Control of Activating Effect in Aromatic Amine Substitution
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Questions and Answers

Why is the main problem encountered during electrophilic substitution reactions of aromatic amines?

  • Formation of multiple isomers
  • Their very high reactivity (correct)
  • Substitution tends to occur at meta-positions
  • Their low reactivity

    • How can the activating effect of the -NH2 group in aniline be controlled during electrophilic substitution reactions?

  • By protecting it with a bromine atom
  • By reducing its reactivity
  • By acetylating it with acetic anhydride (correct)
  • By oxidizing it to nitro group

    • Why does direct nitration of aniline yield tarry oxidation products?

  • Because aniline is a poor nucleophile
  • Due to the activation of benzene ring
  • Nitration at ortho and para positions only
  • Presence of acidic medium (correct)

    • What is the effect of protecting the -NH2 group in aniline through acetylation before nitration?

    <p>Controls the nitration reaction to obtain p-nitro derivative</p> Signup and view all the answers

    What is the role of the anilinium ion formed in a strongly acidic medium during nitration?

    <p>It is meta directing and leads to meta derivative formation</p> Signup and view all the answers

    In what way does the lone pair of electrons on nitrogen in acetanilide affect its activating effect compared to aniline?

    <p>It decreases the activating effect</p> Signup and view all the answers

    Which method is used for the preparation of primary amines by treating an amide with bromine and sodium hydroxide?

    <p>Hoffmann bromamide degradation reaction</p> Signup and view all the answers

    Why can aromatic primary amines not be prepared using the Gabriel phthalimide synthesis method?

    <p>Aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide</p> Signup and view all the answers

    What type of reaction is used for the preparation of amines containing one carbon atom more than the starting amine?

    <p>Ascent of amine series</p> Signup and view all the answers

    What does the reduction of amides with lithium aluminium hydride yield?

    <p>Amines</p> Signup and view all the answers

    Why does migration of an alkyl or aryl group take place in the Hoffmann bromamide degradation reaction?

    <p>To decrease the carbon content of the amine</p> Signup and view all the answers

    Which reagent is used in Hoffmann bromamide degradation reaction for treating an amide to form primary amines?

    <p>Bromine</p> Signup and view all the answers

    What determines the course of reaction of amines?

    <p>The number of hydrogen atoms attached to nitrogen atom</p> Signup and view all the answers

    Which type of amines differ in many reactions due to the number of hydrogen atoms attached to the nitrogen atom?

    <p>Primary amines</p> Signup and view all the answers

    How do amines behave due to the presence of unshared electron pair?

    <p>As nucleophiles</p> Signup and view all the answers

    What type of reaction do amines undergo when they react with acids?

    <p>Acid-base neutralization reaction</p> Signup and view all the answers

    What is the basis for separating amines from non-basic organic compounds insoluble in water?

    <p>Solubility in water</p> Signup and view all the answers

    How can the basic character of amines be better understood according to the given text?

    <p>[H2O] = K/[R−NH2]</p> Signup and view all the answers

    What is the product formed when arenediazonium chloride is treated with fluoroboric acid?

    <p>Aryl fluoride</p> Signup and view all the answers

    Which reducing agent can be used to convert diazonium salts to arenes?

    <p>Phosphinic acid</p> Signup and view all the answers

    At what temperature does the hydrolysis of a diazonium salt solution occur to form phenol?

    <p>283 K</p> Signup and view all the answers

    What is the product when diazonium fluoroborate is heated with aqueous sodium nitrite solution in the presence of copper?

    <p>p-Hydroxyazobenzene</p> Signup and view all the answers

    In a coupling reaction between benzene diazonium chloride and phenol, which position of phenol gets coupled with the diazonium salt?

    <p>Para position</p> Signup and view all the answers

    What do azo products obtained from diazo group coupling reactions typically have?

    <p>Extended conjugate system</p> Signup and view all the answers

    What factor influences the stability of substituted ammonium cations in protic polar solvents?

    <p>Hydrogen bonding</p> Signup and view all the answers

    Which type of amines are generally stronger bases compared to ammonia?

    <p>Tertiary amines</p> Signup and view all the answers

    What is used for the identification of primary, secondary, and tertiary amines?

    <p>p-Toluenesulphonyl chloride</p> Signup and view all the answers

    Which group on aromatic amines enhances their reactivity?

    <p>Amino group</p> Signup and view all the answers

    How can the reactivity of aromatic amines be controlled?

    <p>By treating with acetyl chloride</p> Signup and view all the answers

    What type of amines are used as insect attractants?

    <p>Tertiary amines</p> Signup and view all the answers

    Study Notes

    Electrophilic Substitution Reactions of Aromatic Amines

    • The main problem encountered during electrophilic substitution reactions of aromatic amines is that the -NH2 group is highly activating, making it difficult to control its activating effect.
    • The activating effect of the -NH2 group in aniline can be controlled by protecting it through acetylation before nitration.

    Nitration of Aniline

    • Direct nitration of aniline yields tarry oxidation products due to the highly activating effect of the -NH2 group.
    • Protecting the -NH2 group in aniline through acetylation before nitration allows for controlled nitration.

    Role of Anilinium Ion

    • In a strongly acidic medium, the anilinium ion is formed, which plays a significant role during nitration.

    Acetanilide vs. Aniline

    • The lone pair of electrons on nitrogen in acetanilide reduces its activating effect compared to aniline.

    Preparation of Primary Amines

    • Primary amines can be prepared by treating an amide with bromine and sodium hydroxide.
    • The Gabriel phthalimide synthesis method cannot be used to prepare aromatic primary amines.

    Alkylation of Amines

    • A reaction involving the addition of an alkyl or aryl group to an amine is used to prepare amines containing one carbon atom more than the starting amine.

    Reduction of Amides

    • The reduction of amides with lithium aluminium hydride yields amines.

    Hoffmann Bromamide Degradation Reaction

    • In the Hoffmann bromamide degradation reaction, migration of an alkyl or aryl group takes place, resulting in the formation of primary amines.
    • The reagent used in Hoffmann bromamide degradation reaction is bromine and sodium hydroxide.

    Factors Influencing Reaction Course

    • The course of reaction of amines is determined by the number of hydrogen atoms attached to the nitrogen atom.

    Basic Character of Amines

    • Amines are basic due to the presence of an unshared electron pair, which enables them to react with acids.
    • The basic character of amines can be better understood by considering the number of hydrogen atoms attached to the nitrogen atom.

    Separation of Amines

    • Amines can be separated from non-basic organic compounds insoluble in water based on their basic character.

    Diazonium Salts

    • Arenediazonium chloride treated with fluoroboric acid forms a diazonium fluoroborate.
    • Reducing agents like zinc dust or sodium borohydride can be used to convert diazonium salts to arenes.
    • Hydrolysis of a diazonium salt solution occurs at 100°C to form phenol.
    • Heating diazonium fluoroborate with aqueous sodium nitrite solution in the presence of copper yields a phenol.

    Coupling Reactions

    • In a coupling reaction between benzene diazonium chloride and phenol, the para position of phenol gets coupled with the diazonium salt.
    • Azo products obtained from diazo group coupling reactions typically have bright colors.

    Stability of Ammonium Cations

    • The stability of substituted ammonium cations in protic polar solvents is influenced by the steric factor.

    Basicity of Amines

    • Alkylamines are generally stronger bases compared to ammonia.

    Identification of Amines

    • The Hinsberg method is used for the identification of primary, secondary, and tertiary amines.

    Reactivity of Aromatic Amines

    • The -NH2 group on aromatic amines enhances their reactivity.
    • The reactivity of aromatic amines can be controlled by protecting the -NH2 group or using specific reaction conditions.

    Insect Attractants

    • Primary amines are used as insect attractants.

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    Description

    Learn how to control the activating effect of -NH2 group in aromatic amine substitution reactions by protecting it through acetylation with acetic anhydride. This method helps in directing the substitution to the desired position.

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