A new catalytic dehydrohalogenation method for chlorinated phenols is described, which can be used to break down chlorinated pollutants in wastewater. It uses a system of Pd-C as catalyst with sodium formate as reducing agent. This economic method is easy to perform with a complete degradation of the pollutant within 12 to 30 h at room temperature. The ecoefficieny of the procedure is compared with eleven alternative methods showing the special advantages of the method. IntroductionChlorophenols have been used in pesticides, disinfectants, wood preservatives, personal care formulations, and many other technical products. They are also substantial by-products of the wood pulp bleaching process with chlorine, where they are emitted by wastewaters [1]. However, increasing knowledge about toxicity and environmental fate of these compounds resulted in regulation acts for production and distribution by various governments. In most European countries pentachlorophenol (PCP) has been banned as commercial fungicide; five chlorophenols are listed by the U.S. Environmental Protection Agency as priority pollutant, including PCP and 2,4,6-trichlorophenol, which occur, according to Ramamoorthy and Ramamoorthy [1], in the environment in significant quantities.Several oxidative degradation methods exist for these classes of compounds using H2O2 as oxidant. A French group [2] reported most effective methods for oxidations in homogeneous solution; a recent method developed uses H2O2 in the presence of Fe-TAML as catalyst [3]. An alternative remediation method would be a reductive cleavage of chlorophenols yielding chloride and phenol, the latter being readily biodegradable. While there are several reductive dechlorination methods reported in the literature for aromatic chlorine compounds, most of these methods have been used for monochlorinated compounds [4 -12].It should be mentioned that there are some other procedures for hydrodechlorination of aromatic halides such as hydrodechlorination by special electrochemistry techniques [13] and treatment with iron and photolytic hydrodehalogentions [14], but these methods are not appropriate for practical remediation. PCP has been dechlorinated efficiently with a variety of metals like Ag/Fe in subcritical water at temperatures of 200 to 3508C [15], certainly not useful for remediation of wastewaters. There is an extensive review article about reductive hydrodehalogenations of organic halides [16].Here, the development of an efficient hydrodechlorination method for perchlorinated aromatic compounds in aqueous solution is described, which uses Palladium on charcoal as catalyst and sodium formate as reducing agent. The method was described recently by an Italian group, who employed it on monochlorinated arene derivatives on preparative scale [11]. We have modified the method in order to use it for chlorinated phenols and PCP at environmentally relevant levels and compared it with other existing methods according to its practical use and ecoeffiency. Materials and Methods General Survey ...

New formaldehyde derivatives were prepared in good yields by a short and versatile route. Several crystal structures of corresponding thioacetic acid esters and thiols were determined. The thioacetates were cleaved under acidic or basic conditions affording the thiols in high yield, thus introducing the new substance classes of N-mercaptomethyl-alkylcarboxamides, N-mercaptomethylsulfonamides, and alkoxymethanethiols.The reactivity of formaldehyde is outstanding among aldehydes making it difficult to obtain the pure substance. With traces of water formaldehyde immediately suffers from nucleophilic attack rendering polymeric formaldehyde. This extraordinary reactivity is due to the lack of electron-donating alkyl groups, which stabilize the carbonyl group of larger homologues by the inductive effect.For our syntheses 1 of orally active carbapenems we searched for formaldehyde-derived N-mercaptomethylalkylcarboxamides and HS/O-acetals. Surprisingly, the former compounds have not been prepared yet, whereas the latter could not be prepared by a route proposed in 1912. 2 We wish to report here the synthesis of the following three novel types of formaldehyde derivatives. As they contain a reactive SH group they are versatile C 1 -building blocks in organic synthesis.N-Mercaptomethylcarboxamides represent a first novel class of thiols, prepared by a four-step synthesis starting from carboxamides and formaldehyde according to Scheme 1. The mildest method to prepare N-hydroxymethyl compounds 2 uses an aqueous formaldehyde solution with a catalytic amount of K 2 CO 3 , a reaction first described by Einhorn. 3 Accordingly, amides 1 reacted easily in high yields. However, our attempts to purify the products 2 by column chromatography or recrystallization failed in most cases. The hydroxymethyl group was cleaved, leaving only starting material 1 and formaldehyde. Adduct 2c could be recrystallized from toluene, yielding pure product. The adducts 2 were converted to chlorides 3 using thionyl chloride or oxalyl chloride. The reaction of chlorides 3 with potassium thioacetate produced the desired 4 using a method developed in our group. 1 Acidic or basic cleavage of the thioacetates delivered the corresponding thiols 5 in good yields. Thioacetate 4b was prepared by direct reaction of 2b with thioacetic acid in 64% yield.Scheme 1 General reaction sequence used to prepare 5Starting with pyrrolidin-2-one (1e) the intermediate lactams 2e-4e and the cyclic thiol 5e were produced. Alternatively from the known 4 3-chloromethyl-1,3,4-oxadiazol-2(3H)-ones 3f,g and from 1,3,4-thiadiazol-2(3H)-ones 1h 5 and 1i 5 the cyclic thiols 5f-i were synthesized.Pyrrolidin-2-one (1e) did not easily react with aqueous formaldehyde, so we had to deviate from the standard route. In a modified procedure, 6 a mixture of paraformaldehyde and 1e was heated to 180°C to give 2e, which was chlorinated immediately affording 3e in 40% overall yield after distillation. Crystal structures of thioacetates 4b,i as well as of thiols 5d,g,h,i could be determined. 7 The ...

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