typical exam question
TRANSCRIPT
Typical exam question:
1) Write the overall reaction for the catalytic cycle.
2) Assign oxidation states and d-electron counts for each intermediate in the cylce.
3) Label each reaction involved in the catalytic cycle.
4) Give a plausible intermediate or mechanism for the conversion of A to B.
Water-gas shift reaction
H2O + CO CO2+H2
Fe(CO)5
CO
Fe
CO
COOC
OC
OH-
CO
Fe
CO
COC
OCO
OH
- CO2
CO / - H2
nucleophilicaddition
elimination(d b l ti )
Fe(0) d8 18e CN = 5
Fe(0) d8 18e CN = 5
CO
Fe
CO
HOC
OC
CO2
CO
Fe
COOC
OC H
H
H2O / -OH-
(decarboxylation)
electrophilicaddition
substitution
Fe(0) d8 18e CN = 5
Fe(0) d8 18e CN = 5
H2O + CO CO2+H2
[Pt(i-Pr)3]-
Water-gas shift reaction (contd.)
Suggest a plausible mechanism ?
non-dissociative
associative
CO
Co
CO
HOC
OC
-COCO
CO
CH3
CO
Co
CO
CoOC
OCCO
COCO
CO , H2
O
H
CH3 Co2(CO)8 /
O
HH2 / CO
Alkene hydroformylation (oxo process)
HCoOCOC
HCoOC
OC CO
CoOC
OC
CO
CH3
CoOC
H
COO
CO
H
CO
CoOC
OC
COO
n-butanal
-CO
H2-H2
Suggest a plausible mechanism ?
Suggest a plausible mechanism ?
COCoOC
OC
COO
-CO
addition &1,1'-insertion
Co(I) d8 16e CN = 4
CoOC
OC
CO
Co(I) d8 16e CN = 4
Suggest a plausible intermediate ?
Suggest a plausible intermediate ?
Alkene hydroformylation
(Reppe reaction)
Suggest a plausible mechanism ?
Suggest a plausible intermediate ?
O
HFe
H
OC OCO
+FeOC
OCO
Fe
CO
OC
n-butanal
H
CO / H2
COH
CH3
Fe(II) d6 16e CN = 5
Fe(0) d8 18e CN = 5
CO
Fe
COOC
OC H
H
COH
CH3
CO
Fe(0) d6 14e CN = 4
Monsanto acetic acid process
Suggest a plausible intermediate ?
Substrate is polar – non-concerted process makes more sense.
Concerted vs. SN2 mechanism.
Suggest a plausible mechanism ?
Suggest a plausible intermediate ?
Wacker oxidation
Pd(II) d8 16e CN = 4
Pd(II) d8 16e CN = 4
Pd(II) d8 14e CN = 4
Pd(II) d8 16e CN = 4
Pd(II) d8 16e CN = 4
Pd(0) d10 18e CN = 4
Pd(II) d8 16e CN = 4
+ 2e
- 2e
Alkene Hydrogenation via oxidative addition
Suggest a plausible intermediate ?
Suggest a plausible mechanism ?
Suggest a plausible intermediate ?
Heterolytic alkene hydrogenation (H2 activation)