Chapter 2; Hydrocarbon Frameworks; Alkanes

1. Chapter 2; Hydrocarbon Frameworks; Alkanes Part 2

2. H H H H C C C H H H H H H H C C C H H H IUPAC Nomenclature of Branched Alkanes 6. If alkyl substituent off the main chain contains a branch; number substituent at the point of branching and enclose substituent name in parentheses (). vs.

3. Naming Alky Substituents with Branches (more information on point 6) • Step 1: Identify longest continuous chain starting at point of attachment. • Step 2: Drop -ane ending from name of unbranched alkane having same number of carbons as longest continuous chain and replace by -yl. • Step 3: Identify substituents on longest continuous chain.

4. 1°,2°,3°, and 4° Carbons • 1° Carbon; Carbon bond to one other carbon. • 2 ° Carbon; Carbon bond to two other carbons. • 3° Carbon; Carbon bond to three other carbons. • 4° Carbon; Carbon bond to four other carbons. 3°C 1°C 4° C 2°C

5. 1°,2°, and 3° Hydrogens • 1° H; Bond to a primary carbon • 2° H; Bond to a secondary carbon • 3° H; Bond to a tertiary carbon Three 1° H’s Two 2°H’s One 3° H’s

6. CH3CHCH3 Common and Systematic Names of Branched Subsituents CH3CH2CH2-_

7. 1 3 2 CH3 CH3 CH3CH2CH2CH2 CH3CHCH2CH3 1 3 2 1 2 CH3 CH3 C C CH2 CH3 H Branched Subsituents; C4H9

8. CH3CH2CH2CH2CH2- CH3 CH3 1 2 4 3 CH2 CH3 C CH2 CH3 C CH2 H CH3 Branched Substituents; C5H9

9. Cycloalkane Nomenclature • Cycloalkanes are alkanes that contain a ring of three or more carbons. • 1.Count the number of carbons in the ring, and add the prefix cyclo to the IUPAC name of the unbranched alkane that has that number of carbons. Cyclopentane Cyclohexane

10. CH2CH3 Cycloalkanes • 2. If the number of atoms in the alkyl group is less than the number of atoms in the ring; • Name any alkyl groups on the ring in the usual way. Ethylcyclopentane

11. H3C CH3 CH2CH3 Cycloalkanes • Name any alkyl groups on the ring in the usual way. • 3.List substituents in alphabetical order and count in the direction that gives the lowest numerical locant at the first point of difference. 1,1-dimethyl-3-Ethyl-cyclohexane

12. Cycloalkanes • 4. If the ring has less carbons than the alkyl group; name the ring as a cycloalkyl substituent. 1-cyclopropylpentane

13. Halogen Substituents-F, Cl, -Br, -I • Name halogen substituent by taking halogen stem and adding the suffix –o. • Fluorine Fluoro • Bromine Bromo

14. Crude oil 2.16Sources of Alkanes and Cycloalkanes

15. Petroleum Components

16. End Uses of Petroleum Plastics Asphalt/ Road Oil Boiler Oil Jet Fuel Lubricant, Waxes Diesel/home Heating Gasoline Chemistry in Context, ACS, 3rd Edition

18. Petroleum Refining • Cracking • converts high molecular weight hydrocarbons to more useful, low molecular weight ones • Reforming • increases branching of hydrocarbon chainsbranched hydrocarbons have better burningcharacteristics for automobile engines

19. 2.17Physical Properties of Alkanesand Cycloalkanes • Boiling Point • Water Solubility

20. Boiling Points and Water Solubility of Alkanes • governed by strength of intermolecular attractive forces Intermolecular Force; Attractive force between separate molecules which draws them together to give a definite volume. * Important in Liquids, Solids * Unimportant in Gases

21. Gas Liquid Has Intermolecular Forces No Intermolecular Forces Boiling Point- Temperature at which there is enough Kinetic Energy to Overcome Intermolecular Forces

22. Factors in Determining Which Compound Has a Higher Boiling Point • 1. Determine Type of Intermolecular Force in All Compounds

23. Types of Intermolecular Forces • Dipole/ Dipole Forces (Polar Molecules) • *Stronger Intermolecular Force • Hydrogen Bonds • London or Dispersion or Induced Dipole/ Induced Dipole Forces (NonPolar Molecules) • * Weaker Intermolecular Force

24. Boiling Points of Alkanes • alkanes are nonpolar, so dipole-dipole and dipole-induced dipole forces are absent • only forces of intermolecular attraction are induced dipole-induced dipole (London, Dispersion) forces

25. Factors in Determining Which Compound Has a Higher Boiling Point • Determine Type of Intermolecular Force in All Compounds • Polar Compounds (dipole/dipole force) Have a Higher Boiling Point than Nonpolar Compounds (London Force) • If Decision Can’t Be Made by Rule 1; • Compound with Higher Molar Mass has Higher Boiling Point

26. Boiling Points • increase with increasing number of carbons • more atoms, more electrons, more opportunities for induced dipole-induceddipole forces Heptanebp 98°C Octanebp 125°C Nonanebp 150°C

27. Factors in Determining Which Compound Has a Higher Boiling Point • Determine Type of Intermolecular Force in All Compounds • Polar Compounds (dipole/dipole force) Have a Higher Boiling Point than Nonpolar Compounds (London Force) • If Decision Can’t Be Made by Rule 1; • Compound with Higher Molar Mass has Higher Boiling Point • If Decision Can’t Be Made by Rule 1 or 2; • Compound with Least Amount of Branches has Higher Boiling Point

28. Boiling Points • decrease with chain branching • branched molecules are more compact withsmaller surface area—fewer points of contactwith other molecules Octane: bp 125°C 2-Methylheptane: bp 118°C 2,2,3,3-Tetramethylbutane: bp 107°C

29. Solubility in Water • Generality: Like Dissolves Like • Nonpolar Dissolves Nonpolar • Polar Dissolves Polar • Polar Won’t Dissolve in Nonpolar Alkanes are nonpolar; thus they are not soluble in polar water.

30. 2.18 Chemical Properties of Alkanes • Alkanes are relatively inert • C-H bond is essentially nonpolar • Alkanes are nonpolar molecules • No functional groups or unsaturation in compound. All alkanes burn in air to givecarbon dioxide and water.

31. Combustion Reaction CxHy (g or l) + O2 (g) -> CO2 (g) + H2O (g); -DH CH4 (g) + 2O2 (g) -> CO2 (g) + 2H2O (g); -DH • Isomers differ in respect to their potential energy. • Differences in potential energy can be measured by comparing heats of combustion.

32. 25 + O2 2 25 + 25 O2 25 + O2 2 + O2 2 2 C8H18 + 25/2 O2 -> 8CO2 + 9H2O 5471 kJ/mol 5466 kJ/mol 5458 kJ/mol 5452 kJ/mol 8CO2 + 9H2O

33. Heats of Combustion • decrease with chain branching • branched molecules are more stable (have less potential energy) than their unbranched isomers

34. 2.19Oxidation-Reduction in Organic Chemistry • OIL RIG • Oxidation Involves Loss of electrons • Reduction Involves Gain of electrons

35. Redox Reactions • Oxidation Reactions; Decrease electron density on the carbon atom by forming more C-O, C-N, or C-X bonds (bonds to more electronegative atoms) or by breaking C-H bonds (bonds to less EN atoms). • ReductionReactions; Increase electron density on the carbon atom by breaking C-O, C-N, or C-X bonds or by forming more C-H bonds.

36. O C O HO OH C H OH O C H H H H C H OH C H H H H increasing oxidation state of carbon -4 -2 0 +2 +4

37. HC CH H H C C H H H H H H C C H H increasing oxidation state of carbon -3 -2 -1

38. H H H H C C C Cl H H Cl Cl Cl C H H H Cl Cl H increasing oxidation state of carbon

39. H H C H NH2 C H H H H increasing oxidation state of carbon

40. How to Calculate Oxidation Number on Carbon • Write the Lewis Dot Structure for the molecule. Start off with an oxidation number for carbon of zero. The oxidation number of the carbon atom… • … decreases by one (-1) for each bond to a less electronegative atom or to a metal. • ….increases by one (+1) for each bond to a more electronegative atom • .. Remains the same for each bond to another carbon • ..double/triple bonds count 2X or 3X

41. Oxidation + + HCl CH3Cl Cl2 CH4 Reduction + + CH3Li CH3Cl 2Li LiCl Examples

42. Common Oxidizing Agents

43. Common Reducing Reagents