Organic Chemistry

100 CHAPTER 28 Synthetic Polymers

34. Draw a short section of the polymer obtained from anionic polymerization of


35. Which monomer would give a greater yield of polymer, 5-hydroxypentanoic acid or 6-hydroxyhexanoic acid? Explain your choice.


36. When rubber balls and other objects made of natural rubber are exposed to the air for long periods, they turn brittle and crack. This
    does not happen to objects made of polyethylene. Explain.


37. Why do vinyl raincoats become brittle as they get old, even if they are not exposed to air or to any pollutants?


38. The polymer shown here is synthesized by hydroxide ion–promoted hydrolysis of an alternating copolymer of para-nitrophenyl
    methacrylate and acrylate.
    a. Propose a mechanism for the formation of the alternating copolymer.
    b. Explain why hydrolysis of the copolymer to form the polymer occurs much more rapidly than hydrolysis of para-nitrophenyl
    acetate.


39. An alternating copolymer of styrene and vinyl acetate can be turned into a graft copolymer by hydrolyzing it and then adding
    ethylene oxide. Draw the structure of the graft copolymer.


40. How could head-to-head poly(vinyl bromide) be synthesized?


41. Delrin®(polyoxymethylene) is a tough self-lubricating polymer used in gear wheels. It is made by polymerizing formaldehyde in
    the presence of an acid catalyst.
    a. Propose a mechanism for formation of a segment of the polymer.
    b. Is Delrin®a chain-growth polymer or a step-growth polymer?

head-to-head poly(vinyl bromide)

CH 2 CHCHCH 2 CH 2 CHCHCH 2

Br Br Br Br

para-nitrophenyl acetate

O

O

CH 3 C NO 2

alternating copolymer

polymer

para-nitrophenyl

methacrylate

CH 3

CO

C

O

CO 2

CH 2 + CH 2 CH

CH 3

CO 2

CH 2 C CH 2 CH

CO 2

NO 2 NO 2

−

HO−

H 2 O

− −

CH 3

C

CH 2 C CH 2 CH

O CO 2

O

−

acrylate

3,3-dimethyloxacyclobutane

CH 3

CH 3

O

b-propiolactone.