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Full structure

Full structure

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Full structure

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  1. Full structure

  2. How do we simplify this? • we need a set of rules that is consistent • rules should be based on simple (even obvious) criteria • rules need to make it easier to see the important parts of the molecule

  3. There are three kinds of atoms • Carbon — C • Hydrogen — H • Heteroatoms — everything else in the periodic table

  4. Basis for structure-simplifying rules • Every organic compound has carbon • let’s omit the symbol for carbon • means that the reader will need to know that we don’t explicitly show carbon atoms any more

  5. is simplified to

  6. Next… • Hydrogen is almost always present in an organic compound • Carbon-hydrogen bonds are usually unreactive, so they seldom participate in any reactions • let’s omit the hydrogen atoms bonded to carbon • the reader will now need to know that any hydrogen atom bonded to carbon will not show up in the structural formula as drawn.

  7. is simplified to

  8. Going the other way: Rules for interpreting organic structures • Carbon is always present in every organic molecule • assume carbon is at each end of every bond unless another atom is explicitly specified. • means that there is a carbon atom at the end of every line

  9. becomes

  10. Rules for interpreting organic structures (continued) • Carbon is always tetravalent — it always has four covalent bonds • Hydrogen atoms bonded to carbon atoms are usually omitted from the structure • any carbons with less than four explicitly specified bonds carry hydrogen atoms • there must be enough hydrogen atoms to make up all four bonds to carbon for every carbon atom in the molecule

  11. becomes

  12. What is more visible in this representation? • The substructures of the molecule • 4 rings • a tail hanging off one end • the chemically reactive parts of the molecule • the —O—H group • the carbon-carbon double bond

  13. What advantages do we gain? • we get a better idea of the actual shape of the molecule • we get a better focus on the important parts of the molecule • the drawing is much less busy and simpler to interpret — we can see the functional groups easily

  14. Functional Groups • Most of an organic compound does not react • Carbon-carbon and carbon-hydrogen single bonds almost never react • Carbon-carbon multiple bonds react with many reagents • Heteroatoms represent sites of reactivity in an organic molecule. • The reactive part of a molecule is called the FUNCTIONAL GROUP • multiple bonds are functional groups • heteroatoms are functional groups • C-C and C-H single bonds are not functional groups

  15. So what does this molecule really look like? Three different kinds of representation of the “real” cholesterol molecule

  16. Make-up of simple organic compounds • The compound consists of two parts • the functional group • site of reactivity • “where the action is” • “Vegas Strip” • the “rest of the molecule” • designated by “R”