The novel monomeric compound N-methyleneaminoacetonitrile is produced by reacting glycinonitrile with formaldehyde in the absence of ammonia. The process is conveniently carried out by forming aqueous glycinonitrile in situ using known methods, removing any excess ammonia from the reaction medium and then introducing at least an equimolar amount of formaldehdye. The reaction is allowed to proceed substantially to completion. The novel product has a higher melting point than the previously reported trimer.

BACKGROUND OF THE INVENTION 
This invention relates to the preparation of nitriles and more in 
particular it relates to the production of monomeric 
N-methyleneaminoacetonitrile. 
The previously known N-methyleneaminoacetonitrile trimer has been used as 
an intermediate for many reactions where glycinonitrile is useful, such as 
the production of glycine or the manufacture of imino diacetic acid. It 
has the advantage that it is more stable than glycinonitrile and thus has 
a better shelf life. It is also less soluble in water thus facilitating 
recovery from the reaction medium. It has been found that the monomeric 
compound of this invention has similar utility and advantages to the 
trimer and is simpler to produce. 
N-methyleneaminoacetonitrile trimer, also called N-methylene glycinonitrile 
(trimer) has previously been prepared by several different routes. A 
classical procedure for the preparation of the trimer is that described by 
Klages in J. prakt. Chem. (2), 65, 192 (1902). At the time, Klages 
believed the product to be the dimer. There is further confusion in the 
literature as the trimer product has often been named as the monomer. This 
particular preparative method is not attractive commercially because it 
involves the use of an expensive intermediate, glycinonitrile 
hydrochloride. 
N-methyleneaminoacetonitrile trimer has also been prepared by the reaction 
of formaldehyde, an ammonium halide and an alkali metal cyanide in the 
presence of acid as described by Jay and Curtius, Ber. 27, 59 (1894) and 
later, by Adams and Langley, Organic Synthesis, Coll. Vol. I, 347 (1932). 
Recently, an improvement upon this basic process was described in U.S. 
Pat. No. 2,823,222. 
U.S. Pat. No. 3,167,581, issued Jan. 26, 1965 suggests a continuous 
preparation of trimeric N-methyleneaminoacetonitrile directly from 
formaldehyde, hydrogen cyanide and ammonia. See also U.S. Pat. Nos. 
3,256,314 and 3,096,362 for other prior art processes. 
However, the above processes produce products which are the trimer of 
N-methyleneaminoacetonitrile and not the monomer. The trimeric products 
have a melting point of about 129.degree. C. and have the characteristic 
infrared spectrum shown in FIG. 2. In contradistinction, the process of 
this invention is directed to the production of the hitherto unknown 
monomeric form. This unique product has a melting point of about 
167.degree.-170.degree. C. and the infrared spectrum shown in FIG. 1. 
SUMMARY OF THE INVENTION 
N-methyleneaminoacetonitrile is produced in monomeric form by reacting 
glycinonitrile with formaldehyde, in the absence of ammonia. The process 
can be carried out by producing glycinonitrile in situ, removing unreacted 
ammonia from the reaction medium, and then further reacting it with 
formaldehyde. The process may be carried out at any convenient temperature 
range, but a temperature of about 0.degree. C. to about 50.degree. C. has 
been found to be useful. The product is insoluble in the aqueous reaction 
medium and is easily recovered by filtration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
N-methyleneaminoacetonitrile is the product of the reaction of equimolar 
amounts of formaldehyde and glycinonitrile in accordance with the 
following equation: 
EQU HCHO+H.sub.2 NCH.sub.2 CN.fwdarw.H.sub.2 C.dbd.NCH.sub.2 CN+H.sub.2 O 
While the equation appears to describe a relatively simple reaction, it is 
deceptive as generally it does not proceed as described but yields the 
trimeric form of N-methyleneaminoacetonitrile having the formula: 
##STR1## 
It has now been found that the monomeric form of this compound may be 
prepared directly from glycinonitrile and formaldehyde by carrying out the 
reaction in the absence of ammonia. If ammonia is permitted to be present 
in the reaction mixture, then only the trimeric form will be produced. It 
is not known why this should be the case, but it may be speculated that 
the presence of ammonia allows the production of an intermediate amine 
form which readily yields the trimer. As both glycinonitrile and 
formaldehyde are quite soluble in water, the reaction in conveniently 
carried out in an aqueous medium. Inasmuch as the product is only 
sparingly soluble in water it crystallizes from the aqueous reaction 
mixture during the course of the reaction and is easily recovered by 
filtration. 
The concentration of the glycinonitrile in the starting aqueous solution is 
not critical but should be high enough so that inconveniently large 
volumes of water are not used. Generally, concentrations in the range of 
about 20% to about 75% are useful, and it is most convenient to use any 
reasonable commercial concentration, such as from about 20% to about 40%. 
While the glycinonitrile solution may be prepared directly by admixing it 
with water, glycinonitrile is an unstable substance and preferably is 
prepared in situ immediately prior to its further reaction in accordance 
with this invention. 
Glycinonitrile has been prepared by a number of prior art processes. See 
e.g., U.S. Pat. Nos. 2,085,679, 3,167,582, and 3,875,221. Any convenient 
process may be utilized. For example, the following procedure may be used: 
Charge 219.8 g (3.75 moles) of 29% aqueous ammonia to a stirred 450 ml. 
pressure reactor. Preheat the reactor to 80.degree. C. and pump 71.3 g 
(0.75 mole) of 60% glycolonitrile into the reactor over a period of five 
minutes. Pump in 50 ml of water to wash the glycolonitrile solution into 
the reactor. After allowing the reaction to proceed for six minutes, cool 
the reactor, and recover the product. The reaction generally proceeds 
95-98% to completion under these conditions. 
The glycinonitrile must be free of ammonia. Inasmuch as the above process 
utilizes a large excess of ammonia, it is necessary that it be removed. 
While any convenient method may be utilized, it is simplest to merely 
evaporate the ammonia along with a portion of the water. This is generally 
done at reduced pressures so the temperature may be kept low to reduce the 
risk of decomposition of the glycinonitrile. The temperature is preferably 
kept below about 40.degree. C. Alternatively the ammonia could be 
neutralized with acid, removed using an ion exchange column, etc. However, 
these other methods are generally expensive and thus not commercially 
viable. 
The temperature of the reaction medium is then adjusted to the desired 
temperature range and maintained in that range for the duration of the 
reaction. A temperature in the range of about 0.degree. C. to about 
50.degree. C. has been found to be convenient. As the reaction is 
exothermic a means of cooling the reaction vessel is generally used, 
particularly at lower temperatures. Adding the formaldehyde slowly also 
helps keep the temperature down. 
Acetic acid may be optionally added at this time. Generally about 1/2 mole 
of acetic acid per mole of glycinonitrile may be used, but any amount in 
the range of 0 to about 2 moles of acetic acid per mole of glycinonitrile 
may be used. 
The formaldehyde is then introduced slowly (dropwise) into the reaction 
vessel. It is important that the formaldehyde be added slowly so as to 
control the rate of reaction and thus the temperature. 
The concentration of the formaldehyde is not critical and generally the 
commercial 40% product is suitable. The total formaldehyde should be 
equimolar with the glycinonitrile to produce the highest theoretical 
yield. In practice, a slight excess (about 5%) of formaldehyde is used to 
ensure that the reaction goes to completion. 
After the addition of the formaldehyde, the reaction mixture is maintained 
under reactive conditions for an additional period of time to ensure 
completeness of reaction. Times of one-half hour to one hour are generally 
sufficient. 
The product is then filtered, washed and dried. In order to characterize 
the resulting product, the melting point was determined by the capillary 
method. 
The melting point was determined to be 167.degree. C.-170.degree. C. When 
the familiar trimer was tested using the identical procedure, its melting 
point was 126.degree. C.-131.degree. C. 
The infrared spectrums of both the product of this invention and the prior 
art trimer were then determined by forming a KBr pellet containing 1 part 
of compound per 300 parts KBr. The spectrum was then determined in the 
usual way using a Perkin-Elmer 457 Infrared Spectrograph. 
The product of this invention yielded the spectrum of FIG. 1 while the 
prior art product yielded that of FIG. 2. A number of substantial 
differences appear between the two and in particular the spectrum of FIG. 
1 enhibits a strong band at 1670 cm.sup.-1, characteristic of the 
&gt;C.dbd.N-- bond while the spectrum of FIG. 2 does not. In order to provide 
a better understanding of this invention the following non-limiting 
examples are provided: 
EXAMPLE 1 
An aqueous glycinonitrile solution (0.75 mole) was prepared which was about 
12% glycinonitrile and 15% ammonia. Immediately after cooling the 
reaction, this solution was transferred to a single neck flask. The 
contents were evaporated to 110 g at 40.degree. C. under reduced pressure. 
The resulting solution contained approximately 38% glycinonitrile and no 
free ammonia. 
The solution was transferred to a three neck flask and cooled to 
0.degree.-5.degree. C. in an ice bath. While maintaining this temperature, 
21.5 ml (0.375 moles) of glacial acetic acid were introduced into the 
flask over a period of about one hour. A solution containing 52.1 g (0.765 
moles) of 44.1% formaldehyde (which had been previously clarified by 
filtration) and 21 ml of water was introduced into the flask dropwise over 
a period of two hours 46 minutes. A white solid began to form about two 
minutes after the addition was begun. The temperature was maintained with 
stirring for an additional one hour period, and a resulting product was 
filtered, washed with two 10 ml portions of water and dried in a vacuum 
desiccator. The product weighed 44.4 g. and had a melting point of 
167.degree. to 170.degree. C. Its infrared spectrum is shown as FIG. 1. 
Analysis for nitrogen by the Kjeldahl method gave 41.4% total nitrogen and 
20.4% saponifiable nitrogen. The theoretical values for this compound are 
41.2% total nitrogen and 20.6% saponifiable nitrogen. 
EXAMPLE 2 
Four batches of glycinonitrile were prepared in a similar manner to the 
procedure of Example 1. They were combined prior to the evaporation step. 
The resulting solution was divided into three portions of 147.7 g., which 
were stored in a frozen state. 
The first portion was heated to 40.degree. C. Then a solution containing 
71.7 g. (1.05 mole) of 44.1% formaldehyde and 15 ml water was added 
dropwise over a period of 43 min. The temperature remained at about 
40.degree. C. until crystallization began (about halfway through the 
addition). The solution then had to be cooled in an ice bath to prevent 
the temperature from rising due to heat of crystallization of the product. 
Upon completion of the addition, the mixture was stirred for about 1/2 
hour while heating to maintain the 40.degree. C. temperature. 
The mixture was then cooled to 5.degree. C. and filtered. The product was 
washed with two 10 ml portions of water and then dried in a vacuum 
desiccator. It was then further dried at 50.degree. C. in an oven. The 
yield was 55.7 g. of a tan product having a melting point of 
151.degree.-154.degree. C. and the infrared spectrum of FIG. 1. 
EXAMPLE 3 
Example 2 was repeated using a second portion of glycinonitrile except that 
the reaction was carried out at 30.degree. C. The product (yield 58.5 g.) 
was tan, had a melting point of 150.degree.-155.degree. C. and had the 
infrared spectrum of FIG. 1. 
EXAMPLE 4 
Example 2 was repeated using the third portion of glycinonitrile except 
that the reaction was carried out at 50.degree. C. The tan product (yield 
55.3 g.) had a melting point of 154.degree.-158.degree. C. and had the 
infrared spectrum of FIG. 1. 
The products of Examples 2, 3, and 4 were combined and analyzed for 
nitrogen by Kjeldahl distillation. The composite had 40.2% total N and 
21.0% saponifiable N. 
COMATIVE EXAMPLE 
This example follows the teaching of Organic Synthesis, Coll. Vol. 1, p. 
356 for the production of methyleneaminoacetonitrile. 
265.6 g. (3.78 moles) of 42.7% formaldehyde and 98.0 g. (1.96 moles) of 98% 
ammonium chloride were charged into a 1 liter flask. Chunks of dry ice 
were added to cool the mixture to less than about 5.degree. C. 76 ml (1.33 
moles) of glacial acetic acid was rapidly added. A solution of 107.0 g. 
(2.0 moles) of sodium cyanide in 170 ml of water was added dropwise over a 
period of 1/2 hour. The temperature was maintained at less than about 
15.degree. C. by the addition of dry ice. Halfway through the addition a 
slurry of product began to form. The reaction mixture was allowed to stand 
for 15 min. after the completion of the addition. The product was then 
filtered, reslurried in 300 ml of water, filtered again and washed with 
two 50 ml portions of water. 74.2 g. of a white, crystalline product were 
obtained. The melting point was 126.degree.-131.degree. C. and the product 
had the infrared spectrum of FIG. 2.