Understanding and Drawing Condensed Structural Formulas

Introduction

• Lecturer: Brent Kadrowski
• Topic: Understanding and drawing condensed structural formulas in organic chemistry.
• Prerequisite: Basic understanding of Lewis structures.

Condensed Structural Formulas

• Definition: Abbreviated versions of Lewis structures.
  • Exclude bonds and lone pairs.
  • Convey same connectivity information as Lewis structures.
  • More compact and easier to draw, especially useful in text-based formats.

Example: Butane

• Lewis Structure: All bonds are drawn.
• Condensed Structural Formula:
  • Atoms bonded together are grouped (e.g. CH₃, CH₂).
  • Steps:
    • First carbon: CH₃ (1 carbon, 3 hydrogens)
    • Second and third carbons: CH₂
    • Fourth carbon: CH₃
  • Note: H's are shown together but not bonded to each other. Carbon makes four bonds.

Repeating Groups

• Use of Parentheses: Repeating groups can be represented using parentheses.
  • Example: CH₂CH₂ can be written as (CH₂)₂.

Example: Ethanol (Ethyl Alcohol)

• Structure:
  • Left: CH₃ (1 carbon, 3 hydrogens)
  • Middle: CH₂
  • Right: OH group
• Note: Lone pairs on oxygen not shown in condensed form.

Multiple Representations

• Multiple Correct Forms:
  • Different condensed structural formulas can represent the same Lewis structure.
  • Example: Three CH₃ groups attached to a central carbon can be written as (CH₃)₃ or CH followed by three CH₃.

Converting Condensed Structural Formula to Lewis Structure

• Example:
  • Condensed formula: CH₃CH₂(₃)
  • Central carbon with CH₃ groups: Draw central carbon first, then attach CH₃ groups and proceed with connectivity.

Handling Double Bonds

• Alkenes:
  • Represent carbon-carbon double bonds between carbons.
  • Example: CH₃CH=CHCH₂CH₃
• Carbon-Oxygen Double Bond:
  • Typically not drawn in condensed formulas but can be represented as CO.

Carbon-Oxygen Double Bonds

• Carboxylic Acid:
  • Group: COOH or C(O)OH
• Aldehyde:
  • Group: CHO
  • Important to distinguish from COH (indicating alcohol group).

Conclusion

• Further Learning:
  • Check other videos on skeletal structures for more representation methods.
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