Werner Mikenda

NMR spectra of nitrogen‐containing compounds. Correlations between experimental and GIAO calculated data

Correlations between experimentally determined chemical shifts (15N, 13C, 1H in CDCl3 and DMSO solutions) and GIAO‐calculated isotropic shielding constants, δexpt = a + bσcalcd, are reported that were obtained from a series of nitrogen‐containing heterocycles (5‐, 6‐, 5+6‐, 6+6‐ and 6+6+6‐membered rings). Based on HF, MP2 and B3LYP optimized geometries [6–31G(d,p) basis set], GIAO calculations were performed at the HF, BLYP, and B3LYP levels of theory [6–311++G(d,p) basis set]. The performance of theoretical NMR calculations and the resulting eligibility for routine practical use were assessed from correlation coefficients and from standard deviations of the theoretically predicted shifts. Depending on the experimental conditions and on computational levels, linear regressions between experimental and theoretical data resulted in standard deviations of about 6–12 ppm for all nitrogens, 5–8 ppm for aromatic nitrogens, 1–2 ppm for aromatic carbons and 0.1–0.15 ppm for aromatic hydrogens. Several points that influence the accuracy of theoretically predicted chemical shifts are discussed. Copyright

HYDROGEN BONDING IN 2-HYDROXYBENZOYL AND 2-HYDROXYTHIOBENZOYL COMPOUNDS : SPECTROSCOPIC CHARACTERIZATION AND SPECTROSCOPIC BOND STRENGTH SEQUENCES

SummaryA survey of IR and NMR spectroscopic data is given for 30 2-hydroxybenzoyl and 2-hydroxy-thiobenzoyl compounds, which are representative for various kinds of (thio)carbonyl groups. The data shall provide a basis for a comparison between corresponding intramolecular O-H··O and O-H··S hydrogen bonds and for the evaluation of systematic dependencies. Correlations between vOH frequencies, which are considered as the main characteristic of hydrogen bond strengths, and several other spectroscopic quantities are shown. For O-H··O type associations the bond strength sequence is acid chlorides<tertiary amides<acids≈esters<aldehydes<ketones<secondary and primary amides<(thio)carboxylates, which roughly complies with the sequences obtained for other carbonyl properties, such as oxygen-basicities or vCO frequencies; the outstanding position of tertiary amides is known to arise from steric effects. The vOH frequencies of O-H··S bonds were found to be rather similar to those of corresponding O-H··O bonds, with the exception of thioacids and thioesters, for which significantly lower frequencies have been obtained.ZusammenfassungDer Artikel enthält eine Zusammenstellung IR- und NMR-spektroskopischer Daten von 30 2-Hydroxy-(thio)benzoylverbindungen, die verschiedenste Arten von (Thio)Carbonyl-gruppen repräsentieren. Die Daten sollen als Grundlage für einen Vergleich zwischen einander entsprechenden intramolekularen O-H··O und O-H··S Wasserstoffbrückenbindungen, sowie zur Ermittlung systematischer Zusammenhänge dienen. Korrelationen zwischen vOH-Frequenzen, die als wesentliches Kriterium zur Charakterisierung der Bindungsstärken herangezogen werden, und verschiedenen anderen spektroskopischen Daten werden gezeigt. Bei den Wasserstoffbrückenbindungen des Typs O-H··O nehmen die Bindungsstärken in der Reihenfolge Säurechloride<tertiäre Amide<Säuren≈Ester<Aldehyde<Ketone<sekundäre und primäre Amide<(Thio)Carboxylate zu. Dies entspricht in etwa den Sequenzen, die man auch für andere Carbonyleigenschaften erhält, wie etwa den Sauerstoffbasizitäten oder den vCO-Frequenzen. Die auffällige Sonderstellung der tertiären Amide ist auf sterische Effekte zurückzuführen. Die vOH-Frequenzen der O-H··S Wasserstoffbrückenbindungen sind denen der entsprechenden O-H··O Bindungen sehr ähnlich, ausgenommen Thiosäuren und Thioester, für die wesentlich niedrigere Frequenzen gefunden wurden.

Intramolecular O-H··N hydrogen bonds in 2-hydroxybenzaldimine compounds: Spectroscopic and quantum chemical investigations

SummarySpectroscopic and quantum chemical data that characterize the intramolecular hydrogen bonds in a series of 2-hydroxybenzaldimine compounds (Ph(OH)(CH=N-R);R=-NH(Ph), -OH,-OCH3, -NH2, -Ph, -CHO, -H, -CH3, -(CO)(CH3) are reported. Optimized geometries and vibrational spectra were calculated at HF/6-31G(d,p) and B3LYP/6-31G(d,p) levels, NMR spectra at GIAO-BLYP/6-311++G(d,p)//B3LYP/6-31G(d,p) level of theory. The sequences of calculated frequencies (v(OH) andv(CN)) and chemical shifts (δ(OH)) agree reasonably well with the corresponding experimental data. The consistency of the calculated data is demonstrated by exploiting several correlations between bond distances, vibrational frequencies, chemical shifts, and hydrogen bond energies. In particular, there exists an almost perfect relation between the hydrogen bond strengths, as measured byr(O-H) distances, and the hydrogen bond distancesr(H··N) andr(O··N) It is shown that electrostic potentials and several kinds of partial charges (Mulliken, CHELPG, MK, and NPA) of the nitrogen atoms, to a first approximation, may serve as a means for characterizing the proton acceptor capabilities of the different imino groups.ZusammenfassungIntramolekulare Wasserstoffbrückenbindungen in einer Reihe von 2-Hydroxybenzaldiminverbindungen (Ph(OH)(CH=N-R);R=-NH(Ph), -OH, -OCH3, -NH2, -Ph, -CHO,-H, -CH3, -(CO)CH3) werden mit Hilfe von spektroskopischen und quantenchemischen Daten charakterisiert und untersucht. Optimierte Geometrien und Schwingungsspektren wurden mittelsab initio (HF/6-31G(d,p)) und DFT Methoden (B3LYP/6-31G(d,p)) berechnet, NMR-Spektren mittels GIAO-BLYP/6-311++G(d,p)//B3LYP/6-31G(d,p). Die berechneten Frequenzen (v(OH) undv(CN)) sowie die chemischen Verschiebungen (δ(OH)) stimmen mit den entsprechenden experimentellen Daten gut überein. Die innere Konsistenz der Rechnungen wird durch verschiedene Korrelationen zwischen Bindungsabständen, Schwingungsfrequenzen, chemischen Verschiebungen und Wasserstoffbrückenbindungsenergien demonstriert. Insbesondere findet man eine nahezu perfekte Relation zwischen den Bindungsabständenr(O-H), die als Maß für die Stärken der Wasserstoffbrückenbindungen dienen, und den Wasserstoffbrückenbindungsabständenr(H··N) undr(O··N). Es wird gezeigt, daß die Protonenakzeptorfähigkeiten der unterschiedlichen Iminogruppen in erster Näherung durch elektrostatische Potentiale und verschiedene Partialladungen (Mulliken, CHELPG, MK und NPA) der Stickstoffatome charakterisiert werden können.

O-H ... O(S) hydrogen bonds in 2-hydroxy(thio)benzamides. Survey of spectroscopic and structural data

SummaryFrom a survey of spectroscopic and structural data of six corresponding 2-hydroxybenzamides and 2-hydroxythiobenzamides (amide, N-methylamide, N,N-dimethylamide, piperidide, morpholide, 2,6-dimethylpiperidide) remarkable similarities between O(N)-H ... O and O(N)-H ... S hydrogen-bonds are obtained, concerning both, hydrogen-bond patterns and hydrogen-bond strengths. In dilute solution the OH groups of all compounds are intramolecularly associated to the (thio)carbonyl O (S) atoms with distinctly larger hydrogen-bond strengths for primary and secondary amides [

Hydrogen bonds in α-Na3PS4·8H2O: X-ray diffraction and vibrational spectroscopic study

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Hydrogen Bonding in 2-Hydroxybenzoic, 2-Hydroxythiobenzoic, and 2-Hydroxydithiobenzoic Acid. A Structural and Spectroscopic Study #

(O-H)=2950−3020 cm−1, δ(OH)=12.16−11.99 ppm] and thioamides [

Hydrogen bonding in 2-hydroxy-benzhydrazide and 2-hydroxy-thiobenzhydrazide. Structural and spectroscopic study

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