Why B(CH3)3 cannot be Lewis Base??
It has no electrons to donate.
To determine why B(CH3)3 cannot act as a Lewis base, we need to understand the concept of Lewis acids and bases.
According to the Lewis acid-base theory, a Lewis acid is a substance that can accept a pair of electrons (an electron pair acceptor), while a Lewis base is a substance that can donate a pair of electrons (an electron pair donor).
In the case of B(CH3)3, boron is the central atom and possesses only six electrons in its valence shell. As a result, it lacks a complete octet, which means it can potentially accept a pair of electrons from a Lewis base to complete its octet.
However, B(CH3)3 cannot act as a Lewis base because it lacks an available pair of electrons to donate. Each of the three methyl (CH3) groups is already covalently bonded to the boron atom, and all electrons in these bonds are involved in sharing between the carbon and boron atoms. Therefore, none of these bonds can serve as a lone pair of electrons to act as a Lewis base.
In summary, B(CH3)3 cannot function as a Lewis base because it does not have free electrons available for donation.