The problem of isomerism

OLIMPIA LOMBARDI; SEBASTIAN FORTIN

Buenos Aires

Congreso; 24th International Symposium of the ISPC; 2021

International Society for the Philosophy of Chemistry (ISPC) y CONICET

The problem of isomerism can be expressed bythe following question: Can quantum mechanics account for the existence ofisomers? The difficulty for a positive answer is that, when a molecule isdescribed exclusively in quantum terms, the description cannot distinguishbetween different isomers: since they are quantum systemswith the same number and types of elements, isomers are described by the sameCoulombian Hamiltonian. The strategy in chemistry is to appeal to effectiveHamiltonians, obtained by means of the Born-Oppenheimer approximation, whichembody the structure of the each particular isomer. In this talk we willargue that, although the problem of isomerism can be conceived as a case of theproblem of symmetry (Can quantum mechanics account for the existence of certainmolecular asymmetries?), it cannot solved as other cases of asymmetry, bymerely assuming an externally induced symmetry breaking. In particular, thesymmetric wavefunction of the molecule cannot be reconstructed as asuperposition of asymmetric wavefunctions corresponding to the differentisomers.