Which bond is broken in the formation of ethyl ethanoate?
A good way to work out which bond is broken is to refer to the mechanism of the reaction, which shows which electrons go where and how the bonds of the acid and alcohol are broken and the ester link formed. The bond which is broken is actually the C-O one in the alcohol, so the whole O-H group is free to leave. This group combines with the hydrogen ion coming off the end of the OH group of the carboxylic acid, and that’s where the water product comes from. What you’ve got left is a molecule of what was previously ethanol, but now has one of the carbons possessing a positive charge, because it gave its bonding electrons to the oxygen beforehand. The acid part of what was formerly the ethanoic acid is negatively charged, with the oxygen which lost a hydrogen ion having too many electrons. Positive carbon, negative oxygen – bonding results, forming the C-O-C bond in ethyl ethanoate. The oxygen between the two carbons in the ester comes from the acid. The ethanol lost its oxygen when the C
