Question

2. Briefly explain why ethanol, and not hexane, was used as a solvent in this reaction? 3. Why it is necessary to filter the crude coupling product through a column of anhydrous MgSO4? 4. Briefly explain why aryl bromides and iodides, rather than aryl chlorides or fluorides, are typically used as substrates in Pd-catalyzed coupling reactions. 5. Propose a synthesis for the molecule A shown below, using benzene, phenyl boronic acid, tert-butyl bromide and any inorganic reagents needed. A retrosynthetic scheme is shown. Put the pieces together showing the necessary reactants and reagents.

Answer 1

2) The reactants of this reaction arylbromide and boronic acid both are inoic in nature so polar solvent should be taken for reaction. Between Ethanol and hexane, ethanol is polar so taken in this reaction.

3)Since we are using polar solvent it might contain some ionic compound results from the reaction along with coupling product. There may be some water present. To remove them the crude coupling product filter through anhydrous Magnesium sulfate.

4)Aryl bromide and iodide are usually used for of coupling reaction. This is because Aryl-bromine or aryl-iodine bind easily break down rather than aryl-chloride or fluoride. For the mechanism of pd catalysis oxidative addition takes place by breaking aryl-halide bond. So less is the bond energy more will be oxidative addition. So aryl-bromide and iodine has less bond energy easily breaks.

5) Answer given in paper below..

@ +679 Rez 0 € 928 3 . ovo+at Palet KOH/ solvent Ho