Question

Question 3 (5 points): A student is performing a 1:1 stoichiometric polymerization of 1,4-diamonobutane with sebacoyl chloride. H2 H2 C -NH2 4 sebacoyl chloride 1,4-diaminobutane a) Neglecting the effects of end groups on molar mass, calculate the extent of reaction required to produce this polymer with a number-average molar mass of 25 kg. molel b) The student performed experiments for measuring the molecular weight of the synthesized polymer. It was found that the determined molecular weight was lower than the theoretical weight (25 kg. mole1) the student wanted to achieve. In no more than 3 lines, give experimental values. a reason to the discrepancy between the theoretical and

Answer 1

(a) The polymer can be represented as follows.

[-NH-(CH₂)₄-NH-C(=O)-(CH₂)₈-C(=O)-]_n

The theoretical value for number-average molar mass (M_n) = 25000 g.mol^-1

The molecular weight of the repeating monomer (M_o) = 2*15 + 12*14 + 2*28 = 254 g.mol^-1

Formula: M_n = M_o/(1-p), where 'p' is the extent of reaction

i.e. 25000 g.mol^-1 = 254 g.mol^-1/(1-p)

i.e. 1-p = 0.01016

Hence, the extent of reaction (p) = 0.98984

(b) The discrepancy between the theoretical and experimental values can be attributed to the loss of some weight during the process of isolation of the synthesized polymer.