Unsaturated HC’s

1. Unsaturated HC’s The Alkenes and Alkynes

2. Naming Alkenes & Alkynes • Have double bonds(enes) triple bonds (ynes) • 1st 5 alkenes/ynes • you must use a # for but and higher • Also name cyclos • Dienes/Trienes

3. HTPB • Hydroxyl-terminated polybutadiene

4. Used in rockets of all kinds • Like this one

5. Reactions of alkenes (ynes also but they’re less common) • Alkenes are much more chemically active than alkanes-why? • Electron parties

6. Reactions of alkenes cont’d • Intro video 3 min http://www.youtube.com/watch?v=1qGPWdm2MlI • The most common type of reaction for alkenes is addition: • general pattern • alkene + AB ---> see board • AB can be: • hydrogen • halogen • water • hydrogen halide

7. Hydrogenation • This is the addition of hydrogen • sometimes called catalytic hydrogenation • catalyst is platinum (Pt) • Ex equations • Hydrogenation in food

8. Halogenation • Addition of a halogen (what are halogens?) • no catalyst is required • ex equations • *addition of a halogen is a good test for unsaturation-esp bromine and iodine

9. Hydrohalogenation • Addition of a hydrogen halide (HX) • such as HCl, HBr, HI, HF • Markovnikov’s rule may apply • no catalyst needed • ex equations

10. Hydration • Addition of water • sulfuric acid catalyst • Markovnikov’s rule may apply • *Hydration is often confused with hydrogenation • *conversion of alkenes to alcohols is important in the metabolism of carbohs, fats, proteins. Enzymes are the catalysts.

11. Practice • Hydration of 1-pentene • Hydration of cyclohexene • Hydrochloric acid is added to 1-butene • Hydrobromic acid is added to cyclopentene • Hydration of 2-butene

12. Other reactions of alkenes/ynes • Oxidation-follows general pattern • HC + oxygen --->carbon dioxide + HOH + heat • Polymerization-identical molecules react with each other to produce long chains called polymers • ex: polyethylene, polypropylene

13. Practice rxns  • 1. hydration of 1-butene • 2. hydrogenation of 1-butene • 3. addition of fluorine to 2-pentene • 4. addition of HI to cyclohexene • 5. hydrogenation of cyclobutene • 6. addition of hydrochloric acid to 1-pentene • 7. hydrogenation of cyclopentene • 8. addition of hydrobromic acid to 1-butene • 9. hydration of cyclobutene • 10.addition of iodine to 2-hexene • 11.water is added to 1-pentene

14. 2 rxns for making enes in the lab: 1. Dehydration of an alcohol • what’s a good dehydrating agent? • Example equations here • 2. Dehydrohalogenation -here, an alkyl halide (RX) is treated with KOH to remove a H and an adjacent halogen • ex equations

15. One step further: • Dehydrohalogenation can be used to make alkynes if your starting structure has 2 halogens. • Example equations: • *this will be a 2-step reaction-you must show the middle step also

16. practice • Write complete equations for the following reactions. Name everything except HOH and the catalysts. • 1.) Ethanol undergoes dehydration • 2.) 2-bromopropane is treated with KOH • 3.) 1-iodoethane undergoes dehydrohalogenation • 4.) 1,1-difluoropropane is treated with excess KOH • 5.) 1-butanol is treated with sulfuric acid • 6.) chlorocyclopropane is treated w/KOH • 7.) 1,1-dibromopentane is treated w/excess KOH • 8.) cyclohexanol is dehydrated (that’s cyclohexane w/an OH) • 9. )1-propanol (3 C’s w/ah OH on the 1st one) is treated w/sulfuric acid

17. Fun quiz • 1. cyclopropanol is treated with sulfuric acid • 2. 1,1-dichlorohexane is treated with excess KOH • 3. iodocyclohexane is treated with KOH • 4. 1-butanol is dehydrated • 5. 1-fluorobutane undergoes dehydrohalogenation 

18. Cis/Trans Isomerism Stuff I bet you never knew!

19. Molecules can have an up & a down • examples: • 2-butene • 3-hexene • 2-pentene • 1-butene • 2-methyl-2-butene • other silly exs

20. How are cis/trans isomers relevant to us? • Pheromones (see Justin’s powerpoint) • several types • sex • alarm • aggregate • aggression

21. Bees are a good example

22. The Gypsy Moth Story • The female gypsy moth secretes cis-glyplure to attract males • expt with male moths in a cage and cis-glyplure on a Q-tip • the UAB chemist’s moth problem • gypsy moths aren’t here-YET • they will react to 1 molecule of the pheromone

23. Cis/trans in vision • There is a chemical vital to human vision, in the liver it’s called Rhodopsin • Rhodopsin comes from Greek word for “rose-colored” b/c it has a reddish color in the dark which fades when exposed to light • Rhodopsin in the liver makes its way into the retina where it’s called cis-retinal (or Vitamin A)

24. Cis/trans in vision cont’d • Once in the retina, light hits the cis-retinal and it’s changed into trans-retinal • Interesting note: • the energy reqd to make this change is 250kJ/mole. A photon of sunlight has 165-293 kJ/mole of energy. If we were a little closer or further away from the sun, we couldn’t see anything.

25. Cis/trans in vision con’td • When the cis-retinal changes to the trans form, the shape of the molecule changes and it’s released from the protein that holds it. • Ions are produced and they flow through the optic nerve. We see this as light. • Later, an enzyme changes the trans back to cis, it binds back to the protein and awaits the next exposure to light.

26. Cis/trans in taste • We only taste one and not the other b/c receptors on tongue only fit one • Ex: cis/trans fumaric acid • trans-fumaric acid maleic acid • (cis-fumaric acid)

27. Cis/trans in odors • The geometry of molecules is a main determinant of odor • must fit in olfactory receptors • essential oils of plants give them their pleasant odors • rose, citronella, verbena

28. What about trans fatty acids? • Fatty acids can be either cis or trans • trans fatty acids are bad • they raise bad cholesterol levels • Nerdy video with really good info! 6 min • http://www.youtube.com/watch?v=TNrMIdzvRww

29. Where do we find trans FA’s? • Hydrogenation creates these bad fatty acids. • They are worse for the body than butter and animal fat (lard) • what kinds of foods contain trans fatty acids? • LOTS!

30. What about rubber? • Rubber trees make both cis and trans forms of rubber • ex: smart and stupid balls • cis bounces, trans doesn’t • trans rubber is used to make tires b/c cis is too bouncy

31. Preparation of unsatd HC’s • Fossil fuels contain satd & unsatd HC’s • we can increase the yield of unsatds through a process called cracking • Def cracking: when long, straight-chained HC’s are broken down in to smaller pieces • 2 types of cracking: • thermal • catalytic

32. Car fuels • Def fuel: any chemical that can be used in the operation of an internal combustion engine • How a 2 stroke engine works • http://www.youtube.com/watch?v=LuCUmQ9FxMU&feature=PlayList&p=0D07C0CE4E904876&playnext=1&playnext_from=PL&index=10 • Marshall Brain/s tater gun • http://videos.howstuffworks.com/howstuffworks/190-how-engines-work-video.htm • what makes the “best” fuels? • Those that produce lots of power and not much knocking

33. Knocking! • Def: a premature ignition due to heat and not spark • why is knocking bad? • Loss of energy • engine damage • *diagram here • how does a diesel engine work? • Biodiesel video 3.5 min • http://videos.howstuffworks.com/science-channel/5044-invention-nation-biodiesel-video.htm

34. Gasoline additives • Tetraethyl lead-was in “leaded” gas in the 70’s and earlier • why was it added? • Why is it not added now?

35. Lead poisoning • We can eliminate only about 2 mg of Pb/day through the kidneys • excess lead is stored in bones and soft tissues-lead poisoning video 2 min • http://videos.howstuffworks.com/discovery/34886-howstuffworks-show-lead-poisoning-video.htm • And in kids video 1.5 min • http://videos.howstuffworks.com/discovery/34887-howstuffworks-show-lead-poisoning-in-kids-video.htm

36. Common names of enes/ynes • The IUPAC naming system is fairly new. Many common names predate IUPAC and are still used today. • Ethyne-acetylene • Propene-propylene • ethene-ethylene

37. ethylene • produced in many fruits and vegs as they ripening • acts as a hormone to enhance the softening process

38. Alkynes • ethyne is the most common alkyne • also called acetylene • early cars had carbide lamps • miners and cavers also used them • 2 ways to make ethyne:

39. Making acetylene • One way: • Heating methane to very high temps in the absence of oxygen • 2CH4 -----> HC=CH + 3H2

40. Making acetylene • Another way: • hydration of calcium carbide (go outside!) • CaC2 + 2HOH ----> HC=CH + Ca(OH)2 • *be sure you can write and name everything in these 2 equations :)