Question 1: In the year 1968, the Shell Oil Company reported that adding tertiary phosphine such as PBu3 to the oxo reaction resulted in hydroformylation occurring at less than 100 atm. Although the new catalyst is a less active hydroformylation catalyst than HCo(CO)3, it is a better hydrogenation catalyst. Separation of catalyst from products is enhanced. The ratio of linear to branched product is as high as 9 to 1. Studies of the reaction failed to observe alkyl or acyl-containing intermediates.
a) Describe the greater selectivity of the new catalyst by drawing a suitable transition state.
b) What are the merits and demerits of the new catalyst being a good hydrogenation catalyst?
c) What does the failure to observe intermediates tell you regarding the likely rate-determining step?
d) Why it is simpler to eradicate the products from the catalyst?
Question 2: Draw a catalytic cycle for phosphine-rhodium-catalyzed hydroformylation. The catalyst precursor is:
H(CO)Rh(PPh3)3
Question 3: Describe why increasing the concentration of phosphine in the phosphine-rhodium cycle exhibits the reaction rate, however as well raises the linear or branched product ratio.
Question 4: Rate of Rh/HI-catalyzed carbonylation of 2-propanol to give a mixture of butanoic and 2-methylpropanoic acids is actually a little faster than that for carbonylation of ethanol and up to seven times more fast than that for 1-propanol. If OA is still the rds in the pathway, what can be said regarding the method of that step when 2-propanol is the starting material?