Preliminary Investigation of Organocatalyst Activity Based on C‐Arylcalix[4]‐2‐Methylresorcinarene Sulfonic Acid Materials for Biodiesel Production

Abstract

At present, biodiesel remains an untapped fuel source while crude oil reserves are being depleted. Extensive efforts are necessary to achieve efficient biodiesel production, but catalytic activity in methyl palmitate production remains unsatisfactory. In this study, we report the synthesis and organocatalyst activity of C‐arylcalix[4]‐2‐methylresorcinarene sulfonic acids for biodiesel production. The presence of a methyl group on an aromatic ring is expected to disturb the intramolecular hydrogen bonds; thus, each hydroxyl group could be utilized for the catalytic process. C‐arylcalix[4]‐2‐methylresorcinarene sulfonic acids were prepared from cyclocondensation and sulfonation reactions yielding compounds 1–6 at rates of 66.7%–86.6%. By evaluating the organocatalytic activity of the C‐arylcalix[4]‐2‐methylresorcinarene sulfonic acids, we found that 4 mol% of compound 5 exhibited the highest yield (97.8%) of methyl palmitate at 338 K for 6‐h reaction time, which is remarkable. These findings show that C‐arylcalix[4]‐2‐methylresorcinarene sulfonic acids are promising heterogeneous catalyst materials for biodiesel production.

Review on Calixarene Fluorescent Chemosensor Agents for Various Analytes

“…Calixarene derivatives are well-known host molecules with versatile applications, including chemosensor agents [16][17][18][19][20][21]. Calixarenes consisted of a macrocyclic oligomer framework resulted from the condensation reaction between formaldehyde and tert-butylphenol [22].…”

“…Barata and coworkers (2020) used the calix [4]arene-modified carbazole polymer (20) for the sensor of the nitroaromatic explosive compounds in CHCl3 media. Calixarene 20 showed high sensitivity towards nitroaromatic compounds such as picric acid (PA), 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and nitrobenzene (NB).…”

Utilization of vanillin to prepare sulfated Calix[4]resorcinarene as efficient organocatalyst for biodiesel production based on methylation of palmitic acid and oleic acid

“…Couples of organocatalysts for the methylation of palmitic acid and oleic acid have been reported [ 14 , [29] , [30] , [31] , [32] , [33] , [34] , [35] , 37 , [41] , [42] , [43] , [44] , [45] ]. Table 1 , Table 2 showed that organocatalysts exhibit higher catalytic activity to produce methyl palmitate and methyl oleate in up to 98.3 and 97.6% yield, respectively.…”

“…Unfortunately, the preparation of calix[4]arene and calix[6]arene is difficult and expensive because of complicated reaction and purification processes. Other calix[4]arene derivatives, i.e., calix[4]-2-methylresorcinarenes and calix[4]pyrogallolarenes, have been also investigated as organocatalysts for methyl palmitate production in our previous work [ 32 , 34 ]. They were successfully prepared through a one-pot reaction employing hydrochloric acid in ethanol media in 66.7–88.9% yield.…”

Homo- and Heteromultinuclear Pseudocapsules Assembled from Calix[6]-mono-crown-5 and Alkali Metal Ions

“…Supramolecular capsules and pseudocapsules are objects of significant interest because their fascinating structures and properties may lead to a wide range of applications including catalysts, storage, and drug delivery. − In nature, similar concepts are present for the storage and transport of bioactive species: representative examples are tobacco mosaic virus and apoferritin . Thus, the construction of supramolecular capsules from dimeric to multimeric aggregates has grown significantly in supramolecular and nanomaterials areas. ,− The building blocks that compose the dimeric capsule feature concave or bowl shapes such as tris-oxime, tris­(ureidobenzyl)­amine, calix[4]­urea, ,, calix[4]­pyrrole, and resorcin[4]­arene ,, with a certain degree of rigidity and functional groups favoring intermolecular interactions or reciprocal docking for the encapsulation of organic guests.…”