Nancy decided to alter the amounts of starting materials employed in the hydrobo

Question

Nancy decided to alter the amounts of starting materials employed in the hydroboration-oxidation of 1-octene in order to improve her yield of 1-octanol. She used 1.57 ml of 1-octene, 3 ml of the borane-THF solution, and .9 ml of 30% hydrogen peroxide in her procedure. Appropriately larger amounts of solvent and sodium hydroxide were also used. Nancy was surprised to find that her gas chromatogram of the product mixture contained more residual 1-octene and more trialkylborane than was observed by the other students in her lab. Explain.

Explanation / Answer

First of all 1.57 ml of 1-octene needs theoretical quantity of around 4.5 mL of BH3-THF. First of all that quantity is less so nancy got unreacted 1-octene remains in the mixture.

Next is, amount of 0.9 mL of 30% H2O2 is very less. Theoretically, around 3mL of H2O2 is needed for effective hydroboration. But due to the low amound of hydrogen peroxide, the reaction stops in the trialkyl borane stage itself. For better oxidation of trialkyl borane to 1-octanol, amound of hydrogen peroxide is must. Due to this low amount of hydrogen peroxide, nancy got more amount of trialkylborane.

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