Chapter 28.3, Problem 6P

(a)

Interpretation Introduction

Interpretation: If the reaction is proceeding under thermal conditions then the ring closure of the given compound $\left(\text{2E,4Z,6Z,8E}\right)\text{-2,4,6,8-decatetraene}$ has to be determined.

Concept introduction:

Woodward –Hoffmann rules are the set of rules used to vindicate or predict certain aspects of the stereo chemical outcome and activation energy of pericyclic reactions.

Woodward – Hoffmann rules for Electrocyclic reactions are listed below

$\begin{array}{ccc}\text{Number}\text{of}\text{conjugated}\text{Π}\text{bonds}& \text{Reaction}\text{conditions}& \text{Allowed}\text{mode}\text{of}\text{rong}\text{closure}\\ \text{Even}\text{number}& \text{Thermal}& \text{Conrotatory}\\ & \text{Photochemical}& \text{Disrotatory}\\ \text{Odd}\text{number}& \text{Thermal}& \text{Disrotatory}\\ & \text{Photochemical}& \text{Conrotatory}\end{array}$

(b)

Interpretation Introduction

Interpretation: The configuration of product has to be predicted.

Woodward –Hoffmann rules are the set of rules used to vindicate or predict certain aspects of the stereo chemical outcome and activation energy of pericyclic reactions.

Woodward – Hoffmann rules for Electrocyclic reactions are listed below

$\begin{array}{ccc}\text{Number}\text{of}\text{conjugated}\text{Π}\text{bonds}& \text{Reaction}\text{conditions}& \text{Allowed}\text{mode}\text{of}\text{rong}\text{closure}\\ \text{Even}\text{number}& \text{Thermal}& \text{Conrotatory}\\ & \text{Photochemical}& \text{Disrotatory}\\ \text{Odd}\text{number}& \text{Thermal}& \text{Disrotatory}\\ & \text{Photochemical}& \text{Conrotatory}\end{array}$

Woodward – Hoffmann rules for the configuration of electrocyclic reactions are,

$\begin{array}{ccc}\text{Substituents}\text{in}\text{the}\text{reactant}& \text{Mode}\text{of}\text{ring}\text{closure}& \text{Configuration}\text{of}\text{the}\text{product}\\ \text{Point}\text{in}\text{opposite}\text{directions}& \text{Disrotatory}& \text{cis}\\ & \text{Conrotatory}& \text{trans}\\ \text{Point}\text{in}\text{the}\text{same}\text{directions}& \text{Disrotatory}& \text{trans}\\ & \text{Conrotatory}& \text{cis}\end{array}$

(c)

Interpretation Introduction

Interpretation: If the reaction is proceeding under photochemical conditions then the ring closure of the given compound $\left(\text{2E,4Z,6Z,8E}\right)\text{-2,4,6,8-decatetraene}$ should be determined.

Woodward –Hoffmann rules are the set of rules used to vindicate or predict certain aspects of the stereo chemical outcome and activation energy of pericyclic reactions.

Woodward – Hoffmann rules for Electrocyclic reactions are listed below

$\begin{array}{ccc}\text{Number}\text{of}\text{conjugated}\text{Π}\text{bonds}& \text{Reaction}\text{conditions}& \text{Allowed}\text{mode}\text{of}\text{rong}\text{closure}\\ \text{Even}\text{number}& \text{Thermal}& \text{Conrotatory}\\ & \text{Photochemical}& \text{Disrotatory}\\ \text{Odd}\text{number}& \text{Thermal}& \text{Disrotatory}\\ & \text{Photochemical}& \text{Conrotatory}\end{array}$

(d)

Interpretation Introduction

Interpretation: The configuration of the product has to be predicted.

Concept introduction:

Woodward –Hoffmann rules are the set of rules used to vindicate or predict certain aspects of the stereo chemical outcome and activation energy of pericyclic reactions.

Woodward – Hoffmann rules for Electrocyclic reactions are listed below

$\begin{array}{ccc}\text{Number}\text{of}\text{conjugated}\text{Π}\text{bonds}& \text{Reaction}\text{conditions}& \text{Allowed}\text{mode}\text{of}\text{rong}\text{closure}\\ \text{Even}\text{number}& \text{Thermal}& \text{Conrotatory}\\ & \text{Photochemical}& \text{Disrotatory}\\ \text{Odd}\text{number}& \text{Thermal}& \text{Disrotatory}\\ & \text{Photochemical}& \text{Conrotatory}\end{array}$

Woodward – Hoffmann rules for the configuration of electrocyclic reactions are,

$\begin{array}{ccc}\text{Substituents}\text{in}\text{the}\text{reactant}& \text{Mode}\text{of}\text{ring}\text{closure}& \text{Configuration}\text{of}\text{the}\text{product}\\ \text{Point}\text{in}\text{opposite}\text{directions}& \text{Disrotatory}& \text{cis}\\ & \text{Conrotatory}& \text{trans}\\ \text{Point}\text{in}\text{the}\text{same}\text{directions}& \text{Disrotatory}& \text{trans}\\ & \text{Conrotatory}& \text{cis}\end{array}$