Chapter 28 notes

Chapter 28 notes - Organic Chemistry Fifth Edition, Paula...

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Sheet1 Page 1 Organic Chemistry Fifth Edition, Paula Yurkanis Bruice Chapter 28- Synthetic Polymers Notes (May 14th, 2008) Polymers- a large molecule made by linking together repeating units of monomers, by a process called polymerization. Polymers can be divided into two groups: 1) Synthetic Polymers -synthesized by scientists, do not occur in biological systems 2) Biopolymers -synthesized by organisms, found in nature 28.1 There Are Two Major Classes of Synthetic Polymers Synthetic polymers can be divided into two classes, depending on their method of preparation: 1) Chain-Growth Polymers or Addition Polymers -made of chain reactions ? -monomers used most often in chain-growth polymerization are ethylene and substituted ethylenes. -polymers formed from ethylene or substituted ethylene are called vinyl polymers -Three Mechanisms 1) Radical Polymerization - a radical initiator must be added to the monomer to convert some of the monomer molecules into radicals -All the initiators have an O-O that can be homolytically cleaved - Head to Tail Addition: the head of a monomer is attached to the tail -Because of steric hindrance - 3 steps: Initiation, Propagation, and Termination nM h -M-M-M-M- -ex: DNA, RNA, proteins, etch of the otherh. .why?
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Sheet1 Page 2 -Ways to terminate: 1) 2 radicals combine 2) Disporportionation: one of the chains loses an H atom and gives it to the other 3) A chain reacts with an impurity that consumes the radical - Another thing that could happen is the propagation site can abstract a hydrogen atom from the chain, and a branch can grow off at that point: - Branched polymers are more flexible because they do not pack together as much. -ex: trash bags and beach balls compared to artificial hip joint
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Chapter 28 notes - Organic Chemistry Fifth Edition, Paula...

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