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Organic Chemistry

Organic Chemistry. Introduction Alkanes Nomenclature. Electron Dot structures. C. N. O. F. B. Be. Li. Class exercise 1: Draw the electron dot structure of Carbon. Class exercise 2: Draw the electron dot structure of oxygen and fluorine. Ne. Lewis Dot structures. B. C. N. O. F.

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Organic Chemistry

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  1. Organic Chemistry Introduction Alkanes Nomenclature

  2. Electron Dot structures C N O F B Be Li Class exercise 1: Draw the electron dot structure of Carbon Class exercise 2: Draw the electron dot structure of oxygen and fluorine Ne

  3. Lewis Dot structures B C N O F Li Be

  4. Organic Chemistry • Chemistry of Carbon • Bonding of H,O, X and N

  5. Valence Summary

  6. Complete Structural Formulas Show the bonds between each of the atoms H H   H  C  H H C H   H H CH4 , methane

  7. More Alkanes H H Condensed Structural Formulas H C C H CH3 CH3 H H Ethane H H H H C C C H CH3 CH2 CH3 H H H Propane

  8. IUPAC Names Name # carbons Structural Formula Methane 1 CH4 Ethane 2 CH3CH3 Propane 3 CH3CH2CH3 Butane 4 CH3CH2CH2CH3 Pentane 5 CH3CH2CH2CH2CH3

  9. IUPAC NAMES Name # carbons Structural Formula Hexane 6 CH3CH2CH2CH2CH2CH3 Heptane 7 CH3CH2CH2CH2CH2CH2CH3 Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3 Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3 Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

  10. Learning Check Alk1 A. What is the condensed formula for H H H H H C C C C H H H H H B. What is its molecular formula? C. What is its name?

  11. Solution Alk1 A. CH3CH2CH2CH3 B. C4H10 C. butane

  12. Properties of Alkanes So what exactly do these things do?

  13. Physical Properties of Alkanes 1. Combustion - Alkanes are inflammable, i.e. they burn. 2 2 2. Boiling and melting points a. Both bp and mp increase with increasing carbon number for straight-chain alkanes with formula CnH2n+2 Carbon Number Physical State C1- C4 gases C5 – C16 liquids C17 – C30 oils and greases C30 – C50 paraffin waxes >C50 plastics (polyethylene)

  14. b. Branching tends to lower the boiling point and raise the melting point BP 60oC 58oC 50oC MP -154oC -135oC -98oC Explanation: MP Branching reduces the flexibility of the molecule which reduces the entropy term S in the equation Tmp = H/S. Since S is in the denominator, Tmp increases. BP Branching reduces surface area (more compact structure), and therefore London dispersion forces which control boiling point for these molecules. 3. Solubility – alkanes are nonpolar molecules and therefore insoluble in water, which is polar. Alkanes are hydrophobic. 4. Densities – alkanes are less dense than water, with densities near 0.7 g/mL. Therefore they float on water, e.g. Exxon Valdez oil spill.

  15. Naming Hydrocarbons(nomenclature)

  16. Drawing Structures: It’s All Good 2-butene On a test, choose a method that shows all Hs This is called the “condensed structure” CH3CH=CHCH3 Using brackets can also shorten some formulas: CH3CH2CH2CH2CH2CH3 vs. CH3(CH2)4CH3

  17. Basic Naming of Hydrocarbons Hydrocarbon names are based on: 1)type, 2) # of carbons, 3) side chain type and position 1) name will end in -ane, -ene, or -yne 2) the number of carbons is given by a “prefix” 1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec-

  18. Basic Naming of Hydrocarbons Q - What names would be given to these: 7C, 9C alkane 2C, 4C alkyne 6C, 3C alkene heptane, nonane ethyne, butyne Hexene, propene

  19. Monkeys Eat Peeled Bananas Mnemonic for First Four Prefixes First four prefixes • Meth- • Eth- • Prop- • But-

  20. Other Prefixes • Pent- ? Decade Decimal Decathalon • Oct- • Dec- • Hex-, Hept-, Non-

  21. Straight chain hydrocarbonsLearning Check • Pentane • Propane • Heptane • Ethane • Octane

  22. C2H4 Numbering Carbons 1-pentene Q- draw pentene A- Where’s the double bond? We # C atoms. • Naming compounds with multiple bonds is more complex than previously indicated. • When 2+ possibilities exist, #s are needed. • Always give double bond the lowest number. • Q - Name these 2-butene ethene 3-nonyne

  23. C2H4 Learning Check - Numbering Carbons • Name the following compounds: 2-butene ethene 3-nonyne

  24. C H 3 H C C H 3 3 C H 3 Naming Side Chains • The names of molecules with branches are based on: side chains, root 2,3-dimethylpentane • The “root” or “parent chain” is usually the longest possible hydrocarbon chain. • The root must include multiple bonds if they are present. If a cyclic structure is present it will be the root even if it is not the longest chain. • Side chains are also called “side branches” or “alkyl groups”. Their names end in -yl. Common side chains : -CH3 methyl, -CH2CH3 ethyl, -CH2CH2CH3 propyl

  25. IUPAC Rules for Naming Hydrocarbons • Choose the correct ending: -ane, -ene, or -yne • Determine the longest carbon chain. Where a double or triple bond is present, choose the longest chain that includes this bond. If there is a cyclic structure present, the longest chain starts and stops within the cyclic structure. • Assign numbers to each C of the parent chain. For alkenes and alkynes the first carbon of the multiple bond should have the smallest number. For alkanes the first branch (or first point of difference) should have the lowest #. Carbons in a multiple bond must be numbered consecutively. • Attach a prefix that corresponds to the number of carbons in the parent chain. Add cyclo- to the prefix if it is a cyclic structure.

  26. IUPAC Rules for Naming Hydrocarbons • Determine the correct name for each branch (“alkyl” groups include methyl, ethyl, propyl, etc.) • Attach the name of the branches alphabetically, along with their carbon position, to the front of the parent chain name. Separate numbers from letters with hyphens (e.g. 4-ethyl-2-methyldecane) • When two or more branches are identical, use prefixes (di-, tri-, etc.) (e.g. 2,4-dimethylhexane). Numbers are separated with commas. Prefixes are ignored when determining alphabetical order. (e.g. 2,3,5-trimethyl-4-propylheptane) • When identical groups are on the same carbon, repeat the number of this carbon in the name. (e.g. 2,2-dimethylhexane)

  27. Naming Side Chains Example: use the rules on this handout to name the following structure Rule 1: choose the correct ending ene

  28. Naming Side Chains Rule 2: determine the longest carbon chain ene

  29. Naming Side Chains Rule 3: Assign numbers to each carbon ene

  30. Naming Side Chains Rule 3: Assign numbers to each carbon ene

  31. Naming Side Chains Rule 4: attach prefix (according to # of Cs) 1-hexene ene

  32. Naming Side Chains ethyl methyl methyl Rule 5: Determine name for side chains 1-hexene 1-hexene

  33. Naming Side Chains ethyl methyl methyl Rule 6: attach name of branches alphabetically 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

  34. Naming Side Chains ethyl methyl methyl Rule 7,8: group similar branches 2-ethyl-4-methyl-4-methyl-1-hexene 1-hexene

  35. Naming Side Chains Similar questions will be issued on Moodle and in the tutorial sheets ethyl methyl methyl Rule 7,8: group similar branches 2-ethyl-4,4-dimethyl-1-hexene

  36. Learning Check – Naming propene 2-butene 2,4-dimethyl-2-pentene 1-butyne

  37. a) 3,3-dimethyl-1-pentene b) same C H C H 3 3 C H C C C H C H C H 3 2 C H C H 2 3 c) 5-ethyl-4-methyl-2-heptyne

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