1,2,3,6, Ex and mechanism? What would be observed if the phase-transfer catalyst
ID: 496582 • Letter: 1
Question
1,2,3,6, Ex and mechanism?
What would be observed if the phase-transfer catalyst, tetrabutylammonium bromide, was omitted? Why? It was essential to stir reaction mixture vigorously to obtain acceptable results. Why? Why was it necessary to cool the reaction mixture to room temperature prior to the extractions? Why was the reaction flask rinsed with diethyl ether? Why was the crude reaction mixture extracted twice, not once, with deionized water? Why are cis- and trans-stilbene visible on a TLC plate when viewed with short-wave ultraviolet light? Use the curved arrow notation to draw the mechanism for the formation of cis-stilbene from benzaldehyde. Use the curved-arrow notation to draw the mechanism for the formation of trans-stilbene from benzaldehydeExplanation / Answer
Solution:
1. The phase-transfer catalyst is the key player in industrial process, the terbutylammonium bromide an ia an heterogenous catalyst plays a role of phasetransfer catalyst by converting non-soluble reactant ions in organic solvent to soluble ions. If this phase transfer catalyst is removed two consequences occures in the reaction process one is of lower yield of product and another is of impure products as solvent role in distillation helps in removal of impure ions by organic solvent where phase transfer catalyst role is highest. Hence without phase transfer catalyst achieving optimal yield from the reaction scheme is non-feasible.
2. Yes, stirring is must for the highest conversion achievement as in industry process the reagents are mixed in kL quanitity which needs complete mixing using baffle (or) PFR reactors for achieving complete mixture to gain high yield product.
3. The extraction process are carried out using solvents like toluene, hexane etc.., where they are sensitive to temperature if the reaction mixture is at high temperature then results in solvent vaporization in extraction process hence the reaction mixture must always been cooled down to room temperature before carrying out extraction process.
6. The stilbene product contains hydrolytically active tri-methoxysilyl, (eSi(OCH)3), functional group which is readily soluble in water which on exposure to short-wave UV light favours the appearance the cis and trans form of the product.
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