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chapter 6 o chem

Reaction Schemes and Patterns

Introduction to Reaction Schemes

  • Basic Reaction Model:
    • A + B → E
    • In a reaction scheme, both reactants A and B can yield products, labeled as C, D, and E.
    • The notation displayed signifies that:
    • Reactants (A and B) are added simultaneously, denoted by them being listed together without any separating symbols.
    • Numbers before product labels indicate sequence in which reactants are added (noted with the ‘K’ prefix for adding separately).

Reactants and Solvents

  • Reactants: The chemical starting materials used in a reaction.
  • Solvent: A liquid substance that dissolves a solute (in this case, the reactants) without undergoing any change during the reaction process.
    • Example of solvency: H₂SO₄ + H₂O
  • Important to note that certain solvents can interact with reactants but are not considered a part of the reactants themselves in overall stoichiometry.

Reaction Patterns

  • Types of Reactions:
    1. Substitution Reactions: Involve the substitution of one functional group for another.
    • Commonly occur with alcohols and alkyl halides. For example:
      • AB ⟶ EL
    1. Acid-Base Reactions:
    • General form: H-A + B ⇌ H-B + A⁻
    • Here H-A is an electrophile which interacts with nucleophile B.
    • E-rich nucleophiles donate electrons to electrophiles that generally carry a positive charge.

Nucleophiles and Electrophiles

  • Nucleophile: A species that has a tendency to donate electrons.
    • Has a lone pair of electrons available for chemical bonding.
  • Electrophile: A species that can accept electrons, often has a partial or full positive charge.

Activity: Identifying Electrophiles and Nucleophiles

  • In the analysis of reactions, clearly label each component
    • A: H₃N → Electrophile
    • N possesses a lone pair making it capable of acting as a nucleophile.
    • B: Br-Br → Electrophile (with potential lone pair, nucleophile behavior).
    • Note: Electrophilic bromine can interact with nucleophiles through its density of electrons.
    • C: CH₃Br → Electrophile
    • While possessing a spectator ion can emphasize understanding of nucleophilic substitution reactions.
    • An example setup includes other entities like OCH and CH₃ (again with the appropriate notation).

IUPAC Naming Conventions

  • IUPAC Name Examples:
    • Coventional naming may follow a structural approach:
    • For cycloalkanes:
      • Example:
      • trans-1-chloro-2-isopropylcyclohexane: Assigning R & S configurations is critical.
        • Not categorized as ‘trans’ if configuration is viewed through different stereochemical arrangements.
        • Example notation: (15,2R)-1-chloro-2-iso
  • Note: Accurate naming is necessary for clear communication of compound structure in organic chemistry studies, following systematic variations.