Question

Gutta-percha, a naturally occurring highly crystalline non-elastic rubber, consists of:

• A. \(1,4\)-polyisoprenes in which all the double bonds have \(E\)-configurations
• B. \(1,4\)-polyisoprenes in which all the double bonds have \(Z\)-configurations
• C. A mixture of \(Z\)-\(1,4\)-polyisoprenes and \(E\)-\(1,4\)-polyisoprenes
• D. \(1,4\)-polyisoprenes in which some double bonds have \(Z\)-configurations and some others have \(E\)-configurations

Hint:

Natural rubber → cis-\(1,4\)-polyisoprene → elastic
Gutta-percha → trans-\(1,4\)-polyisoprene → crystalline, non-elastic Cis–trans configuration strongly affects polymer properties.

Answer 1

The Correct Option is A

Step 1: Recall the structure of natural rubber and gutta-percha.
Natural rubber is \emph{cis}-\(1,4\)-polyisoprene (i.e., \(Z\)-configuration).
Gutta-percha is \emph{trans}-\(1,4\)-polyisoprene (i.e., \(E\)-configuration).
Step 2: Relate configuration to physical properties.
\(Z\)-configuration (cis) → coiled chains → elastic and amorphous
\(E\)-configuration (trans) → linear chains → highly crystalline and non-elastic Since gutta-percha is described as highly crystalline and non-elastic, it must have the trans (\(E\)) configuration throughout.
Step 3: Match with the given options. Only option (A) correctly states that gutta-percha consists of \[ 1,4\text{-polyisoprene with all double bonds in } E\text{-configuration}. \]
Hence, the correct answer is \[ \boxed{\text{(A)}} \]