Q7(a). Acetylene on a Ziegler–Natta catalyst: polyacetylene
Write the structure of the polymer formed and the stepwise mechanism involved when acetylene is treated with Ziegler–Natta catalyst. Comment if the product formed is conducting or non-conducting.
Answer in brief
Polyacetylene, –(CH=CH)ₙ–, built by coordination–insertion at titanium; undoped it is only a semiconductor (10⁻⁹ to 10⁻⁵ S cm⁻¹), doped it conducts (10³ to 10⁵ S cm⁻¹).
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CoversZiegler–Natta catalystpolyacetylenecoordination–insertionCossee–Arlman mechanismconducting polymerdoping
All parts of Question 7
- 7(a) Acetylene on a Ziegler–Natta catalyst: polyacetylene10 marks
- 7(b) Ketone with diethyl carbonate: crossed Claisen condensation5 marks
- 7(c) Lactic acid from ethanal through the cyanohydrin5 marks
- 7(d) Phenyl acetate to A, B, C, D: Reimer–Tiemann and Wittig reactions10 marks