Aromatic Amines Handwritten Notes (Organic Chemistry 2, Unit 2)
Download comprehensive handwritten notes on Aromatic Amines, covering Unit 2 of Organic Chemistry 2 for B.Pharm and D.Pharm (3rd Semester). These notes delve into the basicity of amines, the effect of substituents on basicity, synthetic uses of aryl diazonium salts, preparation methods, and electrophilic substitution reactions. View online or download PDF/notes for free.
Keywords: aromatic amines notes, organic chemistry 2, unit 2, B.Pharm, D.Pharm, 3rd sem, basicity of amines, substituent effect, aryl diazonium salts, preparation of amines, electrophilic substitution, aniline, download PDF, free study material, chemistry notes.
Aromatic Amines: Properties, Reactions, and Synthetic Utility (Unit 2, Organic Chemistry 2)
This detailed set of handwritten notes focuses on Aromatic Amines, a vital component of Unit 2 in Organic Chemistry 2, specifically tailored for B.Pharm and D.Pharm students in their 3rd semester. Aromatic amines are organic compounds where an amino group (-NH2, -NH-, or -N-) is directly attached to an aromatic ring. These compounds exhibit distinct chemical properties and reactivity compared to aliphatic amines, largely due to the resonance interaction between the lone pair of electrons on the nitrogen atom and the aromatic pi-system.
Basicity of Aromatic Amines
A central theme in the study of aromatic amines is their basicity. The notes thoroughly explain the "basicity of amines," contrasting aromatic amines with aliphatic amines. Aromatic amines are generally weaker bases than aliphatic amines because the lone pair on the nitrogen atom is delocalized into the aromatic ring via resonance. This delocalization makes the lone pair less available for protonation, thereby reducing basicity. The content further elaborates on the "effect of substituents on basicity." Electron-donating groups (e.g., alkyl, -OCH3) on the aromatic ring increase basicity by making the nitrogen's lone pair more available, while electron-withdrawing groups (e.g., nitro, halo) decrease basicity by further delocalizing the lone pair or by inductive effects. Understanding these substituent effects is crucial for predicting and comparing the basicity of various substituted anilines.
Preparation of Aromatic Amines
The notes provide a comprehensive overview of the "preparation of aromatic amines." Common methods discussed include:
- Reduction of Nitro Compounds: A widely used method, typically involving reagents like Sn/HCl, Fe/HCl, or catalytic hydrogenation of nitrobenzene and its derivatives to yield anilines.
- Hofmann Bromamide Degradation: Conversion of amides to primary amines with one less carbon atom, using bromine and a strong base.
- Gabriel Phthalimide Synthesis: A method for preparing primary amines, avoiding the formation of secondary or tertiary amines.
- Reductive Amination: Formation of amines from carbonyl compounds using reducing agents and ammonia or other amines.
Each method is explained with relevant reaction mechanisms and conditions, providing a practical understanding of how these important compounds are synthesized.
Electrophilic Substitution Reactions of Aromatic Amines
Aromatic amines, particularly aniline, are highly reactive towards "electrophilic substitution reactions." The amino group is a strong activating and ortho-para directing group due to the strong resonance donation of the nitrogen's lone pair to the aromatic ring. The notes cover key reactions such as:
- Halogenation (e.g., Bromination): Aniline undergoes rapid tribromination with bromine water due to the high activation of the ring.
- Nitration: Direct nitration of aniline is complex and often leads to oxidation products; hence, the amino group is usually protected first.
- Sulfonation: Formation of sulfanilic acid.
The content also emphasizes the need for protection of the amino group (e.g., by acetylation) before certain electrophilic substitutions to control reactivity and prevent side reactions.
Synthetic Uses of Aryl Diazonium Salts
A crucial section is dedicated to the "synthetic uses of aryl diazonium salts." These highly versatile intermediates are formed from primary aromatic amines via diazotization. The notes detail various reactions of diazonium salts that are invaluable in organic synthesis, including:
- Sandmeyer Reactions: Replacement of the diazonium group with Cl, Br, or CN using cuprous salts.
- Gattermann Reaction: Similar to Sandmeyer but uses copper powder.
- Balz-Schiemann Reaction: Introduction of fluorine using HBF4.
- Coupling Reactions: Formation of intensely colored azo dyes by reaction with phenols or aromatic amines.
These reactions enable the synthesis of a wide array of substituted aromatic compounds that are otherwise difficult to obtain directly. This comprehensive set of handwritten notes provides a strong foundation in the chemistry of aromatic amines, making it an indispensable resource for pharmacy students.
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