N,N'-diacetic acid-N'-cyanomethyl, salts thereof, and their preparation

Abstract

A novel intermediate useful in the synthesis of ethylenediaminetriacetic acid (ED3A) or its salts. A salt of N,N'-ethylenediaminediacetic acid (ED2AH.sub.2) is condensed with formaldehyde to form a stable 5-membered ring intermediate. The addition of cyanide across this cyclic material forms ethylenediamine N,N'-diacetic acid-N'-cyanomethyl or salts thereof (mononitrile-diacid), which is a useful intermediate in the production of ED3A. The nitrile in aqueous solutions may be spontaneously cyclized to form 2-oxo-1,4-piperazinediacetic acid (3KP) or salts thereof. In the presence of excess base, salts of ED3A are formed in excellent yield and purity.

Description

BACKGROUND OF THE INVENTION

Ethylenediaminetriacetic acid (ED3A) or its salts (such as ED3ANa.sub.3) has applications in the field of chelating chemistry, and may be used as a starting material in the preparation of strong chelating polymers, oil soluble chelants, surfactants and others. Conventional routes for the synthesis of ethylenediaminetriacetic acid were achieved via its N-benzyl derivative, which was subsequently hydrolyzed in alkaline solutions to ED3ANa.sub.3, thus avoiding cyclization to its 2-oxo-1,4-piperazinediacetic acid (3KP) derivative. Syntheses attempted by both the alkaline condensation of chloroacetic acid with ethylenediamine, and the carboxymethylation of the diamine with formaldehyde and sodium cyanide resulted in complex mixtures requiring complex extraction techniques (e.g. almost exclusive solubility of 3KP in boiling dimethylformamide, Can. J. Chemistry 1970, 48(1), 163-175) to generate the desired product, and then in only relatively poor yield. In addition, conventional processes resulted in large quantities of by-product, such as ethylenediaminetetraacetic acid (ED4A). Where the by-products were especially objectionable, complicated blocking techniques were necessary in order to achieve a relatively pure solution.

One example of the synthesis of ethylenediamine-N,N,N'-triacetic acid is shown in Chemical Abstracts 78, Vol. 71, page 451, no. 18369c, 1969. There it is disclosed that ethylenediamine reacts with ClH.sub.2 CCO.sub.2 H in a 1:3 molar ratio in basic solution at 10.degree. C. for 24 hours to form a mixture from which ethylenediamine-N,N,N'-triacetic acid can be separated by complexing the same with Co(III). The resulting cobalt complexes can be isolated through ion exchange.

The instant invention is directed to a novel composition of matter that is useful as an intermediate in the synthesis of ethylenediaminetriacetic acid or its salts in high conversions and excellent yield.

SUMMARY OF THE INVENTION

The problems of the prior art have been overcome by the instant invention, which provides a novel composition of matter useful as an intermediate in the synthesis of ethylenediaminetriacetic acid. Specifically, a mononitrile-diacid is formed by reacting a salt of N,N'-ethylenediaminediacetic acid (ED2AH.sub.2) with formaldehyde to form a stable 5-membered ring intermediate. The addition of cyanide across this cyclic material forms ethylenediamine N,N'-diacetic acid-N'-cyanomethyl or salts thereof (the mononitrile-diacid). This nitrile in aqueous solutions may be spontaneously cyclized to form 3KP or salts thereof, which in the presence of excess base, forms salts of ED3A in excellent yield and purity.

DETAILED DESCRIPTION OF THE INVENTION

Suitable salts of ethylenediaminediacetic acid useful as the starting material in the instant invention include alkali and alkaline earth metal salts, in particular, the sodium and potassium salts. For purposes of illustration, the sodium salt will be used, although it should be understood that other salts may be employed without departing from the spirit and scope of the invention. One suitable reaction scheme for the synthesis of the mononitrile-diacid is the alkaline condensation of formaldehyde with N,N'-ethylenediamine disodium acetate to form a 5-membered ring structure, 1,3-bis(carboxymethyl)imidazolidine, and is illustrated as follows: ##STR1##

The above reaction may be carried out in the presence of additional base. Suitable bases include alkali and alkaline earth metal hydroxides, preferably sodium and potassium hydroxide. Compound (I) is the bridged reaction product of EDDANa.sub.(1.0.fwdarw.2.0) and formaldehyde, which the present inventor has found to be a stable intermediate in the ED3A synthesis. Compound (I) is formed easily between 0.degree. and 110.degree. C. The reaction proceeds quickly and forms readily at pH's greater than about 7.0. Preferably the temperature employed is about 0.degree. to 65.degree. C., most preferably 15.degree. to 65.degree. C., although temperatures higher than 65.degree. C. are operable. Formaldehyde can be used in stoichiometric amounts, although it is preferred that a slight molar excess be used, preferably 0.5%-0.2%. Preferably the concentration of the formaldehyde is 55% or less in aqueous solution. Paraformaldehyde also can be used.

The second step in the reaction scheme is illustrated below: ##STR2##

Compound (II) is readily formed at temperatures between 0.degree. and 110.degree. C. The reaction should be conducted at temperatures at or below the boiling point of the solution. Preferably the reaction is carried out at temperatures from about 0.degree. to about 65.degree. C., most preferably about 15.degree. to 65.degree. C. to enhance the reaction rate. Suitable sources of cyanide include gaseous hydrogen cyanide, an aqueous solution of hydrogen cyanide, or alkali metal cyanide such as sodium cyanide or potassium cyanide, etc. The cyanide may be used in stoichiometric amounts, although slight molar excesses may be used, preferably 0.5%-2.0%.

Compound (II) is useful as an intermediate for the production of ED3A. Specifically, compound (II) may be hydrolyzed to the monoamide-diacid compound (III) (partially hydrolyzed mononitrile diacid), which spontaneously cyclizes to 3KP. Compound (IV) forms readily in the presence of a base such as alkali metal or alkaline earth metal hydroxides. Preferably the base is NaOH. Mole ratios of <3.0M base:1M ED2AH.sub.2 but preferably <2.0M base:1M ED2AH.sub.2 are employed. Higher concentrations of base (i.e. >3.0M base: M ED2AH.sub.2) cause some disproportionation of the diacid mononitrile and some ED4A (ethylenediaminetetraacetic acid) is formed, especially at temperatures >65.degree. C. In particular, the concentration of ED4A is found to be in direct proportion to the amount of excess caustic employed, when high temperature reactions are conducted and high molar ratios of base are employed (>2.0M base: 1M ED2AH.sub.2), which may be attributed to the simultaneous hydrolysis of 3KP and disproportionation of the mononitrile-diacid. When the mole ratio of base to ED2A is <2.0, higher temperatures may be used. Also, in Step III ammonia is eliminated between an amide group and an imino group on the same molecule. However, at lower temperatures (<65.degree. C.) higher amounts of base may be employed (>2.0M) and hydrolysis of compound (II) can proceed directly to ED3A without cyclization. ##STR3##

The 3KPNa.sub.2 is then hydrolyzed by at least the addition of 1 equivalent of caustic, preferably a 1 molar excess of caustic. This amounts to approximately 5% weight excess (free) caustic in solution on a 40% ED3ANa.sub.3 solution. The solution is boiled under atmospheric pressure to the desired concentration. Preferably the reaction is carried out by raising the temperature from the temperature in the formation of compound (IV) reaction to the boil over a period from about 30 minutes to about 6 hours. ##STR4##

The resulting solutions typically give approximately 35-40% ED3ANa.sub.3, with approximately 2% 3KPNa.sub.2 remaining as an unopened ringed structure. This corresponds to about a 94% conversion to ED3ANa.sub.3, with the remaining 6% of mass existing as 3KPNa.sub.2. Acidification of this mass to pH's <6.0 to produce ED3AH.sub.3 is not possible, as cyclization to 3KPH.sub.2 will eventually occur.

The foregoing synthetic scheme results in conversions to ED3ANa.sub.3 in excess of 90%, with the residual proportion being 3KPNa.sub.2 to give a total mass balance of virtually 100%. The reactions are tolerant to a wide pH range.

The following procedure to obtain ED2AH.sub.2 was for experimental purposes only. Far less elaborate schemes for the production of ED2AH.sub.2 are possible. Any schemes known in the art can be employed for the production of ED2AH.sub.2 and its salts, and the instant invention is not to be limited by any particular scheme.

In the following examples, all batches were synthesized from EDDAH.sub.2 (98.20%) obtained by acidification of EDDANa.sub.2 to a pH of 5.50 with nitric acid, while maintaining the temperature of the solution <10.degree. C. The resultant slurry was filtered by means of a Buchner funnel with the vacuum provided by a water aspirator. The filter cake was washed with approximately 7 liters of iced H.sub.2 O. To enhance drying, the cake was then washed with approximately 1 liter of MeOH. The crystals were then placed on 1 inch deep stainless steel trays, dried in a Stokes vacuum dryer, model 338F at 40.degree. C. under a vacuum of 4 mm Hg, for 12 hours. Approximately 2 Kg of a white crystalline powder was recovered. Analysis of this powder showed it to be 98.2% ED2AH.sub.2.

All batches were synthesized on a 0.5 liter scale. 88 g of ED2AH.sub.2 were charged to a 500 ml conical flask and diluted with 180 mls of H.sub.2 O. 50% caustic was used to obtain the sodium salt in the ratio required. The solution was stirred for 30 minutes, and then charged to a 1 liter 5-necked round bottom flask. The conical flask was then washed with 20 mls. of H.sub.2 O, and the washings transferred to the round bottom flask. The round bottom flask was equipped with a magnetic stirring bar, a condenser (ethylene glycol/H.sub.2 O @ 0.degree. C.), A 0-250.degree. C. mercury thermometer, and a J-type thermocouple that provided a signal to a Love proportional controller, which maintained the temperature at the desired level were employed. A Glass-Col heating mantle controlled by the Love controller via a Powerstat variable autotransformer was used to heat the contents of the flask. 37% CH.sub.2 O and 100% HCN were pumped at approximately 1 g/minute and 0.50 g/minute, respectively, by an FMI micro metering pump at a setting of 0.5, via 1/8" Teflon tubing to the flask. A 125 ml addition funnel equipped with a Teflon metering valve, and a condenser with the same coolant as described above, was used as the reservoir for the reactants to be pumped. Table 1 shows the results for the experiments conducted up to the spontaneous cyclization of monoamide-diacid after it has been hydrolyzed. The mononitrile-diacid was not isolated; however, it was identified by HPLC as being the precursor to 3KP. 3KP was more easily quantified by HPLC, and it is that compound which is quantitatively shown in Table 1. Table 2 shows results for ED3A produced for 9 conditions using the compound of the instant invention.

TABLE 1__________________________________________________________________________ % EDDA Moles lc % lc lc % to % Unrxl MassExp Tot wt Comments temp l(mins) EDDA EDDANa2 % ED3ANa3 3KPNa2 Produc EDDA balance__________________________________________________________________________ 220.00 300.00 260.001 - 0 240.75 2NaH/1EDDA 50 0.0 0.247 22.57% 0.00% 0.00% 0.00% 100.00% 100.00%1 - 1 238.98 50.degree. C. 50 55.0 0.245 4.36% 0.30% 11.68% 44.76% 19.32% 64.00%1 - 2 234.04 50 102.0 0.240 3.03% 0.50% 15.15% 50.42% 13.42% 71.84%1 - 3 228.13 50 144.0 0.234 2.13% 0.60% 17.50% 67.55% 9.44% 76.99%1 - 4 221.69 50 199.0 0.227 1.51% 19.21% 72.02% 6.69% 78.71%1 - 5 214.52 50 250.0 0.220 1.14% 20.54% 77.00% 5.05% 82.05%1 - 6 208.17 50 300.0 0.214 0.89% 1.20% 20.90% 82.25% 3.94% 86.19%final 202.88sc2 - 0 240.75 2NaH/1EDDA 65 0.0 0.247 22.57% 0.00% 0.00% 100.00% 100.00%2 - 1 240.75 65.degree. C. 65 15.0 0.247 3.84% 13.94% 52.26% 17.01% 69.27%2 - 2 236.21 65 45.0 0.242 258% 17.68% 66.28% 11.43% 77.71%2 - 3 231.19 65 90.0 0.237 1.49% 20.89% 78.31% 6.60% 84.91%2 - 4 226.19 65 135.0 0.232 1.45% 21.64% 81.12% 6.42% 87.55%2 - 5 220.81 65 186.0 0.227 1.41% 21.81% 81.76% 6.25% 88.01%2 - 6 214.61 65 230.0 0.220 1.36% 21.73% 81.46% 6.03% 87.49%2 - 7 210.35 65 262.0 0.216 1.28% 21.74% 81.50% 5.67% 87.17%2 - 8 205.34 65 990.0 0.211 1.23% 21.60% 80.97% 5.45% 86.42%final 197.00sc3 - 0 240.75 2NaH/1EDDA 80 0.0 0.247 22.57% 0.00% 0.00% 100.00% 100.00%3 - 1 239.86 80.degree. C. 80 10.0 0.246 4.16% 15.92% 59.68% 18.43% 78.11%3 - 2 235.19 80 35.0 0.241 3.66% 18.66% 69.95% 16.22% 86.17%3 - 3 229.91 80 75.0 0.236 3.33% 19.61% 73.51% 14.75% 88.27%3 - 4 223.28 80 136.0 0.229 3.04% 19.50% 73.10% 13.47% 86.57%3 - 5 217.66 80 210.0 0.223 2.89% 19.77% 74.11% 12.80% 86.92%3 - 6 211.34 80 280.0 0.217 2.69% 199.99% 74.94% 11.92% 86.86%final 205.07sc4 - 0 239.10 1.9NaH/1EDDA 50 0.0 0.247 22.73% 0.00% 0.00% 100.00% 100.00%4 - 1 239.10 50.degree. C. 50 30.0 0.247 6.73% 6.34% 23.60% 29.61% 53.22%4 - 2 234.00 1.0 CH2O 50 70.0 0.242 5.00% 10.24% 38.12% 22.00% 60.13%4 - 3 228.81 50 115.0 0.236 4.18% 13.58% 50.56% 18.39% 58.95%4 - 4 223.25 50 165.0 0.231 2.68% 16.40% 61.06% 11.79% 72.85%4 - 5 217.35 50 200.0 0.225 2.16% 17.99% 66.98% 9.50% 76.48%4 - 6 212.72 50 250.0 0.220 1.52% 19.66% 73.20% 6.69% 79.89%4 - 7 208.46 50 285.0 0.215 1.14% 20.75% 77.26% 5.02% 82.27%4 - 8 192.50 50 1280.0 0.199 0.13% 1.10% 23.50% 91.04% 0.57% 91.62%final 138.00 boiled 0.201 0.13% 32.75% 86.36% 0.41% 86.77%so5 - 0 241.10 2.1NaH/1EDDA 50 0 0.247 22.54% 0.00% 0.00% 0.00% 100.00% 100.00%5 - 1 241.10 50.degree. C. 50 40.0 0.247 5.58% 0.10% 9.35% 35.43% 24.76% 60.19%5 - 2 236.01 1.05 CH2O 50 90.0 0.242 3.85% 0.20% 14.31% 54.37% 17.08% 71.46%5 - 3 231.32 50 130.0 0.237 2.75% 0.50% 17.20% 66.20% 12.20% 78.40%5 - 4 225.41 50 186.0 0.231 2.15% 0.80% 18.60% 72.43% 9.54% 81.97%5 - 5 220.92 50 228.0 0.226 1.71% 1.00% 19.41% 76.12% 7.59% 83.71%5 - 6 216.39 50 260.0 0.222 1.49% 1.30% 19.85% 78.75% 6.61% 85.36%5 - 7 211.83 50 1350.0 0.217 0.66% 3.40% 16.01% 71.17% 2.93% 74.10%final 170.21 boiled 0.220 0.92% 5.10% 23.10% 82.02% 3.24% 85.26%so5 - 0 239.10 1.9NaH/1EDDA 80 0.0 0.247 22.73% 0.00% 0.00% 100.00% 100.00%5 - 1 239.10 80.degree. C. 80 15.0 0.247 3.61% 17.05% 63.48% 15.80% 79.36%5 - 2 233.80 1.05 CH2O 80 45.0 0.242 2.01% 18.70% 69.62% 13.24% 82.87%5 - 3 229.09 80 90.0 0.237 2.61% 19.78% 73.64% 11.48% 85.13%5 - 4 222.74 80 145.0 0.230 2.26% 20.36% 75.80% 9.04% 85.75%5 - 5 271.86 80 189.0 0.225 1.32% 20.11% 74.87% 5.81% 80.68%5 - 6 213.47 80 240.0 0.221 1.60% 18.26% 67.98% 7.04% 75.02%5 - 7 208.33 80 285.0 0.215 1.66% 21.35% 79.49% 7.30% 86.79%5 - 8 203.47 80 1282.0 0.210 0.40% 0.10% 20.90% 78.14% 1.76% 79.90%5 - 9 157.60 boiled 0.213 0.60% 0.50% 27.75% 80.30% 2.02% 82.32%6 - 0 241.10 2.1NaH/1EDDA 80 0.0 0.247 22.54% 0.00% 0.00% 0.00% 100.00% 100.00%6 - 1 241.10 80.degree. C. 80 20.0 0.247 3.72% 1.00% 18.17% 71.47% 16.51% 87.97%6 - 2 234.20 1.00 CH2O 80 74.0 0.241 3.44% 1.00% 19.09% 74.92% 15.26% 90.19%6 - 3 229.95 80 110.0 0.236 3.47% 1.00% 19.15% 75.15% 15.40% 90.54%6 - 4 225.49 80 155.0 0.231 3.37% 1.00% 19.44% 76.24% 14.95% 91.19%6 - 5 220.51 80 200.0 0.226 3.14% 1.00% 19.06% 74.81% 13.93% 88.74%6 - 6 215.06 80 238.0 0.220 3.15% 1.00% 19.20% 75.34% 13.98% 89.31%6 - 7 210.36 80 286.0 0.216 3.06% 1.00% 18.81% 73.87% 13.58% 87.45%6 - 8 204.01 80 320.0 0.209 3.08% 1.00% 19.19% 75.30% 13.67% 88.96%6 - 9 198.58 80 1286.0 0.203 2.30% 1.70% 19.39% 78.33% 10.20% 88.53%6 - 10 145.33 boiled 0.206 2.49% 1.80% 21.94% 63.79% 7.99% 71.78%7 - 0 239.10 1.9NaH/1EDDA 80 0.0 0.247 22.73% 0.00% 0.00% 100.00% 100.00%7 - 1 239.10 80.degree. C. 80 26.0 0.247 3.32% 16.83% 62.66% 14.61% 77.27%7 - 2 233.84 1.00 CH2O 80 71.0 0.242 2.87% 19.69% 73.31% 12.63% 85.94%7 - 3 228.66 80 119.0 0.236 2.42% 19.79% 73.68% 10.65% 84.33%7 - 4 223.62 80 160.0 0.231 2.31% 20.21% 75.24% 10.16% 85.41%7 - 5 218.59 80 208.0 0.226 1.99% 20.36% 75.80% 8.76% 84.56%7 - 6 213.40 80 260.0 0.220 1.88% 20.24% 75.36% 8.27% 83.63%7 - 7 207.57 80 1291.0 0.214 0.51% 19.05% 73.90% 2.24% 76.15%7 - 8 127.47 boiled 0.217 0.94% 1.80% 30.58% 72.60% 2.51% 75.11%8 - 0 239.10 1.9NaH/1EDDA 50 0.0 0.247 22.73% 0.00% 0.00% 100.00% 100.00%8 - 1 239.10 50.degree. C. 50 35.0 0.247 1.89% 20.44% 76.10% 8.32% 84.42%8 - 2 233.30 1.05 CH2O 50 117.0 0.241 1.29% 22.46% 83.62% 5.60% 89.30%8 - 3 228.81 50 160.0 0.236 1.07% 23.18% 86.30% 4.71% 91.01%8 - 4 223.96 50 210.0 0.231 0.82% 23.29% 86.71% 3.61% 90.32%8 - 5 218.87 50 297.0 0.226 0.56% 24.16% 89.95% 2.46% 92.42%8 - 6 199.40 50 1261.0 0.206 0.24% 24.96% 92.93% 1.06% 93.99%8 - 7 141.00 boiled 0.206 0.27% 1.10% 35.02% 94.71% 0.84% 95.55%9 - 0 241.10 2.1NaH/1EDDA 50 0.0 0.247 22.54% 0.00% 0.00% 100.00% 100.00%9 - 1 241.10 50.degree. C. 50 30.0 0.247 9.07% 34.05% 0.00% 34.05%9 - 2 235.44 1.00 CH2O 50 112.0 0.241 2.71% 0.60% 16.04% 62.17% 12.02% 74.19%9 - 3 230.22 50 168.0 0.236 2.10% 0.70% 18.36% 71.21% 9.32% 80.52%9 - 4 225.60 50 211.0 0.231 1.55% 1.10% 19.28% 75.96% 6.88% 82.84%9 - 5 220.60 50 250.0 0.226 1.02% 1.20% 20.77% 81.88% 4.53% 86.41%9 - 6 214.87 50 1380.0 0.220 0.89% 3.30% 20.16% 86.42% 3.95% 90.37%9 - 7 112.00 boiled 0.223 1.51% 9.60% 34.28% 82.36% 3.45% 85.81%10 - 0 241.10 2.1NaH/1EDDA 80 0.0 0.247 22.54% 0 0.00% 0.00% 100.00% 100.00%10 - 1 241.10 80.degree. C. 80 30.0 0.247 3.82% 0.70% 19.28% 74.66% 16.95% 91.61%10 - 2 236.36 1.05 CH2O 80 88.0 0.242 3.42% 0.60% 19.50% 75.16% 15.17% 90.33%10 - 3 231.84 80 133.0 0.238 3.32% 0.80% 20.04% 77.84% 14.73% 92.57%10 - 4 226.84 80 196.0 0.232 2.99% 0.50% 17.77% 68.34% 13.27% 81.61%10 - 5 221.45 80 240.0 0.227 3.21% 0.70% 20.42% 78.94% 14.24% 93.18%10 - 6 216.41 80 293.0 0.222 3.09% 0.01% 19.99% 75.07% 13.71% 88.78%10 - 7 210.56 80 1290.0 0.216 2.16% 1.00% 19.30% 75.71% 9.58% 85.30%10 - 8 138.64 boiled 0.218 3.22% 2.50% 28.68% 75.34% 9.29% 84.63%11 - 0 263.10 3.1NaH/1EDDA 35 0.0 0.247 20.65% 0.00% 0 0.00% 100.00% 100.00%11 - 1 263.10 35.degree. C. 35 35.0 0.247 8.47% 2.37% 9.71% 41.01% 50.72%11 - 2 258.10 1.00 CH2O 35 72.0 0.242 4.89% 20.03% 0.00% 20.03%11 - 3 252.90 35 143.0 0.237 7.21% 6.40% 26.22% 34.91% 61.13%11 - 4 247.40 35 182.0 0.232 7.20% 0.60% 6.81% 30.03% 34.86% 64.89%11 - 5 242.74 35 221.0 0.228 6.89% 0.70% 8.25% 36.28% 33.86% 69.64%11 - 6 238.43 35 257.0 0.224 6.60% 1.10% 9.49% 42.78% 31.96% 74.74%11 - 7 233.63 35 1360.0 0.219 2.88% 12.00% 9.08% 79.81% 13.94% 93.75%11 - 8 140.00 boiled 0.222 4.22% 34.30% 5.27% 84.89% 12.10% 96.98%12 - 0 263.10 3.1NaH/1EDDA 50 0.0 0.247 20.65% 0.00% 0.00% 0.00% 100.00% 100.00%12 - 1 263.10 50.degree. C. 50 13.0 0.247 6.20% 0.40% 12.39% 52.18% 30.02% 82.20%12 - 2 257.27 1.00 CH2O 50 54.0 0.242 6.04% 1.80% 11.35% 52.09% 29.24% 82.13%12 - 3 251.81 50 90.0 0.236 4.84% 3.50% 12.49% 63.60% 23.43% 87.03%12 - 4 247.54 50 147.0 0.232 4.22% 4.90% 12.90% 70.25% 20.43% 90.68%12 - 5 243.10 50 1237.0 0.228 3.47% 15.90% 8.07% 89.52% 16.80% 106.32%12 - 6 138.80 boiled 0.231 5.50% 40.00% 5.45% 92.71% 15.02% 107.73%13 - 0 271.10 3.5NaH/1EDDA 35 0.0 0.247 20.04% 0.00% 0 0.00% 100.00% 100.00%13 - 1 271.10 35.degree. C. 35 10.0 0.247 9.60% 4.02% 16.97% 47.89% 64.86%13 - 2 265.99 1.00 CH2O 35 47.0 0.242 7.82% 8.07% 34.07% 39.01% 73.08%13 - 3 261.37 35 90.0 0.238 7.31% 9.19% 38.79% 36.47% 75.26%13 - 4 256.60 35 130.0 0.234 6.70% 0.80% 9.46% 42.86% 33.43% 76.29%13 - 5 252.16 35 186.0 0.230 6.35% 0.80% 10.36% 46.66% 31.68% 78.34%13 - 6 246.06 35 230.0 0.224 6.12% 1.40% 10.54% 49.62% 30.53% 80.15%13 - 7 241.06 35 308.0 0.220 6.16% 2.30% 10.43% 52.44% 30.73% 83.18%13 - 8 235.25 35 1320.0 0.214 2.52% 13.90% 6.98% 80.32% 12.57% 92.89%burned14 - 0 443.96 1.8NaH/1EDDA 65 13.0 0.491 5.30% 18.71% 0.00% 18.71%14 - 1 442.63 65.degree. C. 65 49.0 0.490 10.48% 36.45% 0.00% 36.45%14 - 2 440.98 1.00 CH2O 65 107.0 0.488 16.17% 56.23% 0.00% 56.23%14 - 3 439.19 65 1063.0 0.486 21.12% 73.45% 0.00% 73.45%15 - 0 448.81 1.9NaH/1EDDA 50 25.0 0.491 2.05% 7.21% 0.00% 7.21%15 - 1 447.52 50.degree. C. 50 85.0 0.490 7.06% 24.82% 0.00% 24.82%15 - 2 446.05 1.05 CH2O 50 122.0 0.488 9.97% 35.05% 0.00% 35.05%15 - 3 444.25 50 173.0 0.486 13.01% 45.74% 0.00% 45.74%15 - 4 443.14 50 1238.0 0.485 25.10% 88.25% 0.00% 88.25%15 - 5 441.95 50 0.45 25.52% 89.48% 0.00% 89.48%16 - 0 450.68 1.9NaH/1EDDA 65 10.0 0.491 6.67% 23.55% 0.00% 23.55%16 - 1 449.03 65.degree. C. 65 41.0 0.489 12.47% 44.02% 0.00% 44.02%16 - 2 447.46 1.00 CH2O 65 82.0 0.487 17.76% 62.70% 0.00% 62.70%16 - 3 446.18 65 125.0 0.486 20.24% 71.45% 0.00% 71.45%16 - 4 444.85 65 1080.0 0.486 24.22% 85.25% 0.00% 85.25%17 - 0 450.70 1.9NaH/1EDDA 75 17.0 0.491 14.87% 52.50% 0.00% 52.50%17 - 1 449.45 75.degree. C. 75 48.0 0.490 20.66% 72.94% 0.00% 72.94%17 - 2 448.35 1.05 CH2O 75 98.0 0.488 24.26% 85.65% 0.00% 85.65%17 - 3 447.08 75 75 239.0 0.487 24.97% 88.16% 0.00% 88.16%17 - 4 445.66 75 1233.0 0.486 26.24% 92.64% 0.00% 92.64%17 - 5 407.20 boil boil 0.486 26.41% 85.19% 0.00% 85.19%18 - 0 450.70 1.9NaH/1EDDA 50.degree. C. 10.0 0.491 1.36% 4.80% 0.00% 4.80%18 - 1 449.36 50.degree. C. 50.degree. C. 88.0 0.490 7.60% 26.83% 0.00% 26.83%18 - 2 447.82 1.00 CH2O 50.degree. C. 1365.0 0.488 24.34% 85.93% 0.00% 85.93%18 - 3 392.30 boil boil 0.488 27.84% 86.10% 0.00% 86.10%19 - 0 446.70 1.8NaH/1EDDA 50.degree. C. 41.0 0.491 2.59% 9.06% 0.00% 9.06%19 - 1 445.33 50.degree. C. 50.degree. C. 120.0 0.489 8.63% 30.20% 0.00% 30.20%19 - 2 443.88 1.00 CH2O 50.degree. C. 164.0 0.488 11.36% 39.75% 0.00% 39.75%19 - 3 442.48 50.degree. C. 1400.0 0.486 24.71% 85.46% 0.00% 85.46%19 - 4 343.20 boil boil 0.486 31.79% 86.28% 0.00% 86.28%20 - 0 446.07 1.0NaH/1EDDA 60.degree. C. 60.0 0.491 3.35% 11.71% 0.00% 11.71%20 - 1 444.76 50.degree. C. 50.degree. C. 210.0 0.490 13.30% 46.47% 0.00% 46.47%20 - 2 442.90 1.05 CH2O 50.degree. C. 300.0 0.488 16.72% 58.42% 0.00% 58.42%20 - 3 441.42 50.degree. C. 1250.0 0.486 24.46% 85.47% 0.00% 85.47%20 - 4 353.40 boil boil 0.486 30.01% 86.19% 0.00% 86.19%21 - 0 446.70 1.0NaH/1EDDA 65.degree. C. 16.0 0.491 7.03% 24.60% 0.00% 24.60%21 - 1 444.89 65.degree. C. 65.degree. C. 85.0 0.489 17.26% 60.40% 0.00% 60.40%21 - 2 443.09 1.05 CH2O 65.degree. C. 175.0 0.487 22.05% 77.16% 0.00% 77.16%21 - 3 441.24 65.degree. C. 253.0 0.485 23.83% 83.38% 0.00% 83.38%21 - 4 439.56 65.degree. C. 1240.0 0.483 42.40% 85.38% 0.00% 85.38%21 - 5 380.00 boil boil 0.483 24.96% 75.50% 0.00% 75.50%22 - 0 446.70 1.8NaH/1EDDA 65.degree. C. 25.0 0.491 9.99% 34.96% 0.00% 34.96%22 - 1 444.33 65.degree. C. 65.degree. C. 110.0 0.488 19.71% 68.97% 0.00% 68.97%22 - 2 442.74 1.00 CH2O 65.degree. C. 165.0 0.487 21.34% 74.67% 0.00% 74.67%22 - 3 441.04 65.degree. C. 208.0 0.485 21.40% 74.88% 0.00% 74.88%22 - 4 439.65 65.degree. C. 1292.0 0.483 23.72% 83.00% 0.00% 83.00%22 - 5 394.70 boil boil 0.483 25.87% 81.27% 0.00% 81.27%23 - 0 450.70 1.9NaH/1EDDA 65.degree. C. 33.0 0.491 11.14% 39.33% 0.00% 39.33%23 - 1 448.95 65.degree. C. 65.degree. C. 92.0 0.489 18.65% 65.84% 0.00% 65.84%23 - 2 447.21 1.05 CH2O 65.degree. C. 148.0 0.487 21.69% 76.58% 0.00% 76.58%23 - 3 445.41 65.degree. C. 230.0 0.485 23.32% 82.33% 0.00% 82.33%23 - 4 443.77 65.degree. C. 1276.0 0.483 24.79% 87.52% 0.00% 87.52%23 - 5 408.62 boil boil 0.483 26.43% 85.92% 0.00% 85.92%__________________________________________________________________________ TABLE 2__________________________________________________________________________ % 3KPNa2 moles after % conversionExp Temp .degree.C. M CH2O EDDA:NaOH final wt recyclized mole3KP sampling recyclized__________________________________________________________________________1 50.00 1.05 1.90 373.40 31.39% 0.45 0.48 92.99%2 65.00 1.00 1.90 364.00 31.91% 0.45 0.49 91.91%3 75.00 1.05 1.90 376.40 29.53% 0.43 0.49 88.04%4 50.00 1.00 1.90 372.80 31.77% 0.46 0.49 93.37%5 50.00 1.00 1.80 370.30 32.10% 0.46 0.49 94.00%6 50.00 1.05 1.80 388.95 30.89% 0.46 0.49 94.41%7 65.00 1.05 1.80 393.60 29.71% 0.45 0.48 93.07%8 65.00 1.00 1.80 415.60 24.86% 0.43 0.48 88.82%9 65.00 1.05 1.90 417.70 29.82% 0.48 0.48 98.08%__________________________________________________________________________ % 3KPNA2 % difference % unopened % EDDANa3 % conversion % total convExp after stage 1 at 1 -recycle eKPNa2 by litr to ED3ANa3 on ED3ANa3__________________________________________________________________________1 89.48% -3.51% 2.05% 38.00% 91.28% 95.74%2 85.25% -6.86% 1.88% 38.32% 94.89% 98.23%3 85.19% -2.85% 2.09% 36.55% 93.40% 97.87%4 86.10% -7.27% 2.17% 38.16% 96.58% 100.87%5 86.28% -7.72% 2.28% 37.50% 94.27% 98.99%6 86.19% -8.22% 2.69% 35.39% 93.45% 99.10%7 85.38% -7.69% 2.85% 34.13% 91.20% 98.76%8 81.27% -7.55% 3.08% 32.54% 91.81% 100.56%9 85.92% -13.18% 2.43% 32.10% 91.03% 87.70%__________________________________________________________________________

The data demonstrate that both mass balances and conversions to product are excellent. ED3A was measured by copper(II) salt titration, and 3KP was measured by high pressure liquid chromatography (HPLC). The final column in the Table 1 shows the mass balances for stage 3 (the formation of 3KP) of the reaction. The 9th column in Table 2 shows the percent conversion to product based on recyclization. Recyclization was achieved by acidifying a sample of the reaction mass with HCl to a pH of 2.0. These samples were then allowed to stand in an oven at 40.degree. C. overnight and then on a bench at room temperature for 2 days prior to analysis. This technique was employed to verify the titration results, ensuring that all product was recyclized to 3KPH.sub.2. Mass balances are not as good as those that were titrated, and this may be attributed to HPLC error and dilution error, etc.

Claims

1. A process for the preparation of a compound represented by the following formula: ##STR5## wherein X and Y each represent hydrogen or an alkali metal or alkaline earth metal, comprising:

a. reacting formaldehyde with an alkali metal or alkaline earth metal salt of ethylenediaminediacetic acid to form 1,3-bis(carboxymethyl)imidazolidine, and

b. reacting the product of step a with a cyanide source wherein said process is carried out at a temperature of about 0.degree. to 110.degree. C.

2. The process of claim 1, wherein the reaction of formaldehyde and ethylenediamine dialkali metal acetate is conducted at a temperature from about 0.degree. to about 65.degree. C.

3. The process of claim 1, wherein the reaction of formaldehyde and ethylenediamine dialkali metal acetate is conducted at a temperature from about 15.degree. to about 65.degree. C.

4. The process of claim 1, wherein the reaction of step b is conducted at a temperature from about 0.degree. to about 65.degree. C.

5. The process of claim 1, wherein the reaction of step b is conducted at a temperature from about 15.degree. to about 65.degree. C.

6. The process of claim 1, wherein said formaldehyde is used in a slight molar excess.

7. The process of claim 1, wherein said cyanide source is used in a slight molar excess.

8. The process of claim 1, wherein said cyanide source is selected from the group consisting of hydrogen cyanide and alkali metal cyanide.