General Chemistry Review & Acid/Base Chemistry

Bonding Patterns and Molecular Structure

Understanding atomic bonding and molecular structure is foundational for organic chemistry. Students should be able to identify and draw common bonding patterns, including lone pairs, and recognize their implications in Lewis structures.

• Bonding Patterns: Recognize single, double, and triple bonds; lone pairs; and expanded octets.

• Hybridization: Assign sp, sp2, and sp3 hybridization to atoms in molecules.

• Formal Charge: Calculate formal charge using:

• Bond Angles: Predict bond angles based on electron domain geometry (e.g., tetrahedral: 109.5°, trigonal planar: 120°).

Resonance and Acid/Base Mechanisms

Resonance structures and acid/base chemistry are crucial for understanding reactivity and stability in organic molecules.

• Resonance Structures: Draw resonance contributors and identify the most stable forms.

• Acid/Base Strength: Predict relative acid/base strength using pKa values and molecular structure.

• Bronsted and Lewis Acids/Bases: Identify acids/bases and draw curved arrow mechanisms for proton transfer.

• Conjugate Acid/Base: Relate the strength of acids to their conjugate bases.

Alkanes & Conformational Analysis

Nomenclature and Structure

Alkanes and cycloalkanes are named using IUPAC rules, with attention to substituents and functional groups.

• IUPAC Nomenclature: Name alkanes, cycloalkanes, and haloalkanes (e.g., 1-chlorobutane).

• Functional Groups: Identify alkyl, halo, and other substituents.

Conformational Analysis

Conformational analysis explores the spatial arrangement of atoms in molecules and their energetic implications.

• Newman Projections: Draw and interpret Newman projections for staggered and eclipsed conformations.

• Chair Conformations: Draw cyclohexane chair forms and assign axial/equatorial positions.

• 1,3-Diaxial Interactions: Explain steric strain in cyclohexane due to axial substituents.

Stereochemistry

Chirality and Stereoisomers

Stereochemistry focuses on the three-dimensional arrangement of atoms and its effect on molecular properties.

• Chiral Centers: Determine if a molecule is chiral or achiral.

• Stereoisomers: Identify enantiomers and diastereomers.

• R/S Designation: Assign absolute configuration using the Cahn-Ingold-Prelog rules.

• Meso Compounds: Identify meso compounds (achiral despite chiral centers).

Substitution and Elimination Reactions

Mechanisms and Reactivity

Substitution and elimination are key reaction types in organic chemistry, involving nucleophiles, electrophiles, and leaving groups.

• SN1 and SN2 Mechanisms: SN1: Unimolecular, involves carbocation intermediate. SN2: Bimolecular, concerted mechanism. General Rate Laws:

• E1 and E2 Mechanisms: E1: Unimolecular elimination, carbocation intermediate. E2: Bimolecular elimination, concerted removal of proton and leaving group.

• Leaving Groups: Good leaving groups stabilize negative charge (e.g., halides, tosylates).

• Flow Charts: Use decision trees to determine reaction type based on substrate, nucleophile/base, and solvent.

Alcohols and Alkyl Halides

Nomenclature and Stability

Alcohols and alkyl halides are named according to IUPAC rules, and their stability is influenced by electronic and steric effects.

• Alcohols: Named by replacing the -e of the alkane with -ol (e.g., ethanol).

• Alkyl Halides: Named by prefixing the halogen (e.g., chloromethane).

• Carbocation Stability: Tertiary > Secondary > Primary due to hyperconjugation and inductive effects.

Reactions of Alcohols

• Dehydration (E1/E2): Elimination of water to form alkenes.

• Substitution: Reaction with HX to form alkyl halides.

• Oxidation: Conversion to aldehydes, ketones, or carboxylic acids.

• Tosylates: Formation and use as leaving groups in substitution/elimination.

Alkene Additions

Electrophilic Addition Reactions

Alkenes undergo addition reactions with electrophiles, following Markovnikov or anti-Markovnikov rules.

• Addition of HX: Follows Markovnikov's rule (hydrogen adds to least substituted carbon).

• Acid-Catalyzed Hydration: Addition of H2O to form alcohols.

• Halogenation: Addition of X2 (Cl2, Br2).

• Hydroboration-Oxidation: Anti-Markovnikov addition of water.

• Epoxidation: Formation of epoxides from alkenes.

• Hydration to Ketone: Tautomerization mechanism converts enol to ketone.

Alkynes

Nomenclature and Properties

Alkynes are hydrocarbons with triple bonds, named by replacing the -ane suffix with -yne.

• Bond Strength: Triple bonds are stronger and shorter than double or single bonds.

• Acidity: Terminal alkynes are more acidic than alkenes/alkanes.

Reactions of Alkynes

• Hydrogenation: Addition of H2 to form alkanes.

• Addition of HX and X2: Forms dihaloalkanes.

• Hydration: Forms ketones via tautomerization.

Ethers and Epoxides

Nomenclature and Synthesis

Ethers are named by identifying the two alkyl groups attached to oxygen. Epoxides are cyclic ethers formed from alkenes.

• Williamson Ether Synthesis: Reaction of alkoxide ion with alkyl halide.

• Acid-Catalyzed Dehydration: Forms ethers from alcohols.

• Epoxide Formation: Oxidation of alkenes.

Epoxide Reactions

• Acid-Catalyzed Opening: Nucleophile attacks more substituted carbon.

• Base-Promoted Opening: Nucleophile attacks less substituted carbon.

Spectroscopy

Interpretation of IR and NMR

Spectroscopy is used to determine molecular structure and identify functional groups.

• IR Spectroscopy: Identifies functional groups by characteristic absorption frequencies.

• NMR Spectroscopy: 1H NMR: Chemical shift, integration, splitting patterns. 13C NMR: Chemical shift of carbon atoms.

• Non-equivalent Hydrogens: Recognize chemically distinct hydrogens.

• n+1 Rule: Number of neighboring hydrogens determines splitting:

• Retrosynthesis: Plan multi-step syntheses (up to 4-5 steps).

Additional info:

• Some mechanisms and flow charts are referenced but not shown; students should consult lecture notes or textbooks for detailed stepwise mechanisms.

• Practice drawing structures, mechanisms, and interpreting spectra for exam preparation.