IL35657A - Fungicidal compositions containing acid addition salts of alkyl esters of benzimidazole carbamic acid - Google Patents

Description

35657/2 Fungicidal compositions containing acid addition salts of alkyl esters of benzimidazole carbamic acid B.I, DU PO.HT DE NEM0U1 AM) COMPANY 44 This invention consists in fungicidal compositions containing as an active ingredient an acid addition salt Of an alkyl ester of benzimidazole carbamio acid of the formula in either of its tautomeric forms wherein R is methyl, ethyl, Isopropyl or sec, butyl; A is an acid having an ionization constant greater than 1 X 10 ; such ' and/compositions containing an additional acid having an ionization constant greater than 1 X 10 , such that the final composition in spray concentration has a pH of 4 or less.

By a further feature of the Invention the compositions according to the invention may contain dispersants or crystallization inhibitors .

It is known that the methyl, ethyl, isopropyl and sec* butyl esters of 2-benzimidazolecarbamic acid are useful for the protective or curative control of fungus diseases on living plants, However, these compounds are quite Insoluble the in most solvents. It has been found that/acid addition salts aforesaid are soluble in water or in aqueous acids.

It has further been found that the disease control activity of compositions containing the acid addition salts disease control activity of compositions containing the alkyl esters as suoh.

The compositions according to the invention can be formed in a number of different ways. The benzimidazole carbamic acid esters form isolatable soluble salts with acids having an ionization constant greater than approximately 1 X 10 . However, when the solutions of such salts are diluted to concentrations suitable for disease control applications, the acidity is not sufficient to maintain the compounds in solution. Additional acid must be added to maintai the pH of the spray slurry below approximately 4, preferably 3*0 - 3*2. The additional acid may be supplied by admixing excess liquid or solid acid when the composition is prepared, or by adding the excess acid into the spray tank prior to the addition of the compound of formula I or II* The compositions according to the invention can also be made with weaker acids. Acids with ionization constants as low as 1.5 X 10 ' will react with the benzimidazole carbamic acid esters. However, in the presence of water ftEre must be an excess Of acid above a 1:1 mo]ar ratio of acid to benzimidazole carbamic acid ester and even then, in dilute acid solution, the reaction is very slow and incomplete*, Liquid acids or acids that form liquids with only minor amounts of water readily dissolve the benzimidazole; carbamic acid esters. For example, glacial acetio acid and 70 aqueous glycolic acid will dissolve approximately 10$ by weight of the parent benzimidazolecarbamic acid, methyl ester* Suoh solutions can subsequently be diluted with water down to a pH of about 3*0 without hydrolysis of the salt and separation of the original ester. When these H of the spray solution must again be less than about 4.0 and preferably lees than 3.2.

When the pH of the spray slurry rises above about 3.2 to , there ia a slow formation of insoluble crystals of the free benzimidazol© carbamic acid ester compounds and the enhancement of the disease control activity is reduced. As long as the pll is lower than about 4, the formation of the insoluble phase and t he consequent loss of activity is suficiently slow to have no practical significance.

It has now been further found that, surprisingly, when acidic solutions of the compositions according to the invention are mixed with certain dispersing agents, and the pH is then raised, the crystallization described above is inhibited and the material either remains in solution or possibly forms a colloidal suspension still possessing the improved fungus disease control activity.

To produce the compositions according to the in- the ven ion,/corresponding benzimidazole carbamic acid ester is combined with an acid* The strong mineral acid hydrochloric, sulfuric and nitric acid will react with the benzimidazole carbamic acid ester in water at a 1:1 molar ratio of acid to benzimidazole carbamic acid ester to form acid salts which can be isolated a solid, water soluble compounds. The reaction rate is improved by the use of some excess acid and by heating the reaction mixture. Slightly weaker acids like phosphoric acid exhibit very slow and incomplete reaction under the above conditions but salts may be prepared andisolated in at least A volatile strong acid like HOI may be added to a phosphoric aoid in water to improve the solution rate. After solution is complete the mix is evaporated to dryness and heated to volatilize the HCl. Alternatively, the benzlmidazole carbamic acid ester may be dissolved directly in S5# phosphoric acid with heating, to form supersaturated solutions hich will crystallize out the acid salt upon cooling. Since phosphoric acid is alcohol soluble, it is also possible to carry out the reaction in this medium rather than water.

Acids with low ionization constants, of the order of lO"""* can also form salts with the benzimidazoles carbamic acid esters, e.g« ith acetic or glycolio acid, if the benaimidazole carbamic acid ester is dissolved directly in the liquid acid with little or ho water present. In such cases, the solid salts are not readily isolated but, since additional a&td is necessary to maintain a pH below 4 when diluted to concentrations of use, such concentrated solutions in excess acid are practical and useful.

By selecting an appropriate medium for the reaction, eitheraqueous or organic and by direct o indirect means, almost -5 any acid with an ionization constant greater than 10 can be made to form an acid adduct with the benaimidazole carbamic acid esters.

After the acid salt has been formed, the compositions can bo prepared by either adding the aoid salt to excess acid in solution or by obtaining solid acid salt and formulating it with solid acids or adding to a solution of the acid salt certain surfaoe active agents.

. In a preferred embodiment, dilution water is pre-acidified to a pH of about 3.0 before the add salt is dissolved acid capable of producing a, pH of 3.0 or less, The acid used can be the same as used to form the Bait, or if desired, it can be a different* cid. Useful acids include hydrochloric, nitric, sulfuric, tartaric, citric and p-toluene sulfonic acidS†, The only limitations upon the acids used&r this pH adjustment are (1) that a pH of 3·0 can be attained and (2) that the acid be non*phytotoxic at the use level required.

The most practical limiting factor is the acid cost to reach the desired pBj* The amount of acid added should be suchf that when the composition is at spray concentration, usually 2,000 parts per million of active ingredient or less, the pH of the spraying solution should be pH 4 or lower, and preferably pH 3,2 or lower* If excess acid was used in forming the acid salt, it may not be necessary to add acid at this time. In order to obtain a pH of 3.2 or lower with a minimum weight of acid, the use of"stronger acids such as hydrochloric, nitric, and sulfuric acids is desirable, and the use of hydro-Chloric acid is preferred., In the most preferred aspect of the invention a solid acid salt with a strong mineral acid is isolated, then combined with a sufficient amount of an additional solid acid to maintain a low pH at the expected minimum use concentration. This dry powder form minimizes practical problems of packaging and handling.

All solid, aoictio agents that will give a pH of 4.0 or below at use concentration, i.e., spray concentration of 500 ppm or less of active ingredient, will function effectively in the solid mixtures to maintain the active acid considerations put some limit on the choice of acid. The final dilute composition must not he toxic to plants or animals, and the amount of additive .acid needed to reach the desired pH should be a minimum in order to produce compositions high in active, ingredient content with minimum cost. Preferred acidic materials include sodium or potassium acid sulfate, toluene or xylene sulfonic acid, dodecylbenzene sulfonic acids and organic acids like citric, tartaric and maleic acids. Others which might be used include benzoic, fumarlc, lactic, malonic, salicylic or picric acid.

The amounts needed wiH vary with the acid strength and with the concentration of the active fungicide used# The lower the concentration of active ingredient- needed, the higher the ratio, of acid to active ingredient required to attain the desired pH for making a wettable powder. Effective field concentrations of the acid salts are usually from about 0.0010$ to 0,2?*.

These dry compositions of the invention may also contain other additives common to many wettable powders such as wetting and dispersing agents, inorganic, diluents which act as grinding aids, fluffing and anti-caking agents or corrosion inhibitors to protect farm equipment. Neutral or acidic additives are preferred, to avoid the need for excessive amounts of added acid.. Kaolin clay, attapulgite and neutral fine synthetic silica are examples of suitable diluents. The uses of those conventional additives are illustrated in the examples.

As previously mentioned, in another embodiment, instead of the maintenance of a low pH, precipitation of the 2-benz-imldazolecarbamic acid, alkyl esters by hydrolysis of its presence in the solution of dispersing agents at the time the pH is increased. Best results have been obtained with desugared and partially desulfonated sodium, calcium, or ammonium ligninsulfonates. These are dispersants* rather than wetting agents, emulsifying agents or detergents. Y/ith these agents, 250 ppm will hold 150 ppra of the acid 3alt at a pH 7*5 for a least 24 hours in a non-visible state.

In the formulation of a dry mixture, the ratio of the surfactant to the active salt will depend upon the minimum active use level intended. Minimum use level for many fungi is about 80jppm, A 1:1 mixture of acid salt and surfactant, plus solid acid to give an initial pH of about 3·0 represents a minimum effective level of surfactant. Neutralization must take place after the active ingredient and surfactant are completely dissolved. A more generally useful use level of 150-400 ppm active ingredient made with this composition will then give 150-400 ppm surfactant.

It is not known whether this is a true solution or the active ingredient is in the form of Colloidal crystal too fine to produoe turbidity.

The biological activity remains as high as with true; solutions at low pH. Other dispersing agents such as solutions of methyl cellulose and polyvinyl alcohol at the, same weight rates also inhibit crystallization, but only for a ¾> hours at best, then turbidity develops. If these solutions are applied to plants before the turbidity develops, they show superior activity but their performance falls below that obtained with the low pH solutions, i.e.', the solutions produced with the excess of acid. secticide formulations, tfhich might flock out at low pH.

As mentioned previously, these compositions have outstanding disease control activity when employed to prevent or mitigate damage tp plants. They are particularl suited for the treatment of plants such as vegetables,, field crops, ornamental and fruit bearing tap s, Some of these oompo-sitions are also effective when applied directly to the soil for controlling soil born pathogenic plant fungi.

The compositions can be used to control plant diseases by applying one or more of the active ingredients to the material to be treated for the control of the fungus disease, at dosage sufficient to exert the desired action. In application to plants, fungus disease control is obtained in most instances by spraying th© composition on the plants at a concentration of from 0.001 to 0.200$ active ingredient in the spray. The optimum amount within this range is largely dependent upon well-known variables such as the , articular active ingredien selected, the method of application, and in the case of application to vegetation, the state and condition of growth of the vegetation to be treated and the climatic conditions.

These compositions can also contain carrier material or conditioning agents of the kind used and commonly referred to in the art as pesticldal adjuvants or modifiers, such as inert solids, organic liquid solvents, organic liquid or aqueous solvents, surfactants, non-phytotoxic spray oils, humec ants, enzymes or carbohydrates.

In view of the solubility of the compositions of the invention, water is a suitable, liquid diluent medium? however, the active ingredient oan be used in other mediums such as to 50$ of these liquid compositions. The liquid composition can he diluted to a further extent in large quantities of water to obtain application rates in the order of 500 ppm or less as are commonly used with aqueous sprays.

Where compositions of the invention contain surface active agents, these may be of the anionic, cationic or nonionic type. These agents include, for example, sodium oleate, sulfonated petroleum oils, alkyl aryl sulfonates, sodium lauryl sulfate, polyethylene oxide modified fatty esters, lignin sulfonates and the like. A detailed list of such agents is set forth in an article by McCutcheon in "Detergents and Emulsifiers," 1966 Annual.

Higher levels of surfactant relative to the active component often give unusual and unexpected beneficial results with the acid salt compounds.

The compositions according to the invention can contain, in addition, conventional insecticides, miticides, bacterio cides, nematocides, fungicides or other agricultural chemicals such as fruit set agents, fruit thinning compounds, fertilizer ingredients and the like.

The invention is illustrated by the following Examples.

EXAMPLE 1 Preparation of the hydrochloride of 2-benzimidazolecarbamic acid. methyl ester 14.64- Parts of concentrated hydrochloric acid (36 ) is added to 420 parts of water followed by 28 parts of 2-benzimidazolecarbamic acid, methyl ester. The mixture is heated to boiling, whereupon solution is complete. The solution is poured into shallow pans and evaporated to dryness at room temperature in a current of air. The last traces o e ° - 10a - 55657 /2 The yield is 37.5 parts of crystals of 2-benzlmidazole-carhamic acid, methyl ester hydrochloride dihydrate. Analysis of the crystals indicates: HOI found - 13.77$ Theoretical - 13. 6$ HgO found - 12.3 % Theoretical - 13.7 $ When this product is placed in waters it dissolves rapidly. Following solution* cloudiness develops rapidly and the original ester precipitates from solution. If the water is preacidified to a pit of 3 or below, no separation occurs and the solution remains stable.

EXAMPLE 2 Preparation of the acid sulfate of 2-benzimidazolecarbamic acid, methyl ester .32 Parts of concentrated sulfuric acid is diluted Isl with water, and then pasted with 10 parts of 2-benzimidazolecarbamic acid, methyl ester to obtain wetting of the hydrophobic solid. This paste is then flushed with water the into a beaker and/ olume made up to 600 parts. Upon heating to boiling, the solution is complete. The solution is filtered free of solid impurities and then evaporated at room temperature. Drying is completed at 45°C The pink, granular crystals obtained v;elghed 15.2 parts. The theoretical yield from 10 parts of the ester . would be 15.13 parts if unhydrated.

In order to obtain reasonable solution rates, an excess of acid is used. The excess acid In this case is provided by the ionization of the second hydrogen of the sulfuric acid.

When the acid sulfate is placed in water at the rate of 0,06$, it dissolves much more slowly than the corresponding hydrochloride, but does not show immediate hydrolysis. However, after 30 minutes crystals could be seen floating on the When the acid sulfa e is dissolved in water preacldifled to pH 2,9, the solution rate is still slow, but no separation occurs even after standing overnight.

AMPIJ2 3 Preparation of the nitrate of 2~benzimidazolecarbamic acid.. methyl, este MI , ... . |M| ||1M ηι. , . Ί , ..n r . 6.68 Parts of 70,5% nitric acid is added to 150 parts water and 10 parts of 2-benzimida2olecarbamic acid, methyl ester is then added. Solution of the ester is complete at the boiling point. The solution is then filtered free of solid impurities and evaporated in an air stream/ White whorls of needle-like crystals were xeoovered with a yield of 12.87 parts. Theoretical for the anhydrous salt is 13.3 parts.

Unlike the hydrochloride and the acld sulf te, this example illustrates that no excess acidity is needed to form the nitrate rapidly. When the nitrate salt Is added to water . at a rate of 0.06$, solution is very rapid but is followed lmmediat ely by hydrolysis and precipitation of the original ester. When the nitrate is added to water at pH 2.9, solution is complete and permanent.

Examples of solid, soluble compositions • 3SXAMPM3 4 2-benzimidazolecarbamic acid* methyl ester, hydrochloride hydrate 65$ tartaric aoid 3 , $ low viscosity polyvinyl alcohol 2.5% The above composition is mixed and micropulverized. ingredient When dissolved in water at a rate of 0.1 2 E . actlve er 400 Bign of crystal separation upon prolonged standing.

This composition provides excellent curative control of both apple scab and powdery mildew in a greenhouse ©valuation.

EXAMPLE 5 2-»benaimida¾olecarbamic acid, methyl ester acid sulfate 90≠ sodium acid sulfate mono- hydrate 10$ The above composition is prepared by mixing 2-benzlmidazolecarbamlc acid, methyl ester with aqueous sulfuric acid in a 1:1 molar ratio and dissolving in the manner previously d escribed &r the preparation of the acid sulfate salt. Prior to evaporation, sodium acid sulfate mono-hydrate is also dissolved, and the total mix is then evaporated to yield a crop of mixed crystals containing both aoid salts. ingredient Y/hen dissolved at 0.227 Kg. active/ er 400 liters, solution is complete andiree from hydrolysis, with a pH of 2.96.

Compounds which may be substituted ibr the 2-benzlmidazolecarbamio acid, methyl ester in the above example with like results are: 2-benzlmidazolecarbamic acid, ethyl ester 2-benaimidazolecarbamlc acid, isopropyl ester 2-benzimidazolecarbamio acid, aec. butyl ester EXAMPLE 6. ; 2-benzimidazolecarbamic acid, methyl ester (1*-1) adduct with HN05 35.8i¾ The above components are blended and micro- pulverized to give a water-soluble powder. When dissolved ingredient in water at a rate of 0.0568 Kg. active/per 400 liters, (approximately 150 ppm) the solution is free from hydrolysis and the pH is 2.92.

The above solution is diluted to 80 ppm, 16 ppm and 3.2 ppm with water preacidlfied with raalelc acid to prevent hydrolysis. A 4&-hour apple scap ouratlve te3t is then conducted. In this test, lroculated plants are held 48 hours for disease to develop before spraying to test for the ability to eradicate established disease (i.e. to cure the plants) . Results are as follows: Percent Control of Disease Active Concentration 80 ppm 16 ppm 3.2 ppm S-benzimldasolecarbamio 97.7 100 4 acid, methyl ester, nitrate EXAMPLE 2-benzimidazolecarbamic acid, methyl ester, bisulfate 25$ p-toluene sulfonic acid 2 diatomaceous silica ("Celite" 209) (inert antl-caking diluent) 50$ The above components are mixed and micro ulverized. ingredient When added to water at a rate of 0.114 Kg. active/per 400 liters, this mix is marked by a very r pid solution re|,te. pH of solution is 2.92, Examples of acidified tank mixtures

Claims (1)

1. insufficientOCRQuality