Tuesday, May 15, 2018

organic chemistry - What is the mechanism of trialkylborane oxidation with hydroperoxide?


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This is the mechanism of trialkylborane. In this mechanism I can't understand why should the -OH group leave and the -R group enter in its place to form borate ester. Can someone please explain me that step?



Answer



One aspect is the release of the stable anion OHX.



Another aspect is that BO bonds are much stronger than BC bonds because the empty p-orbital of boron overlaps with one p-orbital with a lone electron pair of oxygen.


BC D298=448±29 kJ mol1


BO D298=809 kJ mol1


values taken from “Bond Dissociation Energies”, in CRC Handbook of Chemistry and Physics, 90th Edition (CD-ROM Version 2010), David R. Lide, ed., CRC Press/Taylor and Francis, Boca Raton, FL.


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