What is electrophilic addition and to which functional group does it apply?

A reaction in which an electrophile attacks an electron-rich pi bond, forming a carbocation intermediate, which is then attacked by a nucleophile. It applies to alkenes (C=C double bonds).

In free radical substitution, the three stages are .......... , .......... and .......... . Curly arrows are .......... used in this mechanism.

In free radical substitution, the three stages are initiation , propagation and termination . Curly arrows are not used in this mechanism.

True or False? In a nucleophilic substitution mechanism, curly arrows must originate from a lone pair or a bond — never from an atom or a formal charge.

True. Curly arrows show electron movement and must start from a lone pair or a bond. Arrows originating from an atom or a formal charge score zero in examinations.

What distinguishes nucleophilic addition-elimination from simple nucleophilic addition?

In nucleophilic addition, the nucleophile adds to a carbonyl compound to give a single product with no atoms lost. In nucleophilic addition-elimination, the nucleophile first adds to an acyl compound to form a tetrahedral intermediate, then a leaving group departs to regenerate a C=O (e.g. acyl chlorides reacting with nucleophiles).

Electrophilic substitution on a benzene ring forms a .......... intermediate. Aromaticity is restored when the intermediate loses .......... , regenerating the delocalised system.

Electrophilic substitution on a benzene ring forms a positively charged intermediate. Aromaticity is restored when the intermediate loses H + , regenerating the delocalised system.

True or False? In elimination reactions, a base removes a hydrogen atom from a carbon adjacent to the C–X bond, forming a C=C double bond as the halide departs.

True. The base abstracts H + from the carbon adjacent to the carbon bearing the halide, and the halide simultaneously departs, forming a C=C double bond. Both the C–H bond and the H must be drawn explicitly in the mechanism.

Name all seven organic reaction mechanisms covered in the AQA A Level course.

Free radical substitution Electrophilic addition Nucleophilic substitution Elimination Nucleophilic addition Nucleophilic addition-elimination Electrophilic substitution

A symbol used in organic reaction mechanisms to represent the movement of a pair of electrons , drawn from a lone pair or a bond to show where electrons move during a reaction step.

A LevelChemistryAQAFlashcardsAdvanced Organic ChemistryOrganic Mechanisms

Organic Mechanisms (AQA A Level Chemistry): Flashcards

Exam code: 7405

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What is electrophilic addition and to which functional group does it apply?

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What is electrophilic addition and to which functional group does it apply?
A reaction in which an electrophile attacks an electron-rich pi bond, forming a carbocation intermediate, which is then attacked by a nucleophile.
It applies to alkenes (C=C double bonds).
In free radical substitution, the three stages are .........., .......... and ........... Curly arrows are .......... used in this mechanism.
In free radical substitution, the three stages are initiation, propagation and termination. Curly arrows are not used in this mechanism.
True or False?
In a nucleophilic substitution mechanism, curly arrows must originate from a lone pair or a bond — never from an atom or a formal charge.
True.
Curly arrows show electron movement and must start from a lone pair or a bond. Arrows originating from an atom or a formal charge score zero in examinations.
What distinguishes nucleophilic addition-elimination from simple nucleophilic addition?
In nucleophilic addition, the nucleophile adds to a carbonyl compound to give a single product with no atoms lost.
In nucleophilic addition-elimination, the nucleophile first adds to an acyl compound to form a tetrahedral intermediate, then a leaving group departs to regenerate a C=O (e.g. acyl chlorides reacting with nucleophiles).
Electrophilic substitution on a benzene ring forms a .......... intermediate. Aromaticity is restored when the intermediate loses .........., regenerating the delocalised system.
Electrophilic substitution on a benzene ring forms a positively charged intermediate. Aromaticity is restored when the intermediate loses H⁺, regenerating the delocalised system.
True or False?
In elimination reactions, a base removes a hydrogen atom from a carbon adjacent to the C–X bond, forming a C=C double bond as the halide departs.
True.
The base abstracts H⁺ from the carbon adjacent to the carbon bearing the halide, and the halide simultaneously departs, forming a C=C double bond. Both the C–H bond and the H must be drawn explicitly in the mechanism.
Name all seven organic reaction mechanisms covered in the AQA A Level course.
1. Free radical substitution
2. Electrophilic addition
3. Nucleophilic substitution
4. Elimination
5. Nucleophilic addition
6. Nucleophilic addition-elimination
7. Electrophilic substitution
Curly arrow
A symbol used in organic reaction mechanisms to represent the movement of a pair of electrons, drawn from a lone pair or a bond to show where electrons move during a reaction step.

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