Question

compare HPLC chromatogram for your recrystallized product with that of methyl 2-nitrobenzoate, methyl 3-nitrobenzoate, and methyl 4-nitrobenzoate. Did the reaction produce a single regioisomer? First HPLC is the recrystallized product.

Batch Filename batch. Ich Vial # 11 22 Injection Volume : 10 ul Date Acquired - 10/22/2019 226 26 PM Date Processed 10/22/2019 234:28 PM Sample Type : Unknown Acquired by Processed by System Administrator System Administrator <Chromatogram> UAU 4000000 PDA Multi 1 254nm 4nm 3000000 2000000 1000000- <Peak Table> Mark Name PDA Ch1 254nm Peak# Ret. Time Area Height Conc U nit 2.0565480 1490 .000 21 2298461522820 .000V 33.598 3048332400 .000 V 4 3.901 96853258960 .000 V 5,63019786026 3937282 0.000 Total 19923458 3968849 D

Answer 1

The reaction did not produce single regioisomer because in the recrystallized product two significant peaks are present at the retention time 3.901 and 5.630. The relative retention time with respect to the peak at 3.901 is = 3.901/5.630 = 0.6928. The methyl-2-nitrobenzoate has retention time 3.893. The methyl-3-nitrobenzoate has retention time 5.601, and methyl-4-nitrobenzoate has retention time 5.716. Thus from the first HPLC graph (where peak at 3.901 is present) it is clear that methyl-2-nitrobenzoate is present in the recrystallized product. the relative retention time with respect to the peak at 3.893 for the two peaks at 5.601 and 5.716 are 0.695 and 0.681. Thus if the relative retention time in the first HPLC graph is compared with these two values, it is clear that the recrystallized product also contains methyl-3-nitrobenzoate.