The general procedure for the synthesis of 3-aminopropane-1-phosphonic acid and [(methylimino)bis(methylene)]diphosphonic acid from formaldehyde is as follows:
Example 1: Preparation of aminotrimethylene phosphonic acid (ATMP) was accomplished by reacting phosphite, ammonia and formaldehyde in the presence of a methanesulfonic acid catalyst. The specific reactants and their molar ratios are as follows: phosphite 100.45 g (1.225 mol), methanesulfonic acid 15.43 g (0.161 mol), ammonia (25% solution) 27.2 g (0.4 mol), formaldehyde (36.6% solution) 103.27 g (1.26 mol), and water 58.07 g. First, phosphite was added to the reactor, followed by water, methanesulfonic acid and ammonia. The reaction mixture was heated to 105°C, at which temperature the gradual addition of formaldehyde was started and the addition process lasted for 2 hours. After formaldehyde addition was completed, the reaction was continued under reflux conditions for 2 hours. The reaction product was analyzed by 31P-NMR spectroscopy and the yield of ATMP was measured to be 59.1%.
Examples 2 and 3 used the same method as Example 1 for the preparation of ATMP, changing only the amount of methanesulfonic acid catalyst. Example 2 used 61.85 g (0.644 mol) of methanesulfonic acid and Example 3 used 42.33 g (0.441 mol) of methanesulfonic acid. Analysis of the reaction products showed an ATMP yield of 76.8% for Example 2 and 72.7% for Example 3. These results indicate that the technique of the present invention enables the preparation of aminopolymethylene phosphonic acid in higher yields in a shorter reaction time than the prior art and without the use of hydrohalic acid reactants.
The reaction product of Example 1 contained 15.9% N-methyliminobis (methylene phosphonic acid) (N-MeIBMPA) and 16.5% phosphite in addition to 59.1% ATMP. The reaction product of Example 2 contains 6.8% N-MeIBMPA and 9% phosphite in addition to 76.8% ATMP. The reaction product of Example 3 contained 8.3% N-MeIBMPA and 12% phosphite in addition to high levels of ATMP. The one-step reactions of all three embodiments were completed in about 4 hours, in contrast to the multi-step procedure starting with phosphorus trichloride, which typically takes more than 6 hours.
Samples of ATMP were prepared using the method of Example 1 but with continuous distillation at the reaction temperature. The proportions of the reactants were the same as in Example 1, with the following amounts of methanesulfonic acid and added water: in Example 4, 36.45 g of water and 61.85 g of methanesulfonic acid (0.644 mol) were added; in Example 5, no water was added, and 61.85 g of methanesulfonic acid (0.644 mol) was added; in Example 6, 40.4 g of water, and 42.33 g of methanesulfonic acid (0.441 mol) were added; in Example 7, water was added 58.07 g, methanesulfonic acid 15.46 g (0.161 mol); Example 8 added water 58.07 g, methanesulfonic acid 30.92 g (0.322 mol). The reactants were added in the same order as in Example 1. Formaldehyde was added from 105°C, with a dosing time of 3 hours for Example 5 and 1.5 hours for Example 4. These embodiments were carried out under continuous distillation of water to effectively remove unreacted formaldehyde. The reaction products were analyzed as follows: embodiment 4 ATMP 69.4%, phosphite 18.6%, N-MeIBMPA 2.7%; embodiment 5 ATMP 74.6%, phosphite 13.3%, N-MeIBMPA 2.6%; embodiment 6 ATMP 67.9%, phosphite 20.4%, N-MeIBMPA 3.5%; embodiment 7 ATMP 64.6%, phosphite 18.1%, N-MeIBMPA 8.4%; Example 8 ATMP 67.7%, phosphite 20.4%, N-MeIBMPA 3.9%.
These results demonstrate the significant advantages of the technology of the present invention, in particular the formation of aminopolyalkylenephosphonic acid in high yields in a short one-step reaction cycle, essentially avoiding the negative effects associated with prior art hydrochloric acid technology. Particularly noteworthy is the fact that the distillate can be recycled without the additional purification step required in the presence of hydrochloric acid and that the gaseous by-product is essentially free of chloromethane.
Example 32: In a closed vessel under autogenous pressure, 45.20 g (0.551 mol) of phosphite, 13.48 g (0.140 mol) of methanesulfonic acid, 9.56 g (0.18 mol) of ammonia (32% solution), and 46.47 g (0.567 mol) of formaldehyde (36.6% solution) were reacted in accordance with the method of Example 1 to prepare an aminopolymerized methylidene phosphonic acid compounds.10% of the ammonia was added with the other components and the remaining 90% of the ammonia was added with formaldehyde starting at 105°C for 3 hours. Analysis of the reaction product showed an ATMP content of 55%.
![[(methylimino)dimethylene]bisphosphonic acid](/CAS/GIF/5995-25-5.gif)