Which one of the following statements is not true?
- Buna-S is a copolymer of butadiene and styrene.
- Natural rubber is a 1,4-polymer of isoprene.
- In vulcanization, the formation of sulphur bridges between different chains makes rubber harder and stronger.
- Natural rubber has the trans-configuration at every double bond.
Answer
(4) Natural rubber has the trans-configuration at every double bond.
Solution
As per NCERT, natural rubber is a linear polymer of isoprene (2-methyl-1,3-butadiene), called cis-1,4-polyisoprene.
⇒ Natural rubber has the cis-configuration (not trans) at every double bond; the trans form is gutta-percha.
∵ Buna-S is a copolymer of 1,3-butadiene and styrene, and vulcanisation forms sulphur cross-links that make rubber harder and stronger, statements (1), (2) and (3) are true.
∴ Statement (4) is not true.
Answer: (4)