Formation Of Intermolecular H-bonds Research Articles

A novel g-C3N4/TiO2 heterojunction for ultrasensitive detection of bisphenol A residues

Semiconductor heterojunction with functional integration can be used as an excellent matrix for the ultrasensitive detection of bisphenol A (BPA) with low molecular affinity. Here, a simple, low-cost and sensitive surface-enhanced Raman scattering (SERS) strategy using g-C3N4/TiO2 heterojunction as substrate was presented for detection of BPA residues in foods. The g-C3N4/TiO2 achieved specific chemisorption for target analyte by the formation of intermolecular H-bond between g-C3N4 and BPA. And, a high-efficiency carrier separation in TiO2 induced by heterostructure could be achieved for charge transfer between the substrate and molecule by a “donor-bridge-acceptor” charge-transfer mode. Due to the synergistic/collaborative contributions of two monomers in heterojunction, the SERS enhancement factor was as high as 3.77 × 107. The detection limit of BPA residues in foods (milk, juice and drinking water) was as low as 10−9 mol·L−1, far below the EU standard. The developed substrate also exhibited excellent stability and anti-interference capability.

Experiment-based Abraham model solute descriptors for 2‑[4-(dibutylamino)-2-hydroxybenzoyl]benzoic acid

ABSTRACT Abraham model solute descriptors for 2‑[4-(dibutylamino)-2-hydroxybenzoyl]benzoic acid were determined from the compound’s published solubility data in 10 organic solvents of varying polarity and hydrogen-bonding character. The calculated hydrogen-bond donor descriptor value, A = 0.548, suggests that intramolecular bond formation occurs between the hydrogen atom on the -OH functional group and one of the two lone pairs of electrons on the oxygen atom of the ketone functional group, >C=O, which would result in the formation of a six-membered hydrogen-bonded ring structure. A much larger A-solute descriptor would be expected if the hydrogen atoms of both the -OH and -COOH functional groups were free to engage in intermolecular H-bond formation with surrounding solvent molecules.

Exploring the influence of hydrogen bond donor groups on the microstructure and intermolecular interactions of amorphous solid dispersions containing diflunisal structural analogues

Drug-polymer intermolecular interactions, and H-bonds specifically, play an important role in the stabilization process of a compound in an amorphous solid dispersion (ASD). However, it is still difficult to predict whether or not interactions will form and what the strength of those interactions would be, based on the structure of drug and polymer. Therefore, in this study, structural analogues of diflunisal (DIF) were synthesized and incorporated in ASDs with poly(vinylpyrrolidone-co-vinyl acetate) (PVPVA) as a stabilizing polymer. The respective DIF derivatives contained different types and numbers of H-bond donor groups, which allowed to assess the influence of these structural differences on the phase behavior and the actual interactions formed in the ASDs. The highest possible drug loading of these derivatives in PVPVA were evaluated through film casting. Subsequently, a lower drug loading of each compound was spray dried. These spray dried ASDs were subjected to an in-depth solid-state nuclear magnetic resonance (ssNMR) study, including 1D spectroscopy and relaxometry, as well as 2D dipolar HETCOR experiments. The drug loading study revealed the highest possible loading of 50 wt% for the native DIF in PVPVA. The methoxy DIF derivative reached the second highest drug loading of 35 wt%, while methylation of the carboxyl group of DIF led to a sharp decrease in the maximum loading, to around 10 wt% only. Unexpectedly, the maximum loading increased again when both the COOH and OH groups of diflunisal were methylated in the dimethyl DIF derivative, to around 30 wt%. The ssNMR study on the spray dried ASD samples confirmed intermolecular H-bonding with PVPVA for native DIF and methoxy DIF. Studies of the proton relaxation decay times and 2D 1H–13C dipolar HETCOR experiments indicated that the ASDs with native DIF and methoxy DIF were homogenously mixed, while the ASDs containing DIF methyl ester and dimethyl DIF were phase separated at the nm level. It was established that, for these systems, the availability of the carboxyl group was imperative in the formation of intermolecular H-bonds with PVPVA and in the generation of homogenously mixed ASDs.

Tannic acid self-aggregation and adsorption onto a polyethersulfone membrane: An all-atom molecular dynamics study

Atomic scale modeling is crucial for characterizing the interactions responsible for fouling, which is a major limitation in the use of membrane filtration technologies for the recovery of polyphenols. In this work, a methodology to model a porous ultrafiltration polyethersulfone (PES) membrane is presented. Subsequently, various systems containing tannic acid (TA) molecules at different concentrations (9 or 30 g/L) were studied, with two additional systems incorporating a PES membrane, through 100 ns all-atom molecular dynamics simulations. The results show that up to 90% of the TAs are self-aggregated, associated with the formation of intermolecular H-bond and π-stacking interactions. Furthermore, adsorption of 48–67% of the TAs onto PES was observed. TA-PES H-bond and π-stacking interactions are also formed. The number of adsorbed TAs molecules over time and the evolution of the mean size of TA aggregates exhibits similar temporal trends, suggesting a parallel progression in both phenomena. Moreover, the same atoms were involved in both aggregation and adsorption, leading to the conclusion that the two phenomena compete. These results shed light on the fouling mechanism, which appears to occur through the formation of a cake layer combined with adsorptive fouling, and could support the design of new antifouling agents adapted for polyphenol filtration.

Uncovering the dependence of ESIPT behaviors and fluorescence properties of two new benzothiazole-based fluorophores on solvent polarity: A TD-DFT study

We have studied the spectral features and excited state intramolecular proton transfer (ESIPT) processes of 2-(2′,4′-dihydroxyphenyl)benzothiazole (OHBT) and 2-(2′-hydroxy-5′-chlorophenyl)benzothiazole (CHBT) using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). To consider the impact of solvent polarity and intermolecular hydrogen bond (H-bond) on the ESIPT behavior and photophysical properties, four solvents including toluene (TL), tetrahydrofuran (THF), methanol (MeOH) and dimethylsulfoxide (DMSO) were used. The simulated absorption and fluorescence wavelengths of OHBT and CHBT are well consistent with the experimental values. According to the results of structures, electron density and infrared (IR) vibrational frequencies, we found that the intramolecular H-bonds in OHBT/CHBT and OHBT-MeOH/CHBT-MeOH are strengthened in the first singlet excited state (S1), which will be benefical to the ESIPT process. The potential energy curves (PECs) verified that the ESIPT processes in OHBT/CHBT and OHBT-MeOH/CHBT-MeOH can take place much easier because of their lower energy barrier. The influences of solvent polarity on ESIPT behaviors and photophysical properties of OHBT and CHBT are summarized below. As the solvent polarity becomes stronger from TL to DMSO, the energy gaps enlarges a little, the maximum absorption and fluorescence peaks at normal form red-shift slightly, and the strengths of H-bond in S1 state become weaker, which makes the ESIPT process occur much harder. The formation of intermolecular H-bond between OHBT/CHBT and MeOH is conducive to promote the ESIPT process of OHBT/CHBT.

Highly Ordered Supramolecular Assembled Networks Tailored by Bioinspired H-Bonding Confinement for Recyclable Ion-Transport Materials

Highly Ordered Supramolecular Assembled Networks Tailored by Bioinspired H-Bonding Confinement for Recyclable Ion-Transport Materials

The role of the polar head group and aliphatic tail in the self-assembly of low molecular weight molecules in oil

The current research explores the involvement of head group size, chemical group type, and aliphatic tail in the molecular self-assembly of various oil structuring agents with similar 18-carbon aliphatic chains and hydroxyl, carbonyl, and/or carboxyl groups, in canola oil. Thermal and mechanical analyses at different molar concentrations emphasized the involvement of van der Waals (vdW) interactions and hydrogen bonds (H-bonds) in the self-assembly process. Higher contribution of vdW-forces in the self-assembly was observed when increasing molecular concentration from medium to high. The presence of H-bonds corresponding with organized crystal structures was detected in samples containing hydroxyl or carboxyl groups using nano-structure analysis. Absence of such groups led to ordered organization only at high concentrations, implying the involvement of vdW interactions. Polarized images demonstrated curved structures for long head group molecules, implying the formation of intermolecular H-bonds with neighboring molecules leading to structure curvature. The current results provide experimental indication to involvement of different forces, i.e. H-bonds and vdW, in the molecular self-assembly of oil structuring agents in oil which can be further exploit while developing new oleogel system based on low molecular weight gelators.

Interaction of exopolysaccharide produced by Lactobacillus plantarum YW11 with whey proteins and functionalities of the polymer complex.

Exopolysaccharide (EPS)-producing lactic acid bacteria have been widely used in fermented milk, but interaction between the EPS and milk proteins has not been well studied. In this study, interaction between the EPS from Lactobacillus plantarum YW11 (EPS-YW11) and whey proteins (WP), and functional properties of the EPS-YW11/WP were investigated. The results showed that EPS-YW11 tended to encase WP by ζ-potential analysis with a decrease in the surface charge of the protein fraction (from -26.00mV to 15.30mV), and an increase in the melting temperature of the protein fraction (from 76.31°Cto 84.48°C)asshownby differential scanning calorimetry. Circular dichroism spectrometry showed that the EPS could induce structural change of WP, that is, increment in the content of α-helixes and random coils, There was stronger interaction between EPS-YW11 and WP at higher temperatures (60°C,90°C)due to formation of intermolecular H-bonds and OH stretching vibration as indicated by infrared spectral analysis. A significant improvement in the texture (hardness, springiness, gumminess, resilience, cohesiveness, and chewiness) of the EPS-YW11/WP complex was also observed when compared to that of the EPS or WP alone. This was confirmed by microstructural observation of the EPS-YW11/WP complex that formed branched and porous structures, and it became more complex and stable with increased temperature treatment. Due to the strong interaction the EPS-YW11/WP exhibited improved functionality. This study identifies the potential of the EPS-YW11 to serve as a functional agent in the processing of fermented dairy products with enhanced textural stability and bioactivities such as cholesterol-lowering, antioxidant, and antibiofilm.

Influence of the Structure of Triazole Derivative Molecules on the Efficiency of Formation of Intermolecular H-Bonds

It is shown by IR spectroscopy and quantum chemical methods that H-bonds in 1,2,4-triazole, 1,2,4-triazole-thiol-5, and 3-methyl-1,2,4-triazole-thiol-5 molecules in the polycrystalline state are formed mainly by the N(1)-H bond and the N(4) atom of the neighboring molecule. In the 1,2,3-benzotriazole molecule, the H-bond is formed between the N(1)-H bond and the whole electronic π-system of the neighboring molecule. The formation enthalpies of H-bonds are estimated from the correlation relation between the shift of the N(1)-H stretching vibration in the associated (bonded) state relative to the free (non-bonded) state and the formation enthalpy of the H-bond for the molecules of triazole derivatives. For 1,2,4-triazole, 1,2,4-triazole-thiol-5, 3-methyl-1,2,4-triazole-thiol-5, and 1,2,3-benzotriazole molecules, these enthalpies are −7.67 kcal/mol, −7.42 kcal/mol, −7.1 kcal/mol, and −9.17 kcal/mol, respectively. It is inferred that the data obtained for the correlation between the negative charge on the N(4) atom and the formation enthalpy of the H-bond can be regarded an evidence that Coulomb interaction is the main contribution to the formation of intermolecular H-bonds in triazoles.

Dissolution of Ketoprofen from Poly(Ethylene Glycol) Solid Dispersions

The effect of solid dispersions (SDs) on the solubility of the nonsteroidal anti-inflammatory drug ketoprofen was determined. Ketoprofen and its SDs with poly(ethylene glycol) PEG-400, -1000, -1500, -2000, and -3000 were studied. Dissolution of ketoprofen from the SDs increased by 1.2 – 1.8 times; the dissolution rate, by 1.7 – 2.4 times. The improved release of ketoprofen from the SDs was proposed to be due to several factors such as solubilization and amorphization of the compound and formation of intermolecular H-bonds. The results could be used to develop rapidly dissolving ketoprofen solid dosage forms.

Bioallethrin degradation by photo-Fenton process in acetonitrile/water and aqueous β-cyclodextrin solutions

Bioallethrin (Bio) is an insecticide that chemically and functionally belongs to the family of the synthetic insecticides named pyrethroids. In this work the degradation of Bio is studied by the photo-Fenton and photo-Fenton-modified processes. The first one produces the complete mineralization of Bio in less than one hour of irradiation. However, due to the low solubility of Bio in water, different modifications of the photo-Fenton process were tested. First, the photo-Fenton process was carried out in mixtures of different acetonitrile/water proportions. Although acetonitrile deactivates the hydroxyl radical, the main oxidizing agent in the photo-Fenton process, a Bio degradation greater than 90% is achieved in 80 min of reaction. Second, degradation of Bio was evaluated by photo-Fenton in a medium with β-cyclodextrin (β-CD), where the Bio solubility could be increased at least thirty-five times. The association constant of Bio to β-CD was measured to be 1933 ± 300 M−1 and molecular simulation results indicate a 1:1 inclusion complex stabilized by the formation of intermolecular H-bonds. The Bio degradation rate in this medium was similar to that observed in aqueous media. The use of β-CD presents a friendly alternative to the environment for the degradation of the pyrethroid insecticide.

Volumetric, isentropic compressibility and viscosity coefficient studies of binary solutions involving amides as a solute in aqueous and CCl4 solvent systems at 298.15 K

The experimental measurements of the density, speed of sound and viscosity coefficient in binary solutions involving water and CCl4 as solvents and formamide, N-methylformamide, N, N-dimethylformamide, N-methylacetamide and N, N-dimethylacetamide as solute in the concentration range (0.00992 mol·kg−1 to 1.07890 mol·kg−1) at 298.15 K are reported. The data are used to obtain the isentropic compressibility (βs) of solutions and Jones-Dole viscosity B and D coefficients for solutes. The derived properties like apparent molar volume (Vϕ) and apparent molar isentropic compressibility (Kϕ) of amides at different concentrations are evaluated. The data of limiting apparent molar volume (Vϕ0) and apparent molar isentropic compressibility (Kϕ0) for amides in both solvent systems (H2O and CCl4) and their concentration variation are examined to study the effect of intermolecular H-bond formation (for the amide molecules), hydrophobic interaction effect in water and amide-CCl4 interactions. It has been observed that there is loss of volume and compressibility of amide molecules in transferring them from pure liquid state to water and gain in transferring to CCl4 solutions (non-aqueous solvent) except for dimethylacetamide. The transfer volumes and compressibilities from CCl4 to water are negative and are attributed to H bond formation between solute molecules. The viscosity B coefficients for the amides are found to be high positive in water while they are of small magnitude in CCl4 medium. All these results are discussed on the basis of solute-solvent interaction, hydrophobic interaction in water and H-bond formation possibilities in CCl4. It is proposed that, the dissolution of dimethylformamide in water takes place substitutionally in water cavities with very little volume change.

Synthesis of porous starch xerogels modified with mercaptosuccinic acid to remove hazardous gardenia yellow

Mercaptosuccinic acid (MSA) molecules were inserted into potato starch, leading to the breaking of intrinsic H-bonds within macromolecular chains of starch and the formation of intermolecular H-bonds between MSA and starch, which could be verified by Fourier transform infrared spectroscopy (FT-TR). MSA modified porous starch xerogels (PSX/MSA) were obtained after freeze-drying the MSA modified starch, and they were characterized by field emission scanning electron microscopy (FESEM), exhibiting the intriguing porous structure due to the separation of starch chains by MSA molecules. The PSX/MSA were then used as the adsorbents to remove gardenia yellow (GY), a natural colorant with genotoxicity. Due to the porous structure of PSX and the introduced carboxyl groups from MSA, the adsorption capacity of the PSX/MSA was much higher than that of the starch xerogels alone (SX). The adsorption behaviors of GY by the PSX/MSA fitted both the Freundlich isotherm model and the pseudo-second-order kinetic model, and the efficient adsorption of GY suggested that the PSX/MSA might be potential adsorbents for the removal of dyes from contaminated aquatic systems.

A theoretical investigation into the strength of N–NO2 bonds, ring strain and electrostatic potential upon formation of intermolecular H-bonds between HF and the nitro group in nitrogen heterocyclic rings C n H2n N–NO2 (n = 2–5), RDX and HMX

Changes in N-NO2 bond strength, ring strain energy and electrostatic potential upon formation of intermolecular H-bonds between HF and the nitro group in nitrogen heterocyclic rings C n H2n N-NO2 (n = 2-5), RDX and HMX were investigated using DFT-B3LYP and MP2(full) methods with the 6-311++G(2df,2p) and aug-cc-pVTZ basis sets. Analysis of electron density shifts was also carried out. The results indicate that H-bonding energy correlates well with the increment of ring strain energy. Upon complex formation, the strength of the N-NO2 trigger-bond is enhanced, suggesting reduced sensitivity, while judged by the increased ring strain energy, sensitivity is increased. However, some features of the molecular surface electrostatic potential, such as a local maximum above the N-NO2 bond and ring, σ + (2) and electrostatic balance parameter ν, remain essentially unchanged upon complex formation, and only a small change in the impact sensitivity h 50 is suggested. It is not sufficient to determine sensitivity solely on the basis of trigger bond or ring strain; as a global feature of a molecule, the molecular surface electrostatic potential is available to help judge the change of sensitivity in H-bonded complexes. Graphical Abstract The strengthened N-NO2 bond suggests reduced sensitivity, while it is reverse by theincreased ring strain energy upon the complex formation. However, the molecular surfaceelectrostatic potential (V S) shows the little change of h 50. The V S should be taken into accountin the analysis of explosive sensitivity in the H-bonded complex.

Aggregation of a Tetrasaccharide Acceptor Observed by NMR: Synthesis of Pentasaccharide Fragments of the Le(a)Le(x) Tumor-Associated Hexasaccharide Antigen.

We report the synthesis of a tetrasaccharide and two pentasaccharide fragments of the Le(a)Le(x) tumor-associated carbohydrate antigen α-L-Fuc-(1→4)-[β-D-Gal-(1→3)]-β-D-GlcNAc-(1→3)-β-D-Gal-(1→4)-[α-L-Fuc-(1→3)]-β-D-GlcNAc-(1→OR). The choice of protecting groups permitted a one-step global deprotection (Na/NH3(l)). The protected chlorohexyl glycoside pentasaccharide was the precursor to the hexyl glycoside, to be used as a soluble inhibitor, and the aminohexyl glycoside analogue, to be conjugated to proteins for surface immobilization and immunization experiments. We observed that a linear tetrasaccharide that contained two N-acetylglucosamine residues and a free OH group gave two distinct sets of (1)H NMR signals when the data were acquired in deuterated chloroform. Data acquisition at variable concentrations and variable temperatures suggests that the second set of NMR signals results from aggregation of the tetrasaccharide driven by the formation of intermolecular H-bonds involving the NHAc. While the formation of intra- and intermolecular H-bonds involving N-acetylgucosamine residues has been reported in non-H-bonding solvents, this is, to our knowledge, the first time that these have lead to the appearance of two distinct sets of signals in the NMR spectra. This aggregation may explain the lack of reactivity observed when an attempt is made to glycosylate such an acceptor using non-H-bonding solvents such as dichloromethane.

Formation and regulation of supramolecular chirality in organogel via addition of tartaric acid

A new 1,8-naphthalimide derivative was prepared in which the C-4 position was substituted by pyridin-4-ol. This derivative shows good gelation property that can gelate most of polar solvents. As an achiral molecule, helical fibre morphology was observed when the compound gelated acetone solvent. When 0.5 eq of D-tartaric acid or L-tartaric acid was added to the gel, the helical morphology was changed from left-handed to right-handed structure. This result was further proved by circular dichroism measurement. FT-IR experiment showed the formation of intermolecular H-bond between the gelator and tartaric acid. The photophysical properties of gelator had no difference before and after addition of tartaric acid; whereas the lamellar structure was varied by addition of tartaric acid.

Langmuir Monolayers of an Inclusion Complex Formed by a New Calixarene Derivative and Fullerene

The design of new molecules with directed interactions to functional molecules as complementary building blocks is one of the main goals of supramolecular chemistry. A new p-tert-butylcalix[6]arene monosubstituted derivative bearing only one alkyl chain with an acid group (C6A3C) has been synthesized. The C6A3C has been successfully used for building Langmuir monolayers at the air-water interface. The C6A3C molecule adopts a flatlike orientation with respect to the air-water interface. The molecular structure gives the molecule amphiphilic character, while allowing the control of both the dissociation degree and the molecular conformation at the air-water interface. The C63AC has been combined with pristine fullerene (C60) to form the supramolecular complex C6A3C:C60 in 2:1 molar ratio (CFC). The CFC complex retains the ability of C6A3C to form Langmuir monolayers at the air/water interface. The interfacial molecular arrangement of the CFC complex has been convincingly described by in situ UV-vis reflection spectroscopy and synchrotron X-ray reflectivity measurements. Computer simulations complement the experimental data, confirming a perpendicular orientation of the calixarene units of CFC with respect to the air-water interface. This orientation is stabilized by the formation of intermolecular H-bonds. The interfacial monolayer of the CFC supramolecular complex is proposed as a useful model for the well-defined self-assembly of recognition and functional building blocks.

A B3LYP and MP2(full) theoretical investigation into explosive sensitivity upon the formation of the intermolecular hydrogen-bonding interaction between the nitro group of RNO2 (R = –CH3, –NH2, –OCH3) and HF, HCl or HBr

The change of the bond dissociation energy in the trigger bond (C–NO2, N–NO2 or O–NO2) upon the formation of the intermolecular hydrogen-bonding interaction between the nitro group of RNO2 (R=–CH3, –NH2, –OCH3) and HF, HCl or HBr have been investigated using the B3LYP and MP2(full) methods with the 6-311++G**, 6-311++G(2d,p) and aug-cc-pVTZ basis sets. The bond dissociation energy (BDE) is increased and the charge of nitro group turns more negative in complex in comparison with those in monomer. The increment (ΔBDE) correlates with the intermolecular hydrogen-bonding interaction energy. Furthermore, it is far larger than the intermolecular H-bonding interaction energy. The analyses of the atoms-in-molecules (AIMs), natural bond orbital (NBO) and electron density shifts show that the electron density shifts toward the trigger bond upon the intermolecular H-bond formation, leading to the strengthened trigger bond and reduced explosive sensitivity.

An Understanding of the Modulation of Photophysical Properties of Curcumin inside a Micelle Formed by an Ionic Liquid: A New Possibility of Tunable Drug Delivery System

The present study reveals the modulation of photophysical properties of curcumin, an important drug for numerous reasons, inside a micellar environment formed by a surfactant-like ionic liquid (IL-micelle) in aqueous solution. Higher stability of the drug inside IL-micelle in the absence and presence of a simple salt (sodium chloride) as well as considerably large partition coefficient (K(p) = 8.59 × 10(3)) to the micellar phase from water make this system a well behaved drug loading vehicle. Remarkable change in fluorescence intensity with a strong blue-shift implies the gradual perturbation of intramolecular hydrogen bond (H-bond) present within the keto-enol group of curcumin along with considerable formation of intermolecular H-bond between curcumin and the headgroup of surfactant-like IL. Very fast nonradiative decay channels in curcumin mainly caused by the excited state intramolecular proton transfer (ESIPT) are thus depleted remarkably in the presence of IL-micelle of reduced polarity and as a result of restricted rotational and vibrational degrees of freedom when bound to the micelle. Moreover, time-resolved results confirm that not only the keto-enol group of curcumin is playing here but also the phenolic hydroxyl groups are also responsible for such modulation in photophysical properties. From a thermodynamic point of view, our system shows good correlation with its stability parameters (higher binding constant with very less hydrolytic degradation rate ~1%) and higher negative value of binding enthalpy of interaction (-ΔH) than total free energy change (-ΔG) implies that the nature of binding interaction is enthalpy driven not entropy alone. Summarizing all the above observations, we have concluded that the modulation of the intramolecular proton transfer is due to the presence of both intermolecular proton transfer as well as strong hydrophobic interaction between curcumin and the IL-micelle.

Hydrogen bonds of anti-HIV active aminophenols

UDC 539.1.047;543.42 Analysis of IR-Fourier spectra from solutions and crystals of antiviral sulfo-containing aminophenols has shown that various types of intramolecular and intermolecular interactions can occur in molecules of these compounds. Three types of intramolecular hydrogen bonds (O-H⋅⋅⋅N, O-H⋅⋅⋅O=S=O, and N-H⋅⋅⋅O=S=O) are formed in CCl4 solutions of the sulfo-containing aminophenols. The formation of intermolecular H-bonds in- volving the NH- and OH-groups and the preservation of the intramolecular O-H⋅⋅⋅O=S=O H-bond are char- acteristic of the anti-HIV active aminophenol crystals. Spectral attributes are determined in order to distinguish between the anti-HIV active and inactive sulfo-containing aminophenols. Introduction. HIV-infection is an infectious disease that develops in an organism as the result of the multi- year presence in lymphocytes, macrophages, and nerve-cell tissue of human immunodeficiency virus (HIV). It is char- acterized by progressive degeneration of the immune system that leads to the death of the patient from secondary diseases, which are described as acquired immunodeficiency syndrome (AIDS), or subacute encephalitis (1). The incorporation into medical practice of highly active antiretroviral therapy (ART), which is used in con- junction with therapy of opportunistic infections, enabled the understanding of HIV-infection to be reconsidered now as a rapidly progressing fatal disease and to treat it as a chronic disease requiring life supporting therapy (2). It seemed necessary to discover new compounds with high anti-HIV activity that were simple to prepare and promising for development based on them of new drugs. Derivatives of aminophenols (AP) are such compounds. It was found that certain AP derivatives exhibit antiradical (3) and antiherpes (4-8) activity. The recently synthesized AP derivatives were capable of suppressing HIV-infection in cell culture (9). The need to study the structures of AP on the molecular level was due to the ability of many drugs to change their pharmacological effect as a function of their polymorphic transformations (10, 11). Widespread use of AP in pharmacology, in particular HIV-therapy, will be possible after identifying the factors that affect their pharma- cotherapeutic activity and also after studying systematically and in detail the electronic structure and determining the behavior of functional groups interacting among themselves and with the environment. Experimental. We studied N-(2-hydroxy-3,5-di-tert-butyl)-4-methylbenzenesulfonamide (AP I), N-(2-methoxy- 3,5-di-tert-butylphenyl)-4-methylbenzenesulfonamide (AP II), N-(2-hydroxy-3,5-di-tert-butylphenyl)-4-methanesul- fonamide (AP III), N-(2-hydroxy-3,5-di-tert-butylphenyl)-4-benzenesulfonamide (AP IV), N-(2-hydroxy-3,5- di-isopropylphenyl)-4-methylbenzenesulfonamide (AP V), and N-(2-hydroxy-3,5-di-isopropylphenyl)-4-benzenesul- fonamide (AP VI):