Question

Write an equation for the reaction between each Lewis acid-base pair, showing electron flow by means of curved arrows. (a) \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2}\right)_{3} \mathrm{~B}+\mathrm{OH}^{-} \longrightarrow\) (b) \(\mathrm{CH}_{3} \mathrm{Cl}+\mathrm{AlCl}_{3} \longrightarrow\)

Short answer

Question: Show the electron flow using curved arrows in the following Lewis acid-base reactions: (a) \((\mathrm{CH}_{3} \mathrm{CH}_{2})_{3} \mathrm{B}\) with \(\mathrm{OH}^{-}\) and (b) \(\mathrm{CH}_{3} \mathrm{Cl}\) with \(\mathrm{AlCl}_{3}\). Answer: (a) \((\mathrm{CH}_{3} \mathrm{CH}_{2})_{3} \mathrm{B} + \mathrm{OH}^{-} \longrightarrow (\mathrm{CH}_{3} \mathrm{CH}_{2})_{3} \mathrm{B} - \mathrm{O} \mathrm{H}\) (b) \(\mathrm{CH}_{3} \mathrm{Cl} + \mathrm{AlCl}_{3} \longrightarrow \mathrm{CH}_{3} - \mathrm{Cl} - \mathrm{AlCl}_{3}\)

Step-by-step solution

Identify the Lewis acid and Lewis base

In this reaction, \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2}\right)_{3} \mathrm{B}\) is the Lewis acid because it can accept an electron pair and \(\mathrm{OH}^{-}\) is the Lewis base as it can donate an electron pair.

Draw the curved arrow indicating electron flow

In order to show the flow of electrons from the Lewis base to the Lewis acid, we should draw a curved arrow originating from the lone electron pair on the oxygen atom of \(\mathrm{OH}^{-}\) pointing towards the boron atom in \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2}\right)_{3} \mathrm{B}\).

Write the final equation with the curved arrow

The final equation showing the electron flow is: \( \\\ (\mathrm{CH}_{3} \mathrm{CH}_{2})_{3} \mathrm{B} + \mathrm{OH}^{-} \longrightarrow (\mathrm{CH}_{3} \mathrm{CH}_{2})_{3} \mathrm{B} - \mathrm{O} \mathrm{H}\) (b) Reaction between \(\mathrm{CH}_{3} \mathrm{Cl}\) and \(\mathrm{AlCl}_{3}\)

Identify the Lewis acid and Lewis base

In this reaction, \(\mathrm{CH}_{3} \mathrm{Cl}\) is the Lewis base as it can donate an electron pair and \(\mathrm{AlCl}_{3}\) is the Lewis acid as it can accept an electron pair.

Draw the curved arrow indicating electron flow

We will now draw the curved arrow showing the flow of electrons from the Lewis base to the Lewis acid. The arrow should originate from the lone electron pair on the chlorine atom of \(\mathrm{CH}_{3} \mathrm{Cl}\) pointing towards the aluminum atom in \(\mathrm{AlCl}_{3}\).

Write the final equation with the curved arrow

The final equation showing the electron flow is: \( \\\ \mathrm{CH}_{3} \mathrm{Cl} + \mathrm{AlCl}_{3} \longrightarrow \mathrm{CH}_{3} - \mathrm{Cl} - \mathrm{AlCl}_{3} \)