CA1069122A - Preparation of dialkali metal hexahydropyrimidine-1, 3-diacetate and dialkalimetal 5-hydroxyhexahydropyrimidine-1, 3-diacetate - Google Patents

Abstract

PREPARATION OF DIALKALI METAL
HEXAHYDROPYRIMIDINE-1,3-DIACETATE AND, DIALKALIMETAL 5-HYDROXYHEXAHYDROPYRIMIDINE-1,3-DIACETATE

Abstract of the Disclosure or,

Description

. 1069122 ~ BACKGROUND OF THE INVENTION
., This invention is in the field of the dialkali metal hexahydropyrimidine-1,3~diacetates acid (Compound No. 1), CH2cOOM ~ ~
,`10 CH2COOM / CH2 N
~ N \ ~ which is also ¦ ¦
r l written as 7H2 fH2 CH2COOM \ ¦ IN
'~ \ CH2 --CH2COOM

., ~ /

wherein M is an alkali metal ion.
Compound No. 1 is prepared by the reaction represented by the following equation:

`~ H

1 C ~ + 2CH2O I 2MCN

.1 ~ ~
l H
.~ /

~? fH2COOM

. ' ~, Disodium hexahydropyrimidine-1,3- diacetate (Compound No. 1) in which M is an alkali metal ion (e.g., Na, K, or Li).

. :
:- . : : . - - . ' . -,: . .~ ' .: : ~
' . . ~ '' ' : ': ':. , N,N'-dicarboxymethyl-1,3-propanediamine (PDDA) can be prepared from Compound No. 1 by the reaction represented by the following equation:

~,~ + ~11+ ~ 1 ; CH2COOM HNCH2CH2CH2NH + CH2O + 2M .
(PDDA) This invention is also in the field of the dialkali metal 5-hydroxyhexahydropyrimidine-1,3-diacetates acid (Compound No. 2), J
~ CH2COOM
: CH2COOM ~ CH2- N

HO ~ ~ l which is also HO-CH CH2 ~ ~ \ written as CH2- N

CH2COOM ) CH2COOM
wherein M is an alkali metal ion.
Compound No. 2 is prepared by the reation represented 20by the following equation:
H

HO ~ ~ +2CH2O + 2MCN
/ . .
H

HO C ~ + 2NH3 CH2COOM ' Disodium 5-hydroxyhexahydropyrimidine-1,3-diacetate (Compound No. 2) - . - 3 - ~;

`' ' 106912Z
in which M is an alkali metal ion (e.g., Na, K, or Li); and N,N'-dicarboxymethyl-2-hydroxy-1,3-propanediamine (Hydroxy-PDDA) can be prepared from Compound No. 2 by the reaction represented by the following equation:

HO~

CH2COOM HNCH2CIH CH2NH + CH2O + 2M .
OH
: 10 (Hydroxy-pDDA) ~ ' Prior art methods of preparing PDDA are taught by Johnson et al, J. Org. Chem. 1962, 27, 2077-2080. See the second column on page 2079 and the first column on page 2080.
The preparation of hexahydropyrimidine, 7 ~ H
. IH CH ~which is also ~ ~
1 2 1 2 ~written as J

~l is taught by Titherly et al, J. Chem. Soc., 1913, 103, 330-340 (.at 334).
Example 11, of Canadian Patent application serial number 262,187 teaches a method for preparing 5-hydroxyhexahydropyrimidine, .. . . .
:' .
~ 4 ~

~ .
, , HO-CH fH2 which is also written as HO ~ N >

2 1 1 H H

Said Canadian patent application Serial No. 262,187 and Canadian patent application Serial No. 259,664 teaches uses of PDDA and Hydroxy-PDDA. Both of said applications are assigned to W.-R.
:10 Grace & Co.
U.S. patent No. 2,407,605 (Bersworth) teaches the preparation of alkali metal salts of polycarboxylic amino acids by reacting an aliphatic amine with formaldehyde and an alkali metal cyanide in an alkaline aqueous medium. Said patent, in its entirety, is incorporated herein by reference.
;, - SUMMARY OF T B INVENTION
In summary, this invention is directed to a method for preparing a dialkali metal diacetate having 'he formula --N\ ,~
> or HO~
N~ ~--N -~

in which M is an alkali metal ion, the method comprising:
(a) forming an alkaline aqueous solution by admixing water, an alkali metal hydroxide, and hexahydropyrimidine or 5-hydroxyhexahydropyrimidine in a vented reaction zone, ~30 . ..

- . . . . .

': '' . '~- . ,' ~ " , .: ' .'- ~' : ', ' ' ' . '' ~0~i9lZZ

~ b) forming the dialkali metal diacetate by feeding an alkali metal cyanide and an aqueous formaldehyde solution into the alkaline aqueous solution in the reaction zone while agitating the resulting reacting mixture in the reaction zone and while maintaining the temperature of the reacting mixture within a range effective for: (i) vaporizing by-product ammonia therefrom; and (ii) forming the dialkali metal diacetate, by feeding the alkali metal cyanide and the formaldehyde solution into the reaction zone, the alkali metal cyanide and the formaldehyde solution being provided in amounts effective for forming the dialkali metal diacetate.

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. DESCRIPTION OF PREFERRED EMBODIMENTS
In a preferred embodiment of our invention as recited in the above Summary the alkali metal cyanide and the formalde-~ hyde solution are fed into the reaction zone at rates effective : for maintaining an excess of unreacted cyanide over unreacted ; formaldehyde in the reacting mixture until an amount of the alkali metal cyanide stoichiometrically equivalent to the amine (hexahydropyrimidine or 5-hydroxyhexahydropyrimidine) originally ~ present in the alkaline aqueous solution has ~een fed into the vented reaction zone.
- In another preferred embodiment ("Embodiment A") this : invention is directed to a method for preparing a dialkali : metal diacetate having the formula . ~
fH2COOM CH2COOM

~; ~ or HO ~ > ":
,,~ ~ ..

.!!, CH2COOM CH2COOM
., in which M is an alkali metal ion, the method comprising: .
(a) forming an alkaline aqueous solution by admixing water, an alkali metal hydroxide, and a member selected from the .- group consisting of hexahydropyrimidine and 5-hydroxyhexahydropy- ::
;:~ rimidine in a vented reaction zone having inlet ports, a conden- -ser, a agitating means, and a heating means, the mole ratio of .` :
group member to alkali metal hydroxide being about 1: 2.4-2.6; .
:, . .
: (b) forming the dialkali metal diacetate by feeding the HCN and an aqueous formaldehyde solution into the alkaline : aqueous solution in the reaction zone while agitating the re-: sulting reacting mixture and while maintaining its temperature within a range effective for: (i) vaporizing by-product .. , -` - 6 -.

.
`' : ' ' .
.i .
.
: ` ` . . .. .
.

... .

ammonia therefrom; and (ii) forming the dialkali metal diacetate.
In certain embodiments of my invention as recited in Embodiment A, supra:
1. The group member is hexahydropyrimidine.
2. The group member is 5-hydroxyhexahydropyrimidine.

3. The alkali metal hydroxide is sodium hydroxide.

4. The HCN is liquid anhydrous HCN.

5. The HCN and the formaldehyde solution are fed into j~:
the vented reaction zone at rates effective for maintaining an 10excess of unreacted cyanide over unreacted formaldehyde in the reacting mixture, until an amount of the HCN stoichiometrically ~ .
;~ equivalent to the group member originally present in the first alkaline aqueous solution has been fed into the vented reaction zone.
?
DETAILED DESCRIPTION OF THE INVENTION
; The Invention as Recited in the Summary ; and th~ Embodiment Thereunder 1 Since, in the process of thi5- invention as recited $, ~; in the above Summary and the preferred embodiment thereunder ~;~20 ,, the alkali metal hydroxide per se is not a reactant (except ~s insofar as it may provide alkali metal ions for the desired product (a dialkali metal acetate)) it is included to establish and maintain a strongly alkaline condition in the reacting mixture of the above Summary - the amount of said hydroxide present in the alkaline aqueous solution described in said summary and consequently in the reacting mixture described therein can be varied over a considerable range. However, we generally prefer to have a mole ratio of the amine (hexahydropyrimidine or 5-hydroxyhexahydropyrimidine) of said summary to said hydroxide ~30 ~;of about 1:0.1-0.4 in the alkaline aqueous solution. Neverthe-... . .
, ':
..

:' .
: ' , .
: . ' less, excellent results can be obtained where said ratio is higher or lower.
We generally prefer to add the alkali metal hydroxide ::
as an aqueous solution (e.g., 30-50% sodium hydroxide or potassium hydroxide or about 10% up to a saturated solution :- i - where using lithium hydroxide). However, solid alkali metal hydroxide can be dissolved in the water or in the admixture of water and hexahydropyrimidine or 5-hydroxyhexahydropyrimidine in the vented reaction zone. We generally prefer to have a weight ratio of amine (hexahydropyrimidine or 5-hyroxyhexahy-dropyrimidine) to water of l:iO.5-2 in the alkaline aqueous solution before adding alkali metal cyanide and formaldehyde -thereto. However, excellent results can be obtained where using more water or where using less water.
We fed the formaldehyde as an aqueous solution prefer-ably an aqueous solution containing 30-50% formaldehyde. However, ' excellent results can be obtained by using a more concentrated or a less concentrated solution of formaldehyde.
We also fed the alkali metal cyanide as an aqueous solution (e.g., about 25-35% alkali metal cyanide). However, excellent results can be obtained where using more concentrated or more dilute alkali metal cyanide solutions.
We generally prefer to feed the formaldehyde as a continuous stream. However, intermittent feeding of the form-aldehyde can be used. Also, the alkali metal cyanide solution can be fed as a continuous stream or as an intermittent stream.
' For obtaining the highest yield of substantially pure dialkali metal diacetate product caution should be used to maintain an excess of alkali metal cyanide over formaldehyde in the reacting ~ :
., - .
,: ' :

:
mixture until an amount of alkali metal cyanide at least stoi-chiometric equivalent to the amine has been added. Neverthe-, r', less, the process (or~method) is operable where this caution p (or precaution) is not observed.
While excellent results can be obtained using ~!" stoichiometric or somewhat less than stoichiometric amounts of , i ..
~ both alkali metal cyanide and formaldehyde, we generally prefer .hr to use a slight excess of each (based on the ~mine charged).
For example, we generally prefer to have the mole ratio of amine to formaldehyde to alkali metal cyanide within a range ~: .
of about 1:2.1-2.3:2.1-2.3.
.,. :
We generally prefer to conduct the reaction at about , 95-105C. However excellent results can be obtained at temper-,' atu~es of about 80-110C. When the reaction is complete or substantially complete, we generally prefer to bring the mixture containing the product (Compound 1 or Compound 2) to a boil, if it was not boiled during reaction, for a short time ;~ to remove the last traces of by-product ammonia therefrom.
.., ~ Reaction time (the time over which the formaldehyde ;! 20 and alkali metal cyanide solutions are added) is generally ,'~ about 2-8 hours.
When the reaction is completed, water can be boiled from the product to form a more concentrated solution of the product (Compound 1 or Compound 2) if desired. The thus con-centrated solution of product can be recovered, or, if desired, ~
the solution of product can be recovered before such concentra- -tion. ~

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The reaction zone should preferably be provided with heating and cooling means. For example, the reaction zone can be a jacketed reactor or a reactor having internal coils. If jacketed, the same jacket can be used for heating and cooling. -If it is a reactor with internal coils, the same set of coils can be used for heating and cooling. Alternatively, two sets of coils can be included one of which is used for cooling and one of which is used for heating. In another alternative the reactor may be jacketed and may also contain coils. In such event the jacket and/or coils can be used for heating and subsequently, if desired, either the jacket and/or the coils can be used for heating.
If desired, the amine (hexahydropyrimidine or 5-hydroxy-hexahydropyrimidine) can be prepared in the vented reaction zone by reacting 1,3-propanediamine or 1,3-diamino-2-propanol, res-pectively, with formaldehyde in an aqueous reaction medium . . .
prior to forming the above-mentioned alkaline aqueous solution.
Alternatively, the hexahydropyrimidine or 5-hydroxy-hexahydropyrimidine can be purchased or prepared elsewhere and placed in the reaction zone.
(The Invention as Recited . ~
,~ Embodiment A and the Embodiments thereunderl - ------- ~:
~ In the process of this invention as recited in the ---'j above Embodiment A and the embodiments thereunder, the alkali ~ .
metal hydroxide: (a) provides alkalinity which converts HCN to -an alkali metal cyanide according to the reaction represented by the equation ` HCN + MOH = MCN + H2O
. (where M is an alkali metal ion); (b) provides alkali metal ions for the desired product (a dialkali metal diacetatel; and :
:.
: .......................................................................... ..
, -- 1 0 --.

10691;Z2 (c) maintains a strongly alkaline condition in the reacting mixture.
The amount of said hydroxide present in the alkaline ~; -aqueous solution described in said Embodiment A and consequently ~; in the reacting mixture described therein can be varied over a considerable range. However, we generally prefer to have a mole - ratio of the amine (group member) of said Embodiment A to said hydroxide of about 1:2.3-2.6 in the alkaline aqueous solution. - ~-Nevertheless, excellent results can be obtained where said ratio is higher or lower providing there is an excess of alkali metal .. . .
'~ hydroxide over the HCN which will be fed.
~; We generally prefer to add the alkali metal hydroxide asan aqueous solution (e.g., 30-50~ sodium hydroxide or potassium ~,,.~, .
;~' hydroxide or about 10% up to a saturated solution where using *; .
~, lithium hydroxide). However, solid alkali metal hydroxide can be dissolved in the water or in the admixture of water and hexa- -~;j~;, .
hydropyrimidine or 5-hydroxyhexahyd~opyrimidine in the vented reaction zone. We generally prefer to have a weight ratio of ` amine (hexahydropyrimidine or 5-hyroxyhexahydropyrimidine) to water of about 1:2-7 in the alkaline aqueous solution before adding HCN and formaldehyde thereto. However, excellent results ,...................................................................... .
can be obtained where using more water or where using less water.
We fed the formaldehyde as an aqueous solution pre-ferably an aqueous solution containing 30-50% formaldehyde.

....
;;~ However, excellent results can be obtained by using a more con-; centrated or a less concentrated solution of formaldehyde.
. . . `
We generally prefer to feed the formaldehyde as a continuous stream. However, intermittent feeding of the form-.. ~
aldehyde can be used. Also, the HCN can be fed as a continuous ;. 30 stream or as an intermittent stream. For obtaining the highest yield of substantially pure dialkali metal diacetate product . ::
. -- 11 --. .

,~. . , , 106~)~2Z

caution should be used to maintain an excess of HCN over formal-dehyde in the reacting mixture until an amount of alkali metal ,- cyanide at least stoichi~.~etric equivalent to the amine has been ~` added. Nevertheless, the process (or method) is operable where such caution (or precaution) is not observed.
While excellent resul~s can be obtained using stoichio- -~
. , .
metric or somewhat less than stoichiometric amounts of both alkali metal cyanide and formaldehyde, we generally prefer to use a slight excess of each based on the amine (group member) charged. For example, we generally prefer to have the mole ratio of amine to formaldehyde to HCN within a range of about 1:2.1-2.
3:2.1-2.3.
We generally prefer to conduct the reaction at abbut 95-100C. However, excellent results can be obtained at tempe~-atures of about 80-110C. When the reaction is complete or substantially complete, we generally prefer to bring the miXture ... .
~ containing the product (Compound 1 or Compound 2) to a boil, if - it was not boiled during reaction, for a short time to remove the last traces of by-product ammonia therefrom.
, 20 Reaction time (the time over which the formaldehyde and HCN solutions are added) is generally about 2-8 hours.
When the reaction is completed, water can be boiled from the product to form a more concentrated solution of the product ~Compound 1 or Compound 2) if desired. The thus concentrated solution of product can be recovered, or, if desired the solution of product can be recovered before such concentration.
`'~ The instant invention will be better understood by -referring to the following specific but nonlimiting procedures.
'~30 It is understood that said invention is not limited by these procedures which are offered merely as illustrations; it is also ~i ';
.. . , . ~ . . , : . . . ...

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understood that modifications can be made without departing from : the spirit and scope of the invention.

The following procedures, while not actually run, will . illustrate certain embodiments of our invention.

A first aqueous solution can be prepared by admixing ~........................................................................ , 1 mole of hexahydropyrimidine, about 140 g of water, and 16 g of an aqueous 50% solution of sodium hydroxide (0.2 mole of NaOH).
A 308 g portion of aqueous 35% solution of sodium cyanide (2.2 moles of NaCN) can be divided into 10 equal portions and one of said portions can be added to and admixed with the first aqueous solution to form a second aqueous solution.
The second aqueous solution can be heated to about 80C in a reaction zone provided with a reflux condenser, agitating means, heating means, and inlet ports.
A 150 g portion of an aqueous 44% formaldehyde solution (2.2 moles of HCHO) can be fed into the reaction zone containing the second aqueous solution at a rate of about 38-40 ml per hour (while: (a) agitating the second aqueous solution; and (b~ main-taining its temperature at about 80C) to form a reacting mixture.
The remaining 9 portions of the aqueous 35% NaCN
solution can be added to the reacting mixture at intervals of about 22-24 minutes to maintain an excess of NaCN over HCHO in the reacting mixture until an amount of NaCN stoichiometrically equal to the hexahydropyrimidine has been added.

The reflux condenser can be removed after about half of the sodium cyanide solution has been added, the temperature of the reacting mixture can be adjusted to the boiling point and said mixture can be boiled to facilitate the removal of the final amounts of by-product ammonia and to remove excess water to produce a product solution analyzing (containing~ about 40%

. , , :, "~

`` 10691Z2 disodium hexahydropyrimidine-1,3-diacetate. Conversion (one pass yield) will be about 95% of theory based on the hexahydro-pyrimidine charged.
The method of Procedure 1 can be modified by adding the formaldehyde solution and the alkali metal cyanide at rates such that an excess of cyanide over HCHO is not maintained in the reacting mixture during reaction. ~here using this modifi-cation conversion (one pass yield) and purity of the desired ... .. :
dialkali metal diacetate salt will be somewhat lower than in the method recited in Procedure 1.
' PROCEDURE 2 The general method of Procedure 1 can be repeated wherein said method is modified by adding the sodium cyanide continuously rather than incrementally as in Procedure 1. Where ,, , ;~ using this method the sodium cyanide can be added at such a rate that an excess of sodium cyanide over formaldehyde is present ; in the reaction zone until at least about 2 moles of NaCN have been added per mole of hexahydropyrimidine. Conversion will be substantially the same as in Procedure 1.
~ 20 ,~ The method of Procedure 2 can be modified by adding the formaldehyde solution and the alkali metal cyanide at rates such that an excess of cyanide over HCHO is not maintained in ~",'?~ the reacting mixture during reaction. Where using this modi-fication conversion (one pass yield) and purity of the desired dialkali metal diacetate salt will be somewhat lower than in the method recited in Procedure 2. -` ' PROCEDU~E 3 ; A first aqueous solution can be prepared by admixing 1 mole of hexahydropyrimidine, about 340 g of water, and 192 g of an aqueous 50% solution of sodium hydroxide (2.4 moles of NaOH) in a reaction zone provided with inlet ports, a reflux .~ ~069~Z2 condenser, agitating means, and heating means.
The temperature of the first aqueous solution can be adjusted to about S0C (if it is not already at such temperature) and sufficient HCN (preferably fed as liquid anhydrous HCN;
however, anhydrous HCN vapor or aqueous HCN solutions can be ` used) can be added to bring the resulting second aqueous solu-tion to its boiling point.
A 150 g portion of an aqueous 44% formaldehyde solution (2.2 moles of HCHO) can be fed into the reaction zone containing .~.~ ., .
the second aqueous solution at a rate of about 38-40 ml per hour i (while: (a) agitating the second aqueous solution; and (b) -maintaining its temperature at its boiling point to form a ~ reacting mixture (or reacting system).
;; HCN to make a total of 59.5 g (2.2 moles) of HCN can be~added to the reacting mixture in substantially equal ~ increments at intervals of about 22-24 minutes to maintain an ?l~ excess of HCN over HCHO in the reacting mixture until an amount of HCN stoiciometrically equal to the hexahydropyrimidine has been added.
The reflux condenser can be removed after about half (1.1 mole) of the HCN has been added, the temperature of the ~; .
reacting mixture can be maintained at the boiling point by providing heat from an external source as required, and said ,: ,i mixture can be boiled to facilitate the removal of the final amounts of by-product ammonia and to remove excess water to ~i produce a product solution analyzing (containing) about 40%

disodium hexahydropyrimidine-1,3-diacetate. Conversion (one pass yield) will be about 95% of theory based on the hexahydro-pyrimidine charged.

.

.' . . ~ ' '.' .
, ' .- ~ . :

~06912 The method of Procedure 3 can be modified by adding the formaldehyde solution and the HCN at rates such that an excess of cyanide over HCHO is not maintained in the reacting mixture during reaction. Where using this modification conver-sion (one pass yield) and purity of the desired dialkali metal diacetate salt will be somewhat lower than in the method recited in Procedure 3.

The general method of Procedure 3 can be repeated wherein said method is modified by adding the HCN continuously ~ 10 '~ rather than incrementally as in Procedure l. ~Ihere using this method the HCN can be added at such a rate that an excess of HCN over formaldehyde is present in the reaction zone until at least about 2 moles of HCN have been added per mole of hexahydro-"~ pyrimidine. Conversion will be substantially the same as in ,~.,.~
Procedure 3.
.j - .
The method of Procedure 4 can be modified by adding ,,~ the formaldehyde solution and the HCN at rates such that an excess of cyanide over HCHO is not maintained in the reacting mixture during reaction. Where using this modification conver-sion (one pass yield) and purity of the desired dialkali metal diacetate salt will be somewhat lower than in the method recited ; in Procedure 4.
~1 .

"
: Disodium 5-hydroxyhexahydropyrimidine-1,3-diacetate -,.;
' can be prepared by the general methods of Procedure l, Procedure 2, Procedure 3, or Procedure 4 wherein 5-hydroxyhexahydropyrimi-dine is substituted on a mole-for-mole basis for the hexahydro-' pyrimidine of said procedures. Conversion will be about 95%

of theory based on the S-hydroxyhexahydropyrimidine charged.

,,, ' ' .

``` 1069~22 `.
r~: The method of Procedure 5 can be modified by adding the formaldehyde solution and the alkali metal cyanide (or HCN) at rates such that an excess of cyanide over HCHO is not main-tained in the reacting mixture during reaction. Where using this modification conversion (one pass yield) and purity of the dialkali metal diacetate salt will be somewhat lower than in the method recited in Procedure 5. -~-,. -:
Potassium hydroxide solution, or a nearly saturated ~ solution of lithium hydroxide can be substituted for the sodium - 10 hydroxide of Procedures 1, 2, 3, 4, or 5. Potassium cyanide or lithium cyanide can be substituted for sodium cyanide in the process of this invention.
; Products, disodium hexahydropyrimidine-1,3-diacetate and disodium 5-hydroxyhexahydropyrimidine-1,3-diacetate, prepared by the above procedures (Procedures 1-5) can be identified by the techniques recited in parent application Serial No. 262,187, to wit:
i 1. Titration with copper (II) chloride solution at 'i pH 6.
i~i 20 2. The products will not chelate copper CII) ions . at pH 9.
3. Gas chromatography of said products after said ~;; products have been acidified (to a pH of 6 or lower), dried, and silylated.
A strong odor of by-product formaldehyde (formed by ..~
the reaction represented by the equation:

fH2COONaCH2--NCH2COOH

i~ 1 2 N H2O ¦ H
X-CH CH + 2H +~ X-CH + HCHO
~` 30 CH2 H

CH2 COONaCH2- NCH2COOH

.
:

`:~ ``` 10691Z2 . ` . . .~
.
in which X is H or OH~ can be detected where acidifying the products of said Procedures 1-5 to a pH of about 6 or lower.
The stoichiometry of the process of this invention is that of the reaction represented by the equation:

.` IH CIH2COOM ..
~; .
X C ~ + 2CH20 + 2MCN X
.:~ I I
: H CH COOM
;, 2 ~ in which X is H or OH and M is an alkali metal ion (e.g., Na, .. ' 10 -- K, or Li).
,~ .
,~ In a fully equivalent modification of the process of this invention as represented by the above equation and as illustrated by Procedures 3, 4 and parts of 5, the alkali metal cyanide (MCN) can be replaced on a mole-for-mole basis (i.e., 1 mole of HCN for each mole of alkali metal cyanide required by the above equation. When this is done (e.g., as in Procedures 3 and 4 and parts of 5) about 1 mole of alkali metal hydroxide is provided for each mole of HCN fed.
As used herein, the term "g" means gram or grams.
;~ As used herein, the term "mole" has its generally accepted meaning, a mole being that quantity of a substance which contains the same number of molecules of the substances as ~, there are atoms in 12 g of pure 12C.
.~, .. . .
,,.~.t, As used herein, the term "percent (%)" means parts per hundred, and the term "parts" means parts by weight unless otherwise defined where used.

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Claims (15)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for preparing a dialkali metal diacetate having the formula or, in which M is an alkali metal ion, said method comprising:
(a) forming an alkaline aqueous solution by admixing water, an alkali metal hydroxide, and an amine selected from the group consisting of hexahydropyrimidine and 5-hydroxyhexahydro-pyrimidine in a vented reaction zone;
(b) forming the dialkali metal diacetate by feeding an alkali metal cyanide and an aqueous formaldehyde solution into the alkaline aqueous solution in the reaction zone while agita-ting the resulting reacting mixture in the reaction zone and while maintaining the temperature of the reacting mixture within a range effective for: (i) vaporizing by-product ammonia there-from; and (ii) forming the dialkali metal diacetate, by feeding the alkali metal cyanide and the formaldehyde solution into the reaction zone, the alkali metal cyanide and the formaldehyde solution being provided in amounts effective for forming the dialkali metal diacetate.

2. The method of Claim 1 in which: (a) the alkali metal ion is sodium; (b) the alkali metal hydroxide is sodium hydroxide;
(c) the alkali metal cyanide is sodium cyanide; and (d) the dialkali metal diacetate is or

3. The method of Claim 1 in which: (a) the alkali metal ion is potassium; (b) the alkali metal hydroxide is potassium hydroxide (c) the alkali metal cyanide is potassium hydroxide;
and (d) the dialkali metal diacetate is or

4. The method of Claim 1 in which the dialkali metal diacetate is

5. The method of Claim 1 in which the dialkali metal diacetate is

6. The method of Claim 1 in which the alkali metal cyanide is fed as an aqueous solution.

7. The method of Claim 6 in which the alkali metal cyanide solution is fed continuously.

8. The method of Claim 6 in which the alkali metal cyanide solution is fed incrementally.

9. The method of Claim 1 in which the alkali metal cyanide and the formaldehyde solution are fed into the reaction zone at rates effective for maintaining an excess of unreacted cyanide over unreacted formaldehyde in the reacting mixture until an amount of the alkali metal cyanide stoichiometrically equivalent to the group member originally present in the alkaline aqueous solution has been fed into the reaction zone.

10. A method for preparing a dialkali metal diacetate having the formula or in which M is an alkali metal ion, the method comprising:
(a) forming an alkaline aqueous solution by admixing water, an alkali metal hydroxide, and a member selected from the group consisting of hexahydropyrimidine and 5-hydroxyhexa-hydropyrimidine in a vented reaction zone having inlet ports, the mole ratio of group member to alkali metal hydroxide being 1:2.4-2.6;
(b) forming the dialkali metal diacetate by feeding HCN
and an aqueous formaldehyde solution into the alkaline aqueous solution in the reaction zone while agitating the resulting reacting mixture and while maintaining its temperature within a range effective for: (i) vaporizing by-product ammonia there-from; and (ii) forming the dialkali metal diacetate, the HCN
and the formaldehyde solution being provided in amounts effective for forming the dialkali metal diacetate.

11. The method of Claim 10 in which the group member is hexahydropyrimidine.

12. The method of Claim 10 in which the group member is 5-hydroxyhexahydropyrimidine.

13. The method of Claim 10 in which the alkali metal hydro-xide is sodium hydroxide.

14. The method of Claim 10 in which the HCN is liquid anhydrous HCN.

15. The method of Claim 10 in which the HCN and the form-aldehyde solution are fed into the reaction zone at rates effective for maintaining an excess of unreacted cyanide over unreacted formaldehyde in the reacting mixture, until an amount HCN stoichiometrically equivalent to the group member originally present in the first alkaline aqueous solution has been fed into the reaction zone.