Question

In detail, write out the Monsanto acetic acid catalytic cycle using (RhL;(CO)2] as the precatalyst Label all steps in the cycle and give the oxidation state of the metal in each intermediate. Identify the rate-determining step of the catalytic cycle Alkyl ligands are typically very strong anionic 6-donors with no T-acceptor ability One of the most common reactions of alkyls is the B-hydride elimination reaction Describe the B-hydride elimination reaction in general terms. Illustrate your answer with relevant drawings using the metal-propyl bond

Answer 1

Ans. Mosanto acetic acid synthesis is a majou process for commercial production of aorta acid from methanol. The methanol is generate from synthesis gas" (co/H2 mixture is this methanol is converted into acetic acid in presence of Rh-catalyse. [Rh (Co), IT- Catalytic cycle :- It begins with oxidative addition of Me I. (produced as a result of interaction between MeoH and the catalyst) to [Rh (Co), Iz] : Co-ordination followed by insertion of co leads to 18-electecon acue complex which generates aceceye iodide and the catalyse through eueductive elimination. HI - & Im Inco to Oguidative addition - A Reductive eliminating I I a II I HO ACH₃ - I 'I a I un II uco. I e IV CH₂ Ľ CH₂-OH YHL e -H Insertion co-ordination. 1 .In IT Phuico. CH₂

The reaction is firest order with respect to MeI and Crn(co), J2] . So, the Oxidative addition of Me I is pecoposed to bel rate determining step. Rate = k [etlz-I]; k= nate constant. •ß-hydride elimination : Elimination reaction generally involves cleavage of a o-bond and a t-bonde formation. But the transition metal complexes participate in a version of elimination reaction where the bond at B-position with respect to the metal- alrye bond is broken. The bond (ie metal - alkye bond is polarized towards the c-atom and promotes elimination of hydride ion from ß-position. Such cuactions are benown as ſo-hydride elimination. ß-hydride wide e M Haride m - TH Ya e It i'm + Am H. ACH eliminatim I 1 W H elimination t hat can • O.S. of Metal does not Change. Total electern count Increases by 2.