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Hydrocarbons

Hydrocarbons. Hydrides of Carbon. C x H y. Carbon has four valence electrons. Wants to form four bonds. Methane. Hydrogen has one valence electron and wants to form one bond. Butane. Propane. Ethane. Methane CH 4. Ethane C 2 H 6. Propane C 3 H 8. Butane C 4 H 10.

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Hydrocarbons

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  1. Hydrocarbons Hydrides of Carbon CxHy

  2. Carbon has four valence electrons. Wants to form four bonds. Methane Hydrogen has one valence electron and wants to form one bond

  3. Butane Propane Ethane

  4. Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10

  5. Ethane Conformations Eclipsed Staggered

  6. Variation of Energy with Rotation of C-C bond in Ethane 12 kJ 0 60 120 180 240 300 360 Angle of Rotation, degrees

  7. 2-methylpropane or isobutane n- Butane C4H10 These two molecules are structural isomers. They differ in the way their atoms are connected They have different chemical and physical properties.

  8. 2-methylpropane or isobutane

  9. n-hexane These structures represent different conformations of n-hexane, not isomers.

  10. n-hexane 2-methylpentane 3-methylpentane 4-methylpentane 2,3-dimethylbutane 2,2-dimethylbutane

  11. These are the five isomers of hexane, C6H14

  12. Methane becomes Methyl Ethane becomes Ethyl Propane becomes Propyl

  13. 1 Methane Methyl 2 Ethane Ethyl 3 Propane Propyl 4 Butane Butyl 5 Pentane Pentyl 6 Hexane Hexyl 7 Heptane Heptyl 8 Octane Octyl 9 Nonane Nonyl 10 Decane Decyl

  14. Find the longest chain 7 carbons. It’s a heptane Add the substituents in alphabetic order 4-ethyl-2-methylheptane Number the atoms

  15. 5 carbon chain. It’s a pentane 3 methyls so use the prefix - tri 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 2,2,4-trimethylpentane not 4,4,2-trimethylpentane

  16. 9 carbon chain It’s a nonane 2 methyl groups and 1 ethyl group 4-ethyl-3,7-dimethylnonane not 6-ethyl-3,7-dimethylnonane

  17. hexane 2-methylpentane 2,3-dimethylbutane 3-methylpentane 2,2-dimethylbutane

  18. What is special about this compound? 3-methylhexane These two compounds are different. The two compounds are mirror images. One Is left handed and the other is right handed.

  19. These molecules are Chiral. They have handedness. Right Handed or R Left Handed or S Put your thumb toward you representing the hydrogen atom, the lightest group. Point your fingers toward the propyl group, the heaviest group. Curl your fingers toward the ethyl group, the second heaviest group.

  20. S-3-ethyl-2-methylhexane

  21. Molecular Formulas for Alkanes are all of the form CnH2n+2 n-octane 2,2,4-trimethylpentane C8H18 n = 8 2n + 2 = 18

  22. Molecular Formulas for Alkenes are all of the form CnH2n 2,4,4-trimethyl-2-pentene 1-octene C8H16 n = 8 2n = 16

  23. trans-2-pentene cis-2-pentene If an alkene has two identical substituents on the two different carbons, they can be named cis or trans. If the identical substituents are on the same side we call themolecule cis. If they are on opposite sides we call the molecule trans. The two compounds shown above are stereoisomers.

  24. If two substituents on one carbon are the same cis and trans do not apply But what do we do if all groups are different?

  25. (E) - 3-methyl-3-heptene (Z) - 3-methyl-3-heptene Instead of cis or trans use E or Z Z means the two heaviest groups are on the same side of the double bond. E means the two heaviest groups are on different sides of the double bond.

  26. cis-3,5-dimethyl-2-hexene (E)-2,4-dimethyl-3-hexene 2-ethyl-4-methyl-1-pentene

  27. Molecular Formulas for Alkynes are all of the form CnH2n-2 1-octyne C8H14 n = 8 2n - 2 = 14

  28. 2-methyl-3-hexyne 3-ethyl-6-methyl-1-heptyne

  29. C5H10 trans-2-pentene cyclopentane

  30. Cycloalkanes CnH2n cyclopropane cyclobutane cyclopentane cyclohexane

  31. Cyclopropane

  32. trans-1,2-dimethylcyclopropane cis-1,2-dimethylcyclopropane

  33. trans-1,2-dimethycyclobutane cis-1-ethyl-3-methylcyclobutane

  34. Cyclohexane Ideal angles are 120 degrees. Actual angles are 109.5 degrees, the tetrahedral angle

  35. Benzene

  36. toluene ortho 1,2-dimethylbenzene methylbenzene meta para 1,4-dimethylbenzene 1,3-dimethylbenzene

  37. Draw all compounds of formula C4H10 Draw all compounds of formula C4H8 Draw all compounds of formula C4H6

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