Quantum chemical studies on tautomerism of barbituric acid in gas phase and in solution

Ab initoand density functional theory (DFT) methods were used to study the tautomers of barbituric acid in the gas phase and in a polar medium. In the gas phase, the tautomers were optimized at the HF/6-31G^*, MP2/6-31G^*and B3LYP/6-31G^*, B3PW91/6-31G^*levels of theory. The self-consistent reaction field theory (SCRF) at the HF/6-31G^*level of theory has been used to optimize the tautomers in a polar medium. The relative stability of the tautomers was compared in the gaseous and polar mediums. The ability of maximum hardness principle to predict the stable tautomer has been studied. The ¹³C-NMR chemical shift for carbon atoms in the tautomers was calculated and the results are discussed.     

Pathways of the reaction of nucleophilic addition of ammonia to formaldehyde in the gas phase and in the complex with formic acid:ab initio calculations

The gradient pathways of the reaction of nucleophilic addition of ammonia to formaldehyde were calculated for free molecules and in the NH₃...H₂CO...HC(O)OH complex by theab initio RHF/6-31G^**, MP2(fc)/6-31G^**, and MP2(full)/6-311++G^** methods. Both reactions proceed concertedly. In the first case, the reaction successively passes through two transitional states with an energy barrier exceeding 35 kcal mol⁻¹. In the case of the complex with formic acid, the reaction follows a conventional pathway, although its activation barrier calculated by the RHF/6-31G^** and MP2(fc)/6-31G^** methods decreases to 12.6 and 3.8 kcal mol⁻¹, respectively. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 13–20, January, 1998.     

Solvation of Na+ in N,N-dimethylformamide + methanol solutions. A nuclear magnetic relaxation study using dynamic solvent isotope effects

Inter- and intramolecular nuclear magnetic quadrupole relaxation measurements have been used to study the system methanol (CH₃OH)+ N,N-dimethylformamide (DMF)+NaI at 25°C. The dynamic behavior of the solvent molecules was investigated, throughout the composition range of the binary mixtures, by means of ¹⁴ N relaxation of DMF and ² H of methanol-d ₁ (CH ₃ OD). The intermolecular relaxation of ²³ Na⁺ in pure DMF was used to obtain information about the symmetry of the solvent electric dipole arrangement in the solvation sphere of the ion. The investigation of preferential solvation around Na⁺ in the binary mixtures was carried out by means of ²³ Na⁺ relaxation measurements using, for the first time, both the CH ₃ OH/CD ₃ OD and the DMF/DMF-d ₇ dynamic isotope effect. The results show that, throughout the composition range, there is preferential solvation by DMF. Furthermore, the use of the isotope effects of both components allowed for the first time a basic check of the reliability of the method since we obtained two independent sets of data for the composition of the Na⁺ solvation shell in the mixtures. The consistency of the two separate data sets demonstrates that the application of the dynamic isotope effect represents a powerful tool in preferential solvation studies.     

Pathways of the reactions of nucleophilic addition of H2O and HF molecules to formaldehyde in the gas phase and in the complex with formic acid:ab initio calculations

The gradient pathways of the reactions of nucleophilic addition of H₂O and HF molecules to formaldehyde in the gas phase and in the XH…H₂CO…HC(O)OH complex (X=OH, F) were calculated by theab initio RHF/6-31G^**, MP2(fc)/6-31G^**, and MP2(full)/6-311++G^** methods. Both reactions proceed concertedly. The formation of H-bonded bimolecular pre-reaction complexes is the initial stage of the gas-phase reactions; at the same time, no indications of the formation of stable π-complexes were found on the potential energy surfaces of systems under study. The calculated energy barriers to the gasphase reactions exceed 40 kcal mol⁻¹, while those to reactions in the complex XH…H₂CO…HC(O)OH (X=OH, F) become more than halved. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2146–2154, November, 1998.     

Raman study of structural defects in SiO2 aerogels

The structure of the silica aerogels was studied by Raman spectroscopy. The spectra of the solid network resembles that of bulk silica with additional bands related to organic groups and a large amount of OH groups.The typical bands due to ring breathing also called defect bands D ₁ and D ₂ located at 490 and 610 cm^–1 are present. However, the evolution of the D ₂ band compared to that of OH band (980 cm^–1) seems apparently, in contradiction with the results previously reported in the literature. During heat treatments between 25 and 300°C the D ₂ and the OH bands increase simultaneously. Generally, in silica glass the defect band D ₂ grows at the expense of the OH groups.This result is explained by the oxidation of the organic compounds which, in this temperature range, leads to the formation of the both species (OH) and those related to siloxane rings. ²⁹Si MAS NMR results are in agreement with the Raman study.     

Structural study of oxalamide compounds: H, C, and DFT calculations

The conformational properties of some N-alkyl, N,N′-dialky, and tetraalkyloxalamides have been investigated, in vacuo and in solvent using DFT methods at the B3LYP/6-31G^∗∗ computational level. Special emphasis has been given on oxalamides with substituents of the type -CH₂CH₂OH. In oxalamides with the N-H group (N-alkyl and N,N′-dialky), the most stable conformations are those in which the oxalamide moiety adopts a planar s-trans arrangement and the amide bonds are trans. A different situation appears in the case of tetraalkyloxalamides, in which the oxalamide moiety always adopts a skewed arrangement and there are conformations with similar energy. A careful study of ¹³C and ¹H NMR spectra together with theoretical calculations (GIAO method) allowed the assignment of the signals of these conformers. The presence of the -CH₂CH₂OH chain produces numerous rotamers. The most stable rotamers, in vacuo, are those with strong intramolecular hydrogen bonds, however in solvent, hydrogen bonds are not crucial to establish the most stable specie and depend on the solvent used.     

A.c. impedance behaviour of processes involving adsorption and reactivity of guanidonium-type cations at Pt(1 0 0) surface

The present paper reports a.c. impedance spectroscopic studies on adsorption of guanidonium (G⁺) and N,N-dimethylguanidonium (DMG⁺) resonant cations at Pt(1 0 0) single-crystal surface. The resulted information provided confirmation of the role of electrosorption of the above-mentioned molecule–ions through evaluation of the associated charge-transfer resistances and capacitances for the Pt(1 0 0) plane in 0.5 M H₂SO₄. These results also provided support for the interfacial ion-pairing mechanism that had been based on the voltammetric and in situ FTIR spectroscopic results published earlier.     

Spectrophotometric and spectroscopic studies of complexation of 8-hydroxyquinoline with π acceptor metadinitrobenzene in different polar solvents

The complexation of electron donor–acceptor complexes of 8-hydroxyquinoline (8HQ) and metadinitrobenzene (MNB) have been studied spectrophotometrically and thermodynamically in different polar solvent at room temperature. A new absorption band due to charge transfer (CT) transition is observed in the visible region. A new theoretical model has been developed which take into account the interaction between electronic subsystem of 8HQ and MNB. The results indicate the extent of charge transfer complexes (CTCs) formation to be more in less polar solvents. Stoichiometry of the complex was found to be 1:1 by straight line method and ¹H NMR between donor and acceptor at the maximum absorption bands. Ionization potential (I_D) and resonance energy (R_N) were determined from the CT transition energy in different solvents. The formation constants of the complexes were determined in different polar solvents from which ΔG° formation of the complexes was estimated and also extinction coefficient of the charge transfer complex (CTC) was calculated. Oscillator strength, transition dipole strengths and maximum wavelength of the CTC (λ_CT) in various solvents and IR spectra of the CTC have also been discussed. It has been observed that all parameters described above changed with change in polarity and concentration of donor.     

Synthesis,spectroscopic properties,and antimicrobial activity of some new 5-phenylazo-6-aminouracil-vanadyl complexes

Six complexes, [VO(L¹-H)₂]?·?5H₂O (1), [VO(OH)(L^2,3?H)(H₂O)]?·?H₂O (2,3), [VO(OH)(L^4,5?H)(H₂O)]?·?H₂O (4,5), [VO(OH)(L⁶?H)(H₂O)]?·?H₂O (6), were prepared by reacting different derivatives of 5-phenylazo-6-aminouracil ligands with VOSO₄?·?5H₂O. The infrared and ¹H NMR spectra of the complexes have been assigned. Thermogravimetric analyses (TG, DTG) were also carried out. The data agree quite well with the proposed structures and show that the complexes were finally decomposed to the corresponding divanadium pentoxide. The ligands and their vanadyl complexes were screened for antimicrobial activities by the agar-well diffusion technique using DMSO as solvent. The minimum inhibitory concentration (MIC) values for 1–4 and 6 were calculated at 30°C for 24–48?h. The activity data show that the complexes are more potent antimicrobials than the parent ligands.     

The Structure of Gallium in Strongly Alkaline,Highly Concentrated Gallate Solutions—a Raman and <Superscript>71</Superscript>Ga-NMR Spectroscopic Study

Highly concentrated alkaline gallate solutions with 0.23≤[Ga(III)]_T≤2.32 mol⋅dm⁻³ and 1≤[NaOH]_T≤15 mol⋅dm⁻³ have been prepared and investigated by Raman and ⁷¹Ga-NMR spectroscopy. Both the Raman and ⁷¹Ga-NMR spectra are consistent with the presence of only one Ga-bearing species in these solutions, the tetrahedral hydroxocomplex, Ga(OH)₄⁻. Contact ion pairs were found to cause variations in the Raman and ⁷¹Ga-NMR parameters that are at the edge of detectability. Other species that have been claimed to exist in the literature, like higher hydroxo complexes (i.e., Ga(OH)₆³⁻) or the μ-oxo-bridged dimer (i.e., (OH)₃Ga-O-(OH)₃²⁻), were not detected by these spectroscopic techniques. If such solution species exist at all, their concentrations are below the detection limit of Raman and ⁷¹Ga-NMR spectroscopy. The behavior of gallium appears to be very similar to that of aluminium under identical conditions, except that the dimeric species detected in aluminate solutions is undetectable in analogous gallates.     

N(nPr)4[B5O6(OH)4][B(OH)3]2 and N(nBu)4[B5O6(OH)4][B(OH)3]2: Clathrates with a diamondoid arrangement of hydrogen-bonded pentaborate anions

Single-crystal X-ray structure analyses of N(nPr)₄[B₅O₆(OH)₄][B(OH)₃]₂,1, and N(nBu)₄ [B₅O₆(OH)₄][B(OH)₃]₂,2, reveal that these materials are novel clathrates, the isotypic host structures of which are three-dimensional assemblies of hydrogen-bonded [B₅O₆(OH)₄]^– ionsand B(OH)₃ molecules. The assembly of only the pentaborate anions is a distorted (i.e., along [102] elongated) fourconnected diamond-related network. The N(nPr) ₄ ⁺ and N(nBu) ₄ ⁺ ions are trapped within the complex three-dimensional channel systems of the host frameworks. Both1 and2 crystallize monoclinically with space groupP2₁/c andZ=4. The cell constants are:1:a=13.592(5),b=12.082(2),c=17.355(6) Å, =106.60(2)° (298K);2:a=13.874(3),b=12.585(1),c=17.588(4) Å, =107.04(1)° (238 K). The results obtained by both¹¹B and¹³C MAS NMR spectroscopy are discussed. Thermogravimetric studies under a flowing inert-gas atmosphere suggest that water, stemming from polycondensation of the hydrous borate species, is released from the clathrates at ca. 443 K (1) and 398 K (2) before the decomposition of the organic cations starts at ca. 603 K (1) and 603 K (2).Author for correspondence. Supplementary Data relating to this article are deposited with the British Library as supplementary publication No. SUP 82172 (82 pages).     

Analysis of ;W and O NMR chemical shifts in polyoxometalates by extended Hückel mo calculations

The extended Hückel molecular orbital (EHMO) calculations have been carried out using cluster approach to polyoxo anions, i.e. calculations have been done for a single octahedron MO₆ of different symmetry and results have been used to analyze ¹⁸³ W and ¹⁷ O NMR spectra. Using five d→d* energy differences for the individual WO₆ the sum Σ1/ (E_d→E_d*) have been calculated and plotted against the ¹⁸³ W chemical shift (from +258 to −670 ppm) for corresponding type of tungsten atom and practically a linear correlation between two parameters have been observed. This points out the electronic nature of the ¹⁸³ W chemical shift. Similar correlation have been found for the ¹⁷O NMR chemical shifts (−90 to +800 ppm) when the plotted against product of the R⁻³ Σ1/ (E_p→E_p*) where the R⁻³ bond length of the corresponding W–O bond. Increasing the ¹⁸³ W nuclear magnetic shielding with the calculated electron population on tungsten atom for closely related anions has been observed, but no general tendency between δ and the calculated electronic charge if the symmetry of polyhedron is changed is expected.     

Experimental and theoretical studies on group 1 metallacarboranes: Synthesis, structure and ab initio calculations of the NMR chemical shifts of the 1-(THF)-1-(TMEDA)-1-Na-2,4-(SiMe3)2-2,4-C2B4H5 and related carboranes

The reaction of gaseous HCl with either the disodium or dilithium compound of the [nido-2,4-(SiMe₃)₂-2,4-C₂B₄H₄]²⁻ dianion (I) in 1:1 stoichiometry in THF produced the monoprotonated species 1-Na(THF)₂-2,4-(SiMe₃)₂-2,4-C₂B₄H₅ (II) or 1-Li(THF)₂-2,4-(SiMe₃)₂-2,4-C₂B₄H₅ (III), in 81% and 80% yields, respectively. This method proved superior to that involving the direct reduction of the closo-C₂B₄ carborane by metal hydrides. II and III were characterized by elemental analysis, ¹H, ¹¹B and ¹³C NMR and IR spectra. Compound II was recrystallized from a mixture THF, hexane and TMEDA (1:2:1) to isolate colorless crystals of the mixed solvated species, 1-(THF)-1-(TMEDA)-1-Na-2,4-(SiMe₃)₂-2,4-C₂B₄H₅ (IV), which were subsequently used for X-ray diffraction studies. The structure of IV showed that the capping metal occupied the apical position above the open C₂B₃ face of the carborane and that a hydrogen atom was bridging the two adjacent boron atoms on that face. The ¹¹B and ¹³C NMR spectra calculated by GIAO (gauge independent atomic orbital) methods at the 6-311G^** level on the B3LYP/6-31G^* optimized geometries of I–III, and a number of related nido- and closo-carboranes, gave excellent agreement with experiment, even in compounds where electron correlation effects are known to be important.     

Thermodynamic Model for the Solubility of Cr(OH)3(am) in Concentrated NaOH and NaOH–NaNO3 Solutions

The main objective of this study was to develop a thermodynamic model for predicting Cr(III) behavior in concentrated NaOH and in mixed NaOH–NaNO₃ solutions for application to developing effective caustic leaching strategies for high-level nuclear waste sludges. To meet this objective, the solubility of Cr(OH)₃(am) was measured in 0.003 to 10.5 m NaOH, 3.0 m NaOH with NaNO₃ varying from 0.1 to 7.5 m, and 4.6 m NaNO₃ with NaOH varying from 0.1 to 3.5 m at room temperature (22 ± 2°C). A combination of techniques, X-ray absorption spectroscopy (XAS) and absorptive stripping voltammetry analyses, were used to determine the oxidation state and nature of aqueous Cr. A thermodynamic model, based on the Pitzer equations, was developed from the solubility measurements to account for dramatic increases in aqueous Cr with increases in NaOH concentration. The model includes only two aqueous Cr species, Cr(OH) ₄ ^– and Cr₂O₂(OH) ₄ ^– (although the possible presence of a small percentage of higher oligomers at >5.0 m NaOH cannot be discounted) and their ion–interaction parameters with Na⁺. The logarithms of the equilibrium constants for the reactions involving Cr(OH) ₄ ^– [Cr(OH)₃(am) + OH^– Cr(OH) ₄ ^– ] and Cr₂O₂(OH) ₄ ^2– [2Cr(OH)₃(am) + 2OH^– Cr₂O₂(OH) ₄ ^2– + 2H₂O] were determined to be –4.36 ± 0.24 and –5.24 ± 0.24, respectively. This model was further tested and provided close agreement between the observed Cr concentrations in equilibrium with Cr(OH)₃(am) in mixed NaOH–NaNO₃ solutions and with high-level tank sludges leached with and primarily containing NaOH as the major electrolyte.     

Solid-state Al and Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures

Partially deuterated Ca₃Al₂(SiO₄)_y(OH)_12−4y-Al(OH)₃ mixtures, prepared by hydration of Ca₃Al₂O₆ (C₃A), Ca₁₂Al₁₄O₃₃ (C₁₂A₇) and CaAl₂O₄ (CA) phases in the presence of silica fume, have been characterized by ²⁹Si and ²⁷Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca₃Al₂(OH)₁₂ and Al(OH)₃ phases were detected. From the quantitative analysis of ²⁷Al NMR signals, the Al(OH)₃/Ca₃Al₂(OH)₁₂ ratio was deduced. The incorporation of Si into the katoite structure, Ca₃Al₂(SiO₄)_3−x(OH)_4x, was followed by ²⁷Al and ²⁹Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of ²⁷Al MAS-NMR components associated with Al(OH)₆ and Al(OSi)(OH)₅ environments. The ²⁹Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From ²⁹Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures.     

Aluminum Solvate Complexes Forming in Acidic Methanol-Acetone Mixtures Studied by <Superscript>27</Superscript>Al NMR Spectroscopy

²⁷Al NMR spectroscopy is a powerful tool for the study of coordination and solvation in both aqueous and nonaqueous solutions. In this study, the complexes coexisting upon dissolution of AlCl₃ in acidic acetone + methanol solutions are shown to consist essentially of mixed hexacoordinated species of the general formula [Al(CH₃OH)_6−n (CH₃COCH₃) _n ]³⁺ (n=1,2 and 3), all exhibiting distinctly different ²⁷Al shielding effects. The relative populations of the various mixed species are found to be highly dependent upon the acetone:methanol mole ratio that in the more acetone-rich mixtures with aluminum become appreciably coordinated by acetone. The results demonstrate that the key factor for the formation of acetone-containing species in acidic methanolic solutions is having the CH₃COCH₃:CH₃OH mole ratio at 3:1.     

Preparation,Structural Characterization and the Molecular Structure of 2,3,5-Trinitro-<Emphasis Type="Italic">p</Emphasis>-xylene

2,3,5-trinitro-p-xylene (TPX) is synthesized by nitration of p-xylene in mixed acid of nitric and sulfuric acid. Single crystal of TPX is cultured from DMF solution using a slow cooling method. The compound is characterized by FT-IR, ¹H NMR and MS techniques. The crystal structure is determined by X-ray⁴ single-crystal diffraction analysis. The crystal belongs to the monoclinic system with space group P_n. Its unit cell parameters are as follows: a = 0.8271(2), b = 0.6011(1), c = 1.0487(2) nm, β = 105.42(2)^∘, V = 0.50263(2) nm³, D_c = 1.593 g/cm³, Z = 2, F(0 0 0) = 248. The molecular structures of TPX have been calculated at the B3LYP/6-31G^** and B3LYP/6-311G^** levels of theory, and its frequencies analysis have also been accomplished at the same level of theory. The thermal decomposition process of the compound was studied using DSC and TG-DTG techniques. The predicted nitro group vibrations with B3LYP/6-311G^** calculation considerably agree with the observed frequencies. The calculated results propose that the structural parameters from the theory are close to those of the crystal structure from the experiments.     

Accurate prediction of 195Pt-NMR chemical shifts for hydrolysis products of [PtCl6]2− in acidic and alkaline aqueous solutions by non-relativistic DFT computational protocols

The ¹⁹⁵Pt-NMR chemical shifts of all possible hydrolysis products of [PtCl₆]^2? in acidic and alkaline aqueous solutions are calculated employing simple non-relativistic density functional theory computational protocols. Particularly, the GIAO-PBE0/SARC-ZORA(Pt) ∪ 6-31 + G(d)(E) computational protocol augmented with the universal continuum solvation model (SMD) performs the best for calculation of the ¹⁹⁵Pt-NMR chemical shifts of the Pt(IV) complexes existing in acidic and alkaline aqueous solutions of [PtCl₆]^2?. Excellent linear plots of δ_calcd(¹⁹⁵Pt) chemical shifts versus δ_exptl(¹⁹⁵Pt) chemical shifts and δ_calcd(¹⁹⁵Pt) versus the natural atomic charge Q_Pt are obtained. Very small changes in the Pt–Cl and Pt–O bond distances of the octahedral [PtCl₆]^2?, [Pt(OH)₆]^2?, and [Pt(OH₂)₆]⁴⁺ complexes have significant influence on the computed σ^{iso 195}Pt magnetic shielding tensor elements of the anionic [PtCl₆]^2? and the computed δ ¹⁹⁵Pt chemical shifts of [Pt(OH)₆]^2? and [Pt(OH₂)₆]⁴⁺. An increase of the Pt–Cl and Pt–O bond distances by 0.001 Å (1 mÅ) is accompanied by a downfield shift increment of 17.0, 19.4, and 37.6 ppm mÅ^?1, respectively. Counter-anion effects in the case of the highly positive charged complexes drastically improve the accuracy of the calculated ¹⁹⁵Pt chemical shifts providing values very close to the experimental ones.     

Complexes of aluminium(III) with picolinic and pipecolinic acids: An27Al-NMR investigation

Summary Aluminium-27 NMR has been employed for the study of the interaction of Al(III) with picolinic (pic-H) and pipecolinic (pip-H) acids in aqueous solution at variablepH. In the reaction with picolinic acid distinct peaks for hydrated Al(III), 1:1 and 1:2 Al-picolinate complexes, as well as a mixed hydroxo-picolinato complex Al(pic)₂OH are observed. An insoluble 1:3 picolinate complex is formed atpH 3. Pipecolinic acid forms 1:1 and 1:2 Al-pipecolinate complexes. No hydroxy-pipecolinate species are formed, however, and the 1:2 complex is deprotonated abovepH 4.5 to colin- (pic-H) und Pipecolinsäure (pip-H) in wäßriger Lösung bei verschiedenenpH angewandt. Bei Al(pip)(H_–1 pip) have been isolated and characterized by elemental analysis, IR and¹H-NMR.

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Komplexe von Aluminium(III) mit Picolin- und Pipecolinsäure: Eine²⁷Al-NMR-Untersuchung

Zusammenfassung ²⁷Al-NMR wurde zur Untersuchung von Wechselwirkungen von Al(III) mit Picolin-(pic-H) und Pipecolinsäure (pip-H) in wäßriger Lösung bei verschiedenenpH angewandt. Bei der Reaktion mit Picolinsäure wurden separate Signale für hydratisiertes Al(III), 1:1 und 1:2 Al-Picolinat-Komplexe und auch für gemischte Hydroxo-picolinat-Komplexe Al(pic)₂OH beobachtet. BeipH3 wird unlöslicher Picolinat-Komplex gebildet. Pipecolinsäure geht 1:1 und 1:2 Al-Pipecolinat-Komplexe ein. Es werden keine Hydroxo-Pipecolinat-Komplexe gebildet. Der 1:2 Komplex wird über einempH von 4.5 deprotoniert und ergibt den unlöslichen Komplex Al(pip)(H_–1 pip). Die [3, 4] as well as those undergoing dialysis treatment for chronic renal failure [5]. taranalyse, IR und¹H-NMR charakterisiert.

     

Crystal Structure and Solid‐State 13C NMR of Methyl α‐d‐Mannofuranoside

The crystal structure of methyl α‐d‐mannofuranoside was determined by X‐ray crystallography. The C‐1–C‐2, C‐2–C‐3, C‐3–C‐4, C‐4–O and O‐4–C‐1 distances within the furanoside ring are 1.513(2), 1.523(2), 1.516(2), 1.445(2) and 1.422(2) Å, respectively. The hydrogen bonding consists of O–H–O interactions which include the anomeric oxygen but exclude the ring oxygen atom. The two hydroxyls OH‐6 and OH‐2 are H‐bond acceptors and donors with H···O distances of 1.92–1.93 Å, whereas the OH‐3 and OH‐5 are only H‐bond donor [H···O distance of 2.04(2) Å]. Additionally, OH‐6 participates in a weak hydrogen bond to the anomeric oxygen [H···O distance of 2.19(3) Å]. The crystalline methyl α‐d‐mannofuranoside adopts an ³ E ring conformation. The analysis of ¹³C CPMAS NMR chemical shifts for solid methyl α‐d‐mannofuranoside confirm such H‐bonding pattern.