DL-mandelic Acid Research Articles

Non-isothermal kinetics of the organocatalytic ring-opening polymerization of ε-caprolactone with metal-free α‑hydroxy acids: Eco-friendly and facile synthesis process

Metal-free and green α‑hydroxy acids (AHA) such as l-malic (MA), DL-mandelic acid (MDL), and citric acid (CA) were successfully and effectively utilized as an effective initiator for the solvent-free ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The performance of AHAs in the polymerization of ε-CL was completely and powerfully investigated via the non-isothermal differential scanning calorimetry (DSC). The proceed of ROP of ε-CL with AHAs could be real-time monitored by the obtained polymerization exotherms at different heating rates. The polymerization exotherms obtained from the ROP of ε-CL with CA occurred at a lower temperature range than MA, and MDA, respectively. From the kinetics study, the average activation energy (Ea) values for the ROP of ε-CL with CA (38.0 ± 1.8 kJ mol−1) were lower than MA (45.2 ± 3.6 kJ mol−1) and MDA (48.8 ± 6.2 kJ mol−1). Using the first-order model fitting, the values of pre-exponential factor (lnA0) for the ROP of ε-CL with CA, MA, and MDA were 7.0 ± 0.3, 8.5 ± 0.2, and 8.9 ± 0.3, respectively. The effectiveness of AHAs in the synthesis of PCL was clarified by conducting a larger-scale (4.0000 g) polymerization using conventional heating and microwave (MW) irradiation methods. From conventional heating, the green AHAs produced PCL with the number average molecular weight (Mn) and dispersity (Đ) values in the range of 5.18 × 103 - 1.43 × 104 g mol−1 and 1.14–2.02, respectively. The irradiation by MW could enhance the synthesis of PCL by reducing the synthesis time. By using the MW power of 450 W and irradiation time of 30 min, the PLC was obtained from the ROP of ε-CL with MA and MDA initiators, and the Mn of the obtained PCL from MW heating was 4.28 × 103 - 8.45 × 103 g mol−1. The mechanism for the ROP of ε-CL with all AHAs was proposed through the activated monomer mechanism.

Growth and characterization of D-Alanine DL-Mandelic acid single crystals for antibacterial activity and optical limiting applications

A promising optically prospective D-Alanine DL-Mandelic acid (DADLMA) an organic single crystal was successfully grown at room temperature by a slow solvent evaporation approach. The monoclinic crystal structure of the title crystal with space group C2 has been verified. The existence of multiple operational groups and linkages in the DADLMA crystal was ensured with the FTIR spectrum. The grown crystal was investigated to determine optical absorption cut-off wavelength (274 nm), energy band gap and linear refractive index by the UV–Visible absorption spectrum. The luminescence response has been observed to probe the compatibility of the material for the production of optical devices and the grown crystal shows a peak at 570 nm. The major focus of our work was to determine NLO properties of the sample and the DADLMA crystal was investigated for the first attempt by Z-scan measurement to bring out third-order nonlinear optical properties. The determined values are β (0.0149 × 10-4 cm/W), n2 (3.351 × 10-10 cm2/W) and χ(3) (1.674 × 10-7esu). The antibacterial activity of the title compound was investigated against a few foodborne pathogens (Streptococcus aureus, Klebsiella pneumoniae, Streptococcus pneumoniae and Escherichia coli) by measuring the zone of inhibition. Existing data indicate that the synthesized crystals are potential candidates for opto-electronic devices, optical limiting devices and biological applications.

Solid-state versatility in tranexamic acid drug: structural and thermal behavior of new salts and cocrystals.

Tranexamic acid (TNA) is an anti-fibrinolytic hemostatic drug widely used in various medical treatments. Six new salts and five cocrystals of TNA are reported here and the crystal structures of the obtained multicomponent compounds were determined using single-crystal X-ray diffraction (SC-XRD) techniques. TNA formed salts with coformers maleic acid (MEA), nicotinic acid, DL-mandelic acid and saccharin. Salt formation with MEA resulted in three different solid forms, namely TNA-MEA (1:1), TNA-MEA (2:1) and TNA-MEA-H2O (1:1:1). All synthesized TNA salt structures were crystallized as anhydrous except for TNA-MEA-H2O (1:1:1). TNA formed cocrystals with phenolic coformers such as catechol (CAT), resorcinol, hydroquinone, pyrogallol (PRG) and phloroglucinol. All cocrystal structures crystallized as hydrates except for TNA-PRG (1:1). The detailed structural investigation using SC-XRD revealed the presence of robust N-H...O and O-H...O hydrogen bonds in TNA salts and cocrystals. In TNA cocrystals, except for TNA-CAT-H2O (1:1:1), the coformer molecules interact with TNA molecules via bridged water molecules. In all the salt structures, TNA exists as cations, in which both carboxylic and amino groups are protonated (-COOH and -NH3+), while in cocrystals TNA exists as zwitterions with total charge zero. All synthesized multicomponent compounds were further characterized by differential scanning calorimetric, thermogravimetric and Fourier transform infrared analyses, and the formation of new multicomponent compounds were assessed based on the melting temperatures, percentage weight loss and stretching frequencies, respectively, corresponding to TNA/coformer molecules. A powder X-ray diffraction study confirmed the bulk purity of the synthesized crystalline multicomponent compounds.

Study on the interactions of tetradecylpyridinium dl-mandelic acid and cetylpyridinium dl-mandelic acid with some small biomolecules in aqueous solution

Interactions of two active pharmaceutical ingredient ionic liquids (API-ILs) tetradecylpyridinium dl-mandelic acid ([TetPy][MAN]) and cetylpyridinium dl-mandelic acid ([CetPy][MAN]) with some small biomolecules have been studied by using conductometric, density and UV–vis spectroscopic techniques. The chosen small biomolecules are glycine, l-alanine, l-valine, l-leucine and glycylglycine (AAGG). The critical micelle concentration (cmc) of [TetPy][MAN] and [CetPy][MAN] in aqueous AAGG solution is calculated from the measured conductance values, thus yielding some thermodynamic parameters of the micellization, such as the standard Gibbs energy change (ΔGm0), the standard enthalpy change (ΔHm0) and the standard entropy change (ΔSm0). On the basis of the experimental densities of ternary solutions of (AAGG + API-ILs + water), apparent molar volume at infinite dilution (V2,φ0), apparent molar expansibility at infinite dilution (Eφ0), transfer partial molar volume (ΔtV0) and hydration number (nH) of AAGG in aqueous API-ILs solution were calculated. The dominant hydrophobic-hydrophilic and hydrophobic-hydrophobic interactions were involved in the investigated systems. The binding constant (Kb) between AAGG and API-ILs has been calculated from UV–vis spectroscopic data. Effect of some factors including concentration, temperature, molecular structure, etc. on the aforementioned parameters and the existing solvent–solute interaction has been discussed.

Crystal Structural Analysis of DL-Mandelate Salt of Carvedilol and Its Correlation with Physicochemical Properties

A 1:1 salt of carvedilol (CVD), an anti-hypertensive drug, with DL-mandelic acid (DL-MA) was crystallized from ethanol and the structure was characterized by X-ray single-crystal diffraction, revealing salt formation by transfer of an acidic proton from the COOH group of MA to the aliphatic (acyclic) secondary amino NH group of CVD. The crystal structure is triclinic, with a P-1 space group and unit cell parameters a = 9.8416(5) Å, b = 11.4689(5) Å, c = 14.0746(7) Å, α = 108.595(8), β = 95.182(7), γ = 107.323(8), V = 1406.95(15) Å3, and Z = 2. The asymmetric unit contained one protonated CVD and one MA anion, linked via an N+–H∙∙∙O¯ strong hydrogen bond and a ratio of 1:1. As previously reported, the thermal, spectroscopic, and powder X-ray diffraction properties of the salt of CVD with DL-MA (CVD_DL-MA) differed from CVD alone. The intrinsic dissolution rate of CVD_DL-MA was about 10.7 times faster than CVD alone in a pH 6.8 buffer.

Molecular interactions between some amino acids and a pharmaceutically active ionic liquid domiphen DL-mandelic acid in aqueous medium at temperatures from 293.15 K to 313.15 K

Molecular interactions between some amino acids (glycine, l-alanine, l-valine and l-leucine) and a pharmaceutically active ionic liquid domiphen DL-mandelic acid ([DOM][MAN]) in aqueous solution at various temperatures have been studied by means of volumetric, conductivity and spectroscopy measurements. Density data were used to derive standard partial molar volume, V2,φ0 standard partial molar expansibility, Eφ0, standard transfer volume, ΔtV0, isobaric thermal expansion coefficient, α0 and hydration number, nH of amino acids. On the basis of the experimental conductivity and fluorescence spectroscopy data, the aggregation behaviour of [DOM][MAN] in aqueous amino acid solutions was investigated. Critical micelle concentration, cmc, aggregation number, Nagg, some thermodynamic functions, ΔGm0, ΔHm0, ΔSm0 and ΔCp0 of micellization for [DOM][MAN] have been obtained. Effect of concentration and temperature on the obtained parameters has been discussed. Binding constant Kb for amino acid-[DOM][MAN] complex estimated using the UV–vis spectroscopic data approved that the solute-solvent interactions were strengthened by elevating the size of alkyl part of amino acids.

Enantioselective liquid-liquid extraction of DL-mandelic acid using chiral diphosphine ligands as extractants.

In order to expand the application range of chiral diphosphine ligands, (S)-BINAP, (S)-SEGPHOS, and (S)-MeO-BIPHEP were employed as extractants to recognize DL-mandelic acid. The results indicated that (S)-SEGPHOS-Cu exhibited considerable ability to recognize DL-mandelic acid with operational enantioselectivity (α) of 2.677. The process of extraction of DL-mandelic acid using (S)-SEGPHOS-Cu as extractant was systematically investigated. Performance factor (pf) was adopted to comprehensively evaluate the extraction. After optimization by response surface methodology (RSM), the optimal extraction condition is temperature of 5.5°C, (S)-SEGPHOS-Cu concentration of 3.0mmol/L, and pH of 8.0. And the predicted and experimental maximum values of pf were 0.26374 and 0.26839, respectively.

Growth and characterization of a nonlinear optical material: l-alanine dl-mandelic acid hemihydrate

l-Alanine dl-mandelic acid hemihydrate (LADLMAH) an organic nonlinear optical chromophore crystal was synthesized using water as solvent and the crystals were grown by a slow solvent evaporation method. The single crystal X-ray diffraction study reveals that the crystals possess to triclinic system with acentric space group P1. The coordination of different moieties present in the compound and molecular structure were elucidated by vibrational and NMR spectroscopic studies. The lower cut-off wavelength is observed down to 258 nm and direct optical band gap was calculated as 5.20 eV. Second harmonic generation was confirmed by Kurtz–Perry powder method. Discrete thermodynamic properties were carried out by TG–DTA techniques. A multiple shot laser technique was adopted to investigate the surface laser damage of the crystal. The microhardness test was carried out employing one of the as-grown hard crystals and there by hardness number (Hv) and Meyer’s index (n) were assessed. The dielectric behaviour of the grown crystal was studied for different temperatures at different frequencies. The third-order optical nonlinearity parameters of LADLMAH were investigated in detail using a Z-scan technique with Nd:YAG laser at 532 nm.

DL-mandelic acid intercalated Zn-Al layered double hydroxide: A novel antimicrobial layered material

DL-mandelic acid (MA) has been intercalated into Zn-Al layered double hydroxide (LDH) by an anion-exchange reaction. After intercalation of MA anions, the basal spacing of the LDH increased from 0.75 to 1.46 nm, suggesting that the MA anions were successfully intercalated into the interlayer galleries of the LDH. The structure and the thermal stability of the samples were characterized by XRD, FT-IR, TG-DTA. Studies of MA release from ZnAl-MA-LDH in hydrochloric solution (pH = 4) imply that ZnAl-MA-LDH is a better controlled release system than pure MA. Meanwhile, the mechanisms of slow release were assessed by using four commonly kinetic models. Finally, the antimicrobial activity of ZnAl-MA-LDH was tested against two kinds of bacteria and a fungus. The study confirms that the mandelic ions intercalated LDHs have the potential application as a slow release preservative in the future.

Preparation and evaluation of a deoxycholic-calix[4]arene hybrid-type receptor as a chiral stationary phase for HPLC.

We report the synthesis and enantioseparation characteristics of two novel covalently immobilized deoxycholic acid derivatives as chiral stationary phases for high-performance liquid chromatography. In the structure of the first stationary phase, the 3-position of deoxycholic acid is substituted with a 3,5-dinitrophenylcarbamoyl group and the second one has an additional calix[4]arene attached to the carboxylic group of the deoxycholic acid. The chromatographic performance of the stationary phases was evaluated with enantioseparation of N-(3,5-dinitrobenzoyl)-dl-leucine, N-(3,5-dinitrobenzoyl)-dl-valine, omeprazole, diclofop-methyl, dl-mandelic acid and (RS)-pregabalin. Comparison of the performance characteristics of the prepared chiral stationary phases provided evidence for the active involvement of the calix[4]arene unit in the chiral recognition process. Both stationary phases are chemically bonded to the silica and can be used in both normal-phase and reversed-phase modes.

Preparation and evaluation of a chiral HPLC stationary phase based on cone calix[4]arene functionalized at the upper rim with l-alanine units.

Here we report a new chiral stationary phase (CSP) immobilized on silica gel based on cone calix[4]arene functionalized at the upper rim with two l-alanine units as new chiral selector that has been used in high-performance liquid chromatography. The CSP was prepared by covalently bonding the allyl groups at the lower rim of calix[4]arene to silica gel by thiol-ene click chemistry reaction. Elemental analysis of the CSP showed that 120 μmol of chiral selector bonded per gram of silica gel. 1-Hexene was used for end-capping of unreacted mercapto groups on silica gel. Since the CSP is chemically bonded to the silica, it can be used in the normal-phase and reversed-phase mode and with halogenated solvents as mobile phases, if desired. The chromatographic performance of the CSP was evaluated in the enantioseparation of the 3,5-dinitrobenzoyl derivatives of some amino acids, diclofop-methyl and dl-mandelic acid.

Growth and characterization of l-asparagine monohydrate admixtured dl-mandelic acid nonlinear optical single crystal

An organic nonlinear optical (NLO) single crystal of l-asparagine monohydrate admixtured dl-mandelic acid (LAMDLMA) has been grown by slow evaporation technique. Single crystal XRD ascertained orthorhombic system with noncentrosymmetric space group for LAMDLMA. The occurrence of prospective functional groups was initially identified by FTIR and FT-Raman spectroscopic studies. UV–visible spectral study assessed the optical quality and band gap energy was evaluated. The title crystal shows excellent resistance to laser radiation with threshold up to 1.36 GW/cm2. The thermal stability and mechanical behavior of LAMDLMA was investigated. The dielectric analysis of the sample reveals the electric field response as a function of frequency. The second order and third-order nonlinear optical response of LAMDLMA was confirmed by Kurtz–Perry and Z-scan technique recommended its suitability in NLO applications.

Growth and characterization of dl-Mandelic acid (C6H5CH(OH)CO2H) single crystal for third-order nonlinear optical applications

An organic conjugated chromophore dl-mandelic acid (DLMA) single crystal was synthesized and grown-up by means of slow evaporation technique. Single crystal X-ray diffraction study proclaimed that the DLMA crystal crystallized in monoclinic system with centrosymmetric space group P21/c. The various characteristic fundamental vibration frequencies were identified by FTIR spectroscopic studies. UV–visible spectral analysis concluded that the lower cut-off wavelength and calculated direct optical band gap of DLMA as 257 nm and 5.40 eV respectively. Thermal property of dl-mandelic acid was established through thermogravimetric and differential scanning calorimetric technique. The electric field response of DLMA crystal was investigated from the dielectric studies at a few selected temperatures and frequencies. The quantum chemical assessments such as HOMO-LUMO, molecular electrostatic potential and NLO activity were calculated and presented. In order to determine mechanical strength of DLMA crystal for various loads using Vickers microhardness tester. The real and imaginary parts of the third-order susceptibility (χ3) were evaluated with the Z-scan technique using closed and open signatures respectively and was found to be Re (χ3) = 4.15 × 10−6 esu and Im (χ3) = 0.47 × 10−6 esu.

Growth, spectral and optical characterization of a novel nonlinear optical organic material: d-Alanine dl-Mandelic acid single crystal

An organic nonlinear optical single crystal, d-alanine dl-mandelic acid was synthesized and successfully grown by slow evaporation solution growth technique at ambient temperature using solvent of aqueous solution. The unit cell parameters were assessed from single crystal X-ray diffraction analysis. The presence of diverse functional groups and vibrational modes were identified using Fourier Transform Infra Red and Fourier Transform Raman spectral analyses. The chemical structure of grown crystal has been identified by Nuclear Magnetic Resonance spectroscopic study. Ultraviolet–visible spectral analysis reveal that the crystal has lower cut-off wavelength down to 259 nm, is a key factor to exhibit second harmonic generation signal. The electronic optical band gap and Urbach energy is calculated as 5.31 eV and 0.2425 eV respectively from the UV absorption profile. The diverse optical properties such as, extinction coefficient, reflectance, linear refractive index, optical conductivity was calculated using UV–visible data. The relative second harmonic efficiency of the compound is found to be 0.81 times greater than that of KH2PO4 (KDP). The thermal stability of the grown crystal was studied by thermogravimetric analysis and differential thermal analysis techniques. The luminescence spectrum exhibited two peaks (520 nm, 564 nm) due to the donation of protons from carboxylic acid to amino group. The Vickers microhardness test was carried out employing one of the as-grown hard crystal and there by hardness number (Hv), Meyer's index (n), yield strength (σy), elastic stiffness constant (C11) and Knoop hardness number (HK) were assessed. The dielectric behaviour of the as-grown crystal was analyzed for different temperatures (313 K, 333 K, 353 K, and 373 K) at different frequencies.

Kinetic study for the oxidation of dl-mandelic acid by tripropylammonium fluorochromate in the absence and presence of picolinic acid and 1,10-phenanthroline

Kinetic study for the oxidation of dl-mandelic acid by tripropylammonium fluorochromate in the absence and presence of picolinic acid and 1,10-phenanthroline

Growth, spectral, thermal, laser damage threshold, microhardness, dielectric, linear and nonlinear optical properties of an organic single crystal: L-phenylalanine DL-mandelic acid

Single crystals of L-phenylalanine dl-mandelic acid [C9H11NO2. C8H8O3], have been grown by the slow evaporation technique at room temperature using aqueous solution. The single crystal XRD study confirms monoclinic system for the grown crystal. The functional groups present in the grown crystal have been identified by FTIR and FT-Raman analyses. The optical absorption studies show that the crystal is transparent in the visible region with a lower cut-off wavelength of 257nm and the optical band gap energy Eg is determined to be 4.62eV. The Kurtz powder second harmonic generation was confirmed using Nd:YAG laser with fundamental wavelength of 1064nm. Further, the thermal studies confirmed no weight loss up to 150°C for the as-grown crystal. The photoluminescence spectrum exhibited three peaks (414nm, 519nm, 568nm) due to the donation of protons from carboxylic acid to amino group. Laser damage threshold value was found to be 4.98GW/cm2. The Vickers microhardness test was carried out on the grown crystals and there by Vickers hardness number (Hv), work hardening coefficient (n), yield strength (σy), stiffness constant C11 were evaluated. The dielectric behavior of the crystal has been determined in the frequency range 50Hz–5MHz at various temperatures.

Effect of the presence of strong and weak electrolytes on the existence of uniaxial and biaxial nematic phases in lyotropic mixtures

ABSTRACTThe lyotropic mixture of potassium laurate/decanol/water presenting only the uniaxial nematic calamitic phase was doped with one strong (potassium chloride, KCl) and 11 weak electrolytes with phenyl-rings (DL-mandelic acid, benzoic acid, DL-phenyllactic acid, phenylacetic acid, phenol and phenylmethanol) and with cyclohexyl-ring (RS-hexahydromandelic acid, cyclohexanecarboxylic acid, cyclohexaneacetic acid, cyclohexanol and cyclohexylmethanol), separately. We also chose two nonpolar dopant molecules, benzene and cyclohexane, for the comparison of them with weak electrolytes, since they are located in the hydrocarbon core of the micelle. The nematic phase sequences, in particular the presence of the biaxial nematic phase, were investigated as a function of the dopant molar concentration and temperature. The laser conoscopy and small-angle X-ray scattering techniques were used to characterise the different nematic phases. Weak electrolytes having –COOH group as polar part were found to be very effective in stabilising the three nematic phases (two uniaxial and a biaxial). Guest molecules with only the –OH group did not show any effect on the stabilisation of other nematic phases. The experimental results are interpreted considering the screening effect of the hydrophilic parts of the dopants on the repulsion between the polar heads of the main amphiphilic molecules at micelle surfaces. This process favours the increase of the more flat micellar surfaces of micelles, which triggers the orientational fluctuations responsible for the biaxial and discotic nematic phases.

Solubility and Dissolution Rate Enhancement of Triamterene by a Cocrystallization Method

A potassium-sparing diuretic, triamterene, shows a low oral bioavailability with wide intersubject variation due to its poor aqueous solubility (45 μg/mL). To improve its solubility, a group of pharmaceutically acceptable coformers were screened with triamterene by slurry and liquid-assisted grinding methods, and dl-mandelic acid (1) and saccharin (2) successfully cocrystallized with triamterene to form one anhydrous and one monohydrate molecular salt, respectively. Both new forms were characterized by spectroscopic methods, thermal analysis, and X-ray diffraction. Their single crystal structures reveal that proton transfer from coformers to the nitrogen atom of the pyrimidine group in triamterene and the coformer anions thus connect to the protonated triamterene by multiple hydrogen bonded heterosynthons. The apparent solubility values and intrinsic dissolution rates of 1 and 2 in simulated gastric fluid (pH 1.20) are higher than those of parent drug, indicating the solubility of triamterene can be effectively improved by cocrystallization. The exposure of 1 and 2 to 0–95% RH levels and accelerated ICH condition of 40 °C/75% RH confirm their stability and the potential of these new forms to envisage new, more efficient formulations of triamterene.

In situ immobilization of a general resolving agent on the magnetic multi-wall carbon nanotube for the direct enantioenrichment of dl-mandelic acid

l-Threonine (l-thr) as a general chiral selector anchored on the surface of magnetic multi-wall carbon nanotube (MMWCNT) was prepared using an in situ electrostatic adsorption and studied as a new magnetically chiral selector for the separation of chiral dl-mandelic acid (dl-MA) as a model sample. By varying the pH, dl-MA was adsorbed on the surface of magnetic chiral selector through hydrogen bonds. It is recognized that MMWCNT with chiral ligands on its surface simultaneously possesses both magnetic property and direct chiral recognition ability. The successful immobilization of l-thr onto the surface of MMWCNT was confirmed by infrared spectra (FT-IR), X-ray diffraction patterns (XRD) and transmission electron microscopy (TEM). The FT-IR and mass spectra of supernatant and elution solutions also confirmed the immobilization of l-thr onto the surface of MMWCNT. The analysis results of specific rotation, HPLC and ultraviolet–visible spectroscopy reveal that the l-thr-MMWCNT show stronger complexation of (+)-enantiomer than (−)-enantiomer. The functional magnetic nanotubes were easily separated from the racemic solution using an external magnetic field which demonstrated its feasibility of recycling the adsorbent. All processes including in situ immobilization, enantioseparation (enantioenrichment) and magnetic separation were done by single process in a short time (only 10min).

A study of the solvent dependence of the structures and the vibrational, 1H and 13C NMR spectra of l- and dl-mandelic acid and l- and dl-3-phenyllactic acid

The structural stability of mandelic acid and 3-phenyllactic acid was investigated by Density Functional B3LYP calculations with the 6-311G∗∗ basis set. The two acids were predicted to have non-planar forms with cisoid α-hydroxy moiety with respect to the CO group as their lowest energy structures. From the SCRF=SMD calculations the stability of both acids is predicted to be significantly dependent on the dielectric constant of the solvent. The infrared and Raman spectra of l-mandelic and l-3-phenyllactic acids were compared to the corresponding solid state spectra of the dl-racemic mixtures. The vibrational wavenumbers were computed at the B3LYP level of theory and tentative vibrational assignments were provided on the basis of combined theoretical and experimental infrared and Raman data of the molecules. The 1H and 13C NMR spectra of both acids were interpreted by experimental and DFT calculated chemical shifts of the two acids. The RMSD between experimental and theoretical 1H and 13C chemical shifts for mandelic acid is 0.961 and 6.119ppm, whereas for 3-phenyllactic acid, it is 0.611 and 5.214ppm, respectively.