typical exam question

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


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 ?

Alkene hydroformylation

(Reppe reaction)


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


Substrate is polar – non-concerted process makes more sense.

Concerted vs. SN2 mechanism.

Wacker oxidation

Pd(II) d8 16e CN = 4





Pd(0) d10 18e CN = 4


+ 2e

- 2e

Alkene Hydrogenation via oxidative addition

Heterolytic alkene hydrogenation (H2 activation)

typical exam question

Documents