The Decision About Cost
Based on the information given, most people would have chosen this option.
When working through the cost analysis, it will be helpful to realize that many costs can be removed from consideration. Since Toluene is a solvent used in equal quantities in both reaction, it can be disregarded. Similarly, the same amount of salicylic acid is used in each reaction so it can also be ignored. This leaves the cost of the reactants and the disposal costs for the volume of products.
The cost data for the reactants shows that the acetyl chloride ifs significantly more expensive than the acetic anhydride. Even though you are required to use twice the volume of the acetic anhydride, the cost of the acetyl chloride is almost twenty times that of the anhydride. Also, the densities of the two materials are close enough to make the per pound price estimates a good judge of the actual cost. In this case, the cost of acetic anhydride is approximately, $430.00 while the cost of acetyl chloride is approximately, $3900.00. This is a difference of $3740.00
Some people might have considered the cost of sulfuric acid. However, the sulfuric acid is a catalyst and only used in trace amounts. Also, the price given is per ton or per 2000 lb. Even with the cost of this amount of sulfuric acid added to the overall cost of reactants, the acetic anhydride reaction is more cost effective.
Moving to the disposal cost section of the problem, it does not become clear that one reaction is more costly than the other. In both cases, the mixed organics and the pH 2 water have the same cost. It is important to convert from the liter measure of the reactants to the gallon measure of the disposal method. There are 3.7 liters per gallon. Knowing this, each gallon holds 211.2 liters. Even if all the reactants were drummed and disposed of, the cost difference would not exceed $300. The reactant cost is the over-riding concern and points to the use of the acetic anhydride.
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