Organic Chemistry Chapter 6 Flashcards

Types of Reactions

• Addition Reactions: Involve combining two reactants to form a single product, with no leftover atoms.

• Example: Ethene (C2H4) plus hydrobromic acid (HBr) yields bromethane (C2H5Br).

• Elimination Reactions: A single reactant breaks down into two products, typically producing a small molecule like water.

• Example: Ethanol (C2H5OH) with an acid catalyst leads to ethene (C2H4) and water (H2O).

• Substitution Reactions: Two reactants swap parts, resulting in two new products.

• Example: Methane (CH4) reacts with chlorine (Cl2) to produce chloromethane (CH3Cl) and hydrochloric acid (HCl).

• Rearrangement Reactions: A single reactant reorganizes its bonds and atoms to form an isomeric product.

Key Concepts

• Isomer: Compounds with the same molecular formula but different structures.
• Mechanism: The detailed process outlining what occurs during a chemical reaction.

Bond Interactions

• Bond Breaking: Involves specific bonds in reactant molecules being broken.

• Bond Formation: Specific bonds in product molecules are formed.

• Covalent Bond Cleavage: Consists of homolytic (symmetrical) and heterolytic (unsymmetrical) cleavage.

• Homolytic Cleavage: Each product fragment retains one electron, creating radicals.

• Heterolytic Cleavage: One fragment retains both bonding electrons, leading to an empty orbital in the other fragment.

• Bond Formation: Can be homogenic (one electron from each reactant) or heterogenic (both electrons from one reactant).

Reaction Types

• Radical Reactions: Occur through symmetrical bond breaking and forming; radicals are highly reactive due to unpaired electrons.
• Polar Reactions: Arise from unsymmetrical bond breaking and forming; common due to the attraction between polar functional groups.

Polarity and Charge

• Polarity: Determined by electronegativity differences across atoms.
• Carbon-Halogen Bonds: Carbon bonded to halogens carries a partial positive charge (S+).
• Carbon-Metal Bonds: Carbon linked with metals carries a partial negative charge (S-).

Polarizability

• Definition: Refers to the change in electron distribution around an atom due to surrounding electric fields; larger atoms with loosely held electrons are more polarizable.

Radical Reactions Steps

• Consist of three phases: initiation, propagation, and termination.

Nucleophiles and Electrophiles

• Nucleophile: Electron-rich species capable of donating electron pairs; examples include ammonia, water, hydroxide ion, and chloride ion.

• Electrophile: Electron-poor species seeking to accept electron pairs; examples include acids, alkyl halides, and carbonyl compounds.

• Carbocation: Positively charged intermediate that acts as an electrophile, accepting electron pairs from nucleophiles.

Thermodynamics of Reactions

• Gibbs Free Energy (ΔG): Indicates energy changes during reactions; calculated as free energy of products minus free energy of reactants.

• Equilibrium Constant: Expressed as ([C][D])/([A][B]).

• Exergonic Reactions: Favorable reactions with negative ΔG; energy released to surroundings.

• Endergonic Reactions: Unfavorable reactions with positive ΔG; energy absorbed from surroundings.

• Enthalpy Change (ΔH): Represents heat change; exothermic reactions release heat (negative ΔH), while endothermic reactions absorb heat (positive ΔH).

• Entropy Change (ΔS): Indicates molecular randomness during reactions; positive ΔS signifies increased randomness, while negative ΔS indicates decreased randomness.

Bond Energy

• Bond Dissociation Energy: The energy required to break a specific bond into two radical fragments in the gas phase.