Methanolic Hydrogen Chloride Research Articles

Comprehensive comparison of fatty acid methyl ester profile in different food matrices using microwave-assisted extraction and derivatization methods and comprehensive two-dimensional gas chromatography coupled with flame ionization detection

Analyzing fatty acids provides key insights into fat composition for industrial applications and their implications for nutrition and health. Typically, fatty acid analysis involves extracting lipids from the matrix and converting them into fatty acid methyl esters (FAME) through a derivatization process before gas chromatography (GC) analysis. Either one-step or two-step procedures can be found in the literature and as official methods. In this work, different methods exploiting microwave-assisted processes were compared with two official methods from the American Oil Chemical Society (AOCS). Especially, two types of microwave-assisted extractions were employed: solvent extraction and extraction with hydrolysis. The extracts were derivatized using either BF3 or a microwave-assisted methanolic hydrogen chloride solution. These combinations of extraction and derivatization methods were compared also with one-step microwave-assisted extraction and derivatization, and two AOCS reference methods, resulting in seven different methods applied to six different food matrices. The performance of the different procedures was compared based on the FAME profile obtained from the comprehensive two-dimensional GC (GC × GC)-FID analysis.Microwave-assisted processes were shown to be effective, yielding results comparable to the official methods in both the one-step and two-step methods. Moreover, it was shown that the BF3 derivatization could be safely replaced with microwave-assisted derivatization with methanolic hydrogen chloride, providing equivalent performances while enhancing operator safety and environmental friendliness. Some discrepancies in the FAMEs profile were highlighted for the sample of oats, the only explicitly requiring acidic hydrolysis for lipid extraction. Further studies are required to understand the reasons behind these differences and develop a suitable modified method. In conclusion, all the methods were evaluated for greenness and blueness with two specific tools: AGREEprep and BAGI.

Safety Case Study. Intrinsic Instability of Concentrated Solutions of Alcoholic Hydrogen Chloride: Potential Hazards Associated with Methanol

Methanolic hydrochloride is a commonly used reagent on the lab scale and on larger scales as well. It is commercially available or can be prepared by bubbling gaseous hydrogen chloride in methanol....

Hybrid Solid-Phase Extraction for Selective Determination of Methamphetamine and Amphetamine in Dyed Hair by Using Gas Chromatography–Mass Spectrometry

Sample preparation is an important step in the isolation of target compounds from complex matrices to perform their reliable and accurate analysis. Hair samples are commonly pulverized or processed as fine cut, depending on preference, before extraction by techniques such as solid-phase extraction (SPE), liquid–liquid extraction, and other methods. In this study, a method based on hybrid solid-phase extraction (hybridSPE) and gas chromatography–mass spectrometry (GC–MS) was developed and validated for the determination of methamphetamine (MA) and amphetamine (AP) in hair. The hair samples were mechanically pulverized after washing with de-ionized water and acetone. The samples were then sonicated in methanol at 50 °C for 1 h and centrifuged at 50,000× g for 3 min. The supernatants were transferred onto the hybridSPE cartridge and extracted using 1 mL of 0.05 M methanolic hydrogen chloride. The combined solutions were evaporated to dryness, derivatized using pentafluoropropionic anhydride, and analyzed by GC–MS. Excellent linearity (R2 > 0.9998) was achieved in the ranges of 0.05–5.0 ng/mg for AP and 0.1–10.0 ng/mg for MA. The recovery was 83.4–96.8%. The intra- and inter-day accuracies were −9.4% to 5.5% and −5.1% to 3.1%, while the intra- and inter-day precisions were within 8.3% and 6.7%, respectively. The limits of detections were 0.016 ng/mg for AP and 0.031 ng/mg for MA. The validated hybridSPE method was applied to dyed hair for MA and AP extraction and compared to a methanol extraction method currently being used in our laboratory. The results showed that an additional hybridSPE step improved the recovery by 5.7% for low-concentration quality control (QC) samples and by 24.1% for high-concentration QC samples. Additionally, the hybridSPE method was compared to polymeric reversed-phase SPE methods, and the absolute recoveries for hybridSPE were 50% and 20% greater for AP (1.5 ng/mg) and MA (3.0 ng/mg), respectively. In short, the hybridSPE technique was shown to minimize the matrix effects, improving GC–MS analysis of hair. Based on the results, the proposed method proved to be effective for the selective determination of MA and AP in hair samples.

Effect of temperature on fatty acid composition and development of unfed Siberian sturgeon (A.baerii) larvae

The fatty acid metabolism in fish is influenced by various factors, including fish species, water temperature, water environment and diet supply. The aim of present work is to investigate the fatty acid composition of yolk-stage Siberian sturgeon larvae reared at three different temperatures. Fertilized Siberian sturgeon eggs were transferred to the Lodi Aquaculture Research Center of the University of Milan, divided in three aquaria, each containing three incubators and incubated at 16°C. After hatching the temperature was switched to 16, 19 and 22°C. Larvae sampling was performed at the end of yolk sac reabsorption. No feed was dispensed during the trial. Eggs and larvae were weighed and fatty acid profile was determined by GC-FID analysis after lipid extraction by chloroform/methanol mixture and fatty acid transesterification by methanolic hydrogen chloride. The fertilized eggs had a weight of 23.27 mg and a lipid content of 2.67 mg/egg. At hatching, the weight was 12.2 (0.17 SD) mg and lipid content 1.9 (0.6 SD) mg/larva. At the end of the trial, larvae mean weight was 33.6 (3.6 SD), 34.7 (1.8 SD) and 36.9 (1.1 SD) mg, while lipid content was 2.0 (0.3 SD), 2.1 (0.3 SD) and 2.0 (0.2 SD) mg for larvae reared at 16, 19 and 22°C respectively, without statistically significant difference. Larvae subjected to the highest water temperature showed a faster yolk-sac absorption. No differences were found across temperatures regarding survival rates and regarding ontogenic development. The fatty acid composition of larvae was affected by the temperature. Larvae reared at 16°C had the lowest amount of saturated fatty acids, mainly due to a lower palmitic acid content, that was offset by a higher level of linolenic and linoleic acid, if compared with larvae reared at 19°C and 22°C. The study suggests that at a lower temperature sturgeon spare unsaturated fatty acid consuming preferably saturated fatty acids, increasing our knowledge of the fatty acid metabolism in this species.

COMPARATIVE STUDY ON THE PHYTOCHEMICAL AND IN VITRO ANTIOXIDANT PROPERTIES OF METHANOLIC LEAF EXTRACT OF JUSTICIA SECUNDA VAHL

Medicinal plants are a primary source of healing and widely used for the treatment of various ailments. This present study evaluates phytochemicals and in vitro antioxidant activities of the methanolic leaf extract of Justicia secunda, Acanthaceae family. Fresh leaves of the plant were collected, and shade dried. The dry leaves were pulverized, and the resultant powder extracted with 0.1% hydrogen chloride (HCl) in methanol, and 1% HCl in methanol respectively. Extracts obtained were subjected to qualitative phytochemical screening and in vitro antioxidant assays. Results obtained confirm the presence of saponinis, tannins, steroids, flavonoids, and alkaloids in equal degree in both 0.1% and 1% HCl methanolic leaf extract. Concentrations of anthocyanins, phenols and phlobatannins were quantitatively higher in 0.1% HCl extract as compared to 1% HCl extract. However, the presence of carbohydrates was not confirmed in either extracts. The results also indicated that phenolic and anthocyanins content of the leaf extracts were significantly higher (p 0.05) in both extracts. The antioxidant scavenging efficacy showed that higher percentage inhibition was observed from the 0.1% HCl methanolic extract of Justicia secunda in its ability to scavenge hydrogen peroxide, 1,1 – diphenylpicrylhydrazyl, and superoxide anion. Overall, from this study, it could be concluded that Justicia secunda may be a good source of phytochemicals and natural antioxidants that will be useful in the food, medicine, and pharmaceutical industries.

Preparation and conformation of 3,4-anhydro-1,2-O-isopropylidene-5-O-mesyl-β-d-tagatopyranose and methyl 4-chloro-4-deoxy-1,3,5-tri-O-mesyl-β-d-fructopyranoside

Abstract The treatment of 3-O-acetyl-1,2-O-isopropylidene-4,5-di-O-methanesulfonyl-β-d-fructopyranose with sodium methoxide led to the crystalline epoxy-sugar 3,4-anhydro-1,2-O-isopropylidene-5-O-methanesulfonyl-β-d-tagatopyranose, the structure of which was determined by X-ray diffraction. Solvolysis of the epoxide with methanolic hydrogen chloride and subsequent mesylation gave methyl 4-chloro-4-deoxy-1,3,5-tri-O-methanesulfonyl-β-d-fructopyranoside which was also characterized by X-ray structure determination.

Solid-Phase Extraction of Sulfur Mustard Metabolites Using an Activated Carbon Fiber Sorbent.

A novel solid-phase extraction method using activated carbon fiber (ACF) was developed and validated. ACF has a vast network of pores of varying sizes and microporous structures that result in rapid adsorption and selective extraction of sulfur mustard metabolites according to the pH of eluting solvents. ACF could not only selectively extract thiodiglycol and 1-methylsulfinyl-2-[2-(methylthio)-ethylsulfonyl]ethane eluting a 9:1 ratio of dichloromethane to acetone, and 1,1'-sulfonylbis[2-(methylsulfinyl)ethane] and 1,1'-sulfonylbis- [2-S-(N-acetylcysteinyl)ethane] eluting 3% hydrogen chloride in methanol, but could also eliminate most interference without loss of analytes during the loading and washing steps. A sample preparation method has been optimized for the extraction of sulfur mustard metabolites from human urine using an ACF sorbent. The newly developed extraction method was applied to the trace analysis of metabolites of sulfur mustard in human urine matrices in a confidence-building exercise for the analysis of biomedical samples provided by the Organisation for the Prohibition of Chemical Weapons.

Efficient deprotection of F-BODIPY derivatives: removal of BF2 using Brønsted acids.

The effective and efficient removal of the BF2 moiety from F-BODIPY derivatives has been achieved using two common Brønsted acids; treatment with trifluoroacetic acid (TFA) or methanolic hydrogen chloride (HCl) followed by work-up with Ambersep® 900 resin (hydroxide form) effects this conversion in near-quantitative yields. Compared to existing methods, these conditions are relatively mild and operationally simple, requiring only reaction at room temperature for six hours (TFA) or overnight (HCl).

Critical profiles of chiral diether-mediated asymmetric conjugate aminolithiation of enoate with lithium amide as a key to the total synthesis of (−)-kopsinine

Chiral diether-mediated asymmetric aminolithiation of indolylpropenoate with lithium amide in toluene at −78 °C for 15 min gave, after aqueous ammonium chloride quench, the corresponding conjugate addition product with 97% ee in 89% yield. If hydrogen chloride in methanol was selected as a quencher, however, aminolithiation at −78 °C for 3 h gave the corresponding adduct with 97% ee in 54% yield, along with recovery of the starting enoate in 39% yield. Based on this finding of an incomplete and slow reaction at −78 °C, the aminolithiation conditions were optimized to be at −60 °C for 15 h and subsequent enolate trap with alkyl halide upon an addition of DMPU afforded the desired aminoalkylation product with 98% ee in 89% yield. Further approach toward total synthesis of (−)-kopsinine was carried out by examining asymmetric aminolithiation with N-hydroxyethylamine equivalent, one-pot piperidine formation, and Claisen condensation.

Orthoamide und Iminiumsalze, LXXXI [1]. Orthoamid-Derivate der 1,3-Dimethylparabansäure / Orthoamides and Iminium Salts LXXXI [1]. Orthoamide Derivatives of 1,3-Dimethylparabanic Acid

1,3-Dimethyl-5-imino-imidazolidine-2,4-dione (7a) undergoes thiolysis (H2S) to give the corresponding imidazolidine-2,4-dione-5-thione derivative 6. The 5-N-methylimino analogue 7b can be obtained from 7a by methylation. Further methylation of 7b affords the crude iminium salt 8c from which the heterocyclic orthoamide derivatives 10, 11 can be prepared. The heterocyclic amide acetal 9a can be obtained from 7a and dimethyl sulfate in methanol and subsequent addition of sodium methanolate in a one-pot reaction. The aminal ester 10 is converted to the amide acetal 9a on treatment with hydrogen chloride in methanol

Asymmetric synthesis of 4-formyl-1-(ω-haloalkyl)-β-lactams and their transformation to functionalized piperazines and 1,4-diazepanes

Chiral piperazine and 1,4-diazepane annulated β-lactams, prepared from the corresponding (3R,4S)-4-imidoyl-1-(ω-haloalkyl)azetidin-2-ones through reduction with sodium borohydride in ethanol, were transformed into novel methyl (R)-alkoxy-[(S)-piperazin-2-yl]acetates and methyl (R)-alkoxy-[(S)-1,4-diazepan-2-yl]acetates upon treatment with hydrogen chloride in methanol. On the other hand, bromination of (3R,4R)-1-allyl-4-formyl-β-lactams and (3R,4S)-1-allyl-4-imidoyl-β-lactams in dichloromethane, followed by sodium borohydride reduction of the resulting dibrominated azetidin-2-ones in ethanol, did not afford the envisaged bicyclic β-lactams but unexpectedly furnished (3R,4S)-1-(2-bromo-2-propenyl)azetidin-2-ones instead.

ChemInform Abstract: Synthesis of 1-(3-Alkyl-2,3-dideoxy-D-pentofuranosyl)uracils with Potential Anti-HIV Activity.

1-(3-Alkyl-2,3-dideoxy-alpha,beta-D-erythro-pentofuranosyl)uracils and 1-(3-alkyl-2,3-dideoxy-alpha,beta-D-threo-pentofuranosyl)uracils have been prepared from (E)-4,5-di-O-acetyl-2,3-dideoxy-aldehydo-D-glycero-pent-2-enose by a Michael addition reaction of the appropriate organocopper reagent followed in subsequent order by glycosidation of the resulting 3-alkyl-4,5-diacetoxypentanal with methanolic hydrogen chloride, protection with p-methoxybenzoyl chloride, and trimethylsilyl triflate catalyzed coupling with 2,4-di-O-(trimethylsilyl)uracil. The nucleosides were deprotected by treatment with 33% methylamine in absolute ethanol and separated by reversed-phase HPLC.

ChemInform Abstract: Cyclocondensation of 6-Acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with Hydroxylamine and Hydrazine.

The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.

Reductive Ring‐Opening of Phthalan and Isochroman: Application to the Stereoselective Synthesis of Tetrahydroisoquinolines and Tetrahydrobenzazepines

AbstractThe reaction of the dianionic intermediates 2a,b resulting from the lithiation of phthalan (1a) and isochroman (1b) with chiral N‐tert‐butylsulfinyl aldimines 9 in the presence of ZnMe2 gave, after hydrolysis, N‐tert‐butylsulfinyl amino alcohols 10 and 13, respectively, with high diastereoselectivity. Successive treatment of compounds 10 and 13 with hydrogen chloride in methanol, thionyl chloride in chloroform and sodium hydroxide led to the formation of tetrahydroisoquinolines 19 and tetrahydrobenzazepines 20. Depending on the structure of the starting chiral imine 9, benzoindolizidine 21, benzoquinolizidine 22 and benzopyrroloazepine 23 are also accessible through this methodology.

3-aminopyrrole-2,5-diones 3*. Synthesis of benzenehexa-carboxylic acid trimethylimide and 1,1′-dimethyl-4-methylamino-[3,3′]bipyrrolyl-2,5,2′,5′-tetraone by the reaction of 1-methyl-3-methylaminopyrrole-2,5-dione with hydrogen chloride

In the presence of hydrogen chloride in aqueous methanol 1-methyl-3-methylaminopyrrole-2,5-dione forms benzenehexacarboxylic acid trimethylimide but gives 1,1′-dimethyl-4-methylamino[3,3′]bi-pyrrolyl-2,5,2′,5′-tetraone when absolute methanol is used.

Stereoselective synthesis of 3-substituted tetrahydroisoquinolines from phthalan and chiral N-sulfinylimines

The reaction of the dianionic intermediate [resulting from the reductive opening of phthalan ( 1) with lithium] with chiral N- tert-butylsulfinyl aldimines 3 in the presence of ZnMe 2 gives, after hydrolysis, N- tert-butylsulfinyl amino alcohols 4 with high diastereoselectivity. Successive treatment of compounds 4 with hydrogen chloride in methanol, thionyl chloride in chloroform and sodium hydroxide yields 3-substituted tetrahydroisoquinolines 6.

Biomimetic Synthesis of Resorcylate Natural Products Utilizing Late Stage Aromatization: Concise Total Syntheses of the Marine Antifungal Agents 15G256ι and 15G256β

Diketo-1,3-dioxin-2-ones underwent retro-Diels-Alder reaction on heating in toluene at 110 degrees C to generate alpha,gamma,-triketo-ketenes. These were trapped with alcohols to provide 2,4,6-triketocarboxylates, which were smoothly aromatized by sequential reaction with potassium carbonate and methanolic hydrogen chloride to give resorcylate esters. The reaction was applied in the total synthesis of the marine antifungal agents 15G256beta (1), 15G256iota (2), and 15G256pi (3) and the mycotoxin S-(-)-zearalenone (4).

Synthesis of trans-4-aryl-3-(3-chloropropyl)azetidin-2-ones and their transformation into trans- and cis-2-arylpiperidine-3-carboxylates

Treatment of arylmethylideneamines with 5-chloropentanoyl chloride in benzene in the presence of 2,6-lutidine afforded novel trans-4-aryl-3-(3-chloropropyl)azetidin-2-ones in good yields. The latter 3-(3-chloropropyl)-β-lactams were transformed selectively into trans-methyl 1-alkyl-2-arylpiperidine-3-carboxylates in high yields and purity upon subsequent treatment with hydrogen chloride in methanol and triethylamine in dichloromethane. These trans-1-alkyl-2-arylpiperidine-3-carboxylates were easily converted into either their cis-isomers upon treatment with hydrazine monohydrate in methanol, or into the corresponding piperidine-1,3-dicarboxylates by reaction with alkyl chloroformates in benzene. Finally, 3-(3-chloropropyl)-1-(4-methoxybenzyl)-4-phenylazetidin-2-one was transformed into the corresponding trans-1- tert-butoxycarbonyl-3-(4-methoxybenzylcarbamoyl)piperidine via a three-step sequence in a good overall yield.

Furan ring opening - isocoumarine ring closure: A recyclization reaction of 2-carboxyaryldifurylmethanes

A general method for the synthesis of isocoumarine derivatives has been developed. Bis(5-R-2-furyl)methylbenzoic acids (R = methyl, ethyl) underwent recyclization and subsequent cyclization into tetracyclic isochromene-1-one derivatives under treatment with hydrogen chloride in methanol. It has been shown that intermediate 4-(5-R-furan-2-yl)-3-(3-oxo-3-R-propyl)-isochromene-1-ones can be obtained selectively by varying a concentration of the hydrogen chloride and reaction times. In the case of R = tert-butyl only corresponding 4-[5-(tert-butyl)-2-furyl]-3-(4,4-dimethyl-3-oxopentyl)-1-isochromenones were isolated regardless of the reaction conditions.

Validation of a one-step extraction/methylation method for determination of fatty acids and cholesterol in marine tissues

A simple and fast direct extraction/methylation with methanolic hydrogen chloride was validated for determination of fatty acids (FA) in marine tissues. Three parameters: reaction time, temperature and presence of non-polar solvent, were studied by an experimental 2 3 full factorial design. The method was validated for five different types of samples; cod liver (high lipid content >60%, mainly triacylglycerol), cod muscle (low lipid content, ≈1%, mainly phospholipids), cod plasma (lipid content, ≈2%, mainly lipoprotein complex, high water amount), cod testis (lipid content ≈3%, high levels of cholesterol), and herring muscle (lipid content ≈7%). The one-step procedure for extraction/methylation of wet tissues was compared with the traditional procedure of extraction of the lipids by the Folch method (chloroform/methanol, 2:1, v/v), followed by methylation. The two methods gave similar FA profiles. The one-step extraction/methylation procedure gave a higher recovery of the total FA than the traditional procedure. Problems with carry-over peaks of cholesterol from previous samples were avoided by application of extra long GC temperature programs. The cholesterol decomposed to some degree under the preceding methanolysis step, giving several peaks in the chromatograms. The decomposition peaks were identified by mass spectrometry as cholestdienes originating from dehydration of cholesterol, a metylether of cholesterol and a cholesteryl chloride. These cholesterol artefacts can be used for quantitative determination of cholesterol in the samples. Standard samples of cholesterol were determined with high accuracy, ( R 2 > 0.99), and cholesterol in cod plasma was compared with good agreement ( R 2 = 0.97) to an enzymatic method.