Equations 5.25a–c on p. 193 show the formation of trialkylboranes from alkenes and BH₃. In the reaction of 2,3-dimethyl-2-butene with BH₃, only two equivalents of the alkene react, even with a large excess of alkene, to give a dialkylborane called disiamylborane.

Give the structure of disiamylborane, and suggest a reason that only two equivalents of alkene react.

Transcribed Image Text:

2 (CH3)2C=CHCH3 + BH3 2-methyl-2-butene "disiamylborane" (a dialkylborane)