Q21-82E - Organic Chemistry (Mcmurry)

Question

Epoxy adhesives are prepared in two steps. S_N2 reaction of the disodium salt of bisphenol A with epichlorohydrin forms a “Pre-polymer,” which is then “Cured” by treatment with a triamine such as H₂NCH₂CH₂NHCH₂CH₂NH_2.

Draw structures to show how the addition of the triamine results in a strengthening of the polymer.

Step-by-Step Solution

Answer

The Ring Opening occurs in the epichlorohydrin to overcome the strain present by the nucleophilic attack.Dehydration forms the polymer. The reactioninvolves the nucleophilic acyl substitution mechanism.

Step 1: Increases the tensile strength

Polymerization increases the tensile strength as it removes the ring Strains of the cyclopropyl ring and leads to a saturated product

Step 2: Remove the Cyclic ring and increases the tensile strength

Therefore, Polymerization leading to the removal of cyclic ring strains increases the tensile strength of the polymer.