Textbook Question
What is the major product of the reaction of 1 mol of propyne with each of the following reagents?
e. aqueous H2SO4, HgSO4
f. R2BH in THF followed by H2O2/HO− /H2O
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10. Addition Reactions
Alkyne Hydroboration
Multiple Choice
Predict the major, organic product for the following reaction.
A
B
C
D
Verified step by step guidance1
Identify the reaction type: The reaction involves hydroboration-oxidation of an alkyne. This is a two-step process where the alkyne is first treated with borane (BH3) and then oxidized with hydrogen peroxide (H2O2) in the presence of sodium hydroxide (NaOH).
Understand the regioselectivity: Hydroboration-oxidation of alkynes typically leads to anti-Markovnikov addition, where the boron adds to the less substituted carbon of the alkyne, resulting in an enol that tautomerizes to a carbonyl compound.
Predict the intermediate: The initial addition of BH3 to the terminal alkyne will result in the formation of a vinyl borane intermediate. This intermediate will have the boron atom attached to the less substituted carbon of the alkyne.
Perform the oxidation step: The vinyl borane intermediate is then oxidized by H2O2 in the presence of NaOH, converting the boron group into a hydroxyl group. This results in the formation of an enol.
Consider tautomerization: The enol formed in the previous step will undergo tautomerization to form the more stable keto form, which is an aldehyde in this case. This is the major organic product of the reaction.
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