Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 27: Q 32. (page 1100)

Question: What cyclic product is formed when each decatetraene undergoes photochemical electrocyclic ring closure?

Short Answer

Expert verified

Answer

Formed cyclic product:

a.

b.

Step by step solution

01

Woodward-Hoffmann rule for photochemical electrocyclic reaction

A thermal reaction with an even number of electron pairs is conrotatory

• If one of the reaction conditions changes — thermal to photochemical or even to odd — the stereochemistry of the reaction changes to disrotatory

• If both reaction conditions change— thermal to photochemical reaction and even to odd — the stereochemistry does not change

02

Product formation

  • It is an electrocyclic ring closure reaction of a compound with four conjugated double bonds, and the ring closure is dis-rotary.
  • A disrotatory process forms the product under photochemical conditions.
  • From the Woodward-Hoffmann rules, photochemical electrocyclic reactions involving (4n) electrons are dis-rotary.
  • Therefore, the product formed is of a 4+2 electron system arising from disrotatory cyclization.
  • Stereochemistry of products - Frontier orbital representation
  • The HOMO is in which the end orbitals are symmetrical.
  • The symmetry is correct for bond formation, so the orbitals rotate in opposite directions to form a new sigma bond.

a. The product formed is cis in configuration.

Cis product

b. The product formed is trans in configuration.

Trans product

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Start your free trial

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Question:Draw the product (including stereochemistry) formed from each pair ofreactants in a thermal [4 + 2] cycloaddition reaction.

Question: What product is formed when each compound undergoes a photochemical electrocyclic reaction? Label each process as conrotatory or disrotatory and clearly indicate the stereochemistry around tetrahedral stereogenic centers and double bonds.

Question: [4 + 2] Cycloadditions with o-quinones such as B are often complex because a variety of products are possible.a. Draw arrows to illustrate how each product is formed when B reacts with styrene, and label the “diene” and “dienophile” components.


b. Draw arrows to illustrate how each product is formed when B reacts with buta-1,3-diene, and label the “diene” and “dienophile” components.


c. o-Quinone C reacts with diene D to form heterocycle E by a process that involves a cycloaddition followed by a [3,3] sigmatropic rearrangement. Use curved arrows to illustrate how this two-step sequence occurs. E is not formed directly from C by a Diels– Alder reaction.

Question: What cyclic product is formed when each decatetraene undergoes thermal electrocyclic ring closure?

Question:Draw a stepwise mechanism for the Carroll rearrangement, a reaction that prepares aγ,δ-unsaturated carbonyl compound from aβ-keto ester and allylic alcohol in the presence ofbase.
See all solutions

Recommended explanations on Chemistry Textbooks

Chemistry Branches

Read Explanation

Chemical Reactions

Read Explanation

Physical Chemistry

Read Explanation

Nuclear Chemistry

Read Explanation

Chemical Analysis

Read Explanation

The Earths Atmosphere

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free