Geuther spent most of his academic career at the University of Jena where he discovered ethyl acetoacetate, a key compound for chemical synthesis and for the discovery of tautomerism.

The experimental work on the hydrolysis of 1,1-dichloroethane, which yielded glycol, and the chlorination of acetaldehyde giving 1,2-dichloroethane provided a good starting point for the development of the theory of the constitution of compounds with the same chemical formula, but different bond structure.

The experimental work of his and others yielded puzzling results and induced debates on the nature of ethyl acetoacetate.

It was long after the death of Geuther when Ludwig Knorr, Geuthers successor at the University of Jena, solved the riddle proving both sides right: the true nature of ethyl acetoacetate was a tautomeric equilibrium between the both suggested structures.

Geuther was planning to build a new chemical laboratory at University of Jena, but died well before the construction had started.