Problems and opportunities arising from unsuccessful experiments or unexpected results

5 Problems and opportunities arising from unsuccessful experiments or unexpected results 

Unsuccessful reactions, leading to little or none of the desired product, occur for many reasons, and an understanding of the cause of a low product yield can be informative. A zero yield of the desired product is considerably worse than a yield of 1% (see discussion of SAG in Section 2.2.2). Consequently, a yield of a few % is an opportunity for investigation of alternative reagents or catalysts, and improved reaction conditions. However, a zero yield usually provides more of a problem and less of an opportunity  

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