Die UV-Spektren α,β-ungesättigter Ester und ihre Beeinflussung durch Lösungsmittel und Komplexbildung

UV Spectra of α,β-Unsaturated Esters and the Influence of Solvents and Complex Formation Positions and intensities of partially overlapped π-π* and n-π* transitions in spectra of methyl and ethyl esters of acrylic, methacrylic and crotonic acid are discussed. Reproducible values were determined by graphical and mathematical band-separations. n-π* bands in gaseous methyl acrylate show vibrationally fine structures. These are compared with fine structures in the spectra of α-methylene-γ-butyrolactone and α, β-dehydrobutyrolactone. In solutions with C_ester lt; 0,1 m self-associations are negligible. The transition-displacements Δv _max due to solvent effects closely correlate with the solvent parameters of KOSOWER . These correlations allow to calculate λ_max-values at which solvents absorb strongly. Equilibrium constants K of EDA-complexes with TCNE and chloranile were determined. With a competition method K was found in the range of 0.9 to 10.3 l · mol^?1.