As the variance for large peaks is greater than that for small peaks, the major products dominate the analysis and differences due to small peaks are masked unless the variables are rescaled. UV-scaling, or scaling to unit variance gives all variables equal influence on the analysis. PCA scores plots for unscaled data are shown in the supporting information. Here, differences along PC1, accounting for 97.3% of the variance in the data, are related to differences between 2-bromo-benzamide 1a, the starting material, and product 2a, the major product.