Question

Which of the following compounds is not a lewis acid?

• A. $B{F}_3$
• B. $SnC{l}_4$
• C. $R-OR$
• D. R - MgX

Answer 1

Answer: (C)

$R-OR$

A Lewis acid is, therefore, any substance, such as the H+ ion, that can accept a pair of nonbonding electrons. In other words, a Lewis acid is an electron-pair acceptor.

$B{F}_3$ is an electron-deficient molecule and has an empty $p-orbital$, so it can accept a pair of electrons, making it a Lewis acid. A Lewis acid can accept a pair of electrons from a Lewis base. The boron in $B{F}_3$ is electron-poor and has an empty orbital, so it can accept a pair of electrons, making it a Lewis acid.

$SnC{l}_4$ is a lewis acid. This is because chlorine being the more electronegative atom, pulls the shared pair of electrons towards itself, making tin electron deficient. As a result, Sn can accept electron pairs from molecules like $N{H}_3$, thereby forming a coordinate bond.

$R-OR$ are Lewis base where $R$ denotes an alkyl group.

$R-MgX$ is Lewis acid where $R$ denotes alkyl group and $X$ denote halogens.

$Hencethecorrectanswerisoption\left(C\right)$.