Final answer:
Hydroboration is a true concerted process where borane adds to the alkene in a single step, with the boron atom adding to the less substituted carbon.
Step-by-step explanation:
The question asks whether hydroboration involves the addition of borane to the alkene in a concerted step. The answer to this question is true. In the hydroboration process, a borane (BH3 or B2H6 in the common diborane form) adds to an alkene. This addition is concerted, meaning that the formation of the bond to boron and the migration of the π electrons to form the B-C bond occur simultaneously in a single step. As such, the boron atom adds to the less substituted carbon (following Markovnikov's rule), and this defines the regiochemistry of the reaction. Hydroboration is followed by oxidation to give alcohols directly. Therefore, the reaction is a two-step process - hydroboration followed by oxidation - but the hydroboration step itself is a concerted process.