Hive Novel Discourse

	Main Index Search Register Login Who's Online FAQ Links
	Main Index Search Register Login Who's Online FAQ Links

	1 Online, 0 Active		You are not logged in

This is a historical archiveThe forum is read-only. Private information has been removed. It is not possible to login.

	Novel Discourse

All posts Subject: TsOH - best Friedel-Crafts catalyst ever ?! Please login to post

psyloxy
(Hive Addict)
06-24-04 21:58
No 515205
User Picture TsOH - best Friedel-Crafts catalyst ever ?!
(Rated as: excellent)

J.Org.Chem., 63,9.1998;2858-2866

full article
very raw OCR'ed w/o pictures

summary

Alkylation of the aromatic nucleus, an important reaction in industry and synthetic organic chemistry, has traditionally been carried out by the well-known Friedel -Crafts reaction employing Lewis acid catalysts such as AlCl₃ and BF, or by using highly reactive organometallic reagents. Although protic acids such as anhydrous HF and concentrated H₂S0₄ have also been used in the alkylation of the aromatic nucleus, the notoriously corrosive, highly toxic, and hazardous nature of these agents has precluded their common use under ordinary laboratory conditions. Various organic sulfonic acids have, on occasion, been used as catalysts in Friedel-Crafts alkylations, but to our knowledge the chemistry and the scope of these reactions for common laboratory use have never been exploited in detail. In the present study we have characterized commercially available p-toluenesulfonic acid monohydrate (TsOH) as an efficient catalyst for the intermolecular coupling of the aromatic nucleus with activated alkyl halides, alkenes, or tosylates under mild conditions in an open atmosphere. In comparison to conventional Friedel-Crafts catalysts such as AlCl₃, BF₃, HF, and concentrated H₂SO₄, the extent of the formation of undesired products from side reactions such as transalkylation, polymerization, etc. was minimal with the TsOH-catalyzed reaction. The ability to recover and reuse the catalyst from the reaction mixtures, minimal generation of environmentally unfriendly waste, high specificity of the reaction, and the low cost of the catalyst are important advantages of the TsOH catalyst over the other conventional Friedel-Crafts catalysts.

Alkylation of Toluene.

A mixture of the desired alkyl substrate (0.05 mol) and p-toluenesulfonic acid monohydrate (11.4 g, 0.06 mol) in 53 mL of toluene (0.5 mol) was refluxed for the appropriate times indicated in Table 1, with magnetic stirring. The reaction mixture was cooled to room temperature, allowing the crystalline catalyst to separate. The solid catalyst was then filtered and washed with hexane (2 x 25 mL). The resultant organic filtrate was washed first with 0.1 M NaHCO₃ solution and then with distilled water and dried over anhydrous Na₂SO₄. The evaporation of the organic solvent in vacuo yielded crude product mixtures which were, subjected to further purification whenever it was appropriate.

--psyloxy--

	https://the-hive.archive.erowid.org	the-hive@erowid.org



Powered by Red Tar Version 3.00, (c) 2018 - 2022. All rights reserved.
Links Erowid Rhodium

	All posts		Subject: TsOH - best Friedel-Crafts catalyst ever ?!		Please login to post


		psyloxy (Hive Addict) 06-24-04 21:58 No 515205				TsOH - best Friedel-Crafts catalyst ever ?! (Rated as: excellent)
						J.Org.Chem., 63,9.1998;2858-2866 full article very raw OCR'ed w/o pictures summary Alkylation of the aromatic nucleus, an important reaction in industry and synthetic organic chemistry, has traditionally been carried out by the well-known Friedel -Crafts reaction employing Lewis acid catalysts such as AlCl₃ and BF, or by using highly reactive organometallic reagents. Although protic acids such as anhydrous HF and concentrated H₂S0₄ have also been used in the alkylation of the aromatic nucleus, the notoriously corrosive, highly toxic, and hazardous nature of these agents has precluded their common use under ordinary laboratory conditions. Various organic sulfonic acids have, on occasion, been used as catalysts in Friedel-Crafts alkylations, but to our knowledge the chemistry and the scope of these reactions for common laboratory use have never been exploited in detail. In the present study we have characterized commercially available p-toluenesulfonic acid monohydrate (TsOH) as an efficient catalyst for the intermolecular coupling of the aromatic nucleus with activated alkyl halides, alkenes, or tosylates under mild conditions in an open atmosphere. In comparison to conventional Friedel-Crafts catalysts such as AlCl₃, BF₃, HF, and concentrated H₂SO₄, the extent of the formation of undesired products from side reactions such as transalkylation, polymerization, etc. was minimal with the TsOH-catalyzed reaction. The ability to recover and reuse the catalyst from the reaction mixtures, minimal generation of environmentally unfriendly waste, high specificity of the reaction, and the low cost of the catalyst are important advantages of the TsOH catalyst over the other conventional Friedel-Crafts catalysts. Alkylation of Toluene. A mixture of the desired alkyl substrate (0.05 mol) and p-toluenesulfonic acid monohydrate (11.4 g, 0.06 mol) in 53 mL of toluene (0.5 mol) was refluxed for the appropriate times indicated in Table 1, with magnetic stirring. The reaction mixture was cooled to room temperature, allowing the crystalline catalyst to separate. The solid catalyst was then filtered and washed with hexane (2 x 25 mL). The resultant organic filtrate was washed first with 0.1 M NaHCO₃ solution and then with distilled water and dried over anhydrous Na₂SO₄. The evaporation of the organic solvent in vacuo yielded crude product mixtures which were, subjected to further purification whenever it was appropriate. --psyloxy--

	All posts		End of thread