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Supported Sulfonic Acids: Solid Catalysts for Batch and Continuous-Flow Synthetic Processes.

Piscopo CG - ChemistryOpen (2015)

View Article: PubMed Central - PubMed

Affiliation: Clean Synthetic Methodology Group, Dipartimento di Chimica dell'Università, Università degli Studi di Parma Parco Area delle Scienze 17°, 43124, Parma, Italy.

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The synthesis of silica-supported sulfonic acids can be achieved with different procedures... This thesis deals with the synthesis and evaluation of the catalytic activity of some supported sulfonic acids as heterogeneous and reusable catalysts in several organic reactions that are of synthetic interest... To achieve further information on the behavior of these catalysts, we analyzed the reactions with silica-supported phenylsulfonic, ethylphenylsulfonic, and propoxyphenylsulfonic acids under solvent-free conditions... Another relevant synthetic process that was investigated using supported sulfonic acid catalysts is the oxidation of methylhydroquinone to methylbenzoquinone with 30 % aqueous hydrogen peroxide... The catalyst that is simply recovered by filtration and washed with hot methanol can be reused twice without loss of activity... The good synthetic results and, in particular, the effective catalyst recyclability achieved in the batch experiments were further developed on a continuous-flow catalytic system... Finally, the catalyst could be used for at least 3000 min without any loss of activity... These results represent the first example of the successful oxidation of aromatic sulfides with 3 % aqueous hydrogen peroxide... The acylation reaction of anisole, catalyzed by silica-supported sulfonic acids was carried out... The above method shows low environmental impact because it avoids the use of halogenated compounds, and acetic acid is the only byproduct... The activity of different catalysts was compared... The supported sulfonic acids used in this work showed very good catalytic activity in different classes of reactions... These catalysts have the advantage of being cheap, safe to handle, and easy to recycle... Reaction conditions are mild, with very good atom economy in most cases, and work-up steps are very easy, satisfying several essential parameters of the “green chemistry” philosophy... Furthermore the application of these catalytic systems to continuous-flow processes resulted in a considerable improvement in efficiency.

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IR spectra of degassed samples and after contact with 20 mbar of water vapor (x, x’): a) bare silica; b) catalyst 16; c) catalyst 24; d) catalyst 21.
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fig02: IR spectra of degassed samples and after contact with 20 mbar of water vapor (x, x’): a) bare silica; b) catalyst 16; c) catalyst 24; d) catalyst 21.

Mentions: Various supported sulfonic acids were prepared according to well-known literature procedures, with slight modifications (Scheme 1 and Scheme 2). To probe the acid behavior of the supported species, the materials and the bare support (as a reference), were analyzed using infrared (IR) spectroscopy in degassed conditions (Figure 1) and under 20 mbar of water vapor (Figure 2). The consequences of the interaction with water were the depletion of the sulfurylic signal in the 1390–1325 cm−1 range and the appearance of a continuous absorption extended from 3500–1700 cm−1. The latter is a kind of “fingerprint” of the formation of H+(H2O)n clusters, and it probes the transfer of protons to the aqueous layers from −SO3H groups, which are converted into −SO3−. Thus, it can be stated that the contact with an aqueous medium results in complete deprotonation of the sulfonic groups.


Supported Sulfonic Acids: Solid Catalysts for Batch and Continuous-Flow Synthetic Processes.

Piscopo CG - ChemistryOpen (2015)

IR spectra of degassed samples and after contact with 20 mbar of water vapor (x, x’): a) bare silica; b) catalyst 16; c) catalyst 24; d) catalyst 21.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4522189&req=5

fig02: IR spectra of degassed samples and after contact with 20 mbar of water vapor (x, x’): a) bare silica; b) catalyst 16; c) catalyst 24; d) catalyst 21.
Mentions: Various supported sulfonic acids were prepared according to well-known literature procedures, with slight modifications (Scheme 1 and Scheme 2). To probe the acid behavior of the supported species, the materials and the bare support (as a reference), were analyzed using infrared (IR) spectroscopy in degassed conditions (Figure 1) and under 20 mbar of water vapor (Figure 2). The consequences of the interaction with water were the depletion of the sulfurylic signal in the 1390–1325 cm−1 range and the appearance of a continuous absorption extended from 3500–1700 cm−1. The latter is a kind of “fingerprint” of the formation of H+(H2O)n clusters, and it probes the transfer of protons to the aqueous layers from −SO3H groups, which are converted into −SO3−. Thus, it can be stated that the contact with an aqueous medium results in complete deprotonation of the sulfonic groups.

View Article: PubMed Central - PubMed

Affiliation: Clean Synthetic Methodology Group, Dipartimento di Chimica dell'Università, Università degli Studi di Parma Parco Area delle Scienze 17°, 43124, Parma, Italy.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

The synthesis of silica-supported sulfonic acids can be achieved with different procedures... This thesis deals with the synthesis and evaluation of the catalytic activity of some supported sulfonic acids as heterogeneous and reusable catalysts in several organic reactions that are of synthetic interest... To achieve further information on the behavior of these catalysts, we analyzed the reactions with silica-supported phenylsulfonic, ethylphenylsulfonic, and propoxyphenylsulfonic acids under solvent-free conditions... Another relevant synthetic process that was investigated using supported sulfonic acid catalysts is the oxidation of methylhydroquinone to methylbenzoquinone with 30 % aqueous hydrogen peroxide... The catalyst that is simply recovered by filtration and washed with hot methanol can be reused twice without loss of activity... The good synthetic results and, in particular, the effective catalyst recyclability achieved in the batch experiments were further developed on a continuous-flow catalytic system... Finally, the catalyst could be used for at least 3000 min without any loss of activity... These results represent the first example of the successful oxidation of aromatic sulfides with 3 % aqueous hydrogen peroxide... The acylation reaction of anisole, catalyzed by silica-supported sulfonic acids was carried out... The above method shows low environmental impact because it avoids the use of halogenated compounds, and acetic acid is the only byproduct... The activity of different catalysts was compared... The supported sulfonic acids used in this work showed very good catalytic activity in different classes of reactions... These catalysts have the advantage of being cheap, safe to handle, and easy to recycle... Reaction conditions are mild, with very good atom economy in most cases, and work-up steps are very easy, satisfying several essential parameters of the “green chemistry” philosophy... Furthermore the application of these catalytic systems to continuous-flow processes resulted in a considerable improvement in efficiency.

No MeSH data available.