Beitr?ge zur quantitativen Bestimmung der Selens?ure

Ohne Zusammenfassung     

Erkennung eines Zusatzes von Alkohol in aetherischen Oelen

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Ueber die quantitative Ermittelung des im Wasser gel?sten Stickstoff- und Sauerstoffgases

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Effects of Aromatic Fluorine Substitution on Protonated Neurotransmitters: The Case of 2‐Phenylethylamine

Fluorination of pharmaceutical compounds is a common tool to modulate their physiochemical properties. We determine the effects of site‐specific aromatic fluorine substitution on the geometric, energetic, vibrational, and electronic properties of the protonated neurotransmitter 2‐phenylethylamine (xF‐H⁺PEA, x=ortho, meta, para) by infrared multiphoton photodissociation (IRMPD) in the fingerprint range (600–1750 cm^?1) and quantum chemical calculations at the B3LYP‐D3/aug‐cc‐pVTZ level. The IRMPD spectra of all ions are assigned to their folded gauche conformers stabilized by intramolecular NH⁺???π hydrogen bonds (H‐bonds) between the protonated amino group and the aromatic ring. H→F substitution reduces the symmetry and allows for additional NH⁺???F interactions in oF‐H⁺PEA, leading to three distinct gauche conformers. In comparison to oF‐H⁺PEA, the fluorination effects on the energy landscape (energy ordering and isomerization barriers) in pF‐H⁺PEA and mF‐H⁺PEA with one and two gauche conformers are less pronounced. The strengths of the intramolecular NH⁺???F and NH⁺???π bonds are analyzed by the noncovalent interaction (NCI) method.