Question

11. Write a short note on hydroboration.
Hydroboration reaction is the addition of
diborane to alkenes and alkynes in ether
to fom trialkyl borane. The reaction is anti
Markonikoff's addition.
BH;-H+RCH=CH2 ->R-CH-CH2-BH,
RCH=CH > (RCH, CH)
RCH=CH,
(RCH, CH,B
Trialkyl borane​

Answer 1

Explanation:

The simplest borane, BH3 , exists as the dimer, B2H6 , or in complexed form with certain ethers or sulfides:

Any of these BH3 compounds adds readily to most alkenes at room temperature or lower temperatures. The reactions usually are carried out in ether solvents, although hydrocarbon solvents can be used with the borane-dimethyl sulfide complex. When diborane is the reagent, it can be generated either in situ or externally through the reaction of boron trifluoride with sodium borohydride:

3Na⊕B⊖H4+4BF3→2B2H6+3Na⊕B⊖F4(11.6.1)