Chapter 3 chem130

Chapter 3: An Introduction to Organic Compounds

• Focus on nomenclature, physical properties, and representation of structure.

Alkanes: Hydrocarbons with Single Bonds

• Alkanes are hydrocarbons containing only single bonds.

• Table 3.1: Nomenclature and Physical Properties of Straight-Chain Alkanes

  • Exhibit a series of molecular formulas, boiling points, melting points, and densities for alkanes with different carbon counts:

    • C1 (CH4): Methane | Boiling Point: -167.7°C | Melting Point: -182.5°C | Density: 0.556

    • C2 (C2H6): Ethane | Boiling Point: -88.6°C | Melting Point: -183.3°C | Density: 0.789

    • C3 (C3H8): Propane | Boiling Point: -42.1°C | Melting Point: -187.7°C | Density: 0.493

    • C4 (C4H10): Butane | Boiling Point: -0.5°C | Melting Point: -138.3°C | Density: 0.573

    • C5 (C5H12): Pentane | Boiling Point: 36.1°C | Melting Point: -129.8°C | Density: 0.626

    • C6 (C6H14): Hexane | Boiling Point: 68.7°C | Melting Point: -95.3°C | Density: 0.660

    • C7 (C7H16): Heptane | Boiling Point: 98.4°C | Melting Point: -90.6°C | Density: 0.683

    • C8 (C8H18): Octane | Boiling Point: 125.7°C | Melting Point: -56.8°C | Density: 0.702

    • C9 (C9H20): Nonane | Boiling Point: 150.8°C | Melting Point: -53.5°C | Density: 0.717

    • C10 (C10H22): Decane | Boiling Point: 174.0°C | Melting Point: -29.7°C | Density: 0.729

  • Note: Density is temperature dependent and measured at 20°C.

Structural Variations of Alkanes

• Linear alkane, branched alkane, cycloalkanes expressed with general formulas:

  • Straight-chain Alkanes: CnH2n+2

  • Branched Alkanes: Same formula, differing structures.

  • Cycloalkanes: CnH2n.

Nomenclature of Alkanes

• Learn to name alkanes by structures:

  • Linear Alkanes: Examples of Kekulé structures and condensed structures.

  • Isomers: C4H8 and C5H10 structural variations illustrated.

Alkyl Substituents

• Removing hydrogen from an alkane leads to an alkyl substituent:

  • Methyl Group: CH3-

  • Ethyl Group: CH3CH2-

  • Propyl Group: CH3CH2CH2-

  • Butyl Group: CH3CH2CH2CH2-

• Replace "ane" of alkane with "yl" to obtain alkyl names.

Nomenclature of Organic Compounds

• Common Names: Represent the general structure.

  • Alcohols, Amines, Ethers, and Alkyl Halides classified.

  • Recognize primary, secondary, tertiary structures through examples.

Classification

• Primary, Secondary, Tertiary Carbons explained:

  • Primary: 1 carbon atom.

  • Secondary: 2 carbon atoms.

  • Tertiary: 3 carbon atoms.

• Butyl Groups: Different butyl groups defined (n-butyl, isobutyl, sec-butyl, tert-butyl).

Solubility and Noncovalent Interactions

• Understand solubility based on interactions:

  • Polar substances dissolve in polar solvents (e.g., water).

  • Solvation as a critical process in dissolved states.

• Noncovalent Interactions: affect the physical properties like solubility and boiling points.

Boiling Points and Attractive Forces

• Factors affecting boiling points stated:

  • Attractive forces exist as van der Waals forces, dipole-dipole, and hydrogen bonds.

  • As molecular size increases, boiling points typically increase due to increased surface area.

Conformation and Stability of Cycloalkanes

• Cycloalkane conformers (like chair and boat forms) have unique stability profiles based on structure and substituent positions.

• Large substituents favor equatorial positions, reducing steric interactions.

Conclusion

• Familiarity gained with nomenclature and properties enhances understanding of organic compound behaviors, focusing on alkanes, their structures, and interactions.