Comparing the Methods of Ethylenediaminetetraacetic Acid Synthesis Negarnikkhoo,A,* Ali Moradi,Bmaryam Kalantari,B

Archive of SID

17th Iranian Chemistry Congress Vali-e-Asr University of Rafsanjan 1-3 september 2014

Comparing the methods of ethylenediaminetetraacetic acid Synthesis NegarNikkhoo,a,* Ali Moradi,bMaryam Kalantari,b

adepartment of chemical engeeniring ,shahid Bahonar university of Kerman ,[email protected] bdepartment of chemical engineering ,shahid Bahonar university of Kerman

Background: The original synthesis of EDTA was from ethylenediamine, sodium salt of monochloroacetic acid and caustic soda [1]. The Second method for EDTA synthesis is alkaline cyanomethylation of ethylenediamine in the presence of cyanide iones and formaldehyde [2] and the third method is double-stage synthesis which the cyanomethylation is separate from the hydrolysis. Formaldehyde and cyanide react with ethylenediamine. The intermediate nitrile is hydrolyzed to tetrasodium EDTA [3].

Methods: The reaction usually is performed according to the followingMethod 1: The reaction is take place o at 90 C for 8 to 10 hours. H2NCH2CH2NH2 + 4 ClCH2CO2Na NaO2CCH2)2NCH2CH2N(CH2CO2Na)2(NaO2CCH2)2NCH2CH2N(CH2CO2Na)2 +4 HCl o (HO2CCH2)2NCH2CH2N(CH2CO2H)2 + 4 NaCl Method 2: The reaction is take place at 85 C by means of feeding cyanide and formaldehyde.H2NCH2CH2NH2 + 4 CH2O + 4 NaCN + 4 H2O (NaO2CCH2)2NCH2CH2N(CH2CO2Na)2 + 4 NH3 After this stage tetra sodium EDTA is acidified and EDTA produced.Method 3: The reaction is take place at 40o C for 24 hours. The ethylenediaminetetraaceto-

nitrile formed and must be hydrolyzed to tetrasodium EDTA.H2NCH2CH2NH2 + 4 CH2O + 4 HCN (NCCH2)2NCH2CH2N(CH2CN)2 + 4 H2O (NCCH2)2NCH2CH2N(CH2CN)2 + 4 NaOH (NaO2CCH2)2NCH2CH2N(CH2CO2Na)2 + 4 NH3 Results: The first, second and third method offer yields of 60%, 90% and 95% respectively. FTIR analysis was used for the detecting of functional groups.

Conclusion: FTIR data for product of method 1 (KBr disk): ῡ= 3435(O-H), 3017(C-H stretch), 1693(C=O), 1415(C-H bend), 1317(C-O), 1249(C-N). FTIR data for product of method 2 (KBr disk): ῡ= 3436(O-H), 3017(C-H stretch), 1692(C=O), 1414(C-H bend), 1317(C-O), 1212(C-N).FTIR data for product of method 3 (KBr disk): ῡ= 3430(O-H), 3008(C-H stretch),1699(C=O),1394(C-H bend),1259(C-O),1088(C-N). Material that produced in first method is contaminated with by products and must be purified. However, this method don‘t have the worried about poisonousness of cyanide. In the second method the yield is high but the principal byproduct is ammonia, which is cyanometylated and makes nitriletriaceto-nitrile. Likewise glycolic acid is formed from the reaction of cyanide and formaldehyde. In the third method, carrying out the synthesis in two stages eliminates impurity-forming reactions and yield a pure EDTA but cyanide is poisonous.

Keywords: EDTA; synthesizing; ethylenediamine; monochloroacetic acid; cyanide

References:

[1] Munz F., US Patent Office, 1938, 2-130-505 [2] Bersworth F.,US Patent Office, 1946, 2-407-645 [3] Ulrich H., Ploetz E.,US Patent Office, 1940, 2-205-995

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