title: Interference of H-bonding and substituent effects in nitro- and hydroxy-substituted salicylaldehydes.
abstract: Two intramolecular interactions, i.e., (1) hydrogen bond and (2) substituent effect, were analyzed and compared. For this purpose, the geometry of 4- and 5-X-substituted salicylaldehyde derivatives (X = NO(2), H or OH) was optimized by means of B3LYP/6-311 + G(d,p) and MP2/aug-cc-pVDZ methods. The results obtained allowed us to show that substituents (NO(2) or OH) in the para or meta position with respect to either OH or CHO in H-bonded systems interact more strongly than in the case of di-substituted species: 4- and 3-nitrophenol or 4- and 3-hydroxybenzaldehyde by ~31%. The substituent effect due to the intramolecular charge transfer from the para-counter substituent (NO(2)) to the proton-donating group (OH) is ~35% greater than for the interaction of para-OH with the proton-accepting group (CHO). The total energy of H-bonding for salicylaldehyde, and its derivatives, is composed of two contributions: ~80% from the energy of H-bond formation and ~20% from the energy associated with reorganization of the electron structure of the systems in question.
authors.affiliation: Faculty of Chemistry, University of Wrocław, Wrocław, Poland. anetka@elrond.chem.uni.wroc.pl
authors.forename: Aneta
authors.initials: A
authors.lastname: Jezierska-Mazzarello
authors.forename: Halina
authors.initials: H
authors.lastname: Szatyłowicz
authors.forename: Tadeusz Marek
authors.initials: TM
authors.lastname: Krygowski
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D006860:Hydrogen Bonding; D017665:Hydroxyl Radical / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009574:Nitro Compounds / Q000737:chemistry*
chemical_list: D000447:Aldehydes; D009574:Nitro Compounds; C013243:salicylaldehyde; D017665:Hydroxyl Radical