Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2001-01-02
2002-12-10
Shah, Mukund J. (Department: 1624)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S566000
Reexamination Certificate
active
06492549
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for preparing alkylene diamine triacetic acid (derivatives).
Alkylene diamine triacetic acid (derivatives), such as ethylene diamine triacetic acid and its salts, have applications in the field of chelating chemistry, such as metal cleaning. A process for preparing ethylene diamine triacetic acid is known from EP 0,546,867. The process disclosed in this reference starts from pure ethylene diamine-N,N′-diacetic acid and comprises four reaction steps, viz.
(i) contacting ethylene diamine diacetic acid or salts thereof, preferably the sodium salt, with formaldehyde
(ii) reacting the resulting product with a cyanide source to form a mononitrile diacid,
(iii) hydrolyzing the product of step (ii) and where necessary cyclizing the resulting monoamide diacetic acid to a ketopiperazine diacid, and
(iv) reacting the resulting ketopiperazine diacetic acid with an alkali metal or alkaline earth metal hydroxide, preferably sodium hydroxide, to obtain ethylene diamine triacetic acid.
The process of this reference thus comprises four individual process steps. It is an object of the present invention to reduce the number of process steps.
Further, the starting material of this process, viz. ethylene diamine diacetic acid, is difficult to synthesize and thus expensive. More in particular, the synthesis of ethylene diamine diacetic acid requires a two-step process: ethylene diamine diacetic acid is either synthesized by the reaction of ethylene diamine with formaldehyde and cyanide with subsequent saponification of the resulting nitrile or by the reaction of ethylene diamine with glyconitrile (HO—CH—CN) with subsequent saponification of the resulting nitrile. It is noted that if any one of these reactions is carried out in a single process step, mixtures of ethylene diamine monoacetic acid, ethylene diamine diacetic acid, and ethylene diamine triacetic acid are obtained. Consequently, to obtain pure ethylene diamine diacetic acid such as is needed as starting material in the above process, a two-step process is indispensable. This makes the synthesis of the starting material quite sophisticated. It is therefore a further object of the present invention to employ a process where inexpensive and easily-synthesizable starting materials can be applied.
Finally, it is an object of the present invention to produce alkylene diamine triacetic acid in high purity.
SUMMARY OF THE INVENTION
It has now surprisingly been found that all the above objectives can be met by a process which comprises the conversion of an alkylene diamine (derivative) to a salt of an alkylene diamine triacetic acid (derivative), wherein the reaction is carried out in the presence of a polyvalent metal ion M
a+
and the entire reaction is carried out under hydrolyzing conditions if any of the reactants contain or form nitrile or amide groups.
DETAILED DESCRIPTION OF THE INVENTION
In particular, it has been found that if alkylene diamine (derivatives) are converted to alkylene diamine triacetic acid (derivatives) in the presence of polyvalent metal ions, the desired alkylene diamine triacetic acid (derivative) is obtained in high purity, whereas if monovalent metal ions instead of the polyvalent metal ions are applied in the same process, mixtures of alkylene diamine diacetic acid, alkylene diamine triacetic acid, and alkylene diamine tetraacetic acid (derivatives) result. In this case a further purification step is necessary to obtain alkylene diamine triacetic acid or a derivative thereof in high purity.
In the process of the present invention it is possible to form salts of the alkylene diamine triacetic acid (derivative) in a single process step starting from alkylene diamine. Consequently, the number of process steps can be reduced considerably and a starting material, viz. alkylene diamine, can be applied which is significantly less expensive than, e.g., the ethylene diamine diacetic acid used in the process of the above reference.
The invention will be described in more detail below. For convenience's sake, the following terminology will be used:
ADA: alkylene diamine
AD1A: alkylene diamine monoacetic acid
AD2A: alkylene diamine diacetic acid
AD3A: alkylene diamine triacetic acid
AD4A: alkylene diamine tetraacetic acid
EDA: ethylene diamine
ED1A: ethylene diamine monoacetic acid
ED2A: ethylene diamine diacetic acid
ED3A: ethylene diamine triacetic acid
ED4A: ethylene diamine tetraacetic acid
The invention pertains to a process for preparing alkylene diamine triacetic acid (derivatives) which comprises the conversion of an alkylene diamine (derivative) of the formula
wherein B is selected from an unsubstituted or substituted alkylene bridge and R is independently selected from H or (salts of) —CH
2
—COOH, —CH
2
—CN, or —CH
2
—CONH
2
, to a salt of an alkylene diamine triacetic acid (derivative) of the formula
with the reaction being carried out in the presence of a polyvalent metal ion M
a+
and the entire reaction being carried out under hydrolyzing conditions if any of the reactants contain or form nitrile or amide groups.
Preferably, the alkylene bridge B in the ADA (derivative) starting material is an unsubstituted or substituted ethylene or propylene bridge. If the bridge is substituted, generally one or more of the bridging carbon atoms may be independently substituted by C
1
-C
6
alkyl groups and preferably C
1
-C
4
alkyl groups. It is preferred that the bridge is unsubstituted, and preferably B is selected from —CH
2
—CH
2
— or —CH
2
—CH
2
—CH
2
— and more preferably B is —CH
2
—CH
2
—. In other words, a preferred ADA (derivative) is an EDA (derivative). Preferably, R stands for H and/or CH
2
COOH moieties, with H being most preferred. The EDA (derivative) thus preferably comprises (salts of) ED2A, ED1A, and EDA, more preferably it comprises (salts of) ED1A and EDA, still more preferably it consists essentially of (salts of) ED1A and/or EDA, even more preferably it comprises (salts of) EDA, and most preferably it consists essentially of (a salt of) EDA.
The product of the process of the present invention is the salt of the AD3A (derivative). This salt consists at least in part of a complex of negatively charged AD3A (derivative) and the positively charged polyvalent metal ions. Of course, if further cations are present during the reaction, the salt may additionally comprise these cations apart from the complex. However, it is essential to the process of the invention that at least part of and preferably all of the AD3A (derivative) formed during the reaction is immediately complexed by the polyvalent metal ion. Without wishing to be bound by any theory, Applicant believes that due to the formation of this complex, the second still remaining NH function in the AD3A (derivative) is blocked. This NH function thus cannot be converted to an N—CH
2
—COOH moiety and the formation of an AD4A (derivative) is therefore avoided. The process of the present invention thus makes it possible to prepare the AD3A (derivative) in high purity. It has been found that if, under the same reaction conditions, instead of the polyvalent metal ion, a monovalent metal ion such as sodium is used, AD4A is indeed formed apart from AD3A. Again without wishing to be bound by any theory, Applicant believes that monovalent metal ions are not able to form a complex wherein the remaining NH function is blocked. This is shown schematically below:
It is noted that, apart from the presence of the polyvalent metal ion, it is essential to the process of the invention that the entire reaction is carried out under hydrolyzing conditions if any of the reactants contain or form nitrile or amide groups. “Hydrolyzing conditions” in the sense of the present invention means that the reaction conditions are such that any nitrile and/or amide group added to the reaction mixture or formed during the reaction is instantaneously converted to a carboxylic acid moiety or the salt thereof. Generally, such hydrolyzing conditions are present when the pH is chosen to be above 9, p
Boonstra Tjerk Oedse
Driessen Johannes Wilhelmus
Heus Martin
Van Doorn Marcellinus Alexander
Akzo Novel NV
Fennelly Richard P.
Shah Mukund J.
Tucker Zacharey C.
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