Wrong Starting Materials Used

FIGURE 11.23 Comparison of target bond forming profiles and target bond maps for original (a) and modified (b) Hamon-Young plans to ( )-twistane. 

Summary of Material and Synthesis Efficiency Performances for the Original and Modified Hamon-Young Plans to ( )-Twistane 

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Plans that are stacked with these kinds of reactions suggest that wrong starting materials were probably used. As a result indirect syntheses necessarily have an increased number of steps to the final target structure. The following corrections are usually found in indirect syntheses ... 

There are several sources of irreproducibility in kinetics experimentation, but two of the most common are individual error and unsuspected contamination of the materials or reaction vessel used in the experiments. An individual may use the wrong reagent, record an instrument reading improperly, make a manipulative error in the use of the apparatus, or plot a point incorrectly on a graph. Any of these mistakes can lead to an erroneous rate constant. The probability of an individual s repeating the same error in two successive independent experiments is small. Consequently, every effort should be made to make sure that the runs are truly independent, by starting with fresh samples, weighing these out individually, etc. Since trace impurity effects also have a tendency to be time-variable, it is wise to check for reproducibility, not only between runs over short time spans, but also between runs performed weeks or months apart. 

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