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Molecular structure and vibrational spectra of 2-trichloromethyl(ethoxycarbonyl)-1-nitroethenes and 2-trichloromethyl(ethoxycarbonyl)-1-bromo-1-nitroethenes were calculated in terms of the density functional theory (B3LYP/6-31G*). The experimental FTIR spectra of these compounds in the range from 4000 to 400 cm−1 were interpreted in detail on the basis of the calculation data. 2-Substituted 1-nitro- and 1-bromo-1-nitroethenes were assigned the structure with trans orientation of the nitro and trichloromethyl (or ethoxycarbonyl) groups, and the ethoxycarbonyl derivatives were assumed to exist in equilibrium between s-cis and s-trans conformers.

The molecular and crystal structure of N,N′-bis-(3,5-di-tert-butyl-4-hydroxybenzyl)urea has been established by single crystal X-ray diffraction and IR spectroscopy. There were also investigated intermolecular hydrogen bonds in its crystal and solutions.

A new type of macrocycle containing 2-thio-4-aminopyrimidine and 6-methyluracil moieties has been studied by IR and UV spectroscopy. The vibrational spectra, conformations and amine–imine tautomerism of the aminopyrimidine fragments have been analysed within the framework of ab initio MO theory (HF/6-31G**, MP2/6-31G**) and density functional theory (B3LYP/6-31G**). According to experimental and theoretical results, the amino form is preferred in these compounds. Both intra- and intermolecular hydrogen bonds of the type NH⋯N are present in crystals, whereas in solutions, conformational equilibria with free NH groups are also obtained.

The molecular and crystal structure and the hydrogen bonding in crystal and in solutions of N-phenyl-N-(3,5-di-tert-butyl-4-hydroxybenzyl)thiourea and N-(3,5-di-tert-butyl-4- hydroxybenzyl)thiourea were studied by single crystal X-ray diffraction and IR spectroscopy. The intermolecular interactions of these compounds are essentially different.

The reactions of 3-benzoylquinoxalin-2-one and its N(1)-alkyl derivatives with 1,2-phenylenediamines were accompanied by ring contraction as a result of the quinoxaline-benzoimidazole rearrangement giving rise to 2-benzoimidazolyl-substituted quinoxalines. The possible pathways of these reaction are discussed.

A series of conformationally heterogeneous and energetically multilevel ω-diphenylphosphoryl- and ω-diphenylthiophosphoryl-substituted aliphatic alcohols, whose molecules are capable of five-, six-, and seven-membered ring closure due to the OH...O=P or OH...S=P intramolecular hydrogen bond (IHB), was studied by IR spectroscopy and molecular mechanics. The data obtained confirm the previous assumption that the energy of IHB (E IHB) differs substantially from the difference of enthalpies of conformers with and without IHB (–ΔH ), which is experimentally determined by the temperature dependence of the intensity of IR ν(OH) absorption bands. The measured –ΔH values can be positive, zero, or negative at significant IHB effects, i.e., at high Δν(OH) and E IHB values.

A new macrocycle including pyrimidine fragments, 12,23,36-trimethyl-24,40-dioxo-15,33-dithia-2,9,13,22,26,35,38,39-octaazatetracyclo[32.3.1.110,14.122,26]tetraconta-1(38),10(39),11,13,23,34,36-heptaene, was synthesized. According to the data of IR and UV spectroscopy and HF/6-31G** quantum-chemical calculations, macrocyclic compounds of this series in crystal exist in the amino form, one NH group of which is likely to be involved in intramolecular hydrogen bond, and the other, in intermolacular hydrogen bond. The strength of the latter depends on the macroring size. In solution, the above structures are supplemented by conformers containing both intramolecularly H-bonded and free amino groups, predominantly with trans structure of the HANACIN fragment. The imino form of the aminopyrimidine moieties is hardly probable.

Esters and amides of 2,2-dichloro-3-(2-furyl)-3-hydroxypropionic acid were prepared by the reaction of furfural with dichloroacetic acid derivatives under the conditions of the Darzens condensation. The structures of the reaction products were confirmed by their1H NMR and IR spectra and chemical transformations.

Electrical and electrooptical characteristics of α-phenoxycyclohexanone, α-phenoxyacetone,p-Me-,p-Cl-,p-Br-,p-NO2-phenoxycyclohexanones, andp-NO2-phenoxyacetone in the solution in CCl4 were determined; these were utilized for the conformational analysis of the general structural fragment Ar-O-C-C=O. The presence of conformers with theac- andsp-structure at the Csp3-Csp2 bond was established in the equilibrium. The content of thesp-form increases with the increase in the polar character of the substituent at thep-position of the benzene ring. Thegauche isomer (sp-G orsp-G′) is realized along the C-O bond in it. In theac-conformers, both thegauche (ac-G) and the trans (ac-T) structures can be realized along the C-O bond.

The IR and Raman spectra and conformations of calix[4]arene, thiacalix[4]arene and their p-tert-butyl derivatives have been analysed within the framework of scaled quantum mechanics (SQM). It is shown that the introduction of four p-tert-Bu groups into the calixarene molecules influences the relative energies of their conformers and the enthalpy of the cooperative intramolecular H-bonding (DeltaH(intra)) almost negligibly. DeltaH(intra), evaluated from Iogansen's rule, amounts to approximately 26-28 kcal mol(-1) for the calixarenes and approximately 20-21 kcal mol(-1) for the thiacalixarenes, which essentially exceeds the enthalpies of non-cooperative H-bonds formed by related phenols. As a result of this strong bonding, bands of stretching, bending and torsion vibrations of an eight-membered cyclic system (OH...)4 arise, e.g., two delta(OH)4 bands are observed in the IR spectra of the most highly symmetric C4 cone conformations of calix[4]arene and thiacalix[4]arene. The "duplication" of the number of OH infrared bands is a good new indicator of cooperativity of intramolecular H-bonding of the calixarenes.

Dialkyl phosphonates bind to the C=N bond of bis(benzylideneimino)toluene, with formation of dialkyl (benzylideneimino)benzylaminobenzyl phosphonates. The complicated character of IR spectra of these compounds is connected with the possibility of formation of dimeric cyclic associates and intramolecular hydrogen bonding. Phosphinic acid reacts with bis(benzylidenimino)toluene in a 2: 1 ratio to affordN,N′-benzylidenebis(α-amino-benzytphosphonic) acid.

Interaction of ethylN,N-(p-methoxybenzal)-p-aminobenzoate with dialkyl phosphonates results in dialkyl (N-p-ethoxycarbonylphenylamino)-p-methoxybenzal phosphonates. In the resulting compounds hydrogen bonds are observed by IR spectroscopy.

1. The IR spectra of a solution of mercaptoethanol in CCl4 and in gas-phase mercaptoethanol have νXH bands for free OH and SH groups and OH...S and SH...O groups in intramolecular hydrogen bonds. This indicates a conformational multiplicity of the ME molecules. 2. A molecular mechanics calculation indicates the possibility of conformational multiplicity for mercaptoethanol. The energy of the intramolecular OH...S hydrogen bond was evaluated.

1. By the reactions of o- and p-(diphenylphosphinyl)phenols and o-(diphenylphosphinothioyl)phenol with acryloyl, methacryloyl, and 2-fluoroacryloyl chlorides the corresponding (diphenylphosphinyl)- and (diphenylphosphinothioyl)phenyl acrylates, methacrylates, and 2-fluoroacrylates were obtained. 2. The IR spectra of the compounds obtained were studied.

1. In the IR spectra of the oxygen- and sulfur-containing derivatives of 2-phospholene and 3-phospholene the stretching vibrations of the =C-H bond differ in their properties for theα- andβ-hydrogens. 2. Theα-hydrogens are more “acid,” and apparently are capable of forming weak H bonds.