3: Representations of Molecules
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- 3.1: Drawing Chemical Structures
- Kekulé Formulas or structural formulas display the atoms of the molecule in the order they are bonded. Condensed structural formulas show the order of atoms like a structural formula but are written in a single line to save space. Skeleton formulas or Shorthand formulas or line-angle formulas are used to write carbon and hydrogen atoms more efficiently by replacing the letters with lines. Isomers have the same molecular formula, but different structural formulas
- 3.2: Conformations of Ethane
- Conformational isomerism involves rotation about sigma bonds, and does not involve any differences in the connectivity or geometry of bonding. Two or more structures that are categorized as conformational isomers, or conformers, are really just two of the exact same molecule that differ only in terms of the angle about one or more sigma bonds.
- 3.3: Conformations of Other Alkanes
- Ethane has only two conformers of note - staggered and eclipsed. Alkanes that are more complex than ethane, like propane and butane have a greater variety in possible conformers and their relative energies.
- 3.4: Conformations of Cycloalkanes
- Overall ring strain decreases in cycloalkane rings that are large enough to allow the carbon-carbon bonds to rotate away from planar structures. For this reason, cyclopentane is significantly more stable, than cyclopropane and cyclobutane.
- 3.5: Conformations of Cycloalkanes
- Overall ring strain decreases in cycloalkane rings that are large enough to allow the carbon-carbon bonds to rotate away from planar structures. For this reason, cyclopentane is significantly more stable, than cyclopropane and cyclobutane.