MONOPERSULFATES OF NITROGEN CONTAINING HETEROCYCLIC (POLY)PERCARBOXYLIC ACIDS

Abstract: Disclosed are monopersulfates of nitrogen containing hetero­ cyclic (poly)percarboxylic acids of formula: wherein: R represents hydrogen or alkyl, (hetero)cycloalkyl, (hetero)aryl, alkylaryl or arylalkyl, said groups being optionally substituted, a carboxylic group or a percarboxylic group, or any other substituents non-reactive in the presence of the percarboxylic group; R¹ represents an alkyl group having more than 5 carbon atoms; n is selected from 0,1 and 2; m is selected from 1, 2 and 3; and the heterocyclic ring may optionally be condensed with at least one further (hetero) aromatic or (hetero)cycloalkyl ring. Also described is a process for the preparation of said salts and their use as bleaching agents.

Description: The invention relates to derivatives of (poly)percarboxylic acids which can be referred to as monopersulfates of nitrogen-containing heterocyclic (poly)percarboxylic acids, to a process for the preparation of said compounds and to their use in bleaching compositions. In particular, the present invention relates to monopersulfates of nitrogen containing heterocyclic (poly)percarboxylic acids of general formula (I): wherein: R represents hydrogen,alkyl,cycloalkyl, heterocycloalkyl, aryl, heteroaryl, alkylaryl or arylalkyl, said groups being optionally substituted, a carboxylic (COOH) or a percarboxylic (CO₃H) group, or any other substituent non-reactive in the presence of the active oxygen of the peroxycarboxylic group;(if m is 2 or 3 said groups R can be the same or different from each other); R¹ represents an alkyl group having more than 5 carbon atoms; n is 0,1 or 2; m is 1, 2 or 3; and wherein the heterocyclic ring may in its turn be condensed with at least one further (hetero) aromatic or (hetero) cycloalkyl ring. The derivatives of general formula (I) constitute a new class of products highly interesting from an industrial point of view, particularly due to their high content of active oxygen per weight unit. In fact, they can find general use, similarly to already known peracids, e.g. in the field of plastics, as polymerization initiators and, in particular, as oxidants for olefin epoxidation and hydroxylation, and in many other oxidative processes in the field of fine chemistry. Particularly interesting and efficient, however, is their application in the field of bleaching, i.e. in detergents. In the past years, organic peracids have attracted increasing interest in the industrial field, due to their excellent properties when used as bleaching agents in compositions for medium/low temperature washing, and particularly in view of energy saving considerations. Consequently, there is considerable research activity aiming at finding new organic peracid compounds having the necessary properties, i.e. high bleaching activity, thermal stability and storage stability or shelf life. The latter requirements are essential for an industrial application and a widespread use of such compounds. Therefore, many mono- and di-percarboxylic acids, straight-chained or cyclic, are known and used, among others, in the field of detergence. Already described percarboxylic acids are, e.g.: diperdodecanedioic acid, monoperphthalic acid, diperazelaic acid and substituted diperglutaric and adipic acids, In conventional preparation processes the oxidation of the substrate is carried out in concentrated H₂SO₄ with a solution of hydrogen peroxide. The above method, when applied to substrates containing salifiable nitrogen atoms of basic character, results in products with a high solubility in the strongly acidic medium. Said high solubility makes it impossible to apply any of the conventional processes of isolation of the percarboxylic acid derivative which may be formed, such as precipitation and extraction with an organic solvent. Surprisingly, it has now been found that the nitrogen containing heterocyclic (poly)percarboxylic acid monopersulfates of general formula (I), salified on the nitrogen atom with the persulfuric anion, can be obtained in a stable form by means of a novel process, which is also an object of the present invention. Therefore, one object of the present invention is to provide novel compounds, i.e. monopersulfates of nitrogen containing heterocyclic (poly)percarboxylic acids having the above formula (I). Another object of the present invention is to provide a simple and inexpensive process for the preparation of the above percarboxylic acid derivatives having the above formula (I) in a stable form. A further object of the present invention is the use of the nitrogen containing heterocyclic percarboxylic acid monopersulfates of formula (I) as bleaching agents in detergent formulations, particularly those for low-medium temperature use. These, and still other objects, which will become evident from the following detailed disclosure, are achieved, according to the present invention, by the monopersulfates of nitrogen containing heterocyclic percarboxylic acids of the above formula (I), and by a process for the preparation thereof which is characterized in that a substrate selected from nitrogen-containing heterocyclic (poly)carboxylic acids or their N-sulfate salts, said substrate corresponding to the desired monopersulfates of formula (I), is reacted with H₂O₂ in concentrated H₂SO₄ and in that said monopersulfate is then separated from the reaction mixture by means of the addition of an organic solvent selected from tetrahydrofuran and ethyl acetate. By use of the present process the monopersulfates of formula (I) are generally obtained as stable solids, salified on their nitrogen atom with H₂SO₅, due to their insolubilization in the reaction medium by the solvent. Stated more precisely, the process according to the present invention comprises the percarboxylation reaction of a substrate selected from a nitrogen-containing (poly)carboxylic acid, or its N-sulfate, corresponding to the desired salt of formula (I), in an acidic medium of concentrated H₂SO₄ with H₂O₂ and the subsequent addition, at the end of the reaction, of a suitable organic solvent which is immiscible with the desired product (by not dissolving it), but which is capable, on the contrary, of completely dissolving the acid reaction medium (concentrated H₂SO₄), as well as the excess of H₂O₂ and the reaction water. This results in the separation, by insolubilization, of the desired (poly)percarboxylic acid product of formula (I) which usually precipitates in a stable solid form. The obtained product may then be filtered, washed with the solvent, dried, etc., according to conventional techniques. As stated above, the substrate used as starting material, is selected from nitrogen-containing heterocyclic (poly)carboxylic acids, or their N-sulfate salts corresponding in structure to the desired (poly)percarboxylic acid monopersulfate of formula (I); these substrates are known, and/or can be prepared according to known processes. Referring to the above formula (I), R preferably is a linear or branched alkyl, (hetero)-aryl, (hetero)-cycloalkyl, alkyl-aryl or aryl-alkyl group, containing an overall number of up to 10, particularly up to 6, carbon atoms, and, in the heterocyclic rings, the presence of N atoms and/or 0 atoms (e.g. 1 or 2 such hetero atoms) is preferred. Said groups may in turn be substituted with one or more (preferably 1 to 3) atoms or groups, the same or different from each other and inert under the reaction conditions under which the preparation takes place, such as, e.g., F, Cl, NO₂, C₁₋₅ alkoxy. Alternatively, R represents any other substituent which does not react with the active oxygen of the percarboxylic group, e.g., a carboxylic group, a percarboxylic group, F, Cl, NO₂, (C₁₋₅)-alkoxy, R₁ represents a linear or branched alkyl group containing more than 5 carbon atoms, preferably having 8 to 20, and particularly 8 to 16, carbon atoms. The above heterocyclic ring may optionally be condensed with at least one other (hetero) aromatic or (hetero) cycloalkyl ring and thus be in the form of e.g. a quinolinic, isoquinolinic, pyrido-indolic group, n is preferably equal to 1, whereas a preferred meaning for R is hydrogen. Specific examples of the generic groups mentioned above are: alkyl: methyl, ethyl, n- and i-propyl, n-, i-. sec.- and tert.butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl and octadecyl; aryl: phenyl, naphthyl, biphenylyl and anthracenyl; heteroaryl: pyrrolyl, imidazolyl, furanyl, pyridinyl, pyranyl, pyrazinyl, indolyl, quinolinyl and isoquinolinyl; cycloalkyl: cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl; heterocycloalkyl: tetrahydrofuranyl, pyrrolidinyl, imidazolidinyl, piperidyl, tetrahydropyranyl and morpholinyl; alkylaryl: tolyl, xylyl, ethylphenyl and methylnaphthyl; arylalkyl: benzyl, phenethyl and naphthylmethyl; alkoxy: methoxy, ethoxy, propoxy, butoxy and pentoxy. Examples of suitable substrates are, e.g., N-octyl-4-piperidine carboxylic acid, N-decyl-4-piperidinecarboxylic acid and N-hexadecyl-4-piperidinecarboxylic acid. For R = COOH, preferably in a non-ortho-position with respect to the nitrogen atom, the percarboxylation of R can be carried out, too, thus resulting in a product of formula (I) with two or more (at the most four) percarboxylic groups. According to a preferred mode of operation, the percarboxylation reaction of the nitrogen containing heterocyclic (poly)carboxylic acids or the corresponding sulfates used as starting material, is carried out by gradually adding H₂O₂ having a concentration within the range of from 70% to 90% by weight to a solution of the substrate in concentrated H₂SO₄ (96-98%), maintaining the reaction temperature throughout the reaction at a temperature lower than 20°C. Alternatively, it has been found that it is possible to salify (as H₂SO₄ salt) the substrate, by working in the absence of H₂O₂ under otherwise the same conditions as described above, and to separate the obtained salt first, said salt being thereafter peroxidized. The amount of H₂SO₄, based on a concentration of 100%, is preferably at least 5 moles per mole of substrate, and most preferred ranges are from 6 to 15 moles. Hydrogen peroxide is preferably used in an amount which is in excess with respect to the substrate and preferably equals at least 5 moles per mole of substrate. The reaction time depends on the nature of the subtrate, the operating temperature, and the final total H₂SO₄/H₂O molar ratio present at the end of the reaction. Said ratio is preferably chosen so as to be of from 1.3 to 4 by adjusting the various parameters concerned. Reaction times of from 30 minutes to 1 hour have proven to be the usual ones. The employed amount of tetrahydrofuran and/or ethyl acetate solvent is preferably not lower than 4 litres/mole of substrate, e.g., 7 litres/mole; furthermore, the solvent is preferably added at a temperature not higher than 10°C. The nitrogen-containing heterocyclic percarboxylic acid monopersulfates of formula (I) usually are solid at room temperature. They can be used to particular advantage in formulations of detergent compositions, e.g., granular formulations,and as bleaching agents in solution within a wide temperature range, due to their high storage stability and thermal stability. The detergent compositions can be formulated according to the usual pertinent techniques, using further components and/or additives. The present invention will now be described in more detail by the following examples. The products prepared in the examples were characterized by elemental analysis, by determining their content of active oxygen (by iodometric titration), and by using the Fourier Transform Infrared Spectroscopy (FT-IR). EXAMPLE 1 5.1 g (0.019 mole) of N-decyl-isonipecotic acid were completely dissolved, at +35°C, in 11.6 g of H₂SO₄ (96%, 0.114 mole). 3.8 g of H₂O₂ (85%, 0.095 mole) were then added to the solution so that the temperature was maintained at or below +15°C. Stirring was then continued for 45 minutes at +15°C. The reaction mixture was then poured into 140 ml of ethyl acetate maintained under stirring at -10°C. After 30 minutes the separated crystalline product was filtered under vacuum over a porous septum and was directly washed on the filter with consecutive portions of ethyl acetate (2 x 30 ml) and ethyl ether (2 x 30 ml). The product was then kept in a CaCl₂-drier under vacuum and at room temperature for 1 hour. Obtained were 4.8 g of crystalline N-decyl-piperidine-4-percarboxylic acid having an active oxygen content of 7.8% (97.4% of the theoretical value). Yield: 62%. Elemental Analysis: Calculated for C₁₆H₃₃NSO₈: C 48.10%; H 8.32%; N 3.50%; 0 (active) 8.01; H₂SO₅ 28.55%. Found: C 48.06%; H 8.41%; N 3.49%; 0 (active) 7.80%; H₂SO₅ 28.5%. Melting point: 78°C (with decomposition). EXAMPLE 2 4 g (0.0113 mole) of N-hexadecyl-4-piperidine-carboxylic acid were added, slowly and under stirring, to 2.5 g of sulphuric acid in a 25 ml beaker, care being taken to maintain the temperature at or below 40°C by use of a cooling bath. Stirring was then continued at 35 to 40°C for 2 hours. The reaction mixture was then poured into 150 ml of ethyl acetate maintained under stirring at 10°C. Stirring was then continued for 30 minutes. The separated N-hexadecyl-4-piperidine-carboxylic acid sulfate was filtered over a porous septum, washed first with ethyl acetate (2 x 30 ml) and then with Et₂0 (2 x 30 ml), and thereafter dried under vacuum at room temperature over CaCl₂. Obtained were 4.1 g of product which was used for preparing the corresponding peracid monopersulfate. 2 g of H₂O₂ (85%, 0.05 mole) were added, under stirring, to 12 g of H₂SO₄ (96%, 0.1175 mole) by maintaining the temperature at or below +5°C. 4.1 g of N-hexadecyl-isonipecotic acid sulfate (0.0091 mole) were added so as to maintain the temperature at or below +15°C. Stirring was then continued at +15°C for 30 minutes. The reaction mixture was poured into 100 ml of ethyl acetate maintained under stirring at -10°C. Thereafter the procedure of example 1 was followed. 3.2 g of crystalline, practically pure N-hexadecylpiperidine-4-percarboxylic acid monopersulfate were obtained. Yield: 73%. Elemental Analysis: Calculated for C₂₂H₄₅NSO₈: C 54.63%; H 9.37%; N 2.89%; O (active) 6.61%; H₂SO₅ 23.58%. Found: C 53.9%; H 9.35%; N 2.89%; O (active) 6.6%; H₂SO₅ 23.41%. Melting point: 84°C (with decomposition). EXAMPLE 3 (Application Example) Bleaching tests were carried out with the novel salt listed in the annexed Tables 1 and 2, at alkaline pH (Table 1) and acid pH (Table 2). The following substance served as comparison: H 48 (Mg salt of monoperphthalic acid), a commercial peracid known in the detergent art, and manufactured by INTEROX Chemical Ltd., London, U.K. (Tables 1 and 2). All tests were carried out at constant temperature (60°C), with an initial concentration of total active oxygen in the bleaching solution (identical for all products) of equal to 200 mg/l. Process For each test, 500 ml of deionized water, contained in a 1000 ml flask equipped with a condenser, was heated to a temperature of 60°C and adjusted to a pH of 9.5 (by adding a few drops of an NaOH solution) (Table 1) and of 3 - 4 (by adding a few drops of diluted H₂SO₄)(Table 2). Then the bleaching product was added with stirring, in amounts shown in the following Tables, and immediately thereafter two cotton specimens of 10 cm x 10 cm,stained with standard stains of red wine at EMPA INSTITUTE of St.Gallen (Switzerland), and marked with the "EMPA 114" mark, were added. The system subsequently was kept under stirring for 60 minutes and, at the end of this time, the specimens, rinsed under running water, were dried and ironed, and were then subjected to an evaluation of the bleaching effect by means of a measurement of the whiteness degree by reflectometry. The results are reported in the following Tables 1 and 2, wherein the data are expressed as % Bleaching, defined as: wherein: A = degree of whiteness (%) of the specimen bleached after the test; B = degree of whiteness (%) of the specimen before the test; C = degree of whiteness (%) of the completely bleached specimen. The degree of whiteness was measured by means of an Elrepho Zeiss reflectometer, assuming MgO = 100% of whiteness, and using a filter N.6 (λ = 464 nm). The data listed in Table 1, concerning tests carried out at alkaline pH, show that the peracid salts of the present invention have a bleaching power which may be compared to the bleaching power of H 48. Likewise, the results, expressed as % Bleaching, listed in Table 2, show that the tested products have a bleaching power in acid solution which is particularly high and higher than that of H 48. This is particularly surprising in consideration of the fact that the peroxidic compounds generally show a very modest and sometimes negligible bleaching activity at acid pH. Test carried out at alkaline pH (9.5) Compound Amounts used in the tests (grams) Initial concentration of total active oxygen (mg/l) % Bleaching - Example 1 (titer = 5.50% of active oxygen) 1.28 200 74.18 - H 48 (titer = 5.5% of active oxygen) 1.86 200 81.0 Test carried out at acid pH (3-4) Compound Amounts used in the tests (grams) Initial concentration of total active oxygen (mg/l) % Bleaching - Example 1 (titer = 7.80% of active oxygen) 1.28 200 78.4 - H 48 (titer = 5.5% of active oxygen) 1.86 200 60.0

Claims: Claims for the following Contacting States : AT, BE, CH, DE, FR, GB, LI, NL, SE Monopersulfates of nitrogen containing heterocyclic (poly)percarboxylic acids of general formula: wherein: R represents hydrogen or linear or branched alkyl, (hetero)aryl, (hetero) cycloalkyl, alkylaryl or arylalkyl containing an overall number of up to 10 carbon atoms, said groups being optionally substituted by at least one substituent selected from F, Cl, NO₂ or (C₁-C₅)-alkoxy; a carboxylic or a percarboxylic group; a F atom, a Cl atom and a (C₁-C₅)-alkoxy group, and wherein the heteroatoms are selected from N and O; R¹ represents an alkyl group having more than 5 carbon atoms; n is an integer selected from 0, 1 and 2; m is an integer selected from 1, 2 and 3; and wherein the heterocyclic ring itself may optionally be condensed with at least one further (hetero)aromatic or (hetero)cycloalkyl ring, the heteroatoms being selected from N and O. Monopersulfates according to claim 1, wherein R¹ represents an alkyl group containing from 8 to 20 carbon atoms. Monopersulfates according to any one of claims 1 and 2, wherein n is 1 and R is hydrogen. Monopersulfates according to any one of claims 1 to 3, wherein the heterocyclic ring is condensed with at least one other (hetero)aromatic or (hetero)cycloalkyl pyridinic ring. compounds according to claim 1, i.e. N-decyl-piperidine-4-percarboxylic acid monopersulfate and N-hexadecylpiperidine-4-percarboxylic acid monopersulfate. Process for preparing the monopersulfates according to claim 1, characterized in that a substrate selected from a nitrogen containing heterocyclic (poly)carboxylic acid and its N-sulfate salt, corresponding to the desired percarboxylic acid of formula (I), is reacted with H₂O₂ in a concentrated H₂SO₄ medium and that the resulting monopersulfate of general formula (I) is separated from the reaction mixture by addition of tetrahydrofuran and/or ethyl acetate. Process according to claim 6, characterized in that a nitrogen containing heterocyclic (poly)percarboxylic acid corresponding to the desired compound of formula (I) is converted into the corresponding H₂SO₄ salt which is then reacted with H₂O₂ in concentrated H₂SO₄. Process according to any one of claims 6 and 7, characterized in that the heterocyclic nitrogen containing (poly)carboxylic acid or its N-sulfate'salt is gradually reacted with H₂O₂ having a concentration of from 70% to 90% by weight in concentrated H₂SO₄ at a temperature lower than 20°C. Process according to any one of claims 6 to 8, characterized in that the amount of H₂SO₄ is at least equal to 5 moles per mole of substrate. Process according to claim 9, characterized in that the amount of H₂SO₄ ranges from 6 to 15 moles per mole of substrate. Process according to any one of the claims 6 to 10, characterized in that an amount of hydrogen peroxide is used which is at least equal to 5 moles per mole of substrate. Process according to any one of claims 6 to 11, characterized in that the final molar ratio of H₂SO₄ to the total H₂O present at the end of the reaction ranges from 1.3 to 4. Process according to any one of claims 6 to 12, characterized in that the amount of tetrahydrofuran and/or ethyl acetate used is not lower than 4 litres per mole of substrate. Process according to any one of claims 6 to 13, characterized in that the tetrahydrofuran and/or ethyl acetate solvent is added at a temperature not higher than 10°C. Use of monopersulfates according to any one of claims 1 to 5 as bleaching agents in detergent formulations. Claims for the following Contracting State : ES Process for preparing monopersulfates of nitrogen containing heterocyclic (poly)percarboxylic acids of general formula: wherein: R represents hydrogen or linear or branched alkyl, (hetero)aryl, (hetero) cycloalkyl, alkylaryl or arylalkyl containing an overall number of up to 10 carbon atoms, said groups being optionally Substituted by at least one substituent selected from F, Cl, NO₂ or (C₁-C₅)-alkoxy; a carboxylic or a percarboxylic group; a F atom, a Cl atom and a (C₁-C₅)-alkoxy group, and wherein the heteroatoms are selected from N and O; R¹ represents an alkyl group having more than 5 carbon atoms; n is an integer selected from 0, 1 and 2; m is an integer selected from 1, 2 and 3; and wherein the heterocyclic ring itself may optionally be condensed with at least one further (hetero)aromatic or (hetero)cycloalkyl ring, the heteroatoms being selected from N and O, characterized in that a substrate selected from a nitrogen containing heterocyclic (poly)carboxylic acid and its N-sulfate salt, corresponding to the desired percarboxylic acid of formula (I), is reacted with H₂O₂ in a concentrated H₂SO₄ medium and that the resulting monopersulfate of general formula (I) is separated from the reaction mixture by addition of tetrahydrofuran and/or ethyl acetate. Process according to claim 1, wherein R¹ represents an alkyl group containing from 8 to 20 carbon atoms. Process according to any of the claims 1 and 2, wherein n is 1 and R is hydrogen. Process according to any one of claims 1 to 3, wherein the heterocyclic ring is condensed with at least one other (hetero)aromatic or (hetero)cycloalkyl pyridinic ring. Process according to claim 1, wherein the monopersulfates are N-decyl-piperidine-4-percarboxylic acid monopersulfate and N-hexadecyl-piperidine-4-percarboxylic acid monopersulfate. Process according to any one of claims 1 to 5, characterized in that a nitrogen containing heterocyclic (poly)percarboxylic acid corresponding to the desired compound of formula (I) is converted into the corresponding H₂SO₄ salt which is then reacted with H₂O₂ in concentrated H₂SO₄. Process according to any one of claims 1 to 6, characterized in that the heterocyclic nitrogen containing (poly)carboxylic acid or its N-sulfate salt is gradually reacted with H₂O₂ having a concentration of from 70% to 90% by weight in concentrated H₂SO₄ at a temperature lower than 20°C. Process according to any one of claims 1 to 7, characterized in that the amount of H₂SO₄ is at least equal to 5 moles per mole of substrate. Process according to claim 8, characterized in that the amount of H₂SO₄ ranges from 6 to 15 moles per mole of substrate. Process according to any one of the claims 1 to 9, characterized in that an amount of hydrogen peroxide is used which is at least equal to 5 moles per mole of substrate. Process according to any one of claims 1 to 10, characterized in that the final molar ratio of H₂SO₄ to the total H₂O present at the end of the reaction ranges from 1.3 to 4. Process according to any one of claims 1 to 11, characterized in that the amount of tetrahydrofuran and/or ethyl acetate used is not lower than 4 litres per mole of substrate. Process according to any one of claims 1 to 12, characterized in that the tetrahydrofuran and/or ethyl acetate solvent is added at a temperature not higher than 10°C. Use of monopersulfates obtained according to any one of claims 1 to 13 as bleaching agents in detergent formulations.

Inventors: ACHILLI, FIORELLA, DR., CAVALLOTTI, CLAUDIO, VENTURELLO, CARLO, DR.
Applicants: AUSIMONT S.P.A.
Application year: 1989
Main classification: C07D211
IPC codes: C11D3, C07D207, C07D223, C07D211