Complex sentence: It is more sensitive to subtle steric differences than Sia2BH, because the rigid hetereocyclic substituents prevent internal rotation to relieve steric hindrance in the transition state.In addition, because 9-BBN is sensitive to electronic factors, it is more reactive towards alkenes than alkynes.
Split into simpler sentences: It is more sensitive to subtle steric differences than Sia 2 BH, because the rigid hetereocyclic substituents prevent internal rotation to relieve steric hindrance in the transition state.In addition. Reflecting its greater sensitivity to electronic factors, 9-BBN is more reactive towards alkenes than alkynes.