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How primary alcohol are prepared from hydroboration oxidation reaction. Explain with mechanism

How primary alcohol are prepared from hydroboration oxidation reaction. Explain with mechanism

Grade:12th pass

4 Answers

Saurabh Koranglekar
askIITians Faculty 10335 Points
4 years ago
Dear student

Please find the link below

Chem.libretexts.org/Bookshelves/Organic_Chemistry/Supplemental_Modules_(Organic_Chemistry)/Alcohols/Synthesis_of_Alcohols/Alcohols_from_Hydroboration-Oxidation_of_Alkenes

Regards
Arun
25750 Points
4 years ago
Hydroboration-Oxidation is a two step pathway used to produce alcohols. The reaction proceeds in an Anti-Markovnikov manner, where the hydrogen (from BH3 or BHR2) attaches to the more substituted carbon and the boron attaches to the least substituted carbon in the alkene bouble bond
Vikas TU
14149 Points
4 years ago
Dear student 
This step begins with the addition of borane in the form of BH3 to the given double bond. This leads to the transfer of a hydrogen atom to the carbon atom that is adjacent to the carbon bonded with the boron atom. The hydroboration step described is now repeated twice, giving three alkenes that are attached to the boron atom from the initial BH3.
The compound that results from the addition of three alkenes to the borane is referred to as trialkyl borane. This trialkyl borane is now treated with a base (or water) and hydrogen peroxide. Thus, the boron-carbon bonds are replaced with carbon-OH group bonds. The conversion of boron into boric acid is also observed. 1-hexene can be converted into 1-hexanol
It can be noted that the BH2 continues adding itself to alkene groups until all the hydrogen atoms are transferred to the alkenes and there are no more hydrogens bonded with the boron atom. Therefore, a single mole of hydroborane can undergo reaction with alkenes in a quantity of three moles.
Now that the trialkyl borane is generated, the second step of the hydroboration process can be executed. In this step, the boron atom comes under attack by the hydroperoxide ion which is nucleophilic in nature. Now, the R group is rearranged along with its bond pair of electrons to the adjacent oxygen atom.
The hydroxide ion is now removed. This process happens thrice to give a trialkyl borate as the product. This trialkyl borate is now subjected to water to yield the required neutral alcohol as a product.
The terminal alkynes can also undergo hydroboration. This proceeds in an anti-Markovnikov way as well. The less substituted carbon which is also least hindered becomes a priority target for the attack of the boron atom. To stop the reaction at the alkenyl group attached borane stage, a bulky reagent of borane must be used. If borane is used by itself, it would result in the hydroboration of both the pi bonds of the alkyne.
The oxidation step of this process begins with the oxidization of the alkyl borane into vinyl alcohol that has an alkene group as well as an OH group. This oxidation occurs due to hydroxide reactions in the basic solution. This alcohol now undergoes tautomerization to yield a stable aldehyde form.
Yashraj
908 Points
3 years ago
 the hydroboration–oxidation reaction is a two-step hydration reaction that converts an alkene into an alcohol. The process results in the syn addition of a hydrogen and a hydroxyl group where the double bond had been. ... Tetrahydrofuran (THF) is the archetypal solvent used for hydroboration.

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