Organic Chemistry 8th Edition Chapter 19 Lecture Notes
Organic Chemistry 8th Edition - Chapter 19: Amines and Heterocyclic Compounds
Page 1: Introduction to Amines
Amines as Bases and Nucleophiles:
A base shares its lone pair with a proton.
A nucleophile shares its lone pair with an atom other than a proton.
Page 2: Types of Amines
Classification of Amines:
Primary Amines: One alkyl group attached to the nitrogen.
Secondary Amines: Two alkyl groups attached to the nitrogen.
Tertiary Amines: Three alkyl groups attached to the nitrogen.
Saturated Heterocyclic Compounds:
Components of heterocyclic structures that contain nitrogen.
Acidity of Amines:
Amines are considered the most common organic bases.
Page 3: Reactivity of Amines
Relative Reactivities:
Overview of compounds with electronegative groups attached to sp3 carbons affecting reactivity.
Amines as Nucleophiles:
Exhibit reactivity in reactions such as SN2 and nucleophilic acyl substitution.
Page 4: Reactions and Mechanisms
Nucleophilic Reactions:
Types of Reactions:
Nucleophilic addition-elimination reactions.
Conformational transformations leading to primary amines, e.g., benzylamine.
Formation of imines and enamines from amines under acidic conditions.
Arenediazonium Salts Formation:
Reaction setup involves primary amines with reagents like NaNO2 at 0°C, producing arenediazonium salts.
Page 5: Alkyl Halide Reactions
Reactivity of Substituted Amines:
Substituted amines are noted to be more reactive than ammonia in reactions with alkyl halides.
Amino Acid Synthesis:
Overview of synthesis processes involving α-bromocarboxylic acids.
Page 6: Gabriel and Other Syntheses
Gabriel Synthesis of Primary Amine:
Detailed mechanism involving phthalimide, alkylation, and hydrolysis leading to primary amine formation.
Synthesis from Nitriles and Azides:
Method of converting nitriles and azides to primary amines.
Page 7: Amines from Amides
Key Reaction Components:
Use of lithium aluminum hydride () in conjunction with amide substrates leads to the synthesis of amines.
Reductive Amination:
Overview of transaminating reactions leading to the formation of amines.
Page 8: Aniline Synthesis and Aromatic Heterocycles
Formation of Anilines:
Reactants such as HNO3 and H2SO4 in conjunction with Pd/C and reducing agents yield aniline derivatives.
Five-Membered Ring Aromatic Heterocycles:
Compounds such as pyrrole, furan, and thiophene discussed concerning their properties and applications.
Page 9: Aromaticity and Reactivity
Aromaticity of Compounds:
Explanation of why certain compounds, like pyrrole, exhibit aromatic characteristics and its weak base nature due to electron donation requirements for stability.
Page 10: Dipole Moments and Delocalization Energy
Dipole Moments:
Analysis of dipole orientation in various molecules.
Delocalization Energy:
The concept that delocalization energy increases with improvement in resonance contributor stability and equivalence.
Page 11: Protonation and Polymerization in Acid
Protonation at the 2-Position:
Mechanism of electrophilic attack placed at the 2-position of aromatic heterocycles.
Pyrrole Polymerization:
Description of pyrrole's behavior in acidic conditions leading to polymeric structures.
Page 12: Acidity Comparisons
Acidity Relations:
Pyrrole demonstrated as more acidic than pyrrolidine due to greater stabilization of conjugate base via electron delocalization.
Nitrogen-Containing Heterocycles:
General discussion on the acidity properties across heterocyclic nitrogen compounds.
Page 13: Electrophilic Aromatic Substitution (EAS)
Mechanisms of EAS Reactions:
General reaction scheme and description of electrophiles in the presence of aromatic systems.
Substitution pattern analysis focusing on the 2-position due to relative stability.
Page 14: 2 vs 3-Position Substitution
Substitution Sites:
Discussion of reaction occurrence when the 2-position is unavailable, leading to preferential substitution at the 3-position.
Page 15: Reactivity Hierarchy in EAS
Reactivity Factors:
Established relative reactivities in electrophilic aromatic substitution, with 5-membered heterocycles exhibiting greater reactivity than benzene.
Electrophilic Cycling Examples:
Various pathways showcasing reactivity depending on electrophilic conditions and substituted groups.
Page 16: Aromaticity of Pyridine
Structural Features of Pyridine:
Confirmations of pyridine's aromatic nature alongside resonance contributors and implications for electronic properties.
Dipole Moment Measurement:
Introduction to the measured dipole moment of pyridine ( = 1.57 D).
Page 17: Acidity of Pyridinium Ion
Comparison with Ammonium Ion:
Evaluation of the pyridinium ion's acidity indicating strength compared to a typical ammonium ion.
Nucleophilic Reactivity of Pyridine:
Structural characteristics enabling pyridine to act as a nucleophile in various reactions.
Page 18: Mechanism of EAS with Pyridine
Electrophilic Aromatic Substitution Pathway:
Detailed branching of substitution mechanics, focusing on 2 vs. 3-position outcomes.
Page 19: Reactivity in EAS
Comparative Analysis:
Evaluation of reactivity in electrophilic aromatic substitution, recognizing that pyridine is less reactive than benzene under these circumstances.
Page 20: Nucleophilic Aromatic Substitution (NAS)
Mechanism Overview:
Description of nucleophilic substitution processes occurring at the 2- and 4-positions of pyridine, noting conditions for reaction feasibility.
Page 21: Reactions with Substituted Pyridines
Side Chain Reactions:
Analysis of side-chain reactions occurring similarly to substituted benzene derivatives.
Page 22: Formation of Diazonium Ions
Stability Comparison:
Examination of keto vs enol form stability in diazonium ion production.
Page 23: Acidity of Methyl Groups
Comparational Acidity Assessments:
Determining which methyl group is more acidic in specified scenarios.
Page 24: Heterocyclic Amino Acids
Role of Amino Acids:
Detailed descriptions of amino acids related to heterocycles such as proline and tryptophan.
Aromatic Properties of Imidazole:
Orbital structures highlighting imidazole characteristics.
Page 25: Resonance in Imidazole
Resonance Contributors:
Detailed evaluations of resonance structures in imidazole and impacts of protonation.
pKa Value:
Summary of imidazole’s pKa value, indicating acid strengths.
Page 26: Antihistamines and Drug Applications
Histamine Overview:
Explanation of histamine structure and respective antihistamine applications.
Drug Categories:
Listing of various antihistamines such as diphenhydramine (Benadryl) and their pharmacological significance.
Page 27: Nucleotide Bases
DNA and RNA Structure Overview:
Content on nucleotide bases of DNA (adenine, guanine, cytosine, thymine) and RNA (adenine, guanine, cytosine, uracil).
Stability proposals of nucleobases in keto form versus enol form.
Porphyrin Ring System:
Mention of heme structures, stability, and their biological importance.
Page 28: Summary of Functional Groups in Organic Chemistry
Group Classification:
Presentation of groups and their characteristics across electrophilic and nucleophilic categorizations.
Functional Group Behavior:
Overview of common reactions that these groups undergo, including nucleophilic acyl substitutions, electrophilic additions, etc.