Control of Activating Effect in Aromatic Amine Substitution

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.