Question

Write equations showing the Lewis acid-base reaction that takes place when:
(a) Methanol $(C{H_3}OH)$ reacts with $B{F_3}$ .
(b) Chloromethane $(C{H_3}Cl)$ reacts with $AlC{l_3}$ .
(c) Dimethyl ether $(C{H_3}OC{H_3})$ reacts with $B{F_3}$ .

Answer 1

To solve this question, we must first understand some basic concepts about Lewis acid-base reactions. Then we need to assess the key points and mechanism to write the correct equations and then only we can conclude the correct answer.

Complete solution:
Before we move forward with the solution of this given question, let us first understand some basic concepts about Lewis acid-base reactions:
Lewis Acids are the chemical species which have empty orbitals and are able to accept electron pairs from Lewis bases. This term was classically used to describe chemical species with a trigonal planar structure and an empty p-orbital.
Lewis bases are the chemical species having a highly localized HOMO (The Highest Occupied Molecular Orbital). These chemical species have the ability to donate an electron pair to a given Lewis acid in order to form a product.
So now, let’s move towards writing the equations:
Step 1: In this step we will write the equation when, Methanol $(C{H_3}OH)$ reacts with $B{F_3}$ :
$C{H_3}OH(base)\,\, + \,\,B{F_3}(acid)\,\, \rightleftarrows \,\,C{H_3}{O^ + }(H){B^ - }{F_3}$
Step 2: In this step we will write the equation when, Chloromethane $(C{H_3}Cl)$ reacts with $AlC{l_3}$ :
$C{H_3}Cl\,\,(base)\,\, + \,\,AlC{l_3}(acid)\,\, \to \,\,C{H_3}^ + \,\, + \,\,AlC{l_4}^ -$
Step 3: In this step we will write the equation when, Dimethyl ether $(C{H_3}OC{H_3})$ reacts with $B{F_3}$ :
$C{H_3}OC{H_3}(base)\,\, + \,\,B{F_3}(acid)\,\, \to \,\,C{H_3}{O^ + }(C{H_3})({B}{F_3})$
And hence, we have written all the required equations of reactions by Lewis Acid-Base Reaction.

Note: Hydrochloric acid cannot be classified as a Lewis acid since it cannot accept an electron pair. However, this compound dissociates into its constituent ions, liberating ${H^ + }$ ions. Due to its inability to accept electron pairs, hydrochloric acid is often referred to as a classical acid rather than a Lewis acid. Also, $HCl$ does not form any adducts when reacted with Lewis bases.