Final answer:
TBAB is usually removed during the work-up phase. Suspending crude solids in warm hexanes and gravity filtration aims to dissolve impurities while allowing the purification of the desired solid product. Both 1H NMR and IR spectroscopy provide distinct features relating to the chemical environments and functional groups that differentiate starting materials, products, and impurities.
Step-by-step explanation:
1. Tetra-n-butylammonium bromide (TBAB) was likely removed from the reaction mixture during the work-up phase, which includes steps such as extraction, washing, and filtration, designed to isolate and purify the desired product from other reaction components, although the provided information does not specify the exact point of removal.
2. Suspending the crude solid in warm hexanes and performing a gravity filtration serves two main purposes: dissolving impurities that are soluble in hexanes and, simultaneously, allowing the less soluble desired product to crystallize. This often improves the purity of the final product by separating it from soluble impurities.
3. 1H NMR spectroscopy can be used to differentiate between the starting material and the product in several ways - by comparing the chemical shifts, integration values, and multiplicity of signals. For instance, the disappearance of signals attributable to functional groups in the starting material and the emergence of new signals corresponding to the product's chemical environment will indicate reaction progress.
4. IR spectroscopy is an effective method to distinguish between the impurities and the product of a Suzuki cross-coupling reaction. It detects differences in functional group vibrations; for example, the presence or absence of certain bond stretches like C-O, C-N, or C=C can help in identifying functional groups specific to either the impurities or the desired product.