkene groups.

Transold dienes undergo Diels-Alder reactions:
Diels-Alder reactions are a type of [4 + 2] cycloaddition reaction that involves the reaction of a diene and a dienophile to form a cyclic compound. Transold dienes, which have a trans double bond configuration, are known to undergo Diels-Alder reactions readily. This statement is true.

In the presence of light, [4 + 2] cycloaddition reactions proceed faster than in the absence of light. However, it is not necessary to carry out these reactions in the presence of light, and they can proceed thermally. Therefore, options A and D are incorrect.

Answer

Explain - D answer..Transold dienes  can't undergo diels - elder rxns...only conjugated dienes in the S- cis confirmation can undergo Diels elder rxns.If a diene is not conjugated,or can't be in the S- cis confirmation,then it can't undergo a Diels elder rxns.Dienes that are located in rings can't rotate ,and so are stuck in either an  S- cis or S- trans  confirmation.But a cyclic dienes can rotate into the S- Cis confirmation , as long as their substitutents are not too big / bulky to prevent easy rotation ..

Similar Chemistry Doubts

Select the correct classification in the following reaction from options I to IV gives below:(I) Conrotatory electrocyclic reaction(II) Disrotatory electrocyclic reaction(III) Valence iso merization(IV) [4S + 2a] Cycloaddition reaction

Diels-Alder reaction is a

Among the following reactions, which one is incorrect?

Following reaction is an example of

Which of the following statements is correct for alkyl halide?

Top Courses for Chemistry

Suggested Free Tests

Related Content

Schools

Competitive Examinations

Quick Access Links

Technical Exams