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FIGURE 5.1 Examples of reactions involving carbon dioxide and leading to intermediates in industrial synthesis. Top: The reaction of carbon dioxide with sodium phenolate to produce sodium salicylate. Bottom: The reaction of carbon dioxide with an epoxide to make a cyclic organic carbonate.

the production of polyacrylic fibers and paints. Ethylene and propylene carbonates have many uses in chemical synthesis—among them reactions with ammonia and amines to form carbamates and subsequent reactions with diamines to yield di(hydroxyethyl) carbamates, which can react further with urea to form polyurethanes.

Figure 5.2 provides a broad summary of current and projected utilization of carbon dioxide. Reactions that use CO₂ to produce organic chemicals or intermediates for the chemical industry are summarized from 6 to 11:00 o'clock on the diagram. The first examples, such as salicylic acid, are in current practice. Also included in Figure 5.2 are reactions that hold promise for extensive utilization in the future. Many of these involve insertion of carbon dioxide into Y—X bonds, often the C—H bond. The products of interest include esters, carbamic esters, salicylic acid, and cyclic carbonates. These reactions

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FIGURE 5.2 Utilization of CO² in synthetic chemistry. SOURCE: Aresta (1998). 6