Complete the following reaction? #"C"_2"H"_5"COOH"+"C"_2"H"_5"OH"->#

This reaction features two reactants:

• propanoic acid #"C"_2"H"_5color(darkblue)("COOH")#, a carboxylic acid containing two carbon atoms
• ethanol #"C"_2"H"_5color(darkblue)("OH")#, an alcohol also of two carbons

Carboxylic acids and alcohols combine spontaneously and reversibly [1] (typically under the presence of concentrated sulfuric acid as a catalyst [2]) to form water molecules along with esters, a group of compounds containing the #-color(darkblue)("COO")-# functional group.

In effect, the hydrogen atom on the carboxyl group combines with the hydroxyl group #-color(darkblue)("OH")# in a fashion similar to that of the reaction between acids and bases where the carboxyl group acts as the acid, while the hydroxyl group serves as the base.

The rest of the two carbon chains will then join at the #-"COO"-# functional group. Note that the carbon chain from the carboxylic acid shall appear in front of the #-"COO"-# group since the rest of the acid does not engage in the reaction. Similarly, the carbon chain from the alcohol, which is connected to the #-color(darkblue)("COO")-# group at an oxygen atom and shall be placed after the functional group.

Hence the (color-coded) overall reaction:

#color(red)("C"_2"H"_5)color(darkblue)("COO")"H"+color(green)("C"_2"H"_5)"OH" rightleftharpoons color(red)("C"_2"H"_5)color(darkblue)(color(black)()"COO"color(black)())color(green)("C"_2"H"_5)+"H"_2"O"#

References
[1] Jim Clark, "Esterfication", https://www.chemguide.co.uk/organicprops/alcohols/esterification.html

[2] Jim Clark, "Esterify", https://www.chemguide.co.uk/physical/catalysis/esterify.html