Organic Chemistry Midterm I Study Guide: Key Concepts and Skills

Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding

Lewis Structures and Bonding

This topic covers the foundational principles of chemical bonding and molecular structure, essential for understanding organic molecules.

• Lewis Structures: Diagrams that represent the arrangement of electrons in a molecule, showing bonds and lone pairs.

• Sigma and Pi Bonds: Sigma (σ) bonds are single covalent bonds formed by head-on orbital overlap; pi (π) bonds are formed by side-to-side overlap of p orbitals, present in double and triple bonds.

• Hybridization and Bond Angles: Predict the hybridization (sp, sp2, sp3) of atoms and the corresponding bond angles in molecules.

• Polar Bonds and Molecules: Identify polar covalent bonds and predict molecular polarity based on electronegativity differences and molecular geometry.

• Bond Lengths and Strengths: Predict relative bond lengths and bond strengths for various covalent bonds (e.g., C-H, C-C, C=C).

Example: In ethene (C2H4), each carbon is sp2 hybridized, forming a sigma bond with the other carbon and three sigma bonds with hydrogens; the double bond consists of one sigma and one pi bond.

Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry

Acid-Base Theory and Reactivity

Understanding acids and bases is crucial for predicting reactivity and mechanisms in organic chemistry.

• Bronsted-Lowry vs. Lewis Acids/Bases: Bronsted-Lowry acids donate protons (H+), while Lewis acids accept electron pairs.

• pKa and Acid Strength: The lower the pKa, the stronger the acid. Compare acidities using pKa values.

• Factors Affecting Acidity: Resonance stabilization, inductive effects, electronegativity, hybridization, and substituents all influence acid strength.

• Resonance Structures: Draw and identify resonance contributors to show electron delocalization.

• Structure and Reactivity: Predict how molecular structure affects acid/base behavior and reactivity.

Example: Acetic acid is more acidic than ethanol because the carboxylate anion is resonance stabilized, while the ethoxide ion is not.

Ch. 3 - An Introduction to Organic Compounds: Nomenclature, Physical Properties, and Structure

Alkanes, Nomenclature, and Physical Properties

This section introduces the classification, naming, and properties of organic compounds, focusing on alkanes and their derivatives.

• Alkanes: Saturated hydrocarbons with only single bonds; identify the number of carbons and hydrogens in a given alkane.

• Nomenclature: Name alkanes and their derivatives (alkyl, aryl, ether, alcohol, amine, etc.) using IUPAC rules.

• Cycloalkanes and Alkyl Halides: Name and draw structures for cycloalkanes and alkyl halides.

• Functional Groups: Recognize and name common functional groups in organic molecules.

• Primary, Secondary, Tertiary, Quaternary: Classify carbon atoms and hydrogens based on their connectivity.

• Physical Properties: Compare boiling points, melting points, and solubility of organic compounds based on structure.

• Conformational Analysis: Draw and compare stabilities of different conformations (e.g., cyclohexane chair conformers).

Example: The chair conformation of cyclohexane is more stable than the boat conformation due to minimized steric strain.

Additional info:

• Students are not required to know sections 1.3, 1.11, 1.12, 2.4-2.5, 2.11, 2.16 (branched substituents), 3.8, 3.9, 3.10, 3.16 for this exam.