Problem 5
Outline the catalytic processes involved in the manufacture of acetic acid (Monsanto process) and acetic anhydride (Tennessce-Eastman process).
Problem 6
(a) Of the following alkenes, which are prochiral: \(\mathrm{PhHC}=\mathrm{CHPh}, \mathrm{PhMeC}=\mathrm{CHPh}, \mathrm{H}_{2} \mathrm{C}=\mathrm{CHPh}\) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{C}\left(\mathrm{CO}_{2} \mathrm{H}\right)(\mathrm{NHC}(\mathrm{O}) \mathrm{Me}) ?\) (b) If an asymmetric hydrogenation procecds with \(85 \%\) ee favouring the \(R\) -enantiomer, what is the percentage of each enantiomer formed?
Problem 9
(a) The hydrogenation of propene is catalysed by \(\mathrm{RhCl}\left(\mathrm{PPh}_{3}\right)_{3}\) or \(\mathrm{HRh}(\mathrm{CO})\left(\mathrm{PPh}_{3}\right)_{3}\). Outline the mechanisms by which these reactions occur, indicating clearly what the active catalyst is in each case. (b) \(\mathrm{HRuCl}\left(\mathrm{PPh}_{3}\right)_{3}\) is a very active catalyst for the hydrogenation of alkenes. However, at high catalyst concentrations and in the absence of sufficient \(\mathrm{H}_{2}\) orthometallation of the catalyst may accompany alkene hydrogenation. Write a reaction scheme to illustrate this process, and comment on its effect on the activity of the catalyst.
Problem 14
Describe briefly why a clean nickel surface (fcc structure) should not be regarded as comprising a perfect closepacked array of atoms, Indicate the arrangements of atoms that an adsorbate might encounter on the surface, and suggest possible modes of attachment for CO.
Problem 15
(a) What advantages are there to using Rh supported on \(\gamma-\mathrm{Al}_{2} \mathrm{O}_{3}\) as a catalyst rather than the bulk metal? (b) In a catalytic converter, why is a combination of platinum-group metals used?
Problem 17
(a) Outline how the gaseous reaction between \(\mathrm{N}_{2}\) and \(\mathrm{II}_{2}\) proceeds in the preschee of a hcterogencous catalyst, and state why a catalyst is needed for the commercial production of \(\mathrm{NH}_{3}\) (b) Suggest why \(\mathrm{V}\) and \(\mathrm{Pt}\) are poor catalysts for the reaction between \(\mathrm{N}_{2}\) and \(\mathrm{H}_{2},\) and give a possible reason why Os (although it is a good catalyst) is not used commercially.
Problem 20
Give a brief discussion of the use of heterogeneous catalysis in selected industrial manufacturing processes.
Problem 21
Comment on each of the following: (a) Zeolite \(5 \mathrm{A}\) (effective pore size \(430 \mathrm{pm}\) ) is used to separate a range of \(n\) - and \(i\) so-alkanes. (b) Zeolite \(Z S M-5\) catalyses the isomerization of \(1,3-\) to \(1,4-\mathrm{Me}_{2} \mathrm{C}_{6} \mathrm{H}_{4}\) (i.e. \(m-\) to \(p\) -xylene), and the conversion of \(\mathrm{C}_{6} \mathrm{H}_{6}\) to \(\mathrm{E} \mathrm{tC}_{6} \mathrm{H}_{5}\)
Problem 25
The catalyst \(\left[\mathrm{Rh}\left(\mathrm{Ph}_{2} \mathrm{PCH}_{2} \mathrm{CH}_{2} \mathrm{PPh}_{2}\right)\right]^{+}\) can be prepared by the reaction of \(\left[\mathrm{Rh}(\mathrm{nbd})\left(\mathrm{Ph}_{2} \mathrm{PCH}_{2} \mathrm{CH}_{2} \mathrm{PPh}_{2}\right)\right]\) \((n b d-27.38)\) with two equivalents of \(H_{2} .\) In coordinating solvents, \(\left[\mathrm{Rh}\left(\mathrm{Ph}_{2} \mathrm{PCH}_{2} \mathrm{CH}_{2} \mathrm{PPh}_{2}\right)\right]^{+},\) in the form of a solvated complex \(\left[\mathrm{Rh}\left(\mathrm{Ph}_{2} \mathrm{PCH}_{2} \mathrm{CH}_{2} \mathrm{PPh}_{2}\right)(\operatorname{solv})_{2}\right]^{\prime}\) catalyses the hydrogenation of \(\mathrm{RCH}=\mathrm{CH}_{2}\) (a) Draw the structure of \(\left[\mathrm{Rh}(\mathrm{nbd})\left(\mathrm{Ph}_{2} \mathrm{PCH}_{2} \mathrm{CH}_{2} \mathrm{PPh}_{2}\right)\right]^{+}\) and suggest what happens when this complex reacts with \(\mathrm{H}_{2}\) (b) Draw the structure of \(\left[\mathrm{Rh}\left(\mathrm{Ph}_{2} \mathrm{PCH}_{2} \mathrm{CH}_{2} \mathrm{PPh}_{2}\right)(\mathrm{solv})_{2}\right]^{+},\) paying attention to the expected coordination environment of the Rh atom. (c) Given that the first step in the mechanism is the substitution of one solvent molecule for the alkene, draw a catalytic cycle that accounts for the conversion of \(\mathrm{RCH}=\mathrm{CH}_{2}\) to \(\mathrm{RCH}_{2} \mathrm{CH}_{3}\). Include a structure for cach intermediate complex and give the clectron count at the Rh centre in each complex.
