Janusz Dabrowski

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.

Infra-red spectra and structure of substituted unsaturated carbonyl compounds—I: Enamino Ketones with primary amino group

The infra-red spectra of eight enamino ketones and their N-deuterated derivatives have been investigated. The spectra of individual isomeric (or tautomeric1) forms of some of these substances have been obtained at low temperatures, and the transformation of these forms into tautomeric mixtures has been observed spectroscopically at room temperature. The cis and trans structures have been assigned for the individual forms of the enamino ketones investigated. For the absorption bands in the 1470–1800 cm−1 region the introduction of the terms: “Enamino ketone bands I, II, and III” has been proposed, bands I and III being assigned for the stretching vibrations of the CC-CO system, and band II for a complex bending vibration of the NH2 group.

Infrared spectra and structure of substituted unsaturated carbonyl compounds: XII. β-Aminoacrolein

Abstract The IR spectra of β-aminoacrolein, the simplest amide vinylogue, have been studied. The solid compound has the trans configuration and this form prevails in solution in polar solvents. Of the two rotational isomers of the trans form, the s-trans seems to predominate in solution. In chloroform and other non-polar solvents, intense bands of the cis form were observed after the trans-cis equilibrium had been established. The band pattern of the cis form is very similar to that of cis-enamino ketones. The absorption bands were assigned on the basis of deuterium substitution and by comparison with previous data on alkylaminoacroleins.

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.

Symmetrically bifurcate hydrogen bonding—III (sym-o,o′ diacyl)-diphenylamines

Abstract Symmetrically bifurcate three-centre hydrogen bonding, , was found in several (sym-o,o′-diacyl)-diphenylamines, [o(RCOC6H4)]2NH.

IR spectra and structure of substituted unsaturated carbonyl compounds. X. β-alkylaminoacroleins

Abstract The ir spectra of β-alkylaminoacroleins have been studied. A frequency assignment shows that, similarly to enamino ketones 7 , the named compounds exist in three forms: (1) cis, (2) trans-s-trans and (3) trans-s-cis. A new nomenclature 7,8 based on the terminology commonly accepted for amides has been employed to describe the absorption bands of the amide vinylogues I and II. The assignments are based on frequency shifts caused by chelation and deuterium substitution.

Symmetrically bifurcate hydrogen bonding—IV : Steric requirements in symmetrically hydrogen-bonded bis(β-acylvinyl)amines and their isomers

Abstract The effect of the size and branching of alkyl substituents R1 and R2 on the formation of all possible stereoisomers of bis(β-acylvinyl)amines, [R1COCR2CH]2NH, has been investigated. IR and NMR data show that steric requirements of these substituents and resonance stabilization of the s-trans system are the main factors determining the position of the dynamic equilibrium.

Electronic spectra of α,β-unsaturated carbonyl compounds—II : An evaluation of increments characteristic of structural features of β-oxy-α,β-unsaturated ketones

Abstract By comparing UV spectra of β-alkoxy-α,β-unsaturated ketones of established steric structure, spectral constants characteristic of the cis/trans configuration change and s-cis/s-trans and O-s-cis/O-s-trans conformation changes have been evaluated. These are: Δλcistrans = 0, Δλs-ciss-trans = 8 nm and ΔλO-s-transO-s-cis = 6 nm. A comparison of cis-s-cis enol ethers with the parent enols yielded the increment for the intramolecular (“chelating”) H-bond, Δγchel = 24 nm. The methanol-induced bathochromic shift has been found to depend strongly on s-cis/s-trans isomerism. The substituent increments have been shown to be dependent on the degree of substitution in the reference molecule. The results obtained have been summarized in a set of spectral increments complementing the basic system of Woodward and the Fiesers.

Symmetrically-branched three-centre hydrogen bond: II. Potential energy surface for the proton motion

Abstract The potential energy surface for the proton motion was calculated within a simple six-electron model of the three-centre branched hydrogen bond. A similar model for an isolated N-H bond has also been considered. The calculations were performed by using a modified version of the CNDO method. According to these calculations, only one minimum in the potential energy surface for the proton motion has been observed. The results for the hydrogen bonded N-H group were compared with those obtained for the isolated N-H bond. It follows that the formation of the hydrogen bond increases the N-H distance by 0.06A whereas the corresponding stretching force constant is considerably lowered.