Which of the following is a monomer of natural rubber?

The correct answer is Option (1) → Isoprene

Natural rubber is obtained from rubber latex and is a linear polymer of isoprene (2-methyl-1,3-butadiene). The isoprene units are joined head to tail with a cis double bond in each unit, so natural rubber is cis-1,4-polyisoprene:

    \( \displaystyle \ce{n CH2=C(CH3)-CH=CH2 -> -[CH2-C(CH3)=CH-CH2]_n-} \)

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Natural Rubber – “Rubber is a natural polymer and possesses elastic properties. It is also termed as elastomer and has a variety of uses. It is manufactured from rubber latex which is a colloidal dispersion of rubber in water. This latex is obtained from the bark of rubber tree and is found in India, Srilanka, Indonesia, Malaysia and South America.
Natural rubber may be considered as a linear polymer of isoprene (2-methyl-1, 3-butadiene) and is also called as cis-1, 4-polyisoprene.”