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Lecture 1

Lecture 1. Describing chemical structures Transforming chemical structures. Communicating Molecular Structures. Lewis. Kekulé. 3-D Kekulé. Molecular Graphics. Lewis Structures. Draw three acceptable Lewis structures for C 2 H 6 O. Propose a structure Place electrons Octet rule

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Lecture 1

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  1. Lecture 1 Describing chemical structures Transforming chemical structures Chemistry 243 - Lecture 1

  2. Communicating Molecular Structures • Lewis • Kekulé • 3-D Kekulé • Molecular Graphics Chemistry 243 - Lecture 1

  3. Lewis Structures • Draw three acceptable Lewis structures for C2H6O. • Propose a structure • Place electrons • Octet rule • Determine charges • Evaluate and repeat if necessary Chemistry 243 - Lecture 1

  4. Kekulé Structures • Each shared electron pair is drawn as a straight line • Lone pairs are often not shown (but are implied) • Hydrogens are often not shown (but are implied) Chemistry 243 - Lecture 1

  5. A “Real” Molecule Chemistry 243 - Lecture 1

  6. Molecular Representations that We Will Be using • Kekulé diagrams • Calculated molecular graphics Chemistry 243 - Lecture 1

  7. Organic Chemistry and Us • Practical • Methods for transforming organic molecules • Making new materials • Theoretical • Understanding how these methods transform organic molecules • All Together Now • Using you knowledge of methods and the underlying theory, predict results of given reactions. Chemistry 243 - Lecture 1

  8. Transforming Molecules Propane B.P. -43 C 2-Bromopropane B.P. 59 C Acetone B.P. 56 C 2-propanol B.P. 82 C Chemistry 243 - Lecture 1

  9. A Chemical Reaction • A reaction involves a change in the bonds in one or more reactants • Energy may be released • Energy may be required • Fun Exercise • Draw the Kekulé structure including all hydrogen atoms and lone pairs for all molecules Chemistry 243 - Lecture 1

  10. What is a Bond? • What is more stable - 2 hydrogen atoms or a hydrogen molecule? • Why? • What holds a hydrogen molecule together? Chemistry 243 - Lecture 1

  11. Hydrogen • 2 H atoms • Electron clouds comprised of the half-filled 1S orbitals • H2 molecule • Electron cloud is comprised of the molecular orbital. • What is a molecular orbital? Chemistry 243 - Lecture 1

  12. Addition and Subtraction Chemistry 243 - Lecture 1

  13. Orbital Combination Chemistry 243 - Lecture 1

  14. Bonding Interactions Chemistry 243 - Lecture 1

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