NO147303B - PROCEDURE FOR THE PREPARATION AND EXTRACTION OF HALOGENACETAMIDES. - Google Patents

Description

The present invention relates to a process for the production of halogenacetamides, particularly halogenacetanilides-> which are useful in agriculture, e.g. such as pesticides and plant growth regulators.

Halogen acylamides and haloacetanilides of the type described here have been prepared by a number of known methods. In a previously known method, described in US patent 2,863,752 (Re 26,961), N-substituted-2-haloacetanilides are prepared by reacting a primary or secondary amine with the acid chloride of haloacetic acid, typically in the presence of caustic soda to neutralize the halogen halide the byproduct. A similar method is described in German specification 1 90 3 198 where the intermediate products and end products are characterized by the N-substituent lower alkoxyethyl where the ethyl group can have one or two methyl groups attached to it.

In yet another known method described in US patent 3,574,746, N-substituted-N-cycloalkenyl-2-haloacetamides are prepared by haloacetylation of the corresponding N-substituted-cycloalkylimine in the presence of an acid acceptor.

Yet another method for the production of 2-haloacetanilides is described in US patents 3,442,945 and 3,547,620

wherein the appropriate starting material, an N-halomethyl-2-halogenacetanilide is reacted with the appropriate alcohol preferably in the presence of an acid scavenger. An analogous method is described in Canadian patent 867 769 where fluoroacylamino-trichloro-methyl-chloromethane is reacted with a thio compound of the formula Me-S-R where Me is halogen or alkali metal, since when the thio compound is used in free form it is necessary to use an acid binder, but when the thio compounds are used in the form of their salts, it is not necessary to add an acid binder.

The procedures in each of the above-mentioned US patents 2,863,752, 3,442,945 and 3,547,620 are also described in US patent 3,875,229 as useful in the preparation of 2-haloacetamides (also referred to as acylamines) exemplified by N-chloroacetyl-N- substituted (hydrogen, lower alkyl, alkoxymethyl, allyloxymethyl or methoxyethyl)-amino-indanes.

As relevant to the present invention involving the alcoholysis of N-haloalkyl-N-substituted-2-haloacylamide or the -2-haloacetanilide intermediate, the aforementioned publications (see, e.g., the above-mentioned US patents 3,442,945, 3,547 620 and 3,875,228) the preparation of the 2-haloacetanilide intermediate by the haloacetylation of the appropriate phenylazomethine. See also US patent 3,637,847.

In another method described in the Journal of the Chemical Society, Volume 1, pages 2087-2088 (1974), N-halogen-N-substituted amides and imides are methylated at the nitrogen-halogen bond using diazomethane to form the corresponding N- halomethyl-N-substituted-amide or -imide followed by condensation with nucleophilic compounds. An example of this process involves the reaction of N-chloro-N-methyl-2-chloroacetamide with diazomethane to form the corresponding N-chloromethyl-N-methyl-2-chloroacetamide, which can then be reacted with a nucleophilic compound.

In the above-mentioned US patent 3,574,746, example 47, respectively 54, N-chloromethyl- and N-bromomethyl-N-substituted-cycloalkenyl-2-haloacetamides are mentioned which are representative of this group of compounds which can serve as starting materials in the present method. Still other known methods for the preparation of some starting materials used in the present invention involve N-haloalkylation of the appropriate aniline followed by N-haloacylation. For example, N-2-chloroethyl or N-2-chloro-1-methylethyl-2-haloacetanilides can be prepared by reacting the corresponding aniline with 2-chloroethyl-p-toluenesulfonate, respectively 2-chloro-1-methylethyl-p-toluenesulfonate , followed by chloroacetylation. Still other methods of preparing the N-haloalkyl starting material involve reaction of the appropriate haloalkane, e.g. 1-chloro-2-bromoethane, with the appropriate aniline followed by chloroacetylation.

In the process for the preparation of N-substituted-2-haloacetanilides by alcoholysis of the corresponding N-haloalkyl 1-2-haloacetanilide starting compound, hydrogen halide is formed as a by-product which has an adverse effect not only on the yield of the desired product, but also has an adverse effect on the natural surroundings. Thus, as indicated in the above-mentioned US patents 3,442,945, 3,547,620 and 3,875,228, it is necessary that this alcoholysis be carried out in the presence of an acid binder. Examples of acid binders which have been used according to the state of the art include inorganic and organic phases such as alkali metal and alkaline earth metal hydroxides and carbonates, e.g. sodium and potassium hydroxide, sodium carbonate, etc., tertiary amines e.g. trimethyl- and triethylamines, pyridine and pyridine bases, ammonia, quaternary ammonium hydroxides and alcoholates; metal alcoholates, e.g. sodium and potassium methylates, -ethylates, etc. Both the hydrogen halide and the acid-binding agent can cause adverse side reactions which are undesirable, and therefore constitute a disadvantage of the known methods.

A significant disadvantage which is usually encountered in the above-mentioned known methods is that the acid binding agent reacts with the by-product hydrogen halide to form insoluble precipitates which must be separated from the reaction mixture and obtained by weighing. Separation of the desired product from waste by-products often requires and/or includes stripping off any solvent used, washing with water, steam stripping of hydrogen halide, dehydration, filtration and/or stabilization of product. Other purification methods include distillation of the fraction under negative or positive pressure, solvent extraction, film distillation, recrystallization, etc. For example, it is indicated in example 4 of each of the above-mentioned US patents 3,442,945 and 3,547,620 that in the production of N-( butoxymethyl)-2'-t-butyl-6'-methyl-2-chloro-acetanilide (common name "terbuchlor") forms the acid scavenger, i.e. triethylamine, a voluminous precipitate of fine needles of triethylamine hydrochloride which must be removed by washing with water, solvent stripping and filtration. The same problem is also described in the above-mentioned US patent 3,574,746 (see column 6, lines 18 - 33).

Another example, when ammonia is used as an acid binder in the production of 2',6<1->diethyl-N-(methoxy-methyl)-2-chloroacetanilide (common name "alachlor" and the active ingredient in the commercial herbicide "Lasso" ) ammonium chloride is formed as a solid by-product in large quantities and must be obtained by weighing.

In some cases, during or after the alcoholysis of the N-haloalkyl starting material, the bulk of the hydrogen halide by-product formed can be removed by conventional distillation. However, the hydrogen halide itself is a gaseous pollutant in the environment. In some cases, however, distillation of the alcohol reactant and the byproduct hydrogen halide leads to the formation of an alkyl halide with water, and water is detrimental to the yield of product. Furthermore, a certain percentage of the hydrogen halide remains in the reaction mixture and must be removed by an acid binder, whereby solid waste products are formed as mentioned above. For example, in earlier work on the alachlor process by a colleague of the inventor, attempts were made to remove HCl by-product with an excess of methanol by conventional vacuum distillation. However, these attempts involved a long delay, i.e. approx. 2 hours, of the N-chloromethyl intermediate and the final product (alachlor) for adverse effects of HC1, water and other by-products and led to greatly reduced yields of alachlor. It was then concluded that an acid binder should be used during or after the distillation stage, thereby relying on the accompanying disadvantages mentioned above.

With a view to energy conservation and environmental considerations with regard to the disposal of process waste, it has become very important to find new methods that eliminate or reduce to a minimum the adverse effect of all kinds of waste, i.e. solids, liquids and/or gases from chemical processes. In some cases, harmful by-products can be further processed to recycle the components. In other situations, the by-products can be purified or transferred to other useful products. However, each of the preceding treatments requires additional capital investment and further processing costs and energy consumption. It is therefore more desirable. as far as possible, to avoid the formation of products that are harmful to the environment.

Another problem in connection with previously known methods for the production of 2-halogenacetanilides is that they are batch processes, with consequent disadvantages, particularly on a commercial scale.

It is therefore an aim of the present invention to provide an improved method for the production of 2-haloacetamides or 2-haloacetanilides which overcomes the disadvantages of the previously known methods. In particular, it is an aim of the present invention to provide the advantages of a method which does not require an acid binder and which produces essentially no solid waste substances and thereby eliminate any raw material, equipment and separation costs and problems with the disposal of solid waste which is harmful to the environment - the lake.

Still other objectives of the present invention relate to a method which is continuous, simple and cheap to operate, conserves energy, reduces environmental pollution and still provides yields and purities which are as great or greater than previously known methods.

The present invention relates to a continuous process for the production of N,N-disubstituted-halogenacetamides, in particular compounds with the formula:

where R is the 2,6-dimethyl-l-cyclohexen-l-yl group or a substituted phenyl group with the formula: 12 3 where R , R and R independently of each other are hydrogen or a lower alkyl group, R 4 is a C-^-alkyl- , chloroalkyl-, alkoxy-alkyl- or chloroalkoxyalkyl group, allyl-, tetrahydrofuryl-, cyclohexyl- or cyclopropylmethyl group, R^ is bromomethyl, mono- or dichloromethyl, and a is 0 or 1, in the reaction of N-halomethyl acylamides with alcohols, and the method is characterized by the fact that an N-halomethyl-N-haloacetamide of the general formula: where X is chlorine or bromine, and R and R<5> are as indicated above, is reacted with an alcohol of the general formula:

where R 4 is as indicated above, in the absence of acid-binding agents at a temperature in the range from -25° to 175°C, the compound of formula (III) being used in excess, and that the reaction mixture is then led from this reaction zone to a separation zone, where a complex mixture of the by-product HX and the compound of formula (III) is rapidly separated from the product stream, which mainly contains the compound of formula (I), at a temperature between 50° and 175°C and a pressure between 1.3 and 400 mbar, and this sequence of reaction and separation steps is optionally carried out in a one-stage reaction separator vessel or repeated several times, after which the complex mixture of HX and the compound of formula (III) is optionally introduced into a recovery system in which the compound of formula (III) is removed from the hydrogen halide, is cleaned and fed back into the first and/or one or more further reaction zones.

With a two-stage working method, depending on turnover

of the N-halomethyl-N-haloacetamide of formula (II) with the alcohol of formula (III) in a first reaction zone and splitting the resulting reaction mixture in a separation zone into a complex

mixture, which contains the majority of the by-product HX and the compound (III), and a product stream which mainly contains the compound of formula (I) and unreacted compound of formula (II), the product stream from the first separation zone led into another reaction zone, in which optionally also a further amount of the compound of formula (III) is introduced for reaction with the unreacted compound of formula (II), and the reaction mixture from the second reaction zone is fed into another separation zone, where a complex mixture of practically the entire residual amount of the by-product HX and the compound of formula (III) is separated from the product stream comprising the compound of formula (I) with traces of impurities.

In the most preferred embodiment, the present method is used to prepare alachlor (2',6'-diethyl-N-(methoxymethyl)-2-chloroacetanilide) by reacting 2',6<1->diethyl-N-(chloromethyl)- 2-chloroacetanilide and methanol as described in example 1 below.

In preferred embodiments, the above reaction/separation process is repeated a number of times to ensure complete transfer of the compound of formula II to the compound of formula I. In the most preferred embodiment, the process is effectively carried out in two steps or reaction/separation series comprising : (A) reacting in a first reaction zone a compound of formula II with a compound of formula III; (B) passing an effluent stream of the reaction mixture from step (A) to a first separation zone from which

wherein most of the by-product HX is rapidly removed as a complex with the compound of formula III and a product stream comprising predominantly a compound of formula I and unreacted compound of formula II;

(C) leading said product stream from the first separation zone to another reaction zone in which also

introducing a further amount of the compound of formula III to react with said unreacted compound of formula II;

(D) passing an effluent stream of the reaction mixture from step (C) to another separation zone from which

substantially all of the remaining by-product HX is quickly removed as a complex with the compound of formula III, and a product stream comprising the compound of formula I and traces of impurities.

Significant features of the present process include: (1) elimination of an added base as used in the known processes as an acid scavenger for liberated hydrogen halide; and simultaneously (2) elimination of recovery systems for the neutralization by-product of (1) and thus elimination from the surrounding environment of the by-product itself, and (3) separation, preferably immediately, and usually within less than 0.5 minutes from the equilibrium of the reaction mixture, of by-product hydrogen halide as a complex with the compound of formula III in the product separation operation or operations of the process.

In preferred embodiments of the invention are

the molar ratio of the compound of formula III to the compound of formula II in step A greater than 1:1 and usually in the range from 2:1 to 100:1, and in the case of the alachlor process, in the range from 2:1 to 10 :1, and preferably from 4:1 to 5:1.

The reaction temperatures in step (A) will depend on the

particular reactants and/or solvents or diluents used. In general, these temperatures will be the temperatures at which mixtures of the alcohols^ of formula III and/or solvents or diluents form complexes, e.g. azeotropic mixtures, with by-product hydrogen halide without particular decomposition of the reactant compound of formula II or the desired product of formula I due to the reaction with hydrogen halide. In general, a temperature in the range from -25° to 125° C or higher is used depending on the melting points and boiling points of the reactants.

In the embodiments of the invention which involve a series of reaction/separation rows or steps, the hydrogen halide concentration is greatly reduced in subsequent reaction zones, and therefore the respective reaction temperatures are generally somewhat higher than the temperatures used in step (A) in order to driving the reaction of the unreacted compound of formula II to completion with additional alcohol. The temperatures in the second and possibly following reaction zones are generally in the range from -25° to 175° C or higher if necessary.

Suitable temperatures and pressures in the separation zone or zones are, respectively, in the ranges of 50° C. to 175° C. and 1.0 to 300 mm Hg absolute, depending on the boiling point of the particular compound of formula III.

Example 1

This example describes the application of the present method in the production of alachlor. This process is effectively carried out in a two-step reaction/separation sequence as follows: Step 1. Molten (45 - 55° C) 2',6<1->diethyl-N-chloromethyl-2-chloroacetanilide is fed into a in series mixing at a rate of 46.67 kg/h and is mixed with substantially anhydrous methanol which is fed to the mixer at a rate of 27.24 kg/h. The mixture is pumped through a thermostatically controlled tube reactor kept at 40 - 45° C of sufficient length to give a residence time of at least 30 minutes. The reaction gives a yield of approx. 92% 2<1>,6'-diethyl-N-(methoxymethyl)-2-chloroacetanilide (alachlor) and hydrogen chloride based on the N-chloromethyl starting material. The HC1 formed is dissolved in an excess of methanol. The reactor effluent is fed to a falling film evaporator operating at 100° C and 30 mm Hg absolute. A complex is removed and fed to a methanol recovery system.

Step 2. The product stream from the evaporator in step 1 comprising predominantly alachlor and unreacted 2<1>,6<1->diethyl-N-(chloromethyl)-2-chloroacetanilide is fed to another in-line mixer to which a further quantity of methanol at a rate of 2 7.24 kg/h. The mixture is then fed to another reaction zone which also comprises a thermostatically controlled tubular reactor held at 60 - 65° C to give a residence time of 30 minutes. The effluent from this reactor is fed to another falling film evaporator, operating at 100° C. and 30 mm Hg absolute, from which a complex of methanol and substantially all residual HC1 is removed. The methanol/HCl complex from the second-stage evaporator is mixed with the methanol/HCl complex from the evaporator in stage 1 and fed to a methanol recovery system from which anhydrous methanol is recovered and recycled to stage 1.

The product stream from the evaporator in stage 2 comprises alachlor in essentially quantitative yield and more than 95% purity together with smaller amounts of impurities. This alachlor can be used effectively as a herbicide as it is prepared.

As can be seen from the preceding example, the reaction/separation process sequence in step 1 itself gives alachlor in high yield. Under optimal conditions with regard to reactant purities and concentrations, temperatures, residence times in the reactor and separation zones, etc., at least one reaction/separation process sequence corresponding to the step 1 operation would therefore be sufficient to provide a commercial quality of alachlor or other compounds within the framework of formula I.

Example 2

This example describes the preparation of 2-chloro-2',6<1->diethyl-N-(ethoxymethyl)-acetanilide.

About 5.5 g (0.02 mol) of 2-chloro-2',6'-diethyl-N-(chloromethyl)-acetanilide are dissolved in 25 ml of ethanol and left in a 45° C bath for 30 minutes. Excess ethanol was quickly removed on a rotary vacuum evaporator at 50°C and 10 mm Hg. 25 ml of fresh ethanol was added to the remaining oil and the mixture was kept at 65°C for 30 minutes. Again, excess ethanol was removed using a rotary evaporator. 5.80 g of a pale amber colored oil was obtained which analyzed (by gas chromatography) 92.8% of the desired product and 1.7% 2-chloro-2<1>,6'-diethylacetanilide (by-product). Yield of product was 94.5%.

Example 3

By following the same procedure, operating conditions and amounts of reactants as described in example 2, but by using isopropanol instead of ethanol, 5.92 g of product was obtained, a light amber colored oil which analyzed 90.2% 2', 6'-diethyl-N-(isopropoxymethyl)-2-chloroacetanilide (89.4% yield) and 1.8% of the secondary amide byproduct, 2',6'-diethyl-2-chloroacetanilide.

Example 4

By following the same procedure as described in examples 2 and 3, but by using 1-propanol as the reactant alcohol, 5.66 g of lemon yellow oil was obtained which analyzed 92.8%

(87.9% yield) of 2<1>,6<1->diethyl-N-(n-propoxymethyl)-2-chloroacetanilide and 1.2% of the corresponding secondary amide by-product.

Example 5

The same procedure as described in examples 2-4 was used in this example, but isobutanol was used as the reactant alcohol, and 6.20 g of an oil product was obtained which analyzed 96.4% (97% yield) of 2<1>.6 '-diethyl-N-(isobutoxy-methyl)-2-chloroacetanilide and 3% of the corresponding secondary amide by-product.

Example 6

By repeating the procedure in examples 2-5, but by using 2-chloroethanol as reactant alcohol, 6.96 g of a light amber colored oil was obtained which analyzed 86.0% (94.0% yield) of 2', 6<1->diethyl-N-(chloroethoxymethyl)-2-chloroacetanilide.

Example 7

By following the same procedure as described in examples 2-6, but by using n-butanol as reactant alcohol, 6.18 g of pale lemon yellow oil was obtained which analyzed 98.8% (99% yield) of 2<1>.6 <1->diethyl-N-(n-butoxymethyl)-2-chloroacetanilide (ie, butachlor) and 1% of the corresponding secondary amine by-product.

In the above examples, NMR analysis indicated that the respective products were consistent with the expected chemical structure.

To further demonstrate the advantages of the present invention and its unexpected nature, the following discussion and additional experimental data are provided in Examples 8-12.

The reaction between compounds such as those represented by formula II and formula III is a reversible second-order reaction. Equation 1 below, exemplified by the reaction in Example 1, illustrates the reaction:

As the reaction is reversible, an equilibrium state occurs; this equilibrium is affected by and depends directly on various factors, e.g. alcohol concentration and/or by-product hydrogen halide concentration. For example, in equation (1), since the alcohol concentration (b), and thus the reactant ratio (b):(a), increases (to a given practical maximum), the equation will shift to the right due to further transfer of starting material (a) and thus form more product (c) and hydrogen halide by-product (d).

Another way to shift the equilibrium of equation (1)

on the right is to remove the hydrogen halide (d), which can be done by adding an acid binder, e.g. tertiary amines such as

triethylamine, as in US Patents 3,547,620, 3,442,945 and Canadian Patent 86,7769 mentioned above. The use of acid binding materials, however, entails other disadvantages as discussed above.

The aforementioned Canadian patent 867,769 suggests that when the thio compound starting material is in the form of an alkali metal salt, the acid binding material is unnecessary. The obvious reason for this is that the mentioned salts themselves produce the basic medium, favorable for the particular reaction described in the mentioned patent. When, on the other hand, the starting thio compound is used in free form, it is necessary to use an acid binder to bind the hydrogen chloride by-product.

Although the method set forth in the above-mentioned US patents 3,547,620 and 3,442,945 is described as preferably being carried out in the presence of an acid binding agent, as exemplified in all the given examples), it is inferred that the same method can be carried out without the addition of an acid binder. However, as mentioned earlier in the discussion of the prior art, attempts to carry out the process described in US patents 3,442,945 and 3,547,620 to prepare the preferred product alachlor without an acid scavenger to remove the byproduct hydrogen halide, led to greatly reduced yields of alachlor .

In order to further determine the comparable results when carrying out the method described in US patents 3,442,945 and 3,547,620 without an acid binder vis-à-vis the present method, the methods described in examples 8-12 below have been carried out. In each of these examples, the N-chloromethyl-2-chloroacetanilide starting material was prepared by reacting the correspondingly substituted N-methyleneaniline and haloacetyl halide as described in the two aforementioned US patents.

Example 8

This example describes the preparation of 2-chloro-2<1>,6<1->diethyl-N-(methoxymethyl)-acetanilide (alachlor) as set forth in example 5 of US patents 3,547,620 and 3,442,945.

100 g 2-chloro-2<1>,6'-diethyl-N-(chloromethyl)-acetanilide

who analyzed 96.0% (0.350 mol) dissolved in approx. 70 g of benzene was added to 65.8 g (2.054 mol) of methanol. An exothermic reaction occurred during the addition. The reaction mixture was refluxed (at 63° C.) and an excess (about 63.3 g) of triethylaraine was added dropwise over 1.5 hours. During this addition, the temperature rose to approx. 70° C where it was maintained for approx. 10 minutes after the end of the triethylamine addition. After cooling to 30° C., the reaction mixture was washed with 2 x 170 ml of water. The product, in a heavy oily layer, was stripped of solvent and dehydrated by vacuum distillation to a final temperature in the distillation vessel of approx. 70° C at 1 mm Hg. The remaining amber oil weighed 96.15 g and assayed 90.4% product and 4.9% 2-chloro-2',61-diethylacetanilide (by-product) by gas chromatography. There was no unconverted starting material in the product. The yield of product was 92.0%.

Example 9

This example describes the preparation of alachlor as indicated in example 5 of US patents 3,547,620 and 3,442,945, but without the use of an acid binder.

100 g 2-chloro-2',6'-diethyl-N-(chloromethyl)-acetanilide

who analyzed 96.0% (0.350 mol) dissolved in approx. 70 g of benzene was added to 66.9 g of methanol (2.059 mol). Upon addition, an exothermic reaction occurred and the reaction mixture was further heated under reflux (63° C.) for 1 hour. No acid scavenger was added. After refluxing, excess methanol and solvent were removed by vacuum distillation until a final temperature in the distillation vessel of 70° C. at 1 mm Hg. About. 96.20 g of a pale lemon yellow oil was obtained which contained (by gas chromatographic analysis) 83.7% product, 7.5% by-product 2-chloro-2<1>,6'-diethylacetanilide and 5.5% unreacted out-

corridor material. The product yield was 85.8%.

As will be seen, the omission of acid binder in this example led to a reduction in yield of 6.2%. In this procedure, the reaction did not go to completion

right. As a result, the byproduct HCl reduced the carryovers and the unreacted starting material was found as a contaminant in the product.

Example 10

This example describes the production of alachlor as stated in example 5 of the aforementioned US patents 3,547,620 and 3,442,945, but without the use of an acid binder and under optimal temperature conditions.

100 g of 2-chloro-2",6'-diethyl-N-(chloromethyl)-acetanilide which assayed 96.0% (0.350 mol) dissolved in about 70 g of benzene was added to 66 g (2.0)59 mol ) methanol. An exothermic reaction occurred which raised the temperature of the reaction mixture to 45°C where it was held for 1 hour. No acid scavenger was added. Excess methanol and solvent were removed under vacuum distillation to a final temperature in the still of about 80°C at 1 mm Hg. About 96.20 g of oil was recovered which analyzed (by gas chromatography) 85.8% product, 6.2% by-product, 2-chloro-2',6<1->diethyl-acetanilide and about 4, 6% unconverted starting material.The yield of product was 87.4%.

By optimizing the reaction conditions in the absence of

an acid binder, an increase in product quality (2.7%) and yield (1.6%) was achieved, but the basic problem, i.e. incomplete reaction, was still not solved.

Example 11

This example describes the preparation of alachlor by the present method according to the embodiment which uses a single-stage reactor. The starting materials used here were the same as those used in Examples 8-10. 10 g of 2-chloro-2',6'-diethyl-N-(chloromethyl)-acetanilide assaying 96.0% (0.035 mol) was added to approx. 6.0 g (0.1873 mol) methanol. An exothermic reaction occurred which raised the temperature of the reaction mixture to approx. 45° C where it was maintained for 30 minutes. Excess methanol was removed rapidly on a rotary vacuum evaporator to a final still temperature of 70°C at 1 mm Hg. You got approx.

9.80 g pale lemon yellow oil which analyzed 91.0% product, 1.7% byproduct 2-chloro-2',6'-diethylacetanilide, and 2.4% unreacted starting material by gas chromatography. The yield of product was 94.4%.

By using only a single step, the quality and yield of the desired product is thus significantly improved over that according to the state of the art, despite the fact that the reaction was not complete (2.4% starting material in the product). Comparison with Examples 8, 9 and 10 shows an obvious improvement, although no acid binder was used.

Example 12

This example describes the preparation of alachlor in the absence of added acid scavenger according to the preferred embodiment of the present process using a multi-stage reactor.

10 g of 2-chloro-2<1>,6'-diethyl-N-(chloromethyl)-acetanilide assaying 96.0% (0.0350 mol) was dissolved in 6.0 g (0.1873 mol) of methanol. An exothermic reaction occurred which raised the temperature to 45° C where it was held for 1/2 hour. Excess methanol was removed rapidly on a rotary vacuum evaporator to a final still temperature of 45°C at 1 mm Hg. Another addition of 6.0 g (0.1873 mol) of fresh methanol was

■ added, and the reaction mixture was heated to 65° C. and held at this temperature for 1/2 hour. Excess methanol was removed as before and approx. 9.80 g of pale lemon yellow oil was recovered which assayed 95.8% product, 1.4% 2-chloro-2',6<1->diethylacetanilide and no unreacted starting material. The yield of product was 9 9.4%.

A summary of the comparison results for the methods described in Examples 8-12 is shown in the following table. In this table, the "starting material" is unreacted 2',6'-diethyl-N-(chloromethyl)-2-chloroacetanilide and "byproduct" refers to 2',6'-diethyl-2-chloroacetanilide, which is the essential acetanilide- by-product of the process in each of these examples. Smaller amounts of acetanilide and other byproducts are formed in addition to the large amounts of hydrogen halide evolved, and in the case of Example 8, triethylamine hydrochloride formed neutralization byproduct. The product yield percentages are calculated here for the 2',6'-diethyl-N-(chloromethyl)-2-chloroacetanilide starting material.

An analysis of data in the above table shows as the prominent features and decided advantages of the present method, i.e. examples 11 and 12, vis-a-vis the method according to the state of the art exemplified in examples 8-10; (1) considerable increase in yield of alachlor; (2) improvement in the purity of alachlor; (3) markedly reduced yield of by-product; (4) increased transfer of starting material when working without added base; and (5) absence of solid neutralization product present in large amounts in the base-added process of Example 8 which represents the best prior known process for making alachlor. These technical advantages are in addition to the previously mentioned economic and ecological advantages.

In carrying out the present method, no solvent is required, but in many cases a solvent or diluent can be used to moderate the reaction and/or assist in the dissolution, dispersion and/or recovery of reactants, by-products and products. Suitable solvents or diluents include those which are inert under the conditions necessary for the reaction, such as petroleum ether, carbon tetrachloride, aliphatic and aromatic hydrocarbons, e.g. hexane, benzene, toluene, xylenes, etc, and halo-generated hydrocarbons, e.g. monochlorobenzene.

An advantage of the present method is that the reactant of formula III can be easily separated from its complex with by-product hydrogen halide, purified and recycled to one or more reaction steps in the process. Similarly, the hydrogen halide itself can be readily recovered for use in many useful commercial operations, e.g. pickling of metals, oxychlorinations, electrolysis to elemental chlorine and hydrogen, etc., or otherwise obtained by weighing without harming the environment.

In a suitable feedstock recovery/recycling system, exemplified with respect to the methanol/HCl complex formed in the alachlor process described in Examples 1, 11 and 12 above, the methanol/HCl complex from the separation stage or stages is fed to a distillation system from which pure - set methanol.

Furthermore, with regard to the present method will;

although technical grade reactants, i.e. of the compounds of formulas II and III, are suitable, higher purities of

these reactants give higher quality compounds of formula I. Although in some cases the compounds of formula III, e.g. methanol, containing smaller amounts of water can be used, it is more advantageous to use anhydrous compounds because water can cause hydrolysis of the reactants of formula II and lead to the decomposed product of formula I. However, it will be understood that in special cases where R is hydrogen , water itself can be used as the compound of formula III to form some compounds of formula I by hydrolysis of the N-haloalkyl intermediate. For example, it has been stated in the prior art that 2'-t-butyl-6<1->ethyl-N-(chloromethyl)-2-chloroacetanilide is hydrolyzed with water in the presence of an acid binder to form the corresponding N-hydroxymethyl compound which is useful as a herbicide (see eg Example 1 in British Patent 1,088,397).

Accordingly, it will be seen that in some embodiments of the present process the presence of some water may be detrimental to the product yield, but not in other embodiments, depending on the reactivity of the water with other reagents and end products as will be understood by those skilled in the art. Similarly, it is preferred, as hydrogen halide adversely affects product quality,

to use reactants which are essentially free of hydrogen halides such as HCl.

The compounds of formula I produced by the present method are known compounds. Representative compounds of formula I are set forth in prior publications described above under the prior art and other publications not cited.

Claims (9)

1. Procedure for the production and extraction of haloacetamides with the general formula: where R is the 2,6-dimethyl-l-cyclohexen-l-yl group or a substituted phenyl group with the formula: 12 3 where R , R and R independently of each other are hydrogen or a lower alkyl group, R<4>is a C^_^ alkyl, chloroalkyl, alkoxyalkyl or chloroalkylalkyl group, allyl, tetrahydrofuryl, cyclohexyl or cyclopropylmethyl group , R is bromomethyl, mono- or dichloromethyl, and a is 0 or 1, in the reaction of N-halomethyl acylamides with alcohols, characterized in that an N-halomethyl-N-haloacetamide with the general formula: where X is chlorine or bromine, and R and R<5> are as indicated above, is reacted with an alcohol of the general formula: where R 4 is as indicated above, in the absence of acid-binding agents at a temperature in the range from -25° to 175°C, the compound of formula (III) being used in excess, and that the reaction mixture is then passed from this reaction zone to a separation zone, where a complex mixture of the by-product HX and the compound of formula (III) is rapidly separated from the product stream, which mainly contains the compound of formula (I), at a temperature between 50° and 175°C and a pressure between 1.3 and 400 mbar, and this sequence of reaction and separation steps is optionally carried out in a one-stage reaction separator vessel or repeated several times, after which the complex mixture of HX and the compound of formula (III) is optionally introduced into a recovery system in which the compound of formula (III) is removed from the hydrogen halide, purified and fed back into the first and/or one or more further reaction zones. 2. Method according to claim 1, characterized in that in a two-step working method, after reacting the N-halomethyl-N-haloacetamide of formula (II) with the alcohol of formula (III) in a first reaction zone and dividing the formed reaction mixture into a separation zone to a complex mixture, containing the majority of the by-product HX and the compound (III), and a product stream which mainly contains the compound of formula (I) and unreacted compound of formula (II), the product stream from the first separation zone led into another reaction zone, in which possibly also a further amount of the compound of formula (III) is introduced for reaction with the unreacted compound of formula (II), and the reaction mixture from the second reaction zone is fed into another separation zone, where a complex mixture of practically the entire residual quantity of the by-product HX and the compound of formula (III) is separated from the product stream comprising the compound of formula (I) with traces of impurities. 3. Method according to claim 2, characterized in that the temperature in the first reaction zone is kept between -25° and 125°C and in the second reaction zone between -25° and 175°C. 4. Method according to claim 1, characterized in that the alcohol of formula (III) is used in a 2- to 100-fold molar excess. 5. Method according to claim 2, characterized in that the complex mixture of HX and the compound of formula (III) is fed from the second separation zone into a recovery system, in which the compound of formula (III) is separated from the hydrogen halide, purified and fed back to the first and/or second reaction zone. Process according to claim 1 for the production of 2',6'-diethyl-N-(methoxymethyl)-2-chloroacetanilide, characterized in that methanol is reacted with 2<1>,6<1->diethyl-N-(chloromethyl)-2 -chloroacetanilide in a molar ratio of 2 to 100:1 at a temperature between 25 and 65°C for 15 to 30 minutes in the absence of an acid binder and that the reaction mixture is introduced into a separation zone from which a complex mixture of HC1 and methanol from a product stream which mainly contains the end product, this sequence of reaction and separation steps possibly being repeated several times. 7. Method according to claim 6, characterized in that in a first reaction step methanol is reacted with 2',6'-diethyl-N-(chloromethyl)-2-chloroacetanilide in a molar ratio of 2 to 10:1, and that the first separation step is a short distillation zone , where the temperature is maintained between 50° and 100°C and the pressure between 40 and 400 mbar, whereby a complex mixture of methanol and most of the HCl by-product and a product stream containing predominantly 2<1>,6<1->diethyl-N -(methoxymethyl)-2-chloroacetanilide and unreacted 2<1>,6<1->diethyl-N-(chloromethyl)-2-chloroacetanilide are removed, the product stream from this first separation zone being passed to another reaction zone at 25° to 65° C, where a further amount of methanol is also added for reaction with the unreacted 2<1>,6'-diethyl-N-(chloromethyl)-2-chloroacetanilide, and in an amount corresponding to that in the first reaction zone in the time period of 15 to 30 minutes amount consumed, and that the reaction mixture is fed from the second reaction zone into another short distillation zone, which works under the same conditions as the first short distillation zone, where a complex mixture of methanol and virtually all of the remaining HCl by-product is separated from a product stream containing mainly 2',6'-diethyl-N-(methoxymethyl)-2-chloroacetanilide and traces of pollutants. 8. Method according to claim 6, characterized in that the complex mixture of methanol and HC1 from the separation steps is combined and fed into a methanol recovery system from which HC1 is removed and the recovered methanol is purified and returned to the first and/or second reaction step. 9. Method according to claim 6, characterized in that the residence time of the reaction mixture in the short distillation zones is less than 30 seconds.