Month: November 2022

Corrosion resistance and antibacterial activity of procyanidin B2 as a novel environment-friendly inhibitor for Q235 steel in 1 M HCl solution was written by Huang, Li;Yang, Kun-Peng;Zhao, Qing;Li, Hui-Jing;Wang, Jin-Yi;Wu, Yan-Chao. And the article was included in Bioelectrochemistry in 2022.SDS of cas: 29106-49-8 The following contents are mentioned in the article:

Flavonoids, alkaloids, glucosides and tannins with good corrosion inhibition are the main natural components in plants. In this work, procyanidin B2 (PCB2), a natural flavonoid, was firstly isolated from Uncaria laevigata. Corrosion inhibition, chem. reactivity and adsorption of PCB2 on Q235 carbon steel were described by exptl. and theor. studies. The inhibition performance of PCB2 as a green corrosion inhibitor was evaluated by electrochem. and gravimetric tests. The binding active sites and activities thereof on the steel surface were illustrated by quantum chem., and the equilibrium configuration was predicted by mol. dynamics simulation. PCB2 exhibits good corrosion inhibition on Q235 steel over a wide temperature range. The electrochem. results show that PCB2 is a mixed inhibitor, and its inhibition efficiency increases with the addition of PCB2 concentration Moreover, the protective film is formed on the steel and the active corrosion sites are blocked significantly by surface anal. Addnl., the theor. calculation proves a strong interaction between PCB2 mol. and carbon steel. Besides, the antimicrobial activity was also preliminarily studied. This suggests that PCB2 exhibits better antimicrobial activity against many Gram-pos. and Gram-neg. bacteria. As a novel green corrosion inhibitor and antimicrobial agent, PCB2 is worthy of further exploitation. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8SDS of cas: 29106-49-8).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. Under appropriate conditions, inorganic acids also react with alcohols to form esters. To form these esters, a wide variety of specialized reagents and conditions can be used. A multistep synthesis may use Grignard-like reactions to form an alcohol with the desired carbon structure, followed by reactions to convert the hydroxyl group of the alcohol to the desired functionality.SDS of cas: 29106-49-8

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Formation and nature of non-extractable residues of emerging organic contaminants in humic acids catalyzed by laccase was written by Zhou, Yue;Sun, Feifei;Wu, Xuan;Cao, Siqi;Guo, Xiaoran;Wang, Qilin;Wang, Yongfeng;Ji, Rong. And the article was included in Science of the Total Environment in 2022.Synthetic Route of C13H12O2 The following contents are mentioned in the article:

Formation of non-extractable residues (NERs) is the major fate of most environmental organic contaminants in soil, however, there is no direct evidence yet to support the assumed phys. entrapment of NERs (i.e., type I NERs) inside soil humic substances. Here, we used ¹⁴C-radiotracer and silylation techniques to analyze NERs of six emerging and traditional organic contaminants formed in a suspension of humic acids (HA) under catalysis of the oxidative enzyme laccase. Laccase induced formation of both type I and covalently bound NERs (i.e., type II NERs) of bisphenol A, bisphenol F, and tetrabromobisphenol A to a large extent, and of bisphenol S (BPS) and sulfamethoxazole (SMX) to a less extent, while no induction for phenanthrene. The type I NERs were formed supposedly owing to laccase-induced alteration of primary (active groups) and secondary (conformation) structure of humic supramols., contributing surprisingly to large extents (23.5%-65.7%) to the total NERs, particularly for BPS and SMX, which both were otherwise not transformed by laccase catalysis. Electron-withdrawing sulfonyl group and bromine substitution significantly decreased amount and kinetics of NER formation, resp. This study provides the first direct evidence for the formation of type I NERs in humic substances and implies a “Trojan horse” effect of such NERs in the environment. This study involved multiple reactions and reactants, such as 4,4′-Methylenediphenol (cas: 620-92-8Synthetic Route of C13H12O2).

4,4′-Methylenediphenol (cas: 620-92-8) belongs to alcohols. The oxygen atom of the strongly polarized O―H bond of an alcohol pulls electron density away from the hydrogen atom. This polarized hydrogen, which bears a partial positive charge, can form a hydrogen bond with a pair of nonbonding electrons on another oxygen atom. Alcohols may be oxidized to give ketones, aldehydes, and carboxylic acids. These functional groups are useful for further reactions. Oxidation of organic compounds generally increases the number of bonds from carbon to oxygen (or another electronegative element, such as a halogen), and it may decrease the number of bonds to hydrogen.Synthetic Route of C13H12O2

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Interactions between Leu. mesenteroides and L. plantarum in Chinese northeast sauerkraut was written by Yang, Xiaozhe;Hu, Wenzhong;Xiu, Zhilong;Ji, Yaru;Guan, Yuge. And the article was included in LWT–Food Science and Technology in 2022.Name: (2R,3R,4S,5R,6S)-2-(Hydroxymethyl)-6-(isopropylthio)tetrahydro-2H-pyran-3,4,5-triol The following contents are mentioned in the article:

LAB are mostly used microorganisms for traditional fermented foods, e.g. Chinese northeast sauerkraut. However, the interactions between these strains are little known in mixed culture. This study aimed to explore the interaction between Leu. mesenteroides and L. plantarum based on metabolomics and transcriptomics during single- and mix-cultured fermentation of Chinese northeast sauerkraut. Metabolomics anal. revealed that the mixed culture showed different metabolite profiles in comparison with single culture. Higher levels of 4-vinylphenol (4.51%), 2,6-diaminopimelic acid (4.47%), Et dodecanoate (5.53%) were observed in mix-cultured samples than that with Leu. mesenteroides. In addition, the levels of 4-isopropylbenzoic acid (3.54%), 2,3-butanediol (7.23%), 1-octadecene (5.15%), Et dodecanoate (5.53%) were higher than that with L. plantarum. The most influenced pathway was carbohydrate metabolism, which was mostly related to 116 genes considered as DEGs in C_30 vs. D_30 groups (CD), according to transcriptomics anal. Addnl., 69 genes were considered as significantly DEGs in C_30 vs. A_30 groups (CA) which were considerably mapped to amino acid metabolism These results provided integrated views into the adaptive responses of the two strains to mix-cultured fermentation, which was useful for the rational development of mixed cultures in sauerkraut industry. This study involved multiple reactions and reactants, such as (2R,3R,4S,5R,6S)-2-(Hydroxymethyl)-6-(isopropylthio)tetrahydro-2H-pyran-3,4,5-triol (cas: 367-93-1Name: (2R,3R,4S,5R,6S)-2-(Hydroxymethyl)-6-(isopropylthio)tetrahydro-2H-pyran-3,4,5-triol).

(2R,3R,4S,5R,6S)-2-(Hydroxymethyl)-6-(isopropylthio)tetrahydro-2H-pyran-3,4,5-triol (cas: 367-93-1) belongs to alcohols. Alcohols are among the most common organic compounds. They are used as sweeteners and in making perfumes, are valuable intermediates in the synthesis of other compounds, and are among the most abundantly produced organic chemicals in industry. Under carefully controlled conditions, simple alcohols can undergo intermolecular dehydration to give ethers. This reaction is effective only with methanol, ethanol, and other simple primary alcohols.Name: (2R,3R,4S,5R,6S)-2-(Hydroxymethyl)-6-(isopropylthio)tetrahydro-2H-pyran-3,4,5-triol

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Hydrogel Skin-Covered Neurons Self-Assembled with Gustatory Cells for Selective Taste Stimulation was written by Le-Kim, Trang Huyen;Koo, Bon Il;Yun, Jun Su;Cho, Seung-Woo;Nam, Yoon Sung. And the article was included in ACS Omega in 2019.SDS of cas: 923-61-5 The following contents are mentioned in the article:

Many tech. challenges exist in the coculture of multiple types of cells, including medium optimization, cell-to-cell connection, and selective data acquisition of cellular responses. Particularly, mixed cellular responses limit the precise interpretation of intercellular signal transduction. Here, the authors report the formation of an agarose gel skin on neurons closely assembled with gustatory cells to selectively stimulate gustatory cells by retarding the diffusion of tastants to neurons. The signal transmission, triggered by denatonium benzoate, from gustatory cells to neurons was monitored using intracellular calcium ion concentrations The agarose gel skin efficiently suppressed the direct transfer of tastants to neurons, decreasing the number of responsive neurons from 56 to 13% and the number of calcium ion signals per neuron from multiple to single. The assembly of neurons with gustatory cells induced the high level of neuronal responses through taste signal transduction from gustatory cells to neurons. However, the calcium ion signal peaks of free neurons coated with agarose gel were much shorter and weaker than those of neurons closely assembled with gustatory cells. This work demonstrated that agarose gel skin is a simple, fast, and effective means to increase the signal selectivity of cellular responses in the coculture of multiple types of cells. This study involved multiple reactions and reactants, such as (2R)-3-(((2-Aminoethoxy)(hydroxy)phosphoryl)oxy)propane-1,2-diyl dipalmitate (cas: 923-61-5SDS of cas: 923-61-5).

(2R)-3-(((2-Aminoethoxy)(hydroxy)phosphoryl)oxy)propane-1,2-diyl dipalmitate (cas: 923-61-5) belongs to alcohols. A strong base can deprotonate an alcohol to yield an alkoxide ion (R―O−). For example, sodamide (NaNH2), a very strong base, abstracts the hydrogen atom of an alcohol. Secondary alcohols are easily oxidized without breaking carbon-carbon bonds only as far as the ketone stage. No further oxidation is seen except under very stringent conditions.SDS of cas: 923-61-5

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Optimization of muscle cell culture media using nonlinear design of experiments was written by Cosenza, Zachary;Block, David E.;Baar, Keith. And the article was included in Biotechnology Journal in 2021.SDS of cas: 65-22-5 The following contents are mentioned in the article:

Optimizing media for biol. processes, such as those used in tissue engineering and cultivated meat production, is difficult due to the extensive experimentation required, number of media components, nonlinear and interactive responses, and the number of conflicting design objectives. Here we demonstrate the capacity of a nonlinear design-of-experiments (DOE) method to predict optimal media conditions in fewer experiments than a traditional DOE. The approach is based on a hybridization of a coordinate search for local optimization with dynamically adjusted search spaces and a global search method utilizing a truncated genetic algorithm using radial basis functions to store and model prior knowledge. Using this method, we were able to reduce the cost of muscle cell proliferation media while maintaining cell growth 48 h after seeding using 30 common components of typical com. growth medium in fewer experiments than a traditional DOE (70 vs. 103). While we clearly demonstrated that the exptl. optimization algorithm significantly outperforms conventional DOE, due to the choice of a 48 h growth assay weighted by medium cost as an objective function, these findings were limited to performance at a single passage, and did not generalize to growth over multiple passages. This underscores the importance of choosing objective functions that align well with process goals. This study involved multiple reactions and reactants, such as 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride (cas: 65-22-5SDS of cas: 65-22-5).

3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride (cas: 65-22-5) belongs to alcohols. A strong base can deprotonate an alcohol to yield an alkoxide ion (R―O−). For example, sodamide (NaNH2), a very strong base, abstracts the hydrogen atom of an alcohol. A multistep synthesis may use Grignard-like reactions to form an alcohol with the desired carbon structure, followed by reactions to convert the hydroxyl group of the alcohol to the desired functionality.SDS of cas: 65-22-5

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

A Comparative and Comprehensive Characterization of Polyphenols of Selected Fruits from the Rosaceae Family was written by Hameed, Ahsan;Liu, Ziyao;Wu, Hanjing;Zhong, Biming;Ciborowski, Michal;Suleria, Hafiz Ansar Rasul. And the article was included in Metabolites in 2022.Name: (2S,3R,4S,5S,6R)-2-(3-Hydroxy-5-((E)-4-hydroxystyryl)phenoxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol The following contents are mentioned in the article:

The present research presents a comprehensive characterization of polyphenols from peach, pear, and plum using liquid chromatog. coupled with electrospray ionization quadrupole-time-of-flight-mass spectrometry (LC-ESI-QTOF-MS/MS), followed by the determination of their antioxidant potential. Plums showed the highest total phenolic content (TPC; 0.62 mg GAE/g), while peaches showed the highest total flavonoid content (TFC; 0.29 mg QE/g), also corresponding to their high scavenging activities (i.e., DPPH, ABTS, FRAP, and TAC). In all three fruit samples, a total of 51 polyphenolic compounds were tentatively identified and were mainly characterized from hydroxybenzoic acids, hydroxycinnamic acids, hydroxyphenylpentanoic acids, flavanols, flavonols, and isoflavonoids subclasses. Twenty targeted phenolic compounds were quantified using high-performance liquid chromatog. with photodiode array detection (HPLC-PDA). The plum cultivar showed the highest content of phenolic acids (chlorogenic acid, 11.86 mg/100 g), whereas peach samples showed the highest concentration of flavonoids (catechin, 7.31 mg/100 g), as compared to pear. Based on these findings, the present research contributes and complements the current characterization data of these fruits presented in the literature, as well as ensures and encourages the utilization of these fruits in different food, feed, and nutraceutical industries. This study involved multiple reactions and reactants, such as (2S,3R,4S,5S,6R)-2-(3-Hydroxy-5-((E)-4-hydroxystyryl)phenoxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol (cas: 27208-80-6Name: (2S,3R,4S,5S,6R)-2-(3-Hydroxy-5-((E)-4-hydroxystyryl)phenoxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol).

(2S,3R,4S,5S,6R)-2-(3-Hydroxy-5-((E)-4-hydroxystyryl)phenoxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol (cas: 27208-80-6) belongs to alcohols. A strong base can deprotonate an alcohol to yield an alkoxide ion (R―O−). For example, sodamide (NaNH2), a very strong base, abstracts the hydrogen atom of an alcohol. Alcohols may be oxidized to give ketones, aldehydes, and carboxylic acids. These functional groups are useful for further reactions. Oxidation of organic compounds generally increases the number of bonds from carbon to oxygen (or another electronegative element, such as a halogen), and it may decrease the number of bonds to hydrogen.Name: (2S,3R,4S,5S,6R)-2-(3-Hydroxy-5-((E)-4-hydroxystyryl)phenoxy)-6-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Towards in situ continuous feeding via controlled release of complete nutrients for fed-batch culture of animal cells was written by Rawat, Jyoti;Gadgil, Mugdha. And the article was included in Biochemical Engineering Journal in 2020.Related Products of 65-22-5 The following contents are mentioned in the article:

Small-scale culture of animal cells in suspension is of importance for many applications. At a small-scale, fed-batch is achieved either by manual bolus feeding or the use of liquid handling robots. In this study, we report an alternate application of a hydrogel for in situ continuous delivery of a nutrient feed comprising 18 amino acids, vitamins, antioxidants, and trace elements. We show that amino acid release is sustained for at least seven days. Importantly, release rates of individual amino acids can be independently modulated by changing their loading. We demonstrate the application of this hydrogel for complete in situ feeding of nutrients to a suspension adapted CHO cell line expressing IgG leading to 2.7-fold and 4-fold improvement in integral viable cell d. (IVCD) and volumetric productivity resp. This is similar to improvements obtained by bolus liquid feeding. Further, supplying glucose from the same hydrogel to eliminate manual feeding led to a 1.8-fold increase in IVCD accompanied by a 3-fold increase in volumetric productivity as compared to batch culture. In summary, this study provides a proof-of-concept that hydrogels can enable completely closed in situ feeding for mammalian cell culture requiring no external intervention. Such continuous in situ delivery can potentially enable closed culture systems maintaining nutrients at low levels mimicking physiol. concentrations This study involved multiple reactions and reactants, such as 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride (cas: 65-22-5Related Products of 65-22-5).

3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride (cas: 65-22-5) belongs to alcohols. The oxygen atom of the strongly polarized O―H bond of an alcohol pulls electron density away from the hydrogen atom. This polarized hydrogen, which bears a partial positive charge, can form a hydrogen bond with a pair of nonbonding electrons on another oxygen atom. Secondary alcohols are easily oxidized without breaking carbon-carbon bonds only as far as the ketone stage. No further oxidation is seen except under very stringent conditions.Related Products of 65-22-5

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Optimization of an ultrasound-assisted extraction method for the determination of parabens and bisphenol homologues in human saliva by liquid chromatography-tandem mass spectrometry was written by Moscoso-Ruiz, Inmaculada;Galvez-Ontiveros, Yolanda;Cantarero-Malagon, Samuel;Rivas, Ana;Zafra, Alberto. And the article was included in Microchemical Journal in 2022.Formula: C13H12O2 The following contents are mentioned in the article:

Parabens and bisphenols are endocrine disrupting chems. (EDCs) widely used in our daily lives. The main route of human exposure to these compounds is through the diet. This makes human saliva an important matrix for identification of these contaminants and evaluation of human exposure. In this work a multiresidue method to det the presence of methyl-, ethyl-, propyl-, isopropyl-, butyl- and isobutylparaben; and bisphenol A, B, C, E, F, M, P, S, Z, AP, AF and FL in human saliva samples has been developed. Sample treatment involves an initial step of protein pprotein in acidic medium and a second step of analyte extraction Extraction parameters were optimized using univariant and multivariant strategies. Microwave assisted extraction (MAE) and ultrasound assisted extraction (UAE) were compared and UAE was chosen the optimal extraction technique. The compounds were analyzed by ultra-high performance liquid chromatog. coupled to tandem mass spectrometry (UHPLC-MS/MS). The calibration in matrix was applied and the limits of detection and quantification were from 0.1 to 0.4 ng g-1 and from 0.3 to 1.0 ng g-1, respectivley. Accuracy was evaluated in terms of recovery (85.6 to 113.5%) with a relative standard deviation < 15% in all cases. The anal. method was successfully applied to quantify the target EDCs in ten human saliva samples, with some parabens being the most frequently detected compounds This study involved multiple reactions and reactants, such as 4,4′-Methylenediphenol (cas: 620-92-8Formula: C13H12O2).

4,4′-Methylenediphenol (cas: 620-92-8) belongs to alcohols. The oxygen atom of the strongly polarized O―H bond of an alcohol pulls electron density away from the hydrogen atom. This polarized hydrogen, which bears a partial positive charge, can form a hydrogen bond with a pair of nonbonding electrons on another oxygen atom. Tertiary alcohols cannot be oxidized at all without breaking carbon-carbon bonds, whereas primary alcohols can be oxidized to aldehydes or further oxidized to carboxylic acids.Formula: C13H12O2

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

A flexible thermoelectric film based on Bi₂Te₂ for wearable applications was written by Liu, Changxin;Zhao, Kaiyuan;Fan, Yuhang;Gao, Yu;Zhou, Zhenghui;Li, Mengze;Gao, Yunfei;Han, Zhitao;Xu, Minyi;Pan, Xinxiang. And the article was included in Functional Materials Letters in 2022.Safety of 4,4′-Methylenediphenol The following contents are mentioned in the article:

In recent years, with the development of the Internet of Things (IoT) and wearable technol., the research and exploration of thermoelec. materials have been greatly promoted. However, traditional thermoelec. materials are rigid and brittle. Thermoelec. devices made of these materials usually cannot be closely attached to the heat and cold sources that provide temperature differences, thus limiting the application of thermoelec. materials. Therefore, manufacturing new high-performance flexible thermoelec. devices is still a huge challenge. In this work, polyimide/copper (PI/Cu) substrate was deposited by electron deposition technol. The flexible thermoelec. thin film device was fabricated by bonding N-type and P-type bismuth telluride (Bi₂Te₂) slurries onto the PI/Cu substrate. Then, the PDMS film was coated on the device to make the device waterproof and oxidation resistant. The output voltage and maximum power of this device, at the temperature of 80 K, reach 97.5 mV and 60 uW, resp. After 200 cycles of cyclic bending experiments, 90% high conductivity retention can be maintained. It demonstrates that the new flexible thermoelec. thin film has good flexibility and excellent stability. This work provides a simple method for the preparation of flexible thermoelec. thin films and opens up a new way for its application in the sensing equipment and wearable device of the IoT. This study involved multiple reactions and reactants, such as 4,4′-Methylenediphenol (cas: 620-92-8Safety of 4,4′-Methylenediphenol).

4,4′-Methylenediphenol (cas: 620-92-8) belongs to alcohols. Alcohols are among the most common organic compounds. They are used as sweeteners and in making perfumes, are valuable intermediates in the synthesis of other compounds, and are among the most abundantly produced organic chemicals in industry. Converting an alcohol to an alkene requires removal of the hydroxyl group and a hydrogen atom on the neighbouring carbon atom. Dehydrations are most commonly carried out by warming the alcohol in the presence of a strong dehydrating acid, such as concentrated sulfuric acid.Safety of 4,4′-Methylenediphenol

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Novel random PBS-based copolymers containing aliphatic side chains for sustainable flexible food packaging was written by Guidotti, Giulia;Soccio, Michelina;Siracusa, Valentina;Gazzano, Massimo;Salatelli, Elisabetta;Munari, Andrea;Lotti, Nadia. And the article was included in Polymers (Basel, Switzerland) in 2017.Related Products of 115-84-4 The following contents are mentioned in the article:

In the last decade, there has been an increased interest from the food packaging industry toward the development and application of biodegradable and biobased plastics, to contribute to the sustainable economy and to reduce the huge environmental problem afflicting the planet. In this framework, the present paper describes the synthesis of novel PBS (poly(butylene succinate))-based random copolymers with different composition containing glycol sub-units characterized by alkyl pendant groups of different length. The prepared samples were subjected to mol., thermal, diffractometric and mech. characterization. The barrier performances to O₂, CO₂ and N₂ gases were also evaluated, envisioning for these new materials an application in food packaging. The presence of the side alkyl groups did not alter the thermal stability, whereas it significantly reduced the sample crystallinity degree, making these materials more flexible. The barrier properties were found to be worse than PBS; however, some of them were comparable to, or even better than, those of Low D. Polyethylene (LDPE), widely employed for flexible food packaging. The entity of variations in the final properties due to copolymerization were more modest in the case of the co-unit with short side Me groups, which, when included in the PBS crystal lattice, causes a more modest decrement of crystallinity degree. This study involved multiple reactions and reactants, such as 2-Butyl-2-ethylpropane-1,3-diol (cas: 115-84-4Related Products of 115-84-4).

2-Butyl-2-ethylpropane-1,3-diol (cas: 115-84-4) belongs to alcohols. Alcohols are among the most common organic compounds. They are used as sweeteners and in making perfumes, are valuable intermediates in the synthesis of other compounds, and are among the most abundantly produced organic chemicals in industry. Alcohols may be oxidized to give ketones, aldehydes, and carboxylic acids. These functional groups are useful for further reactions. Oxidation of organic compounds generally increases the number of bonds from carbon to oxygen (or another electronegative element, such as a halogen), and it may decrease the number of bonds to hydrogen.Related Products of 115-84-4

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts