US3915974A - Pyrazine compounds - Google Patents

Abstract

Certain pyrazines have been found to be useful as detergent builders in laundry formulations. Exemplary is 1,4,5,6tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile.

Description

United States Patent [1 1 [11] 3,915,974

Cairncross Oct. 28, 1975 PYRAZINE COMPOUNDS 3,684,809 8/1972 Mookherjee 260/250 BC Inventor: Allan Cairncross, Wilmington, Del. OTHER PUBLICATIONS [73] Assignee: E. I. Du Pont de Nemours and Fischer, Chern- Abstf- 25130109 Company, Wilmington, Dell Khalilov, Chem. Abstr. 63:6495a (1965). 22 Fi June 29 1973 Cariati, Chem. AbStl. 79Z38097f(197 3).

Ber 40, 4855-4856 (1907). [21] Appl' Mager et al., Recueil Trav. Chim. 77, 842-849 (1958). [52] US. Cl. 260/250 BC; 252/; 252/;

252/524; 260/250 B Primary ExaminerRiChard J Gallagher [5]] Int. (31. C071) 241/08 Attorney, Agent, or Firm-Anthony P. Mentis [58] Field of Search 260/250 R, 250 EN, 250 B,

260/250 BC 57 ABSTRACT [56] References Cited Certain pyrazines have been found to be useful as detergent builders in laundry formulations. Exemplary is UNITED STATES PATENTS l,4,5,6-tetrahydro-5,6-di0x0-2,3- 2,675,385 4/1954 Webb et a1. 260/250 BN pyrazinedicarbonitrile 3,024,235 3/1962 Magcr v 260/250 B 3,641,076 2/1972 Booth 260/250 R 9 Claims, N0 Drawings PYRAZINE COMPOUNDS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the use of certain pyrazines as detergent builders, to detergent compositions containing such pyrazines, and to certain useful metal salts of said pyrazines.

2. Description of the Prior Art Certain pyrazines have been reported in the literature, as for example 1,4,5,6-tetrahydro-5,6-diox-2,3- pyrazinedicarbonitrile [Bredereck & Schmititzer, Ann. 600, 95-108 (1956)]; pyrazinetetracarboxylic acid and its dipotassium salt [Chattaway & Humphrey, J. Chem. Soc. 1929, 645]; pyrazine-2,6-dicarboxylic acid, its calcium salt and several other of its metal salts [Stoehr & Detert, J. prakt. Chem. 55, 248 (1897); and Mager & Behrends, Rec. trav. chim, 77, 827 (1958)]. Permanganate oxidation of 2,3-dichloroquinoxaline to 5,6- dihydroxypyrazine-2,3-dicarboxylic acid is described by Mager & Behrends, Rec. trav. chim. 77, 842 (1958) [Chem. Abs. 53, 10241 (1959)] and the acid is disclosed to form a compound containing four silver atoms when reacted with silver nitrate. A precursor, 2,3-dihydroxyquinoxaline (regarded to be a tautomeric form of 2,3-diketotetrahydroquinoxaline) is indicated to form insoluble compounds with Ca, Sr, and Ba ions. Mattews and Walton, Inor. Chem. 10, No. 7, 1433 (1971) disclose insoluble pyrazine carboxylate complexes with metals such as silver, copper, cobalt and nickel. Non of these prior art materials have been disclosed as possible components of detergent compositions.

DESCRIPTION OF THE INVENTION It has now been found that certain pyrazines, their esters, and certain of their water soluble salts are effective complexing agents for calcium and magnesium.

They have the ability of being able to complex calcium and magnesium in neutral to basic (pH 7-12) aqueous solutions wherein the complex itself remains in at least metastable solutions. This property makes the pyrazine compounds useful as builders in detergent compositions, as for example, replacements for sodium tripolyphosphate. The pyrazine compounds have also been found to have surfactant properties, particularly those where R in the formula below has eight or more carbon atoms.

One aspect of the invention comprises a detergent composition containing a surfactant and a pyrazine compound selected from the group consisting of a. a compound of the formula wherein R and R alike or different, are CN or COOR in which R is H, alkyl, oxaalkyl, (alkylphenyl)oxaalkyl, of 1-48 carbon atoms; and water soluble salts thereof; and

b. 2,6-pyrazinedicarboxylic acid, pyrazinetetracarboxylic acid, 3,5-bis(methoxycarbonyl)-2,6- pyrazine--dicarboxylic acid, and 3,6-bis (methoxycarbonyl)-2,5-pyrazinedicarboxylic water soluble salts thereof;

the said pyrazine compound being present in an amount effective to chelate calcium ions in a basic medium.

A detergent composition is defined as a material which has a cleansing action like soap but is not directly derived from fats and oils. Such a composition generally contains synthetic detergents and may also contain soaps if desired, Synthetic detergents are surface active agents containing both hydrophilic and hydrophobic groups. Three types are generally recognized. (l) Anionic detergents which have negatively charged ions attached to the oil-soluble portion of the molecule and examples are sodium salts of organic sulfonates or sulfates such as alkylaryl sulfonates, e.g., sulfonates of dodecylbenzene. (2) Cationic detergents which ionize so that the oil-soluble portion is positively charged as for example quaternary ammonium halides. (3) Nonionic detergents which do not ionize but acquire hydrophilic character from a polar segment, such as polyoxyethylene.

The synthetics are usually used in combination with other active ingredients such as polyphosphates, polysilicates, sodium carboxymethylcellulose, sodium hydroxide and sodium carbonate, and with inert diluents such as sodium sulfate and water. A typical heavyduty detergent might consist of 20% organic surfactant, 45% phosphate detergent builders, 25% sodium sulfate, silicates, other inorganic builders, 10% miscellaneous, including perfumes, optical brighteners, soilsuspending agents and moisture.

The pyrazine is present in an amount effective to complex calcium and/or magnesium at a pH range of 7 to 12 and the resulting complex in water soluble at such pH range. The complex is water soluble when formed but may gradually become insoluble. The amount of the pyrazine in the detergent composition can vary over a wide range. A preferred range is 10 to 45% of the pyrazine compound by weight based on the total weight of the detergent composition. A more preferred range is 15-35%.

Certain of the above monoester and diester pyrazines appear to be new compounds of the formula:

acid, and

wherein R and R alike or different, are selected from the group OH, alkoxy, oxaalkoxy, (alkylphenyl)oxaalkoxy each of 1-48 carbon atoms, and, together, are 0, with the proviso that only one of R and R is OH; and with the further proviso that when R and R are alkoxy groups, each alkoxy group contains 4-48 carbon atoms; and watersoluble salts thereof.

The new esters are easily prepared. The lower diesters, that is, where R and R contain up to 3 carbon atoms, are obtained by conventional esterifcation procedures, e.g., by reacting l,4,5,6-tetrahydro-5,6-dioxo- 2,3-pyrazinedicarboxylic acid, its monosodium or monammonium salt, with a lower alcohol under acidic reaction conditions. Mixed diesters are produced when mixed alcohols are used. To obtain monoesters or diesters of alcohols containing four or more carbon atoms, l,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylic anhydride is heated with the desired alcohol. Simple heating of the anhydride and alcohol produces the monoester; further heating in the presence of an excess of the alcohol and an acid esterification catalyst, e.g. HCl, HBr, H 80 and p-toluenesulfonic acid, etc., produces the diester. A mixed diester is prepared when mixed alcohols are used. The alcohols correspond to the formulas HR and HR where R and R are as previously defined with the proviso that they are not OH, since water, when reacted with the anhydride will not produce an ester.

Salts of 5,6-dihydroxy-2,3-pyrazinedicarbonitrile, the enol form of 1,4,5,6-tetrahydro-5,6-dioxo-2, 3- pyrazinedicarbonitrile, can be readily prepared. The water-soluble alkali metal salts, i.e., the lithium, sodium and potassium salts, are useful as detergent builders.

SPECIFIC EMBODIMENTS OF THE INVENTION In the following illustrative examples all parts are by weight and temperatures are in degrees Centrigrade unless otherwise stated.

EXAMPLE I A. Calcium Chelating Activity by preventing of calcium carbonate precipitation The calcium chelating activity (CCA) ofa compound is roughly determined by an alkaline titration process as follows: A dry 2-g sample of the compound is dissolved in 50 ml of water and the pH of the solution is determined. (1) Hampshire NTA and Its Salts, A Bulletin on Nitrilotriacetic Acid and its Sodium Salts; Hampshire Chemical Corporation, Nashua, New Hampshire If the solution is below pH 7, sufficient l N sodium hydroxide is added to bring it to the neutral point. Aqueous sodium carbonate (2%, ml) is added, and the pH of the solution is adjusted to 11.5 with additional so dium hydroxide. The solution is then diluted to a volume of 100 ml and titrated within 1 to 2 minutes with aqueous calcium acetate (44.1 g monohydrate per liter, equivalvent to 25 mg CaCO per ml) to a distinct and permanent turbidity. If desired, a different amount of the candidate compound can be used and the amounts of other materials adjusted in proportion according to the above recipe. The CCA is expressed in terms of milligrams of CaCO chelated per gram of compound, calculated as follows:

(ml Ca acetate) X 25 CCA mg Cacoa/g wt of sample Table IA presents the results of the test described in Part A above on known detergent builders and on various pyrazines. Pyrazine compounds capable of chelating calcium, by the aforesaid alkaline titation procedure, to the extent of at least mg of CaCO per gram of pyrazine, are preferred. More preferred are those compounds which chelate at least 200 mg of CaCO The dioxo compounds No. 10 and No. l l in Table IA below form water soluble calcium complexes in the presence of carbonate at pH 7-12. This can be attributed to their ability to form stable enolate anions in basic solutions as evidenced by changes in their infrared absorption spectra under certain conditions. The tautomerism can be illustrated by the equation The pure compounds are indicated to be predominantly in the dioxo form since they show high carbonyl absorption and none attributable to hydroxyl or aromatic double bonds in the infrared. In basic environment, however, they are indicated to shift into the pyrazinolate form since they then show no carbonyl absorption and strong absorption in the aromatic double bond regions. In the usual basis (sodium salt) detergent compositions, these builders are most likely present as the diand trisodium salts.

Monoethyl ester of l,4,5,6-tetrahydro- 5,6-dioxo-2,3-pyrazinedicarboxylic acid TABLE IA Continued Compound Calcium Chelating Ability 2,6-Pyrazinedicarboxylic acid Pyrazinetelracarboxylic acid O=T (T-COA z )n a Mono(n-dodecyl) ester of l,4,5,6-tetra hydro-5,6-dioxo-2,3-pyrazinedicarboxylic acid Disodium salt of 5,6-dihydroxy-2,3- pyrazinedicarbonitrile 3.5 -Bis(methoxycarbonyl)-2,6-pyrazinedicarboxylic acid 3,6-Bis(methoxycarbonyl)-2,5-pyrazinedicarboxylic acid 12 TABLE lA-Continucd Chelatir g No. Compound Ability Mono-Alfol-I2l6"**** ester of l,4,5,6- tetrahydro-S,6-dioxo-2,3-pyrazinedicarboxylic acid (ave) (ave.)

Mono(n-octyl) ester of l,4,5,6-tetrahydro-5,6-diox0-2.3-pyrazinedicarboxylic acid H Di-( n octyl l ,4 ,5 ,6-tetrahydro-5,6- dioxo-2.3-pyrazinedicarboxylate 30 O (iCO (CH CH,-, O CCO (CH CH Di-(n-dodecyl)1.4.5.6-tetrahydro-5 ,6- dinxo-2,3-pyrazinecarboxylate (2) Sample not soluble to the extent of 2% at pH l 1.5 and could not be tested by this method.

B. Calcium Chelating Activity by Calcium Ion Selective 65 termine the amount of unchelated calcium ion. A suit- Electrode able instrument is Calcium ElectrodeModel 9220 sold The calcium chelating activity ofa compound may be by Orion Research, Inc. The procedure used is as folmeasured by using a calcium selective electrode to delows: a buffered solution was prepared containing 0.03M ammonium chloride, 0.07M ammonium hy- TABLE II droxide and 2 X lO M calcium carbonate (200 ppm CaCO with pH 9.5. To 250 ml of this solution was added enough test compound so that the same number f mol s of r "Clomx 0 e compound we e present as moles of cal Compound (ml/g ofcmpd) CCA cium carbonate. The potential of the calcium IOI'l selective electrode was recorded and compared with a cali Nitrilotriacetic acid 0 508 bration curve to determine the amount of unchelated sl ii i etic acig 23.35 ltrl otrtacetic aci calc um on and by difference the amount of chelated Dimethy, 145'6 te"ahydm 56 calcium 1011. di0xo-2,3-pyrazinedicarboxylate 20.0 125 Table 18 presents the data for two pyrazines and two g Y l 0 740 ioxo-Z, -pyrazinedicarboxy ate known detergent bullders. These data are probably IA5,6 Twahydm 56 dimo more meaningful than the data 1n Table IA. For exam- 2 3 pyrazinedicarbonilrile 0 603 ple, several compounds in Table IA had apparent CCA }y 'f above 5,000. Such high CCA values are unlikely for 448 1,4,5 ,6-Tetrahydro-5 ,6-dioxothey lmply one chelant molecule may complex five or 2 3-pyrazinedicarbonitrile 200 more calcium ions. Indeed compound No. 6 which Pyrazinetetracarboxylic i 0 320 shows CCA above 5,000 by a method A shows only pyrazlnemmcarboxyllc l Pyrazinetetracarboxyllc acid 10.0 310 CCA 104 by Method B.

TABLE 18 Calcium Chelating No. Compound Ability Known Detergent Builders O C--C(CH CO{) (Na); 364 Sodium Citrate 4 Sodium Tripolyphosphate 269 ll. Pyrazines 6 0 C CO, (CH CH,O), C H, I04

-OC --CO (H)z(N8) monosodium salt of the mono carbitoP ester of l,4,5,6 tetrahydro-5,6-dioxo- 2,3-pyrazinedicarboxylic acid oi $3430 0! 22:; O=C Co CH Dimethyl l,4,5,6-tetrahydro -S,6-dioxo -2,3- pyrazinedicarboxylate "Calculated on anhydrous basis. if a hydrate,

EXAMPLE 2 B. Various Bleaching Agents The effect of each bleaching agent was determined by adding an excess of the bleaching agent to 10 ml of Effect of Bleachin A ents on Chelatin Activities g g g a stock solution (0.13% by volume) of the sodium salt CIOFOV of l,4,5,6-tetrahydro-5,6-dioxo-2,3- The following data show [b6 effect on calcium chelat- Pyrazinedicarbonitrile After a hort time a 1-m] 5aming activities of adding Clorox to the mixtures in the test procedure of Example 1. clorox is an aqueous solution containing 5.25% sodium hypochlorite.

ple of the mixture was diluted to ml and its ultraviolet absorbance measured immediately and again after 5 days. The following table presents the data obtained.

TABLE Ill TABLE lV-Continued Absorbance at 325 nm TESTRESULTS Bleach Amount l5-30 min 5 Days Test Water 5 Mix- Pyrazine STPP Hardness Average *b. Unit Reading q Q95 ture (ppm) Cotton Dacron Nylon 1.01 ercarbonate 0.050 g 0.97 0.23 erborate 0.053 g 0.94 0.35 50% H OJ ml 094 012 2a None 35 150 4.8 10.4 14.0 Beads O Bleaeh" 0 050 g 0.98 0.99 2b 15 20 150 l m 013 015 2c PTA, 25 10 150 5.2 10.5 14.2 .g 1 10 2d PTA, 35 0 150 5.3 10.4 13.6 3a None 35 250 5.4 8.9 14.6 C m 31 PTA, 15 250 6.2 10.0 14.3 3c PTA, 10 250 6.5 11.2 14.8 ""Beads 0 Bleach did not give a clear solution in the stock solution. In this 3d PTA 35 o 1 250 3 1 [3 14A, nstance a l0-ml sample of the first lOO-ml mixture was diluted to 100 ml for the 4a N056 35 150 5 3 1 l l 14 9 JV absorbance lest. Beads 0 Bleach contains a triple salt of potassium nonopersulmcl 4b DPDN,15 20 150 5.4 11.0 13.7 15 4c DPDN,25 10 150 5.3 10.7 14.4 4d DPDN,35 0 150 5.2 11.3 14.2 The data in the Table show that only Clorox reacts 5a None 35 250 5.5 10.0 10.2 id] 5b DPDN,l5 20 250 S.l 9.0 14.8 p 5c DPDN,25 10 250 5.4 9.0 14.6 EXAMPLE 3 5d DPDN,35 0 250 5.4 10.0 14.9

20 4 STPP sodium tnpolyphosphate ebum Yellowmg Test of Pyrazme Detergent Builders FDA: 26 pyminedimbxyc acid PTA pyrazinetetracarboxylic acid dihydrate The Sebum yellofwlng test [Spangler Cross and DPDN l,4.5.6-tetrahydro-5.6-dioxo-2,Lpyrazincdicarbonitrile chafama, J. Am. Oil Chemists Soc., 42, 723 (1965); Chem. Abs. 63, 10179h (1965)] was applied to some )yrazines of Example 1. 25 EXAMPLE 4 Test "fixtures of Pyrfizine detergent builder i P Sebum Yellowing Test of Pyrazine Detergent Builders )ared with the followmg approximate composition: The sebum yellowing test was also used for companson of pyrazines with sodium tripolyphosphate and so- Detergent builder (pyrazine and/or STPP) 35% dium citrate in three different detergent systems. The fgg zi' g' i zg j $E37$ Salt :2 test mixtures in this example contained 33% by weight I I v i sulfate 2 38% of builder and the detergent components were as fol- Nater lows:

Testfabric" (a standard soiled fabric for use in wash ests sold by Testfabric, Inc., New York, N.Y.) is first 5 bnufi 33% i I i i etergent 1." Cl leslzed m a'washlng F wlth heavy duty Linear C C alcohol ethoxylate (Neodol 45-11) 2.0 gent, contaming no brightener or antiredeposition Linear tridecylbenzenesulfonate, sodium salt 10.0 l n Tallow soap, sodium salt 2.0 followed f f a com Sodium silicate solids, 1/2.35 Ni o/s10, 7.5 nercial cleaner. It is then rinsed and dried at low tem- 40 sodium ulfat 27.5 aerature. Swatches (3 inches X 5 inches) are soiled B 32?; If vith sebum and dried for 0.5 hour at 140F. Ten soiled fffgj zll 330 watches (4 cotton, 3 Dam-on" and 3 nylon) are Linear tridecylbeneenesulfonate, sodium salt l2.0 vashed in a Terg-o-Tometer (a laboratory size deter- Nap/Sm gency test unit sold by US. Testing Co. Hoboken, NJ.) C. Nonionic Formulation Detergent builder 33.0 water of predetermmed hardness a; Mg ex Linear c,.-c., alcohol ethoxylate (Neodol 45-11 12.0 messed as CaCO at pH 10 and containmg 0. l of the sodium silicate solids, U235 Nap/5,0: est mixture. The Terg-o-Tometer cycles are: wash, Water 0 minutes; rinse, 2 minutes; dry, 1 hour at 230F. The oiled, washed and dried swatches are spread out over- 50 The test condmons were: 4 inches X 6 Inches Light and then rated for yellowness (designated as swatches for cotton, 0.15% concentration of detergent 1nits) determined with a color difference meter (Huntformulatlon, mcludmg f water comammg r-Gardner Automatic Model AC-l; Gardner Lab., hardness of 150 PP and adlusmd to P 95; 1200p; Q Bethesda, Md) A higher unit reading indi lO-mmute wash, S-mmute rinse, 30-minute drying ates more yellowness, or less cleaning. umes- The test results in Table w below indicate that in this evaluation, Overall, the dlsodlum Salt of est 2,6-pyrazinedicarboxylic acid, pyrazinetetracarmethYI D Y ,oxyfic acid and l,456 tetrahydro 56 dioxo z,3 pyrazmedicarboxylate (SMDPDC) performs as well as yrazinedicarbonitrile are close to sodium tripolyphosmpolyphosphme (STPP) 9 better than hate (STPP) in effectiveness as detergent builders. 60 dlum citrate (SCIT). ln the non-ionic detergent system TABLE Iv C, most of the pyrazlnes perform as well as STPP.

TABLE V TEST RESULTS "est Water Test Results in b" Unit Values lix- Pyrazine STPP Hardness Average b" Unit Reading Formulation ure (ppm) Cotton "Dacron" Nylon Builder A B C la None 35 4.4 9.7 11.9 STPP 6.3 6.3 6.1 lb PDA, 15 20 150 4.9 10.1 13.7 SClT 8.1 8.6 6.9

17 TABLE V-Continued TABLE VI Cntinued Test Results in b" Unit Values Formulation Builder A MDPDC 7.5 9.0 6.3 SMDPDC 6.2 6.5 4.6 SDPDN 8.8 8 .9 .9 SPDA 10.3 9.9 7.4 SPTA 8.8 8.1 7.6

STPP sodium tripolyphosphate SCIT sodium citrate MDPDC dimethyl l,4.S.6-tetrahydro-5,6-dioxo-2.3 pyrazinedicarboxylate SMDPDC disodium salt of MDPDC SDPDN disodium salt of 1.4.5.6-tctrahydro-S.6-dioxo-2,3-pyrazinedicarbonitrile SPDA disodium salt of 2.6-pyrazinedicarboxylic acid SPTA letrasodium salt of pyrazinetetracarboxylic acid EXAMPLE 5 Sebum particulate Test of Pyrazine Detergent Builders Test Results in ARd Values Formulation Builder A C SMDPDC 11.4 5.9 18.6 SDPDN 14.1 8.3 19.8 SPDA 9.6 7.5 17.1 SPTA 11.6 10.6 18.3

EXAMPLE 6 Comparative Detersive Performance of l,4,5,6-Tetrahydro-5 ,6-dioxo-2,3- pyrazinedicarbonitrile 1,4,5,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarbonitrile was tested as a detergent builder in Terg-o-Tometer wash tests involving wash mixtures containing 25 g/liter of Testfabric soiled cloth and 3.6 g/liter of test mixture in water of 250 ppm CaCO hardness adjusted to pH 9.4. The test mixtures corresponded to those used in Example 3 and contained builder. The Terg-o-Tometer conditions were l20F., 15 minutes, 125 rpm. The fabrics were evaluated for reflectance increase over starting soiled cloth by means of a Photovolt reflectometer with green filter. In this test higher reflectance increase values are measures of increased whiteness and indicate higher performance of the detergent composition, i.e., greater effectiveness in removing and preventing redeposition of soil on the fabric. The results are shown in the following table.

TABLE VII Test Mix- Reflectance Increase ture Detergent Builder Cotton "Dacron" Dacron"/Cotton Orlon" Viscose 1a None 9.9 27.1 22.1 25.4 18.2 lb STPP 10.4 22.6 25.3 27.8 34.9 It: NTA 11.8 25.8 25.1 27.5 34.9 1d DPDN 12.2 30.4 25.5 28.1 21.9 2a Tide" XK 14.2 24.1 25.7 29.2 37.2 2b 25/75 DPDN/STPP 12.2 27.9 26.2 27.7 28.2 2c /50 DPDN/STPP 9.6 27.4 26.2 27.2 25.2 2d 75/25 DPDN/STPP 10.9 27.1 22.7 27.2 22.2 3a "Tide XK 11.7 18.4 27.7 31.0 40.9 3b 25/75 DPDN/NTA 7.0 28.4 29.9 29.2 26.9 3c 50/50 DPDN/NTA 9.7 27.9 25.7 31.5 26.2 3d 75/25 DPDN/NTA 8.5 28.7 28.0 28.5 25.5

"Tide" XK Commercial detergent with hrightener and antideposition agent.

STPP Sodium tripolyphosphate. NTA Nitrilotriacetic acid.

DPDN 1.4.5.6-Tctrahydro-5 .6-dioxo-2.3-pyrazinedicarbonitrilc.

results of the test are expressed in terms of the differences (ARd) between the before and after readings. The larger the ARd value, the cleaner the washed cloth. In this example the detergent formulations and test conditions of Example 4 were used. The results indicate that the disodium salt of 1,4,5,6-tetrahydro-5,6- tetrahydro-S,6-dioxo-2,3-pyrazinedicarbonitrile (SDPDN) is the best of the pyrazines in overall performance, being comparable to sodium citrate (SCIT) but less effective than sodium tripolyphosphate (STPP). In

In this test for removal of particulate soil only the general procedure of Example 6 was followed, except that the results are expressed in final Rd values measured with a color difference meter. In addition to controls with sodium tripolyphosphate and sodium citrate, test mixtures containing no builder were also used for comparison purposes. The test mixtures, except in the the anionic detergent System n f the pyrazines no builder controls, each contained 33% of builder.

perform about as well as STPP.

TABLE VI Test Results in ARd Values The final wash solutions contained 1.5 g per liter of formulation in tap water of 150 ppm hardness, were adjusted to pH 9.1, and were used at 120F wash temperature. The pH of each wash mixture was measured before adjustment to pH 9.1 and again after the wash cycle was completed. Each test involved six swatches of soiled cloth, and duplicate tests were conducted. The detergent components of the test mixtures were as follows:

B. LAS Formulation- Same as B formulation in Example 4. C. Nonionic Formulation- Same as C formulation in Example 4.

In this test none of the pyrazines matched sodium tripolyphosphate (STPP) in performance, but dimethyl 1,4,5,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarboxylate (MDPDC) and its disodium salt (SMDPDC) were about equal to sodium citrate (SCIT).

TABLE VIII Test Results Rd Values* Formulation B Formulation C Formulation D In each run a difference of over 0.5 in the comparative Rd values is considered significant.

A 'slurry of 0.42 g (2.59 mmole) of l,4,5,6-

.tetrahydro-S,6-dioxo-2,3-pyrazinedicarbonitrile in ml of 2N l-ICl was heated to reflux and a homogeneous amber solution was produced. During additional refluxing overnight, a grey power was precipitated. The pow- I der, isolated by filtration, washed with acetone on the filter and dried in a vacuum oven at 100C., weight Anal. Calcd for C H O N C, 33.19; H, 3.25; N,

1935. Found: C, 33.11; H, 3.05; N, 19.05.

B. Dimethyl l,4,5,6-Tetrahydro-5 ,6-dioxo-2,3-

pyrazinedicarboxylate A slurry of 7.0 g (32.2) mmoles) of the monoammonium salt of 1,4,5,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarboxylic acid in 100 ml of absolute methanol was cooled in an ice bath as dry hydrogen chloride was passed slowly over the magnetically stirred solution for 3 hours. The heterogeneous mixture was then warmed to room temperature and stirred an additional 3 days. The mixture was filtered, the filtrate was evaporated to dryness, and the filtered solid and residual materials were combined (wt, 6.89 g). The product was recrystallized from methanol and 4.80 g of white needles melting at 250252C was obtained. The purified product was identified as dimethyl 1,4,5,6-tetrahydro- 5,6-dioxo-2,3-pyrazinedicarboxylate.

Anal. Calcd for C H N O 42.11; H, 3.53; N, 12,28. Found: C, 41.71; H, 3.65; N, 12.08 41.89. 3.77 12.22

IR (Nujol): 3.08, 3.17, 5.53, 5.67, 5.73, 5.86, 6.67,

TABLE IV Test Results pH Values Run I Run 11 Run I Run II Run 1 Run II ipH fpH ipH fpH ipH fpH ipH fpH ipH fpH ipH fpH None 7.5 8.3 7.3 8.1 7.4 8.1 7.6 8.2 9.1 8.7 9.1 8.7 STPP 8.2 8.9 8.2 9.0 8.1 8.9 8.2 9.0 9.1 8.8 9.0 8.9 SCIT 7.6 8.6 7.6 8.5 7.7 8.4 7.8 8.6 9.1 8.7 9.2 8.8 MDPDC 5.2 8.9 5.2 8.8 5.3 8.7 5.3 8.6 5.9 8.8 5.9 8.8 SMDPDC 9.0 8.8 8.9 8.9 8.9 8.8 8.9 8.9 9.3 8.9 9.3 8.9 SDPDN 7.9 8.7 7.9 8.8 7.9 8.8 7.9 8.8 9.2 8.8 9.2 8.9 SPDA 7.9 8.4 7.8 8.3 8.0 8.4 8.0 8.3 9.1 8.8 9.2 8.8 SPTA 8.6 8.5 8.5 8.5 8.7 8.7 8.6 8.5 9.3 8.8 9.2 8.7

ipH initial pH reading, before adjustment to pH 9.1. fpH final pH reading.

EXAMPLE 8 7,21, 7.62, 7.83, 9.12, 10.31, 10.52, 11.60, 12.40,

Preparation of the Pyrazines 12.92, 13.13 UV (ethanol): X 290mm K 56.

NMR (dime thyl sulfoxide-d singlet, 3.78.8(6H);

broadened singlet, 11,188(2H). singlet, 11,188

l,4,5,6-Tetrahydro-5 ,6-dioxo-2,3- pyrazinedicarboxylic Acid Monosodium Salt Dihydrate H O=C/ C-CN (1) A. 5

.2H,o NaOH o=c C-CN (2) HCl A solution of 19.8 g (0.1 mole) of l,4,5,6-tetrahydro 1 5,6-dioxo-2,3-pyrazinedicarbonitrile dihydrate and 300 ml of 2N NaOH (0.6 mole) was boiled and spraged vigorously with nitrogen to remove ammonia. The initial liquid level was perodically maintained by adding water. When no more ammonia could be detected in the off gases, the solution was poured into 200 ml of 6N HCl (1.2 moles). The precipitate was filtered and recrystallized from 500 ml of boiling water (decolorizing hot with a little activated charcoal) to give 21.6 g of 1,- 4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylic acid monosodium salt dihydrate with an IR identical with an analytically pure well-characterized sample.

Anal. Calcd for C H N O Na: C, 29.92; H, 2.73; N, 10.85; Na, 8.90. Found: C, 28.79; H, 2.53; N, 10.95; Na, 8.40.

IR (Nujol): 2.89 and 3.15 82 NH and/or OH, 3.5-4.0 and 5.88 C 11, 6.32 and 6.55 H O, C=C, and/or CO UV 1 297 nm (a 15,400).

D. 1,4,5,6-Tetrahydro-5,6-dioxo-2,3- pyrazinedicarboxylic Acid (C=O); 1685 cm (COOH); 1600, 1570 cm (C=C/C=N).

UV: .L 296 nm (5 15,600).

HRMS: No molecular ion, M --H O, meas. m/e

181.9660; calcd for C H O N 181.9964.

1,4,5 ,6-Tetrahydro-5 ,6-dioxo-2,3-

Anhydride E. pyrazinedicarboxylic A mixture of 65 g of finely ground 1,4,5,6- tetrahydro-S ,6dioxo-2,3-pyrazinedicarboxylic acid, 500 ml of thionyl chloride, and 3.3 ml of dimethylformamide catalyst under nitrogen was cautiously warmed with stirring to reflux and refluxed overnight. The mixture was cooled to room temperature, filtered under nitrogen and dried under a nitrogen stream to give 54.6 g (93.3%) of 1,4,5,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarboxylic anhydride, a yellow solid, dec.

Anal. Calcd for C,H,N,0,; c, 39.57; H, 1.11; N, 15.39; Cl, none. Found: C, 39.41; H, 1.82; N, 15.69; Cl, 3.06. 39.44 1.77 15.16

IR (Nujol) shows strong anhydride absorption at 1780 and 1850 cm.

The SOC1 is used in stoichiometric excess for ease in carrying out the reaction. Dialkylformamides containing from one to six carbon atoms in the alkyl group are useful.

F. Mono(n-dodecyl) Ester of l,4,5,6-Tetrahydro-5,6- di0xo-2,3-pyrazinedicarboxylic Acid A mixture of 1 g of 1,4,5,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarboxylic anhydride and 20 ml n-dodecyl alcohol was heated under nitrogen with stirring at C for 4 hours and filtered hot through a medium sintered glass funnel. The filter was rinsed with hexane and the filtrate diluted with 100 ml of hexane giving a white precipitate which was filtered, rinsed with 100 ml of hexane and air-dried to give 1.38 g of 1,4,5,6- tetrahydro-S,6-dioxo-2,3-pyrazinedicarboxylic acid m0no(n-doclecyl) ester. Recrystallization of 1.33 g from 20 ml of benzene gave 0.85 g of white solid, mp, 162.8164.6C.

Anal. Calcd for C,,H,,N,0,= C, 58.68; H, 7.66; N, 7.60 Found: C, 58.89; H, 7.74; N, 7.33 59.13 7.81 7.43.

IR (Nujol): OH/NH at 3150-3400 cm, CO H at 2550 (broad), ester at 1770, C=O at 1710, 1650.

NMR (DMSO-d broad peak at 8 9.85 (2.64 H, a ca. triplet 4.10 (1.72 H, 13 OCHr). and singlet 1.15 [(CH and triplet 0.75 (-CH;,) of area 23.05.

Mass spectrum (trimethylsilylated): strong m/e 584 for tris(trimethylsilylated) parent ion.

IQI

C-CO;

a mixture of 15.09 g of l,4,5,6-tetrahydro-5,6-dioxo- 2,3-pyrazinedicarboxylic anhydride and 300 ml of Carbitol was heated under nitrogen with stirring at 100C for 4 hours. After standing 4 days at 25C, the mixture was diluted with 1.5 liters of dioxane, stirred for 2 hours and filtered to remove 2.24 g of insoluble whilte solid impurity. The filtrate was treated with 82.5 ml of 1.00N NaOH, precipitating a white solid which was filtered, rinsed with dioxane, and dried overnight over P 0 at 25C/0.02 mm to give 20.2 g of mono- Carbitol ester of l,4,5,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarboxylic acid monosodium salt.

Anal. Calcd for C H N O Na: C, 42.61; H, 4.47; N, 8.28; Na, 6.79. Found: C, 41.25; H, 4.37; N, 7.88; Na, 7.30.

IR (Nujol): quite sharp overall, broad OH/NH 2600-3300 em, strong sharp C O, X Y at 1630, 1680, 1725. Lack of absorption between 1500 and 1630 probably rules out CO Na.

The usual titration with calcium acetate of a pH 1 1.5 solution of this product containing added Na CO did not reach an endpoint until extra Na- CO was added. The apparent, but probably not actual, calcium chelating activity was greater than 5 g of CaCO chelated/- gram of product.

H. Di(n-dodecyl) pyrazinedicarboxylate 1,4,5 ,6-tetrahydro-5 ,6-dioxo-2,3-

+ HO(CH,) CH= cat. 5

A mixture of 1.00 g of l,4,5,6-tetrahydro-5,6-dioxo- 2,3-pyrazinedicarboxylic anhydride and 20 ml of ndodecyl alcohol was heated with stirring under nitrogen at C. for 2 hours. Then 0.2 ml of concentrated sulfuric acid catalyst was added and the heating continued for another 5 hours. The mixture was filtered hot and the solid on the filter was rinsed with n-dodecyl alcohol. The product was precipitated from the fitrate with nhexane to give 1.65 g of white solid, di-(n-dodecyl) 1,4,5 ,6-tetrahydro-5 ,6-dioxo-2,3- pyrazinedicarboxylate. This was recystallized from 200 ml of n-hexane/60 ml benzene to give 1.63 g, mp, 145.8 146.3C. Its solubility is low in benzene, hexane, and diluted NaOH.

Anal. Calcd for C H O N C, 67.13; H, 9.77; N,

5.22. Found: C, 67.50; H, 9.76; N, 5.07.

UV: h 294 nm (6 13,500).

IR (KBr): no --CO H, has ester 5.72 p

NMR (CDCl;;): broad peak 8 10.0 ppm (L9H, NH), triplet at 4.35 (4.0 H, -OCH ca. singlet 1.30 and ca. triplet 0.90 (47.0 H, (CH- and CH Mass spectrum: intense m/e 536 parent ion, 324

(MCO C H 323, 201, 183.

When the n-dodecyl alcohol above is replaced by a higher alcohol such as that corresponding to the formula HO(CH CH O) C H the resulting pyrazine is di(3,6,9,l2,15, 18,21 ,24,27,30,33,36,39,42,45,48,5 l 54,57,60,63,66,69-tricosaoxahenheptacont-1-yl) 1,4,- 5,6-tetrahydro-5,6-dioxo-2, 3-pyrazinedicarboxylate of the formula l. 3,5-Bis(methoxycarbonyl)-2,6-pyrazinedicarboxylic Acid and 3,6-Bis(methoxycarbonyl)-2,5- pyrazinedicarboxylic Acid.

Pyrazinetetracarboxylic dianhydride (1 15.1 g, 0.525 mole) was dissolved in 1,000 ml of absolute methanol under nitrogen. After 2 hours the solution was treated with a small amount of Darco, filtered, concentrated to a slush, and filtered. The filtered solid was partially dried, rinsed with carbon tetrachloride and dried. The dried product (67.2 g) was an approximately 90/10 mixture of 3,6-bis (methoxycarbonyl)- 2,5-pyrazinedicarboxylic acid/3,5-bis (methoxycarbonyl)-2,6-pyrazinedicarboxylic acid. Pure 3,6-isomer, mp., 210-211C. (dec.), was isolated from this mixture by recrystallization from methanol.

1 Pyrazinctetracarboxylic dianhydride is described in Chem. Abs. 71, 12448821 (1969).

Anal. Calcd for C H N O C, 42.26; H, 2.84; N, 9.89. Found: C,41.l6; H,2.71; N, 9.36 41.22 2.79 9.51.

UV (ethanol); 14. max. 280 nm (K 28.2) and 320 nm IR (Nujol): 947, 738 and 722 cm The residue from the recrystallization filtrate was a mixture containing the 3,5- and 3,6-isomers in a ratio of about 7:3. Infrared analysis of the mixture showed absorption at 1025, 929, 757 and 704 cm, which is not shown by the pure 3,6-isomer.

EXAMPLE 9 Salts of 2,3-Dihydroxy-5,6-pyrazinedicarbonitrile from 1 ,4,5 ,6-Tetrahydro-5,6-dioxo-2,3- pyrazinedicarbonitrile l,4,5,6-Tetrahydro- ,6-dioxo-2,3- pyrazinedicarbonitrile is tautomeric with 2,3- dihydroxy-S,6-pyrazinedicarbonitrile but in the absence ofa base exists almost entirely in the dioxo form, as indicated by its strong IR carbonyl adsorption. In the presence of a base it readily forms a dianion with low 'carbonyl IR absorption and can form stable salts.

A. Ammonium Salt A solution of 5.0 g of 1,4,5,6-tetrahydro-5,6-dioxo- 2,3-pyrazinedicarbonitrile in 100 ml of anhydrous ammonia was stirred for 2 hours at -35C. and then warmed to room temperature. A tan solid (5.1 g) remained after evaporation of the ammonia. Pure diammonium salt of 2,3-dihydroxy-5,6- pyrazinedicarbontrile was obtained in the form of light yellow needles, mp, 230C (dec), by recystallization of the crude salt from water.

Anal. Calcd for C H N O C, 36.73; H, 4.11; N,

42.84. Found: C, 36.37 H, 4.03; N, 40.00.

IR: No carbonyl absorption. Strong absorption for CN, NH and/or OH, and aromatic double bonds.

B. Sodium Salt The disodium salt of 2 ,3-dihydroxy-5 ,6- pyrazinedicarbonitrile is readily formed by mixing aqueous solutions of the dioxo compound and sodium hydroxide in 1:2 molar ratio. The salt solution has a pH 7 and gives dry solid when the water is stripped away by evaporation. Alternatively, the salt can be prepared from the oxo compound and sodium cyanide in acetonitrile containing about 20% of dissolved hydrogen cyanide, the salt being isolated by evaporation of the solvent and HCN. The salt can be recrystallized from water. Infrared analysis shows strong absorption by conjugated cyano and multiple NH and/or OH groups. Acidification of an aqueous solution and extraction with ether yields 1 ,4,5 ,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarbonitrile from the extract.

C. Calcium Salt A mixture of 8.11 g (50 mmoles) of l,4,5,6- tetrahydro-S,6-dioxo-2,3-pyrazinedicarbonitrile, 8.81 g (50 mmoles) of calcium acetate monohydrate and 50 ml of water was refluxed for 1 hour, cooled to 0C. and filtered. The filtered white solid (9.70 g, 82.2%) was the dihydrate of the calcium salt of 2,3-dihydroxy-5,6- pyrazinedicarbonitrile. The filtrate yielded 1.84 g (15.6%) of the same product.

Anal. Calcd for C O N,Ca.2H O: C. 30.50; H, 1.71; N,23.70; Ca, 16.97. Found: C, 30.86; H, 1.66; N, 23.83; Ca. 19.01 19.06.

The calcium salt dihydrate was also obtained in 87% yield of filtered solid by carrying out the above procedure with sodium hydroxide present in an amount equivalent to the calcium acetate.

Other salts can be made in analogous manner.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A compound of the formula wherein R and R alike or different, are selected from the group OH, alkoxy, oxaalkoxy, (alkylphenyl)oxaalkoxy each of l-48 carbon atoms, and, together, are -O, with the proviso that only one of R and R can be OH; and with the further proviso that when R and R are both alkoxy groups, each alkoxy group contains 4 48 carbon atoms; and

b. water soluble alkali metal salts thereof.

2. The compound of claim 1 in which R is ethoxy and R is OH; monoethyl ester of l,4,5,6-tetrahydro- 5,6-dioxo-2,3-pyrazinedicarboxylic acid.

3. The compound of claim 1 in which R is .O(CI-I,C- H O) C I-l and R is OH; mono [2-(2-ethoxyethoxy)ethyl] ester of 1,4,5,6-tetrahydro-5,6-dioxo2,3- pyrazinedicarboxylic acid.

tetrahydro-S,6-dioxo-2,3-pyrazinedicarboxylic acid.

8. The compound of claim 1 in which R and R together are O; pyrazinedicarboxylic anhydride.

9. The compound of claim 1 in which R and R are each n-dodecyloxy; di(n-dodecyl) l,4,5,6-tetrahydro- 5 ,6-dioxo-2,3-pyrazinedicarboxylate.

l,4,5,6-tetrahydro-5,6-dioxo-2,3-

Claims (9)

1. A COMPOUND OF THE FORMULA

2. The compound of claim 1 in which R4 is ethoxy and R5 is OH; monoethyl ester of 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylic acid.

3. The compound of claim 1 in which R4 is O(CH2CH2O)2C2H5 and R5 is OH; mono (2-(2-ethoxyethoxy)ethyl) ester of 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylic acid.

4. The monosodium salt of the compound of claim 3.

5. The disodium salt of the compound of claim 3.

6. The compound of claim 1 in which R4 is O(CH2CH2O)nCH3, where n 7.2 average, and R5 is OH; mono(monomethyl ether of polyoxyethylene) ester of 1,4,5 6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylic acid.

7. The compound of claim 1 in which R4 is n-butoxy and R5 is OH; mono(n-butyl) ester of 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylic acid.

8. The compound of claim 1 in which R4 and R5 together are -O-; 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylic anhydride.

9. The compound of claim 1 in which R4 and R5 are each n-dodecyloxy; di(n-dodecyl) 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxylate.