Correlations of AM1 and PM3 theoretical data, 13C-NMR substituent chemical shifts (13C-SCS) and IR carbonyl group wave numbers ν(C3═O) were studied using dual substituent parameter (DSP) models for ...5-substituted indole-2,3-diones. For the C7 atom a reverse substituent effect attributed to extended π-polarization was observed. On the other hand, the DSP approaches for the C3 atom showed normal substituent effects with some contribution of reverse effect supported strongly by 13C-SCS correlations. In the ν(C3═O) and p(C3═O) DSP correlations the field effect contribution predominates over the resonance effect, which justifies the using of earlier suggested vibrational coupling (V-C) model for 5- and 6-substituted indole-2,3-diones.
1
H,
13
C, and
15
N NMR chemical shifts have been measured for 2-aminopyridine
N
-oxide (
1
), its eleven derivatives (
2
–
10
,
13
,
14
), and 3-Cl and 3-Br substituted 4-nitropyridine
N
-oxides (
...11
,
12
). δ(
15
N) of pyridine ring nitrogen in 2-acetylaminopyridine
N
-oxides are 5.9–11.5 ppm deshielded from those in 2-aminopyridine
N
-oxides. When amino and acetylamino substituents are in 4-position, δ(
15
N) of ring nitrogen is 21.3 ppm deshielded in the acetylated derivative. The strong resonance interaction between 2-amino and 5-nitro groups reflects in the decrease of amino nitrogen shielding about 5.3–17.9 ppm. Also,
1
H and
13
C NMR spectral data are in agreement with
15
N NMR results reflected as deshielded amino protons and carbons C-2 and C-5. The pyridine nitrogen chemical shift in all amino- and acetylamino derivatives vary between −101.2 and −126.7 ppm, which has been connected with the tautomeric balance in our earlier studies.
1
H and
13
C NMR chemical shifts have been determined and assigned based on PFG
1
H,
13
C HMQC, and HMBC experiments for 3-(4′-X-benzyl)-4-chromenones (
Ia
, X = CN and
Ib
, X = NO
2
), ...3-(4′-X-benzyl)-4-thiochromenones (
IIa
, X = Cl and
IIb
, X = Br), (
E
)-3-(4′-X-benzylidene)-4-chromanones (
IIIa
–
IIIe
, X = OCH
3
, CH
3
, Cl, N(CH
3
)
2
, Br), (
Z
)-3-(4′-X-benzylidene)4-thiochromanones (
IVa
–
IVd
, X = Cl, Br, F, OCH
3
), 2-benzyl-1,2,3,4-tetrahydro-1-naphthol (
V
), 2-benzyl- and (
E
)-2-benzylidene-1-tetralones (
VI
and
VII
), and (
E
)-2-benzylidene-1-benzosuberol (
VIII
). The crystal structures have been determined for the following seven compounds: derivatives of 4-chromanones (
IIIa
–
IIId
), 1-tetrahydronaphtol (
V
), and 1-tetralones (
VI
and
VII
). The molecular features and intermolecular interactions in crystal state have been discussed.
Lithium, sodium and potassium derivatives of (benzo)salicylaldehydes have been prepared and characterized by
1H and
13C NMR in order to see how the metal cation and benzoannulation affect spectral ...parameters. There is no qualitative effect of the alkali metal atom in the compounds studied (from this point of view salicylaldehydes remind β-diketones). On the other hand,
1H chemical shifts of the hydroxyl and formyl protons and
13C chemical shifts of C2 (bearing OX, X
=
H, Li, Na or K) and of that the formyl carbon show the most significant variations being the best indicators of aromatic character of the six-membered quasi-ring of salicylaldehyde. In contrast, C1 (bearing formyl moiety) is almost inert to the alkali cations but reflects nicely the position of benzoannulation.
Background, aims, and scope Since toxaphene (polychlorocamphene, polychloropinene, or strobane) mixtures were applied for massive insecticide use in the 1960s to replace the use of DDT, some of their ...congeners have been found at high latitudes far away from the usage areas. Especially polychlorinated bornanes have demonstrated dominating congeners transported by air up to the Arctic areas. Environmental fate modeling has been applied to monitor this phenomenon using parallel zones of atmosphere around the globe as interconnected environments. These zones, shown in many meteorological maps, however, may not be the best way to configure atmospheric transport in air trajectories. The latter could also be covered by connecting a chain of simple model boxes. We aim to study this alternative approach by modeling the trajectory chain using catchment boxes of our FATEMOD model. Polychlorobornanes analyzed in biota of the Barents Sea offered one case to study this modeling alternative, while toxaphene has been and partly still is used massively at southern East Europe and around rivers flowing to the Aral Sea. Materials and methods Pure model substances of three polychlorobornanes (toxaphene congeners P26, P50, and P62) were synthesized, their environmentally important thermal properties measured by differential scanning calorimetry, as evaluated from literature data, and their temperature dependences estimated by the QSPR programs VPLEST, WATSOLU, and TDLKOW. The evaluated property parameters were used to model their atmospheric long-range transport from toxaphene heavy usage areas in Ukraine and Aral/SyrDarja/AmuDarja region areas, through East Europe and Northern Norway (Finnmarken) to the Barents Sea. The time period used for the emission model was June 1997. Usual weather conditions in June were applied in the model, which was constructed by chaining FATEMOD model boxes of the catchment's areas along assumed maximal air flow trajectories. Analysis of the three chlorobornanes in toxaphene mixtures function as a basis for the estimates of emission levels caused by its usage. High estimate (A) was taken from contents in a Western product chlorocamphene and low estimate (B) from mean contents in Russian polychloroterpene products to achieve modeled water concentrations. Bioaccumulation to analyzed lipid of aquatic biota at the target region was estimated by using statistical calculation for persistent organic pollutants in literature. Results The results from model runs A and B (high and low emission estimate) for levels in sea biota were compared to analysis results of samples taken in August 1997 at Barents Sea. The model results (ng g⁻¹ lw): 4-95 in lipid of planktovores and 7-150 in lipid of piscivores, were in fair agreement with the analysis results from August 1997: 21-31 in Themisto libellula (chatka), 26-42 in Boreocadus saida (Polar cod), and 5-27 in Gadus morhua (cod) liver. Discussion The modeling results indicate that the application of chained simple multimedia catchment boxes on predicted trajectory is a useful method for estimation of volatile airborne persistent chemical exposures to biota in remote areas. For hazard assessment of these pollutants, their properties, especially temperature dependences, must be estimated by a reasonable accuracy. That can be achieved by using measurements in laboratory with pure model compounds and estimation of properties by thermodynamic QSPR methods. The property parameters can be validated by comparing their values at an environmental temperature range with measured or QSPR-estimated values derived by independent methods. The chained box method used for long-range air transport modeling can be more suitable than global parallel zones modeling used earlier, provided that the main airflow trajectories and properties of transported pollutants are predictable enough. Conclusions Long-range air transport modeling of persistent, especially photo-resistant organic compounds using a chain of joint simple boxes of catchment's environments is a feasible method to predict concentrations of pollutants at the target area. This is justified from model results compared with analytical measurements in Barents Sea biota in August 1997: three of six modeled values were high and the other three low compared to the analysis results. The order of magnitude level was similar in both modeled (planktovore and piscivore) and observed (chatka and polar cod) values of lipid samples. The obtained results were too limited to firm validation but are sufficient to justify feasibility of the method, which prompts one to perform more studies on this modeling system. Recommendations and perspectives For assessment of the risk of environmental damages, chemical fate determination is an essential tool for chemical control, e.g., for EU following the REACH rules. The present conclusion of applicability of the chained single-box multimedia modeling can be validated by further studies using analyses of emissions and target biota in various other cases. To achieve useful results, fate models built with databases having automatic steps for most calculations and outputs accessible to all chemical control professionals are essential. Our FATEMOD program catchments at environments and compound properties listed in the database represent a feasible tool for local, regional, and, according our present test results, for global exposure predictions. As an extended use of model, emission estimates can be achieved by reversed modeling from analysis results of samples corresponding to the target area.
Two quantum chemical models have been derived for the prediction of
13C NMR chemical shifts of novel PCB acids obtained from PCBs by catalytic carbonylation.
13C isotropic shielding constants were ...calculated employing the GIAO (gauge-independent atomic orbital) method with density functional theory (DFT). The best results were obtained by cluster calculations, which took the solvent effects into account properly. In this approach, a solvent molecule (acetone) was attached by a hydrogen bond to every hydrogen atom present in a PCB acid, and the geometry of the molecular cluster was optimized employing the AM1 method. For 158 chemical shifts, the cross-validated standard error was 2.8
ppm and the cross-validated correlation coefficient was 0.94.
In contradiction with earlier reports
1H,
13C and
15N NMR spectra show that β-2′-pyridylaminocrotonoyl-2-pyridylamide is the only form present in chloroform solution. According to the X-ray data the ...same tautomer exists also in the crystal state. The studied amide has a dimeric form where the monomer molecules are held together by two intermolecular hydrogen bonds. The NMR spectral data show that there is also an intramolecular hydrogen bond in each monomer subunit. The dilution experiments and variable-temperature
1H NMR runs show that β-2′-pyridylaminocrotonoyl-2-pyridylamide tends to form the dimers also in chloroform solution at higher concentrations. The ESI-TOF MS measurements at different concentrations confirm that there is a dimerization process taking place in solution. The calculated energetic effect of dimerization of β-2′-pyridylaminocrotonoyl-2-pyridylamide in vacuum is equal to −34 kJ/mol (exothermic process). X-ray analysis shows that the molecule in crystalline state is not planar. The ab initio RHF/6-31G** calculations approximate well the X-ray determined molecular geometry of β-2′-pyridylaminocrotonoyl-2-pyridyl-amide.
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