Using the resonance structures of the intermediates the observation that the electrophilic substitution of 3-phenylpropanenitrile occurs at ortho and para positions, but reaction with 3-phenylpropenenitrile occurs at the meta position is to be explained. Concept introduction: In aromatic electrophilic substitution reactions of monosubstituted benzenes, the resonance and inductive effects of the substituent group already present decides the orientation of the electrophile and reactivity. If both the effects reinforce each other and release electron towards the ring then the substituent group is an o- and p- director and activator. If on the other hand, if they reinforce and withdraw electrons from the ring then the substituent is meta orienting. If the two effects oppose each other then resonance effect decides the orientation and the inductive effect plays a role in determining the reactivity. To explain: Using the resonance structures of the intermediates, the observation that the electrophilic substitution of 3-phenylpropanenitrile occurs at ortho and para positions, but reaction with 3-phenylpropenenitrile occurs at the meta position is to be explained.

Question

Explain why methyl trifluoroacetate, CF3CO2CH3, is more reactive than methyl acetate, CH3CO2CH3, in nucleophilic acyl substitution reactions.

Answer 1

Question

Chapter 16.SE, Problem 60AP

Interpretation Introduction

Interpretation:

Using the resonance structures of the intermediates the observation that the electrophilic substitution of 3-phenylpropanenitrile occurs at ortho and para positions, but reaction with 3-phenylpropenenitrile occurs at the meta position is to be explained.

Concept introduction:

In aromatic electrophilic substitution reactions of monosubstituted benzenes, the resonance and inductive effects of the substituent group already present decides the orientation of the electrophile and reactivity. If both the effects reinforce each other and release electron towards the ring then the substituent group is an o- and p- director and activator. If on the other hand, if they reinforce and withdraw electrons from the ring then the substituent is meta orienting. If the two effects oppose each other then resonance effect decides the orientation and the inductive effect plays a role in determining the reactivity.

To explain:

Using the resonance structures of the intermediates, the observation that the electrophilic substitution of 3-phenylpropanenitrile occurs at ortho and para positions, but reaction with 3-phenylpropenenitrile occurs at the meta position is to be explained.

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