HYDRBORATION OF 1-methylcyclopentene

MECHANISM FOR REACTION OF ALKENES WITH BH₃

Step 1: 

A concerted reaction. The p electrons act as the nucleophile with the electrophilic B and the H is transferred to the C with syn stereochemistry .

Step 2: 

First step repeats twice more so that all of the B-H bonds react with C=C

Step 3: 

Peroxide ion reacts as the nucleophile with the electrophilic B atom.

Step 4: 

Migration of C-B bond to form a C-O bond and displace hydroxide. Stereochemistry of C center is retained.

Step 5: 

Attack of hydroxide as a nucleophile with the electrophilic B displacing the alkoxide.

Step 6: 

An acid / base reaction to form the alcohol.