Ethylene oxide is an important industrial chemical. Although most ethers are unreactive, ethylene oxide is quite reactive. It resembles $\mathrm{C}_{2} \mathrm{H}_{4}$ in its reactions in that addition reactions occur across the \(\mathrm{C}-\mathrm{O}\) bond in ethylene oxide. a. Why is ethylene oxide so reactive? (Hint: Consider the bond angles in ethylene oxide as compared with those predicted by the VSEPR model.) b. Ethylene oxide undergoes addition polymerization, forming a polymer used in many applications requiring a nonionic surfactant. Draw the structure of this polymer.

To determine the reactivity of ethylene oxide, we need to consider its molecular structure and apply the VSEPR model. Ethylene oxide has the formula \(\mathrm{C}_{2}\mathrm{O}\), which corresponds to a ring structure with one oxygen and two carbons. According to the VSEPR model, the bond angles around an oxygen atom with two single bonds and two lone pairs should be approximately 109.5 degrees (tetrahedral molecular geometry). However, in ethylene oxide, the ring causes strain as the bond angles within the ring are forced to be around 60 degrees, much smaller than the expected tetrahedral angle. This makes the \(\mathrm{C}-\mathrm{O}\) bond highly strained and vulnerable to attacks from nucleophiles, leading to increased reactivity.

Now, let's draw the structure of the polymer formed through the addition polymerization of ethylene oxide. During addition polymerization, the strained \(\mathrm{C}-\mathrm{O}\) bond of ethylene oxide breaks and the monomers join together. The polymer formed has a repeating unit structure derived from ethylene oxide: \(-\mathrm{C}\mathrm{H}_{2}\mathrm{C}\mathrm{H}_{2}\mathrm{O}-\) In the structure of the polymer, the bond angle around the oxygen atom approaches the expected value of the VSEPR model due to the opened ring, which reduces strain and creates a more stable configuration. To represent the polymer, we can use the following notation for the repeating unit: \(\mathrm{[-CH_{2}CH_{2}O-]}_{n}\) Here, "n" denotes the number of repeating units present in the polymer chain. The resulting polymer is called poly(ethylene oxide) and is widely used as a nonionic surfactant in various applications.