Which of the following reaction is not accompanied by elimination of a byproduct molecule?

addition polymerization

The correct answer is option 1. addition polymerization.

Addition polymerization involves the process where monomers with double or triple bonds react to form a polymer without the elimination of any byproduct molecule. This type of polymerization includes mechanisms such as free radical polymerization, anionic polymerization, and cationic polymerization.

Addition Polymerization: In this process, monomers add to the growing polymer chain one at a time, and the polymer grows without the loss of any small molecules. For example, the polymerization of ethylene to form polyethylene involves the opening of the double bonds of ethylene molecules to form long chains of polyethylene without producing any byproducts.

Condensation Polymerization: This process, on the other hand, involves the reaction of monomers with the elimination of small molecules such as water, alcohol, or hydrochloric acid. Examples include the formation of polyesters (e.g., polyethylene terephthalate) and polyamides (e.g., Nylon-6,6), where each step of the polymerization results in the loss of a small molecule.

Addition polymerization is not accompanied by the elimination of a byproduct molecule, whereas condensation polymerization is. Therefore, the correct answer is addition polymerization.