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Organic Mechanism

Organic Mechanism. By: Duyen Vuong 12D. Content. Organic Mechanism Vinyl polymers Low density poly(ethene), LDPE Free radical formation High density poly(ethene), HDPE Ziegler- Natta catalyst Bibliography. Organic mechanisms. To manufacture of poly(ethene)

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Organic Mechanism

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  1. Organic Mechanism By: Duyen Vuong 12D

  2. Content • Organic Mechanism • Vinyl polymers • Low density poly(ethene), LDPE • Free radical formation • High density poly(ethene), HDPE • Ziegler- Natta catalyst • Bibliography

  3. Organic mechanisms • To manufacture of poly(ethene) • used to make polymers from vinyl monomers • Mostly covalent bonds • 2 types: • LDPE • HDPE

  4. Vinyl polymers • from vinyl monomers (contain double carbon- carbon bonding) • largest family of polymers • made from the monomer ethylene/ ethene • form a long chain of many thousands of carbon atoms containing only single bonds between atoms

  5. Examples of Vinyl Polymers • polypropylene • Polystyrene • poly(vinyl chloride) • Polyisobutylene/ type of rubber • poly(methyl methacrylate) • polytetrafluoroethylene

  6. Objective C.9.1 • Describe the free- radical mechanism involved in the manufacture of low- density polyethene

  7. Low density poly(ethene) • Carried out at very high pressures (1000-3000 atm) • At temperature about 500K (227ºC) • Average polymer molecule contains between 4 x 10³ to 4 x 10^4 carbon atoms • With short branches • Has a density of about 0.92g cm^-3 • Used mostly for packaging • Formed under free radical formation

  8. Free radical formation • Definition- molecules with unpaired electrons • Highly reactive due to unpaired electrons • Biology example- PEROXIDATION (producing ATP inside the body) • Elements example- oxygen (ROS- reactive oxygen species) , transition metals (Cu- copper, can lose and gain electrons easily) • Progress= initiate  propagation  termination

  9. Initiate • First step • Homolytic fission • when a bond is broken, each of the bonded atoms or groups takes one of the bonding pair of electrons. • Not heterolytic fission • when a bond is broken and two electrons go to one of the element/compound • Examples: • Cl2 (UV light) 2Cl· • Br2  2 Br·

  10. Propagation • Each step must have odd number of unshared electrons • Two compounds containing one unshared electron each never, ever, ever combine • Unpaired electrons wanted will swipe one of themselves to pair with • Leading us back to the beginning • adding of more and more monomer molecules to the growing chains • Examples: • Cl · + CH4 · CH3 + HCL • · CH3 + Cl2  CH3Cl + Cl · • Cl · + CH4 -> · CH3 + HCL • · CH3 + Cl2 -> CH3Cl + Cl·

  11. Termination • Each of two unpaired compounds form radical–radical combination(coupling) or a disproportionation • Examples: • · Cl+ · Cl -> Cl2 • · CH3+ · CL-> CH3Cl • · CH3+ · CH3->C2H6

  12. Examples of the free radical formation

  13.  

  14. OR

  15. Objectives C.9.2 • Outline the use of Ziegler- Natta catalyst in the manufacture of high- density polyethene

  16. High density poly(ethene) • Carried out at pressures (1-50 atm) • At low temperature about 350K (77ºC) • Using Zieler- Natta catalyst • Maily of linear chains with very little branching • Higher density 0.96 g cm^-3 • More rigid structure • Used to make containers and pipes

  17. Ziegler- Natta catalyst • method of vinyl polymerization • discovered by two scientists: Ziegler and Natta in the 1950s • Can’t make some other kinds of monomers, such as poly(vinyl chloride) • Suspension of titanium (III) or titanium (IV) chloride together with an Alkyl- aluminum compound • Catalyst and co catalyst: • TiCl3 and Al(C2H5)2Cl • TiCl4 with Al(C2H5)3

  18. Industry process

  19. Chemical process • TiCl3 can arrange itself into a number of crystal structures • each titanium atom is coordinated to six chlorine atoms= octahedral geometry

  20. • Ti- • transition metal • Have six empty orbitals (4s and five 3d-orbitals ) • Needs 2 electrons to fill up the orbital • Filled 1 up by Al(C2H5)2Cl

  21. Combine with vinyl monomer like propylene nth(C3H6) • two electrons in the π-system of a carbon-carbon double bond fill the left over empty orbital • Form a complex

  22. Several pair of electrons shift position • The propylene monomer migrates

  23. Bibliography • http://www.stopagingnow.com/images/free_radical.jpg • http://img125.imageshack.us/img125/4794/background1qa5.jpg • http://media.photobucket.com/image/background/tatcalaquakhu/Backgrounds10.jpg • http://www.exrx.net/Nutrition/Antioxidants/Introduction.html • http://www.answers.com/topic/monomer • http://69.90.174.246/photos/display_pic_with_logo/90327/90327,1220853365,8.jpg • http://www.adobetutorialz.com/content_images/AdobePhotoshop/ART-D/tutorial402/cool-abstract-background.jpg • http://www.thegioiwallpaper.com/wallpaper/Background-15/ • http://www.ucc.ie/ucc/depts/biochemistry/students/Images/science_background.jpg • http://www.uku.fi/~poso/thc_reseptorissa.jpg.jpg • http://buzzert.zanneth.com/images/wallpaper/Liquid%20Plasma.jpg • http://www.economicexpert.com/a/Ziegler:Natta:catalyst.htm • http://www.exrx.net/Nutrition/Antioxidants/Introduction.html • http://chemistry2.csudh.edu/rpendarvis/Radicals.html • http://www.chem.uky.edu/courses/che230/RBG/handouts/freeradchainrules.html • http://www.sciencecollege.co.uk/SC/reaction_mechanisms/freeradical.jpg • http://www.steve.gb.com/images/molecules/halogen_compounds/chloromethane_%28free_radical_mechanism%29.png • http://pslc.ws/mactest/ziegler.htm • http://media-2.web.britannica.com/eb-media/60/1660-004-390F09C4.gif • http://pslc.ws/mactest/radical.htm

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