Why is selecting a proper reactant crucial in chemical synthesis?

Selecting a proper reactant is crucial in chemical synthesis primarily because it determines the yield and type of product formed. In organic chemistry, the choice of reactants influences not just the chemical pathways that can be followed, but also the efficiency of conversion from reactants to desired products. The chemical properties, such as reactivity, functional groups, and sterics, of the reactants dictate how well they will engage in the reactions, what byproducts might be generated, and ultimately, how much of the desired product can be obtained.

For instance, if the chosen reactant does not have the right functional group or structure, the expected reaction may not occur at all, potentially resulting in a very low yield or the formation of entirely different products. This is particularly important for minimizing waste and maximizing efficiency in a laboratory setting, ensuring that the synthetic process is as effective as possible in producing the desired compounds.

While safety, simplification of processes, and reaction speed are important considerations in chemical synthesis, they are secondary to the core reason that the correct reactant directly affects the chemical outcome regarding yield and correctness of the product formed.