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Oxalic acid

About: Oxalic acid is a research topic. Over the lifetime, 11584 publications have been published within this topic receiving 173263 citations. The topic is also known as: ethanedioic acid & H2ox.


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TL;DR: The results show that deliquescence can transform API to cocrystal or reverse the reaction given the right conditions and the interplay between moisture uptake and dissolution determines the liquid phase composition, supersaturation, and cocystal formation rates.
Abstract: The purpose of this study is to determine the mechanisms by which moisture can generate cocrystals when solid particles of cocrystal reactants are exposed to deliquescent conditions (when moisture sorption forms an aqueous solution). It is based on the hypothesis that cocrystallization behavior during water uptake can be derived from solution chemistry using models that describe cocrystal solubility and reaction crystallization of molecular complexes. Cocrystal systems were selected with active pharmaceutical ingredients (APIs) that form hydrates and include carbamazepine, caffeine, and theophylline. Moisture uptake and crystallization behavior were studied by gravimetric vapor sorption, X-ray powder diffraction, and on-line Raman spectroscopy. Results indicate that moisture uptake generates cocrystals of carbamazepine−nicotinamide, carbamazepine−saccharin, and caffeine or theophylline with dicarboxylic acid ligands (oxalic acid, maleic acid, glutaric acid, and malonic acid) when solid mixtures with cocry...

125 citations

Journal ArticleDOI
TL;DR: In this paper, an integrated process for the production of high octane gasoline from maple wood by hydrolysis of maple wood into aqueous carbohydrate solutions followed by an integrated phase hydrodeoxygenation of the sugar solutions.

125 citations

Journal ArticleDOI
TL;DR: The intrinsic dissolution rate (IDR) profile of TMZ-oxalic acid and TMZ-succinic acid cocrystals in buffer of pH 7 is comparable to that of temozolomide, and those with succinic acid and oxalic Acid exhibited both an improved stability and a comparable dissolution rate to the reference drug.
Abstract: The antitumor prodrug temo-zolomide (TMZ) decomposes in aque-ous medium of pH 7 but is relativelystable under acidic conditions. PureTMZ is obtained as a white powderbut turns pink and then brown, whichis indicative of chemical degradation.Pharmaceutical cocrystals of TMZwere engineered with safe coformerssuch as oxalic acid, succinic acid, sali-cylic acid, d,l-malic acid, and d,l-tarta-ric acid, to stabilize the drug as a coc-rystal. All cocrystals were character-ized by powder X-ray diffraction(PXRD), single crystal X-ray diffrac-tion, and FT-IR as well as FT-Ramanspectroscopy. Temozolomide cocrystalswith organic acids (pK a 2–6) werefound to be more stable than the refer-ence drug under physiological condi-tions. The half-life (T 1/2 ) of TMZ–oxalic and TMZ–salicylic acid mea-sured by UV/Vis spectroscopy in pH 7buffer is two times longer than that ofTMZ (3.5 h and 3.6 h vs. 1.7 h); TMZ–succinic acid, TMZ–tartaric acid, andTMZ–malic acid also exhibiteda longer half-life (2.3, 2.5, and 2.8 h, re-spectively). Stability studies at 408Cand 75% relative humidity (ICH con-ditions) showed that hydrolytic degra-dation of temozolomide in the solidstate started after one week, as deter-mined by PXRD, whereas its cocrystalswith succinic acid and oxalic acid wereintact at 28 weeks, thus confirming thegreater stability of cocrystals comparedto the reference drug. The intrinsic dis-solution rate (IDR) profile of TMZ–oxalic acid and TMZ–succinic acid coc-rystals in buffer of pH 7 is comparableto that of temozolomide. Among thetemozolomide cocrystals examined,those with succinic acid and oxalic acidexhibited both an improved stabilityand a comparable dissolution rate tothe reference drug.Keywords: crystal engineering ·cocrystals · stability · temozolo-mide · X-ray diffraction2274

124 citations

Journal ArticleDOI
TL;DR: A method for the preparation of anatase TiO2, which is stable to a temperature as high as 900 °C, without using any complex cationic dopants is presented in this article.
Abstract: A method for the preparation of anatase TiO2, which is stable to a temperature as high as 900 °C, without using any complex cationic dopants is presented. The synthetic procedure involves the reaction of titanium tetraisopropoxide (TTIP) with trifluoroacetic acid (TFA) followed by hydrolysis and sol−gel conversion to the xerogel and further calcination. The retention of the anatase phase to high temperatures can be attributed to the presence of small amounts of fluorine in the lattice, which is gradually removed between 500 and 900 °C as confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopic analysis. Samples prepared with a 1:16 TTIP/TFA composition calcined at 900 °C showed significantly higher photocatalytic activity compared to the control sample, standard commercial photocatalyst Degussa P25, and samples prepared using acetic acid and oxalic acid. The high-temperature anatase phase stability, determined by X-ray diffraction and Raman spectroscopy, coupled with its ...

124 citations

Journal ArticleDOI
TL;DR: In this paper, the electrodeposition of PANi films on mild steel from aqueous oxalic acid is reported, and PANi-coated iron samples exhibit very good protection against corrosion and are much more effective than polypyrrole coated ones.

123 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023292
2022561
2021266
2020352
2019482
2018455