Whether in addition of H − X to a π bond, X ends up on the carbon that forms lower or higher potential energy carbocation should be determined. Concept introduction: The carbon-carbon double bond in alkene consists of a strong σ bond (formed by overlap of s p 2 hybridized orbital on each carbon) and a weak π bond (formed by overlap of pure p orbital on each carbon). Due to unsaturation, alkene shows addition reaction where the double bond provides loosely held π electrons and is readily attacked by any electron deficient group like H + ions released from acids. The loosely held π electrons are present, therefore, behave as base though weak one. In addition reactions of alkenes, the electrophilic and nucleophilic part of reagent may add across the double bond from opposite sides and in such case, the addition is known as anti or trans addition. The addition of reagent may occur from the same side of the double bond and in such case, the addition is known as syn or cis addition.

Question

A benzene ring alters the reactivity of a neighboring group in the so-called “benzylic” position, similarly to how a double bond alters the reactivity of groups in the “allylic” position. Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates. a) Use resonance structures to show the delocalization of the positive charge, negative charge, and unpaired electron of the benzyl cation, anion, and radical.

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Question

Chapter 8, Problem 17CTQ

Interpretation Introduction

Interpretation: Whether in addition of H−X to a π bond, X ends up on the carbon that forms lower or higher potential energy carbocation should be determined.

Concept introduction: The carbon-carbon double bond in alkene consists of a strong σ bond (formed by overlap of sp2 hybridized orbital on each carbon) and a weak π bond (formed by overlap of pure p orbital on each carbon). Due to unsaturation, alkene shows addition reaction where the double bond provides loosely held π electrons and is readily attacked by any electron deficient group like H+ ions released from acids. The loosely held π electrons are present, therefore, behave as base though weak one.

In addition reactions of alkenes, the electrophilic and nucleophilic part of reagent may add across the double bond from opposite sides and in such case, the addition is known as anti or trans addition. The addition of reagent may occur from the same side of the double bond and in such case, the addition is known as syn or cis addition.

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A benzene ring alters the reactivity of a neighboring group in the so-called “benzylic” position, similarly to how a double bond alters the reactivity of groups in the “allylic” position. Benzylic cations, anions, and radicals are all more stable than simple alkyl intermediates. a) Use resonance structures to show the delocalization of the positive charge, negative charge, and unpaired electron of the benzyl cation, anion, and radical.

Zaitsev's rule is useful in selecting which carbon adjacent to a carbocation will form the double bond in the alkene product. True or False

a) This alkene can be prepared via Wittig reaction. Draw structural formulas for the aldehyde and the Wittig reagent. • Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner. • Draw the Wittig reagent in the ylide form. • If more than one combination of Wittig reagent and aldehyde is possible, draw only one set.