Krystyna Kamieńska-Trela

Infrared spectra and structure of substituted unsaturated carbonyl compounds—III. Enamino ketones with tertiary amino group

Abstract Infrared spectra of several enamino ketones containing the structural unit OCCCN(Alk)2 have been examined and the band splitting occurring in a number of spectra was shown to be due to rotational isomerism. The νCO frequency of one of the conformational isomers shows an abnormal spectral behaviour moving upwards under the action of methanol and heavy water. It was established by means of solvent shift measurements that the CO and CC stretching vibrations are strongly coupled. The limitations of the applicability of B ellamy s solvent method of assigning characteristic frequencies are discussed.

Correlation of the 13C13C spin—spin coupling constants with the stretching force constants of single and double carbon—carbon bonds

Abstract Linear correlations between the spin—spin carbon—carbon coupling constants and the carbon—carbon stretching force constants for single and double bonds have been found through analysis of the available literature data. The corresponding equations are K s CC = 0.0344 J s CC +3.25 and K d CC = 0.180 J d CC −3.25 for single and double bonds respectively.

Ab initio study of the NMR shielding constants and spin-spin coupling constants in cyclopropene

SummaryAb initio calculations of parameters which characterize the NMR spectrum are presented for the cyclopropene molecule. The London orbitals CHF (or GIAO-CHF, Gauge-Independent Atomic Orbital Coupled Hartree-Fock) results for the shielding constants are in good agreement with the experimental data, accurately determined, and with otherab initio values. The calculations of the NMR spin-spin coupling constants have been performed using the Multiconfiguration Time-Dependent Hartree-Fock (MC TDHF) approach. Different basis sets and MC SCF wavefunctions were used to estimate the accuracy of the results. Good agreement is obtained with the coupling constants estimated using the available experimental data.

Electronic spectra of α,β-unsaturated carbonyl compounds—III : β-alkylamino and β-dialkylamino acrylamides

Abstract Several β-alkylamino, β-dialkylamino and β-aziridino acrylamides have been synthesized and their configuration and conformation established by means of NMR and IR. Cis and trans isomers have been isolated in some cases, and their respective π → π* absorption maxima assigned. Configuration does not appreciably affect the frequency of this transition.

Carboncarbon and carbonchalcogen spinspin coupling constants in chalcogen-substituted acetylenes

Abstract CarbonCarbon and carbonchalcogen spinspin coupling constants have been determined for chalcogen-substituted phenyl-, alkyl- and silyl-acetylenes. The changes in the CC couplings involving acetylenic sp carbons are explained in terms of the electronegativities of the substituent. The chalcogen-carbon coupling dependence on carbon hybridization previously noted for tellurium derivatives is confirmed.

Estimation of the total range of 1JCC couplings in heterocyclic compounds: pyridines and their N-oxides, the experimental and DFT studies

A very large set of one-bond spin-spin carbon carbon coupling constants, 1J(CC), has been measured for 32 variously mono- and disubstituted pyridine N-oxides and for 14 substituted pyridines. The N-oxides studied were 2-, 3- and 4-monosubstituted isomers, and a series of disubstituted compounds. A variety of substituents has been employed (CH3, COCH3, C5H4NO, CN, F, Br, Cl, OH, OCH3, NH2, N(CH3)2 and NO2), which allowed us to study substituent effects thoroughly. Good linear relationships between 1J(C3C4) in 3- and/or 4-substituted pyridine N-oxides and 1J(CipsoCortho) in benzenes and between 1J(C2C3) in 2- and/or 3-substituted pyridine N-oxides and 1J(CipsoCortho) in benzenes have been found. An analogous linear relationship has been observed between 1J(C3C4) in 3- and/or 4-substituted pyridines and 1J(CipsoCortho) in benzenes. It has been also concluded that, by analogy to 1J(CC) couplings in substituted benzenes, those in pyridines and their N-oxides are the substituent electronegativity dependent. The estimated total range covered by 1J(CC), couplings in substituted compounds varies, in the case of 1J(C2C3) couplings for example, from 25 Hz in 2-lithiopyridine N-oxide to ca. 100 Hz in 2,3-difluoropyridine N-oxide and from 18 Hz in 2-lithiopyridine to 92 Hz in 2,3-difluoropyridine. The DFT calculations have been carried out for the parent compounds and for a set of their 2-lithio, and variously substituted fluoro derivatives. The DFT data reproduced very well the experimental coupling values and revealed that the Fermi contact contribution is the dominating factor which governs the magnitude of the CC coupling across one bond.

Correlation of the 13C—13C spin—spin coupling constants with the stretching force constants of triple carbon—carbon bonds

Abstract A linear correlation between the spin—spin carbon—carbon coupling constants and the carbon—carbon stretching force constants for triple bonds has been found through analysis of the carbon-13 NMR and Raman frequency data for alkyl, silyl, germyl and stannyl acetylenes. The derived equation is K t CC = 0.0295 J t CC + 11.04.

One-bond CC spin—spin coupling constants in derivatives of benzene. Non-linearity of 1J(CC) vs substituent electronegativity☆

A set of one-bond CC coupling constants has been determined for mono- and disubstituted benzenes. Large 1J(CC) values have been found within the benzene rings bearing highly electronegative substituents such as halogens, methoxy and nitro groups and small values for those with electropositive substituents. The total range of 1J(CC) couplings observed in our work is larger than 50 Hz. These large variations of CC spin—spin couplings are interpreted in terms of Fermi-contact contributions and the redistribution of s-electrons within a CC bond under influence of substituents. Contrary to some previous findings the data obtained in the present work indicate that the relationship between 1J(CC) and the substituent electronegativity is not linear.

The linear relationship between the one-bond spin—spin coupling constants 1JCC and the product of the electronegativities Ex·Ey of substituents at the CC triple bond

Abstract The linear equation connecting the one-bond spin–spin coupling constants between carbon nuclei, J CC , and the product of the electronegativities of substituents at the CC triple bond is derived using a large number of data for variously substituted acetylenes. The equation 1 J CC = 23.23 E x · E y + 15.45 provides a means for estimation of unknown 1 J CC s and for calculation (and/or verification) of electronegativities of substituents. The equation allows one to estimate a total range of about 350 Hz for 1 J CC s. The smallest value (30 Hz) is predicted for dicaesium acetylide, Cs 2 C 2 , and the largest one for difluoroacetylene, F 2 C 2 (383 Hz). The electronegativities of tin and lead, which constituted a subject of long-lasting controversy in the literature, calculated using the equation are equal to 1.74 and 1.64, respectively.

Structural increments in UV spectra of conjugated carbonyl compounds: Part I. The α-alkyl substituted enaminones

Abstract The configuration and conformation of a series of α-alkyl-β-monoalkyl- and α-alkyl-β-dialkylamino-α,β-unsaturated carbonyl compounds have been established by means of IR and 1 H NMR spectroscopy. A comparison of the maximum absorption of the S 0 → S 1 (π,π * ) transition of derivatives of related structures yielded the spectral constants characteristic of structural features. These are: Δλ g−Z g−E = 12−17 nm (Δν s−Z s−E = −1320 to −1820 cm −1 , Δλ H-bond intra = 17−22 nm (Δν H-bond intra = −2060 to −2690 cm −1 ), Δλ Z−s−Z α-alk = 13 nm (Δν Z−s−Z α-alk = −1340 cm −1 ) and Δλ N-alk 2 NH-alk = 11 nm (Δν N-alk 2 NH-alk = −1330 cm −1 ). The applicability of the system of spectral increments described for simple enamino aldehydes, ketones and amides has been entirely corroborated.