Condensation polymerisation — practice questions

Identify and draw the monomers: Ethane-1,2-diol: $HO-CH_2-CH_2-OH$ Benzene-1,4-dicarboxylic acid: $HOOC-C_6H_4-COOH$

Align the reactive groups. Place the monomers end-to-end so the reacting –OH and –COOH groups are adjacent. $HO-CH_2-CH_2-OH + HOOC-C_6H_4-COOH$

Show the elimination of water. The –OH from the carboxylic acid and the –H from the alcohol are removed to form $H_2O$.

Form the ester link ($-O-CO-$) between the remaining fragments. The process repeats at the other end of the monomers to form a long chain.

Draw the repeating unit. The unit consists of one of each monomer fragment. Enclose it in square brackets, with bonds extending through the brackets to show continuation, and add 'n' to denote a polymer.

Repeating Unit: $-[O-CH_2-CH_2-O-CO-C_6H_4-CO]-_n$

Identify the monomers: Hexanedioic acid: $HOOC(CH_2)_4COOH$ 1,6-diaminohexane: $H_2N(CH_2)_6NH_2$

Align the reactive groups. The –COOH group of the acid reacts with the –NH₂ group of the amine.

Show the elimination of water. The –OH from the acid and an –H from the amine are removed to form $H_2O$.

Form the amide link ($-CO-NH-$).

Construct the repeating unit. The repeating unit contains one fragment from each monomer: $-[CO(CH_2)_4CONH(CH_2)_6NH]-_n$. Note that the convention can also start with the amine fragment: $-[NH(CH_2)_6NHCO(CH_2)_4CO]-_n$. Both are correct.

Draw two repeating units. To do this, we draw the sequence of atoms from the repeating unit twice, joined together, with continuation bonds at both ends.

Structure showing two units: $...-CO(CH_2)_4CONH(CH_2)_6NH-CO(CH_2)_4CONH(CH_2)_6NH-...$