This image shows some kind of formula that could be converted to TeX. Storing formulas as images makes it harder to change them. TeX also helps making sure that they all use the same font and size.
A replacement has been proposed:

${\displaystyle {\ce {\underbrace {R3-\!\!{\overset {\displaystyle R1 \atop |}{\underset {| \atop \displaystyle R2}{N}}}\!\!\!\!:} _{tertiary \atop amine}}}+\underbrace {\ce {R4X}} _{{\text{halogeno-}} \atop {\text{alkane}}}{\ce {->\underbrace {\underbrace {R3-{\overset {\displaystyle R1 \atop |}{\underset {| \atop \displaystyle R2}{N+}}}\!\!-R4} _{{quaternay \atop ammonium} \atop cation}+\underbrace {X^{-}} _{halide \atop anion}} _{quaternay\ ammonium\ salt}}}}$

In your article, replace the image with:

<math chem>\ce{\underbrace{R3-\!\!\overset{\displaystyle R1 \atop | }{\underset{ | \atop \displaystyle R2}{N} }\!\!\!\!:}_{tertiary \atop amine} }
+ \underbrace\ce{R4X}_{\text{halogeno-}\atop\text{alkane} }
\ce{-> 
\underbrace{\underbrace{R3-\overset{\displaystyle R1 \atop | }{\underset{ | \atop \displaystyle R2}{N+} }\!\!-R4}_{ {quaternay \atop ammonium} \atop cation} +
\underbrace{X^-}_{halide\atop anion} }_{quaternay\ ammonium\ salt}
}</math>