The mechanism for each step in the pathway given for bio synthesizing epi -Aristolochene is to be shown using curved arrows. Further the steps that involve electrophilic addition(s) to the alkene and that involve carbocation rearrangement(s) are to be identified. Concept introduction: While drawing curved arrows the head of the curved arrow starts from the nucleophilic source (either negatively charged or neutral) and ends in an electrophilic sink (either positively charged or neutral). The formation of a new bond should lead to the breaking of a bond that already exists as the octet rule cannot be violated. In electrophilic addition reactions, the first step is the attack of the π electrons of the double bond on the hydrogen of another reactant to yield a carbocation. One of the carbon in C=C gets attached to hydrogen while the other acquires a positive charge. In the second step, the carbocation formed can rearrange to give another more stable carbocation either by a hydride shift (shift of hydrogen atom with its electron pair) or by an alkyl shift (shift of an alkyl group with its electron pair) between neighboring carbons. In the last step the carbocation produced reacts with a negatively charged ion or eliminates a proton to give the product. To show: The mechanism for each step in the pathway given for bio synthesizing epi -aristolochene using curved arrows. Further to identify the steps that involve electrophilicaddition(s) to the alkene and that involve carbocation rearrangement(s).

Question

H3C CH3 H3C NA C→XT Br Br₂ CH₂Cl₂ H3C Electrophilic addition of bromine, Br₂, to alkenes yields a 1,2-dibromoalkane. The reaction proceeds through a cyclic intermediate known as a bromonium ion. The reaction occurs in an anhydrous solvent such as CH₂Cl₂. CH3 Br In the second step of the reaction, bromide is the nucleophile and attacks at one of the carbons of the bromonium ion to yield the product. Due to steric clashes, the bromide ion always attacks the carbon from the opposite face of the bromonium ion so that a product with anti stereochemistry is formed. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions Br CH3 H3C CH3

Answer 1

Question

Chapter 7.SE, Problem 33MP

Interpretation Introduction

Interpretation:

The mechanism for each step in the pathway given for bio synthesizing epi-Aristolochene is to be shown using curved arrows. Further the steps that involve electrophilic addition(s) to the alkene and that involve carbocation rearrangement(s) are to be identified.

Concept introduction:

While drawing curved arrows the head of the curved arrow starts from the nucleophilic source (either negatively charged or neutral) and ends in an electrophilic sink (either positively charged or neutral). The formation of a new bond should lead to the breaking of a bond that already exists as the octet rule cannot be violated.

In electrophilic addition reactions, the first step is the attack of the π electrons of the double bond on the hydrogen of another reactant to yield a carbocation. One of the carbon in C=C gets attached to hydrogen while the other acquires a positive charge. In the second step, the carbocation formed can rearrange to give another more stable carbocation either by a hydride shift (shift of hydrogen atom with its electron pair) or by an alkyl shift (shift of an alkyl group with its electron pair) between neighboring carbons. In the last step the carbocation produced reacts with a negatively charged ion or eliminates a proton to give the product.

To show:

The mechanism for each step in the pathway given for bio synthesizing epi-aristolochene using curved arrows. Further to identify the steps that involve electrophilicaddition(s) to the alkene and that involve carbocation rearrangement(s).

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H3C CH3 H3C NA C→XT Br Br₂ CH₂Cl₂ H3C Electrophilic addition of bromine, Br₂, to alkenes yields a 1,2-dibromoalkane. The reaction proceeds through a cyclic intermediate known as a bromonium ion. The reaction occurs in an anhydrous solvent such as CH₂Cl₂. CH3 Br In the second step of the reaction, bromide is the nucleophile and attacks at one of the carbons of the bromonium ion to yield the product. Due to steric clashes, the bromide ion always attacks the carbon from the opposite face of the bromonium ion so that a product with anti stereochemistry is formed. Draw curved arrows to show the movement of electrons in this step of the mechanism. Arrow-pushing Instructions Br CH3 H3C CH3

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