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This educatory experiment uses an inexpensive pH meter to determine an approximate negative logarithm of the acid dissociation constant (pK a) value of 4,4′-trimethylenedipiperidine (TMDP). Using a pH meter and statistical data analysis by Excel tool presents an excellent opportunity to deepen student engagement with the Henderson-Hasselbalch equation and acid/base dissociation constant (K a/K b). Furthermore, students understand the importance determination of K a/K b and its relationship with the concentration and strength of acid/base. Four different concentrations of TMDP aqueous solutions were prepared and a series of pH readings were collected using a calibrated pH meter. Some statistical parameters were calculated and analyzed using the statistical program in Excel. Finally, students identified an unknown pK a for TMDP and compared their obtained value with a predicted pK a using software like ChemAxon. The experiment is inexpensive, safe, simple, and clean, and less experienced students can perform it. In addition, all pH recordings can be readily accessible for analysis and descriptive statistics by the Excel formula.

Given the abundance of functional groups, meso- and macro-pores, and a high surface area, the piperazine-based poly(amic acid) was employed as a heterogeneous catalyst in the multicomponent reaction to prepare pyrrolidinone scaffolds in a green solvent, acting as a medium for mass transfer and crystallization solvent. The important parameters of the reaction were investigated to find the optimal reaction conditions. A conversion of 100% was obtained at reflux conditions within 30–100 min using a catalytic amount of 200 mg of piperazine-based poly(amic acid) per 2 mmol of reactants (100 mg of cat./1 mmol of reactant). The piperazine-based poly(amic acid) exhibited high recyclability and the recovered catalyst could be used in successive runs without worthy loss in its activity. This work revealed the catalytic activity of the piperazine-based poly(amic acid) as a promising functional polymeric heterogeneous catalyst for organic synthesis. [ABSTRACT FROM AUTHOR]

The negative logarithm of the acid dissociation constant values (pKa1 and pKa2) of 4,4′-trimethylenedipiperidine (TMDP) was determined by a pH metric titration at 298 K. The experimentally determined pKa values were compared with the predicted pKa values by chem-bioinformatics software like ACD/Labs and ChemAxon. This experiment gave an excellent opportunity to deepen engagement with the Henderson–Hasselbalch equation, acid/base dissociation constant (Ka/Kb), and half equivalence point. [ABSTRACT FROM AUTHOR]

This work presents a new catalytic application of 4,4'-trimethylenedipiperidine for the efficient synthesis of a series of dihydro-[1,2,4] triazolo[1,5-a]pyrimidines. According to the principles of green chemistry, the reaction was performed (o)ina solvent mixture comprised of water and ethanol (1:1 v/v) at reflux temperature and (b) solvent-free grinding in a mortar by a pestle. The organocatalyst could be reused up to 10 runs, and no reduction of catalytic activity was detected. A variety of substituted dihydro-[1,2,4] triazolo[1,5-a]pyrimidines were obtained in good to excellent yields under eco-friendly conditions. 4,4'-Trimethylenedipiperidine is commercially available and easy to handle, and it also shows high thermal stability and good solubility in water. This work revealed that this organocatalyst, a hydrogen bond donor to active carbonyl groups and simultaneously a Lewis base through the nitrogen atom of second piperidine moiety, could play a vital role in the promotion of the one-pot multi-component reactions. The main merits of the current methodology include short reaction time, wide substrate scope, use of a metal-free catalyst and green solvents, and simple work-up process. Furthermore, this organocatalyst can be an alternative to piperidine for organic transformations. Key words: organocatalyst, annulation, heterocycles, one-pot synthesis, three-component reaction. Dans le cadre des presents travaux, nous presentons une nouvelle application de la 4,4'-trimethylènedipiperidineý comme catalyseur pour synthetiser une serie de dihydro-[1,2,4]triazolo[1,5-a]pyrimidinesý. Selon les principes de chimie verte, nous avons effectue la reaction (a) dans un melange de solvants compose d'eau et d'ethanol (1:1 v/v) à reflux et (b) par pulverisation sans solvant dans un mortier à l'aide d'un pilon. Nous avons pu reutiliser l'organocatalyseur jusqu'à 10 fois sans observer aucune reduction de l'activite catalytique. Nous avons obtenu une variete de dihydro-[1,2,4]triazolo[1,5-a]pyrimidines dans des rendements allant de bons à excellents en conditions ecologiques. La 4,4'=-trimethylènedipiperidine est commercialement disponible et facile à manipuler. Elle presente egalement une grande stabilite thermique et une bonne stabilite dans l'eau. Ces travaux montrent que cet organocatalyseur--un donneur de liaison hydrogène à des groupes carbonyle actives et à la fois une base de Lewis grâce à l'atome d'azote du deuxième groupe piperidine--peut jouer un rôle crucial dans la catalyse de reactions monotopes multicomposants. Les principaux avantages de cette methode sont un temps de reaction court, une grande variabilite de substrats et l'emploi d'un catalyseur sans metal et de solvants ecologiques, ainsi qu'un traitement simple du melange reactionnel. De plus, cet organocatalyseur peut servir de substitut à la piperidine dans les transformations organiques. [Traduit par la Redaction] Mots-cles : organocatalyseur, annelation, heterocycles, synthèse monotope, reaction à trois composants., Introduction The current trend in the design and development of the novel catalysts and processes is to follow some basic principles of green chemistry, e.g., ([alpha]) use of non-toxic, non-hazardous [...]

Green synthesis methods are considered as a safer alternative to the conventional synthetic processes due to their eco-friendly nature, cost-effectiveness, and easy handling. In the present study, an eco-friendly and sustainable method for the synthesis of stable arenediazonium has been developed using saccharin as a cheap and mild acidic agent and tert-butyl nitrite as a diazotization reagent for the first time. These stable intermediates were used in the azo coupling reaction with 4-hydroxybenzaldehyde via telescoped dediazotization. The current method has advantages such as reduced waste by avoiding solvent for the purification of intermediate in diazotization step, cost-effectiveness, simple experimental procedure, good yield of azo dyes, metal-free waste, and environmentally benign conditions. An interesting aspect of this study is the recovery of saccharin from the reaction, which could be reused.

The energy efficiency of the microwave-assisted synthesis of pyrrolidinones was demonstrated using catalytic loading of 1,1’-butylene-bis(3-sulfo-3H-imidazol-1-ium) chloride as a sulfonic acid functionalized ionic liquid in ethylene glycol as green solvent. The effect of electron donating and electron withdrawing groups on aniline derivatives was studied under conventional heating and microwave irradiation. Furthermore, the cation effect of ionic liquids containing sulfonic groups on the catalytic efficiency for the synthesis of ethyl-1-phenyl-2-(4-chlorophenyl)-4-hydroxy-5-oxo-2,5-dihydro-1H-pyr-role-3-carboxylate was investigated under conventional heat. The experimental results exhibited that there is a relationship between catalytic efficiency and the number of sulfonic groups and imidazolium moieties linked by carbon spacer.

This educatory experiment uses an inexpensive pH meter to determine an approximate negative logarithm of the acid dissociation constant (pKa) value of 4,4′-trimethylenedipiperidine (TMDP). Using a pH meter and statistical data analysis by Excel tool presents an excellent opportunity to deepen student engagement with the Henderson-Hasselbalch equation and acid/base dissociation constant (Ka/Kb). Furthermore, students understand the importance determination of Ka/Kb and its relationship with the concentration and strength of acid/base. Four different concentrations of TMDP aqueous solutions were prepared and a series of pH readings were collected using a calibrated pH meter. Some statistical parameters were calculated and analyzed using the statistical program in Excel. Finally, students identified an unknown pKa for TMDP and compared their obtained value with a predicted pKa using software like ChemAxon. The experiment is inexpensive, safe, simple, and clean, and less experienced students can perform it. In addition, all pH recordings can be readily accessible for analysis and descriptive statistics by the Excel formula. [ABSTRACT FROM AUTHOR]