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What does hydroboration–oxidation of a terminal alkyne form?

Answer 1

Hydroboration-oxidation of a terminal alkyne forms an aldehyde.

The reaction takes place in two steps.

Step 1 is the syn addition of a B-H bond across a π bond in the alkyne.

Instead of BH₃, we use a bulky borane like disiamylborane or 9-borabicyclo[3.3.1]nonane (BBN).

This increases the proportion of addition to the less substituted carbon atom and prevents hydroboration across both π bonds,

In Step 2, the organoborane is oxidized with alkaline hydrogen peroxide.

The initial product is an enol, which rapidly tautomerizes to an aldehyde.

Hydroboration-oxidation converts a terminal alkyne into an aldehyde with the same number of carbon atoms.

For example, but-1-yne is converted to butanal.

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Answer 2

Ruby Allen

The hydroboration-oxidation of a terminal alkyne forms an enol.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.