Chapter 16 Alkanes and Aromatic Hydrocarbons

1. Chapter 16Alkanes and Aromatic Hydrocarbons Organic Compounds Bonding in Hydrocarbons Naming Alkanes Properties of Alkanes

2. “The most important hypothesis in all of biology…is that everything that animals do, atoms do. In other words, there is nothing that living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics.” Richard Feynman (1918-1988)

3. Organic Compounds • Contain carbon • Have covalent bonds • Have low melting points • Have low boiling points • Burn in air (oxygen) • Are soluble in nonpolar solvents • Form large molecules

4. Alkanes • Contain C and H only • Contain single bonds C-C • Have 4 bonds to every carbon (C) atom • Are nonpolar

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

6. 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

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

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

9. 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?

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

11. Reactions of Alkanes Combustion alkane + O2 CO2 + H2O + heat

12. Combustion In the Cell Metabolic oxidation is combustion C6H12 O6 + 6O2 6CO2 + 6H2O + heat glucose

13. Learning Check Alk2 Complete the combustion reaction for C3H8 + O2 + Balance your equation

14. Solution Alk2 Step 1 C3H8 + O2 CO2 + H2O Step 2 C3H8 + O2 3 CO2 + 4 H2O Step 3 C3H8 + 5 O2 3 CO2 + 4 H2O

15. Learning Check Alk3 Complete and balance the reaction for the complete combustion of C7H16

16. Solution Alk3 Step 1 C7H16 + O2 CO2 + H2O Step 2 C7H16 + O2 7 CO2 + 8 H2O Step 3 C7H16 + 11 O2 7 CO2 + 8 H2O

17. Haloalkanes An alkane in which one or more H atoms is replaced with a halogen (F, Cl, Br, or I) CH3Br 1-bromomethane Br (methyl bromide) CH3CH2CHCH3 2-bromobutane Cl chlorocyclobutane

18. Learning Check HA1 Name the following:

19. Solution HA1 Name the following: bromocyclopentane 1,3-dichlorocyclohexane

20. Substituents List other attached atoms or group in alphabetical order Br = bromo, Cl = chloro Cl Br CH3CHCH2CHCH2CH2CH3 4-bromo-2-chloroheptane

21. Learning Check HA2 The name of this compound is: Cl CH3 CH3CH2CHCH2CHCH3 1) 2,4-dimethylhexane 2) 3-chloro-5-methylhexane 3) 4-chloro-2-methylhexane

22. Solution HA2 The name of this compound is: Cl CH3 CH3CH2CHCH2CHCH3 3) 4-chloro-2-methylhexane

23. Haloalkanes as Anesthetics Halothane (Fluothane) F Cl F C C Br F H Fluothane is a haloalkane that is widely used as an anesthetic, which is a compound that decreases the ability of the nerve cells to conduct pain.

24. Chapter 16Haloalkanes, Alkenes, and Alkynes Alkenes and Alkynes Geometric Isomers of Alkenes Addition Reactions

25. Saturated and Unsaturated Compounds • Saturated compounds (alkanes) have the maximum number of hydrogen atoms attached to each carbon atom • Unsaturated compounds have fewer hydrogen atoms attached to the carbon chain than alkanes • Unsaturated compounds contain double or triple bonds

26. Alkenes • Carbon-carbon double bonds • Names end in -ene H2C=CH2 ethene (ethylene) H2C=CH-CH3 propene (propylene) cyclohexene

27. Alkynes • Carbon-carbon triple bonds • Names end in -yne HCCH ethyne(acetylene) HCC-CH3 propyne

28. Naming Alkenes and Alkynes When the carbon chain has 4 or more C atoms, number the chain to give the lowest number to the double or triple bond. 1 2 3 4 CH2=CHCH2CH3 1-butene CH3CH=CHCH3 2-butene CH3CHCHCH3 2-butyne

29. Learning Check HA3 Write the IUPAC name for each of the following unsaturated compounds: A. CH3CH2CCCH3 CH3 B. CH3C=CHCH3 C.

30. Solutions HA3 Write the IUPAC name for each of the following unsaturated compounds: A. CH3CH2CH=CHCH3 2-pentyne CH3 B. CH3C=CHCH3 C. 2-methyl-2-butene 3-methylcyclopentene

31. Cis and Trans Isomers • Double bond is fixed • Cis/trans Isomers are possible CH3 CH3 CH3 CH = CH CH = CH cis trans CH3

32. Hydrogenation • Adds a hydrogen atom to each carbon atom of a double bond H H H H Ni H–C=C–H + H2 H–C–C–H H H ethene ethane

33. Products of Hydrogenation Adding H2 to vegetable oils produces compounds with higher melting points • Margarines • Soft margarines • Shortenings (solid)

34. Learning Check HA4 What is the product of adding H2 (Ni catalyst) to 1-butene?

35. Solution HA4 What is the product of adding H2 (Ni catalyst) to 1-butene? Ni CH2=CHCH2CH3 + H2 CH3CH2CH2CH3

36. Adding Halogens Halogens also add to the double bond of an alkene. H2CCH2 + Cl2

37. Learning Check HA5 Write the product of the following addition reactions: CH3CH=CHCH3 + H2

38. Solution HA5 Write the product of the following addition reactions: CH3CH=CHCH3 + H2 CH3CH2CH2CH3

39. Unsaturated Fatty Acids • Fatty acids in vegetable oils are omega-6 acids (the first double bond occurs at carbon 6 counting from the methyl group) • A common omega-6 acid is linoleic acid CH3CH2CH2CH2CH2CH=CHCH2CH=CH(CH2)7COOH 6 linoleic acid, a fatty acid

40. Trans Fats • In vegetable oils, the unsaturated fats usually contain cis double bonds. • During hydrogenation, some cis double bonds are converted to trans double bonds (more stable) causing a change in the fatty acid structure • If a label states “partially” or “fully hydrogenated”, the fats contain trans fatty acids.

41. Trans Fats • In the US, it is estimated that 2-4% of our total Calories is in the form of trans fatty acid. • trans fatty acids behave like saturated fatty acids in the body. • Several studies reported that trans fatty acids raise LDL-cholesterol. Some studies also report that trans fatty acid lower HDL-cholesterol • The trans fatty acids controversy will continue to be debated.

42. Fats and Atheroschlerosis • Inuit people of Alaska have a high fat diet and high blood cholesterol levels, but a very low occurrence of atherosclerosis and heart attacks. • Fat in the Intuit diet was primarily from fish such as salmon, tuna and herring rather than from land animals (as in the American diet).

43. Omega-3 Fatty Acids • Fatty acids in the fish oils are mostly the omega-3 type (first double bond occurs at the third carbon counting from the methyl group). • linolenic acid 18 carbon atoms CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH  • eicosapentaenoic acid (EPA)20 carbon atoms CH3CH2(CH=CHCH2)5(CH2)2COOH

44. Atherosclerosis • Plaques of cholesterol adhere to the walls of the blood vessels • Blood pressure rises as blood squeezes through smaller blood vessels • Blood clots may form • Omega-3 fatty acids decrease the “sticking” of blood platelets (fewer blood clots) • Omega-3 fatty acids can increase bleeding time

45. Learning Check HA6 (1) Ture or (2) False A. ____ There are more unsaturated fats in vegetable oils. B. ____ Vegetable oils have more omega-3 oils than found in fish. C. ____ Hydrogenation of oils converts some cis-double bonds to trans- double bonds. D. ____ Animal fats have more saturated fats.

46. Solution HA6 (1) True or (2) False A. _T__ There are more unsaturated fats in vegetable oils. B. _F__ Vegetable oils have more omega-3 oils than found in fish. C. _T__ Hydrogenation of oils converts some cis-double bonds to trans- double bonds. D. _T__ Animal fats have more saturated fats.