Diethyl Methylphosphonate Research Articles

Synthesis of the C1-C15 Fragment of Incednine

We report on our progress towards the synthesis of the exotic, delicate and tense polyketidic macrolactam of incednine. This work constitutes a significant advancement towards the total synthesis of a family of molecules of biological and medicinal interest. Some of the key features of this synthesis required evolutions from the initially designed strategy, leading to the use of a HWE to build the C2-C9 tetraene. For this purpose, a polyfunctionalized phosphonate was used and obtained through an unprecedented Pd-catalyzed cross-coupling involving the zinc anion of diethyl methylphosphonate. The resulting desired C1-C15 fragment displays a carboxylic acid ester at C1 and a vinyl iodide at C15, both functions being ready for subsequent amide coupling with the C16-C23 fragment and final Suzuki cyclization respectively.

Ether-Modified Nonflammable Phosphate Enabling Anion-Rich Electrolyte for High-Voltage Lithium Metal Batteries.

Phosphate-based localized high-concentration electrolytes (LHCE) feature high flame retardant and satisfactory cathodic stability for lithium metal batteries. However, stable cycling of those electrolytes at ultra-high upper cut-off voltages for long-term stability remains challenging. Herein, an ether-modified phosphate, diethyl (2-methoxy ethoxy) methylphosphonate (DMEP), is designed for high-voltage applications. The ether modification enhances the stability of the Li+-DMEP-FSI- coordination structure, promoting the formation of cation-anion aggregates (AGG) dominated solvation structure, which favors the generation of LiF-rich cathode electrolyte interphase layers compared to triethyl phosphate (TEP)-based LHCE. Consequently, cathode degradation, including transition-metal dissolution and electrode cracking, is well-suppressed. The LiNi0.8Co0.1Mn0.1O2 (NCM811)||Li full cells using DMEP-based LHCEs show more than 90.7% capacity retention at an ultrahigh upper cut-off voltage of 4.7 V after 100 cycles. Notably, DMEP-LHCE exhibits enhanced safety than that of TEP-LHCE, suggesting its versatility and potential for next-generation lithium metal batteries.

Two-dimensional photonic crystal acetylcholinesterase hydrogel and organohydrogel sensors for efficient detection of organophosphorus compounds

Sensors capable of detecting organophosphorus (OP) compounds have attracted the most attention owing to severe OP contamination worldwide. Despite many years of research, the developed OP sensors mainly focused on detecting water-soluble OPs in proper environments and the exploration of OP sensors suitable in resource-limited areas is extremely challenging. Here, a simple two-dimensional photonic crystal (2D PC) hydrogel featuring capabilities of effectively quantitative determination of OP compounds is facilely constructed by immobilizing the enzyme acetylcholinesterase (AChE) onto a bovine serum albumin (BSA) protein hydrogel. Owing to the specific interaction between AChE and OP compounds, the OP compounds are easily bound to the hydrogel, triggering volume phase transition and resulting in apparent Debye diffraction ring variations. The resulting hydrogel sensors show a limit of detection (LoD) of 2.23 nM for trichlorfon and 0.07 nM for diethyl methylphosphonate (DMPP), respectively. On the basis of the hydrogel, a responsive organohydrogel is facilely fabricated utilizing a solvent exchange strategy to meet the requirements of applications in harsh environments and detection of the non-water-soluble OP compounds. The organohydrogel sensors, however, demonstrated a LoD of 0.70 μM for trichlorfon and 4.46 μM for DMPP, respectively. This work provides new light on the development of next-generation stable, low-cost, and portable field sensing devices.

Thermophysical Properties for Alkylphosphonate and Alkylphosphate Compounds

Organophosphorus compounds have a wide range of applications; they are commonly used as drugs or pesticides or in the production of ion batteries. However, some organophosphorus compounds, which were developed as warfare nerve agents, are neurotoxic and potentially lethal to living organisms. On the basis of the literature search, certain properties of these compounds are not well known. Knowledge of thermodynamic properties and the availability of reliable data are fundamental in the development of methods for detecting, treating, and safely analyzing decontamination. For research purposes, substitutes, called simulants, which have similar molecular structures and properties but are less toxic, are often employed. This work presents a thermodynamic study of four organophosphorus nerve agent simulants: trimethyl phosphate, triethyl phosphate, dimethyl methylphosphonate, and diethyl methylphosphonate. Differential scanning calorimeter and a Tian–Calvet type calorimeter were used to analyze their phase behavior and measure the liquid heat capacities, respectively. Vapor pressures were experimentally determined with the static method. Ideal-gas heat capacities were calculated using the R1SM approach, which combines the rigid rotor–harmonic oscillator model, the one-dimensional hindered rotor model, and the mixing model. The results obtained were compared with the data from the literature and simultaneously correlated to obtain a highly reliable thermodynamic description.Graphical

Synthesis And Anticancer Activity Of New Hybrid 3-Methylidene-2,3-Dihydro-1,8-Naphthyridinones.

Synthesis of molecular hybrids, obtained by combination of two or more pharmacophoric groups of different bioactive substances in order to produce more efficient drugs, is now a frequently used approach in medicinal chemistry. Following this strategy, we synthetized a library of 3-methylidene-1-tosyl-2,3-dihydro-1,8-naphthyridin-4(1H)-ones, combining a 1,8-naphthyridin-4-one motif with an exo-methylidene bond conjugated with a carbonyl group, pharmacophoric units that are present in many natural, biologically active compounds with anticancer potential. We reasoned that such bifunctional conjugates may have enhanced cytotoxic activity. The title compounds were synthesized in a four step reaction sequence. β-Ketophosphonate, obtained from methyl N-tosylnicotinate and diethyl methylphosphonate, was reacted with various aldehydes giving 3-diethoxyphosphoryl-2,3-dihydro-1,8-naphthyridin-4(1H)-ones as keto-enol tautomers. Later, these compounds were transformed into 3-methylidene-1-tosyl-2,3-dihydro-1,8-naphthyridin-4(1H)-ones applying the Horner-Wadsworth-Emmons methodology. Then, the cytotoxicity of the new compounds was assessed on two cancer cell lines, promyelocytic leukemia HL-60 and breast cancer adenocarcinoma MCF-7, and for comparison, on human umbilical vein endothelial cells HUVEC. The most active and selective analog, 2-ethyl-3-methylidene-1-tosyl-2,3-dihydro-1,8-naphthyridin-4(1H)-one 4 a was chosen for more detailed studies on HL-60 cell line, to determine molecular mechanisms of its anticancer activity. It was shown that 4 a strongly inhibited proliferation and induced apoptosis which could be attributed to its ability to cause DNA damage.

Understanding Synthesis Parameters for Thionation of Phosphonates Associated with the Chemical Weapons Convention through Principal Component Analysis

Thiophosphonates, a class of the organophosphate compounds, are of pharmaceutical and agricultural significance. Albeit their broad scope for peaceful uses, they may also be precursors and markers to toxic chemicals, such as the nerve agent VX and other V-series agents, leading to their inclusion into the Annex on Chemicals of the Chemical Weapons Convention (CWC). Considering that they are related to chemical warfare agents and the position of our laboratory as an Organization for the Prohibition of Chemical Weapons (OPCW) Designated Laboratory for analysis of authentic environmental samples, this study aims to contribute to the understanding of the synthesis of thiophosphonates through O,O’-diethyl methylphosphonate conversion to O,O’-diethyl methylphosphonothioate using Lawesson’s reagent, exploring different conditions previously reported by the literature, in order to further build a compound library for CWC verification purposes. Synthesis of the compounds has been carried out in sealed, pressure tubes, adding novelty to the present study. Reactions were followed by gas chromatography and 31P nuclear magnetic resonance, and principal component analysis was employed to understand the intricate factors influencing thiophosphonate synthesis yield as duration, temperature and solvent. The research aims to reinforce or challenge existing scientific knowledge, providing insights into parameters related to phosphonate thionation using Lawesson’s reagent, contributing to a deeper understanding of this chemical reaction.

Preparation of multifunctional silicon‐phosphorus acrylate particles for the simultaneous improvement of the flame retardancy and mechanical performance of polylactic acid

AbstractPolylactic acid (PLA) is a biodegradable plastic that currently has limited application owing to its poor fire resistance and brittleness. Herein, a multifunctional silicon‐phosphorus acrylic resin(P/Si‐ACR) is designed to endow both flame retardancy and toughness to PLA. P/Si‐ACR is prepared by seeded emulsion polymerization with polysiloxane as the core layer and diethyl methylphosphonate acrylate and 9, 10‐dihydro‐9‐oxa‐10‐phosphophenanthrene‐10‐oxide acrylate as the shell materials. P/Si‐ACR has a particle size of approximately 200 nm and glass transition temperatures of −38 and 152°C for the core and shell layers, respectively. Addition of 7 wt% P/Si‐ACR to PLA increases the notched impact strength and elongation at break by 124% and 46%, respectively. This improved mechanical performance is due to the elasticity of silicone rubber and the promotion of crystallization by P/Si‐ACR. Combustion testing revealed that the limiting oxygen index increases from 19.1% to 22.5%, while the peak heat release rate decreases by 36%. This enhanced flame retardancy is due to the synergistic effect of phosphorus and silicon, with the former promoting graphitization and inhibiting the free radical degradation of PLA, and the latter stabilizing the char residue. Therefore, P/Si‐ACR is a promising multifunctional modifier that can achieve an optimal balance among flame retardancy, crystallization performance, and toughness in polymers.

Ultraviolet and infrared light decontamination and the secondary pollution products of G-series nerve agent simulant model molecules contaminating TiO2/Ti surfaces

• Photo-decontaminations of G-series nerve agent simulant model molecules were tested under scanning 266-nm laser, UVA/UVB/UVC, and IR. • Photodecomposition products and the reaction pathways were discussed on the basis of GC, Mass, XPS, EDXS, and FT-IR. • Cleavages of P−CH 3 , P H, P O, C–H, PO−CH 2 CH 3 , and POCH 2 −CH 3 bonds of DMMP, DMP, DEMP, and DEP were fully discussed. • Dissociative adsorption and photocatalytic dissociation were discussed with active species of O 2 ― , h + and •OH. • MeOH and EtOH were major products dependent on light exposure, wavelength, photon flux, and the chemical groups. Ultraviolet (UV) photodecontamination of chemical warfare agents (CWAs) has been an attractive way for decontamination of target areas unapproachable by a wet chemical method. Herein, decontamination was demonstrated using UV and infrared lamps and a home-built scanning 266-nm pulse laser under air and N 2 conditions for the G-series nerve agent simulant model molecules of dimethyl methylphosphonate, dimethyl phosphite, diethyl methylphosphonate, and diethyl phosphite contaminating TiO 2 /Ti sheets. Volatile secondary photodecomposition products were examined by gas chromatography and mass spectrometry, and nonvolatile surface residues by X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction crystallography, and Fourier-transform infrared spectroscopy. The wavelength- and power-dependent mechanisms of the formation of diverse secondary products, the role of active O 2 − , h + and •OH species, and the mechanisms of dissociative adsorption and photodecontamination were fully discussed and found valuable for the development of a remote laser photodecontamination method applicable to diverse CWA-contaminated target areas.

Synthesis of novel α-aminophosphonates by methanesulfonic acid catalyzed Kabachnik–Fields reaction

A series of novel α-aminophosphonates of diethyl (2,4-difluorobenzylamino)methylphosphonate derivatives (4a–4g) have been synthesized by applying three-component Kabachnik–Fields reaction, using fluoro derivatives of aldehydes and substituted amines, diethyl phosphonate in the presence of a catalytic amount of methanesulfonic acid (MSA) in good yields with high enantioselectivities (up to 98% ee). The enantioselectivitiy of compounds (4a–4g) was confirmed by chiral HPLC. The direct Kabachnik–Fields reaction with high reactivity under mild reaction conditions and significantly used for synthesis of the α-aminophosphonate. The novel products were characterized by spectral and analytical data.

UV light decontamination and secondary pollution products of G-series chemical warfare model molecules contaminated on Mo and MoOx surfaces

Understanding decomposition mechanism and analysis of secondary products for a chemical warfare agent (CWA) simulant on a contaminated target area are very important for better treatments of contaminated primary and secondary pollutants, and the development of a decontamination method. Herein, UV light (lamp and 266-nm laser high power pulses) photodecomposition method was introduced for the decontamination of G-series dimethyl methylphosphonate, dimethyl phosphite, diethyl methylphosphonate, and diethyl phosphite CWA model molecules contaminated on Mo and MoOx surfaces under various conditions. The secondary gas products were fully examined by gas chromatography and mass spectrometry, and the surface residues were also examined by scanning electron microscopy, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy before and after UV decontamination. Density function theory was employed to calculate the bond dissociation energies of the major chemical bonds for the CWA simulants. The full database for the photodecontamination products, the decomposition mechanism, the bond energies, and the roles of active species of O2−, h+ or OH reported in the present study provide valuable information on the development of future remote UV laser CWA decontamination system.

Synthesis and Characterization of the Structure of Diethyl [(4-{(1H-Benzo[d]Imidazol-1-yl)Methyl}-1H-1,2,3-Triazol-1-yl)(Benzamido)Methyl]Phosphonate Using 1D and 2D NMR Experiments

The biheterocyclic derivative of the phosphonic glycine analogue is prepared selectively by reaction between the α-azidoamino diethyl methylphosphonate and the 1-(prop-2-yn-1-yl)-1H-benzo[d]imidazole. The dipolar -1,3 cycloaddition reaction using Click Chemistry was carried out in a solvent water/ethanol mixture in a ratio of 1:1. Copper sulphate pentahydrate and sodium ascorbate are used in the reaction in catalytic amounts. The compound [diethyl [{4-[(1H-benzo[d]imidazol-1-yl)methyl]-1H-1,2,3-triazol-1-yl}(benzamido) methyl] phosphonate was isolated pure as a white powder, after chromatography on a silica gel column (ethyl acetate/hexane acetate: 1/1). The yield of pure product is 90%, after recrystallization in an ether/hexane mixture. The structure of the -1,4 isomer is attributed to the compound obtained by means of 1D and 2D NMR and based on data from the literature concerning the cycloaddition reaction via Click Chemistry. Two-dimensional NMR spectroscopy played a major role. The analysis of the different correlations between adjacent hydrogens and carbons, and also between hydrogens and distant carbons, confirmed the proposed structure.

Improving Quantification of tabun, sarin, soman, cyclosarin, and sulfur mustard by focusing agents: A field portable gas chromatography-mass spectrometry study

Commercial gas chromatograph-mass spectrometers, one of which being Inficon's HAPSITE® ER, have demonstrated chemical detection and identification of nerve agents (G-series) and blistering agents (mustard gas) in the field; however most analyses relies on self-contained or external calibration that inherently drifts over time. We describe an analytical approach that uses target-based thermal desorption standards, called focusing agents, to accurately calculate concentrations of chemical warfare agents that are analyzed by gas chromatograph-mass spectrometry. Here, we provide relative response factors of focusing agents (2-chloroethyl ethyl sulfide, diisopropyl fluorophosphate, diethyl methylphosphonate, diethyl malonate, methyl salicylate, and dichlorvos) that are used to quantify concentrations of tabun, sarin, soman, cyclosarin and sulfur mustard loaded on thermal desorption tubes (Tenax® TA). Aging effects of focusing agents are evaluated by monitoring deviations in quantification as thermal desorption tubes age in storage at room temperature and relative humidity. The addition of focusing agents improves the quantification of tabun, sarin, soman, cyclosarin and sulfur mustard that is analyzed within the same day as well as a 14-day period. Among the six focusing agents studied here, diisopropyl fluorophosphate has the best performance for nerve agents (G-series) and blistering agents (mustard gas) compared to other focusing agents in this work and is recommended for field use for quantification. The use of focusing agent in the field leads to more accurate and reliable quantification of Tabun (GA), Sarin (GB), Soman (GD), Cyclosarin (GF) and Sulfur Mustard (HD) than the traditional internal standard. Future improvements on the detection of chemical, biological, radiological, nuclear, and explosive materials (CBRNE) can be safely demonstrated with standards calibrated for harmful agents.

Photo-decontamination of chemical warfare dimethyl methylphosphonate, dimethyl phosphite, diethyl methylphosphonate, diethyl phosphite model molecules on Al and oxidized Al foils

Decontamination of organophosphorus chemical warfare nerve agents (CWNAs) is gaining importance for human security. Herein, we have employed a dry-photodecontamination method for CWNA model molecules of dimethyl methylphosphonate, dimethyl phosphite, diethyl methylphosphonate, and diethyl phosphite contaminated on aluminum (Al) and oxidized Al foils. For understanding their photo-degradation pathways, the photo-decomposition secondary chemical products generated as a result of UVC-decontamination were fully examined for the contaminated Al and oxidized Al target areas in a closed reactor system by gas chromatography and mass spectrometry. Solid residues were also fully examined by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. Density functional theory at the B3LYP/6–31 G level was used for geometric optimization, and the electronic energy state calculation was conducted on the level of TD-SCF/B3LYP/6–31 G. The new results further deepen the photo-decomposition mechanism of CWNAs, the development of dry UV light photo-decontamination methods, and the treatment of secondary by-products.

The decisive role of pericyclic reactions in the thermal decomposition of organophosphorus compounds

The understanding of the thermal decomposition chemistry of chemical warfare nerve agents is largely limited by the scarcity of kinetic data. Because of the high toxicity of these molecules, experimental determination of their chemical properties is very difficult. In the present work, a comprehensive detailed kinetic model for the decomposition of sarin and some simulants, i.e. di-isopropyl methyl phosphonate (DIMP), diethyl methylphosphonate (DEMP), and triethyl phosphate (TEP) were developed, containing possible molecular and radical pathways. The importance of unimolecular pericyclic decomposition led to evaluate precisely the rate constants of these reactions with high level theoretical calculations. The QCISD(T)/cc-PV∞QZ//B2PLYPD3/6–311+G(2d,d,p) level of theory was selected after a benchmark. The contribution of hindered rotors was included with the 1D-HR-U approach. Tunneling was taken into account for H-atom transfer. Transition state theory was used to calculate high-pressure limit rate constants and pressure dependent rate constants were calculated using Master Equation modeling. The model was validated against experimental pyrolysis and oxidation experimental data available in literature. Flux analyses showed that whatever the conditions are, the first step of decomposition of the studied phosphorus compounds are pericyclic eliminations leading to successive decompositions, whereas bond-breaking or H-atom abstraction remain negligible, even at high temperature.

Experimental thermochemical data of CWA simulants: Triethyl phosphate, diethyl methylphosphonate, malathion and methyl salicylate

This work focuses on the determination of important thermochemical properties of several chemical warfare agent (CWA) simulants: diethyl methylphosphonate (DEMP, CAS 683-08-9, 1), triethyl phosphate (TEP, CAS 78-40-0, 2), malathion (CAS 121-75-5, 3) and methyl salicylate (MS, 119-36-8, 4). Enthalpies of vaporization ΔlgHmo (298.15 K) (1: 56.8 ± 0.8 kJ mol−1; 2: 63.9 ± 0.9 kJ mol−1; 3: 101.4 ± 1.8 kJ mol−1; 4: 59.3 ± 0.8 kJ mol−1) and vapor pressures psat (298.15 K) (1: 43.9 Pa; 2: 12.5 Pa; 3: 1.4 mPa; 4: 14.5 Pa) were determined by the transpiration method in the ambient temperature range. The results were compared with existing literature values and critically evaluated. Data of DEMP 1, TEP 2 and MS 4 show agreement with most literature vaes, while results of malathion 3 show a significant disagreement with the scarce available literature p-T data.

Synthesis and Cytotoxic Evaluation of 3-Methylidenechroman-4-ones.

In the search for new anticancer agents, a library of variously substituted 3-methylidenechroman-4-ones was synthesized using Horner–Wadsworth–Emmons methodology. Acylation of diethyl methylphosphonate with selected ethyl salicylates furnished 3-diethoxyphosphorylchromen-4-ones which were next used as Michael acceptors in the reaction with various Grignard reagents. The adducts were obtained as the mixtures of trans and cis diastereoisomers along with a small amount of enol forms. Their relative configuration and preferred conformation were established by NMR analysis. The adducts turned up to be effective Horner–Wadsworth–Emmons reagents giving 2-substituted 3-methylidenechroman-4-ones, which were then tested for their possible cytotoxic activity against two leukemia cell lines, HL-60 and NALM-6, and against MCF-7 breast cancer cell line. All new compounds (14a–o) were highly cytotoxic for the leukemic cells and showed a moderate or weak effect on MCF-7 cells. Analog 14d exhibited the highest growth inhibitory activity and was more potent than carboplatin against HL-60 (IC50 = 1.46 ± 0.16 µM) and NALM-6 (IC50 = 0.50 ± 0.05 µM) cells. Further tests showed that 14d induced apoptosis in NALM-6 cells, which was mediated mostly through the extrinsic pathway.

Thermodynamic Studies on a Hydrogen Bonded Acidic 3,5-Bis(trifluoromethyl)phenol-functionalized Polymer as a Gas Chromatography Stationary Phase for Selectively Speciating Chemical Warfare Agents.

We describe for the first time hydrogen bonded acid (HBA) polymer, poly{methyl[3-(2-hydroxyl, 4,6-bistrifluoromethyl)phenyl]propylsiloxane}, (DKAP), as stationary phase for gas chromatography (μGC) of organophosphate (OP), chemical warfare agent (CWA) surrogates, dimethylmethylphosphonate (DMMP), diisopropylmethylphosphonate (DIMP), diethylmethylphosphonate (DEMP), and trimethylphosphate (TMP), with high selectivity. Absorption of OPs to DKAP was one-to-several orders of magnitude higher relative to commercial polar, mid-polar, and nonpolar stationary phases. We also present for the first-time thermodynamic studies on the absorption of OP vapors and quantitative binding energy data for interactions with various stationary phases. These data help to identify the best pair of hetero-polar columns for a two-dimensional GC system, employing a nonpolar stationary phase as GC1 and DKAP as the GC2 stationary phase, for selective and rapid field detection of CWAs.

Probing Coherent Vibrations of Organic Phosphonate Radical Cations with Femtosecond Time-Resolved Mass Spectrometry.

Organic phosphates and phosphonates are present in a number of cellular components that can be damaged by exposure to ionizing radiation. This work reports femtosecond time-resolved mass spectrometry (FTRMS) studies of three organic phosphonate radical cations that model the DNA sugar-phosphate backbone: dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), and diisopropyl methylphosphonate (DIMP). Upon ionization, each molecular radical cation exhibits unique oscillatory dynamics in its ion yields resulting from coherent vibrational excitation. DMMP has particularly well-resolved 45 fs ( cm) oscillations with a weak feature at 610–650 cm, while DIMP exhibits bimodal oscillations with a period of ∼55 fs and two frequency features at and 670–720 cm. In contrast, the oscillations in DEMP decay too rapidly for effective resolution. The low- and high-frequency oscillations in DMMP and DIMP are assigned to coherent excitation of the symmetric O–P–O bend and P–C stretch, respectively. The observation of the same ionization-induced coherently excited vibrations in related molecules suggests a possible common excitation pathway in ionized organophosphorus compounds of biological relevance, while the distinct oscillatory dynamics in each molecule points to the potential use of FTRMS to distinguish among fragment ions produced by related molecules.

Nano catalytic synthesis of flavanone phosphonates using domino Knoevenagel-phospha-Michael route

Novel derivatives of diethyl (4-oxo-2-phenylchroman-3-yl) methyl phosphonate have been synthesized under optimal conditions using domino-Knoevenagel-phospha-Michael reaction catalyzed by nano-zinc oxide. The combination of recovery and reusability of catalyst, simple and applicable approach, good reaction time and good yields of products make this method as a suitable route for this purpose. The structures of the products were determined by FT-IR, 1H-, 13C- and 31P- Nuclear Magnetic Resonance spectroscopies, and elemental analysis.

Waveguide-enhanced Raman spectroscopy of trace chemical warfare agent simulants.

We report the measurement of waveguide-enhanced Raman spectra from trace concentrations of four vapor-phase chemical warfare agent simulants: dimethyl methylphosphonate, diethyl methylphosphonate, trimethyl phosphate, and triethyl phosphate. The spectra are obtained using highly evanescent nanophotonic silicon nitride waveguides coated with a naturally reversible hyperbranched carbosilane sorbent polymer and exhibit extrapolated one-σ detection limits as low as 5ppb. We use a finite-element model to explain the polarization and wavelength properties of the differential spectra. In addition, we assign spectral features to both the analyte and the sorbent, and show evidence of changes to both due to hydrogen bonding.