IL22048A - Herbicidal compositions - Google Patents

Description

This invention relates to herbicides and herbicidal compositions, and to their use in the -control or destruction of uhdesired vegetation. ∑t is an object ©f the invention to provide herbicide© and herbicidal compositions capable of effecting extensive and long-lasting control of undesirable vegetation, including the killing of plant roots and of seedlings at or soon after sprouting, and generally for the non-selective control of mono- and dicotylge&onous plants, and particularly for nonselective defoliation or kill of brush and trees. the invention is based on the discovery that the tri- and monohydrates pentafluorochloroaeetone, Q ^QOGF^Ql and hexafluoroacetone, GF_00eF_ have excellent herbicidal 3 3 properties; ¾der normal conditions, pentafluorochloroaeetone is a gaseous compound having a boiling point of + 8°C., and a melting point of -133°°. , and hexafluoroacetone is a gaseous compound having a boiling point of -27°C., and a melting point of -129°C ¾e tito monohydrates are normally solids which melt at 40°C in the case of hexafluoroacetone monohydrate and 26-26.5°C in the case of pentafluorochloroaeetone monohydrate. i e trihydrates are at atmospheric pressure water-white liquids within the temperature range bounded by the melting point which is below 0°G (-11°C in the case of hexafluoroacetone trihydrate and -5°0 in the case of pentafluorochloroaeetone trihydrate) and boiling point (about 105°G in both cases).

Our recent study of the freezing characteristics of the liquids has indicated that they are i fact reproducible constant boiling mixtures having empirical formulae appoximating to trihydrates. In many respect they behave as true compounds, Each, monohydrate can be made by reacting the ketone ¾rith suffieeht water or sufficient trihydrate to form the monohydrate.

Bach trihydrate can be made be reacting the ketone or its monohydrate with sufficient water to form the trihydrate.

Alternatively, eaeh trihydrate can be made by heatin the monohydrate to disproportionate it to trihydrate and ketone. This occurs at temperatures above about 40°C.

The following Examples illustrate the production of the hydrates. %© apparatus employed included a single-necked flask provided with a magnetic stirrer, and at the top of the neck with a dry ice-acetone col finger. Incoming reactants charged oonsieted of water and hexa luoroacetone. About 92.5 g. (5.144 mol.) of wa e were introduced into the flask. With constant stirring of the flask contents, hexafluo oacetone vapour was fed into the cold finger in which it condensed, and from which it dropped as liquid into the water. During a period of about 6 hours, about 577 g. (3.48 mol.) of hexafluoroacetone were thus fed into the flask, and were absorbed in the water. During addition of the hexafluoroacetone, the contents of the flask warmed up to about 40°C. At this stage, the flask contained about 680 g. of liquid material, and the mol ratio of hexafluoroacetone to water was about 1 : 1.48* The contents of the flask were split into two approximatel equal fractions each containing about 1.74 mol of hexafluoroacetone and about 2.57 niol of water. To the first fraction of about 344 g. an additional 157 g. (0.95 mol.) of hexafluoroacetone were added in the manner described above in a suitable flask equipped with a cold finger, when this amount had been added no more was absorbed. The temperature in the flask was about 15-30°C. The contents of the flask comprised a slightly moist mass composed of long, needle-like white solid crystals containing hexafluoroacetone and water in a mol ratio of about 2.69 : 2.57 and having a melting point of about 40°C, consistuted by the monohydrate, CF,C0CF_.H 0. The neck of the 3 3 -2 flask was connected to a distillation column having a cooled head. On heating the contents of the flask gradually up to a final pot temperature a little below 105°C., the solids melted at about 40°C, and there was distilled over a gas which, when condensed in a dry ice trap, gave about 196 g. (I.l8 mol.) of water white liquid. The gas discharged from the distillation column during distillation was subjected to infrared analysis, which showed the C=0 group and otherwise the known pattern of hexafluoroacetone. The condensate obtained on cooling the gas was distilled in a separate operation, and found to have the b.p. of anhydrous hexafluoroacetone -27°C.

When the discharge of hexafluoroscetone from the top of the distillation column ceased, t e latter was put on reflux maintained at 105°G. On ta&e-off of product from the colum » the temperature, including the pot temperature, remained at about 105°© over the entire distillation operation until the pot was substantially dry and empty. During distillation there was produced an off-gas which when condensed at about room temperature, gave about 146 g. (0.65 mol.) ©f water white liquid. The latter was analyaed by nuclear magnetic resonance and was found to contain 2.9 (by weight) of fluorine and 2.68 of hydrogen, the corresponding theoretical values for being 51.8 and 2.73¾. ¾?he found values indicate about 71.1 hexafluoroace one and 24*3$ H^ , as compared with theoretical values of about 75.5$- and 24.5^ respectively. In the formula Q^SOCSP^.^O, χ calculated on the basis of the hydrogen analysis equals 2.92 mol and on the basis of the fluorine analysis equals 2.73 mol. The Infrared absorption spectrum showed the presence of fluorine atoms and hydroxyl groups. Phase studies showed that th© substance was a constant boiling composition corresponding to Further, hexafluoroacetone was quantitatively recovered by distilling a sample of the product in the presence of concentrated sulphuric acid. ¾hus, on being heated, the substantially solid crystalline monohydrate, disproportionated to hexafluoroaeetone, 0F¾0OCF_, and hexafluoroacetone trihydrate, 3 C _S00_.1_0, which under normal conditions is a water white li uid constituting a definite, stable distillable material having a boiling point of about 105°G. , miscible with water in all proportions, and having a specific gravity at O ■ r O C, of about l.o, and a melting point of about -11 C.

EXAMPLE B To the second fraction of Example A, i.e. about 336 g. of liquid material containing about 1.74 mol of hexaf luoroacetone and about 2,57 mol of water at about room temperature, there was added about 46 g. (2.56 mol.) of water. The result was a water white liquid containing hexaf luoroacetone and water in a raol ratio of about I.74 to about 5.13, corresponding to the trihydrate, CF COCF ,.3H 0. This liquor was distilled, and boiled constantly at about 105°C. until the pot was substantially dry and empty showing that the distillate was the same as the pot residue distilled at about 105°C., in Example A. Infrared analysis of the distillate of Example B showed it to be the same as the hexaf luoroacetone trihydrate produced in Example A. Ml 11 11 ni»— ■ i.ni rptf'iiii'Ut-Uiii iJiuvJ. li-Hi1 flurilit-u μιυυϋ ll Ll.u μιυιΐυυΐ uf Djuuipl . D The following Examples illustrate the production of the mono- and trihydrates of pentafluorochloroacetone.

EXAMPLE C About 195 g. of pentafluorochloroacetone were condensed into a flask cooled in a dry ice-acetone slush. About l8 g, of water were added gradually to the pentafluorochloroacetone at a temperature a little above 0°C; when all the water had been added there was formed in the flask a slightly moist mass composed of white solid crystals containing pentafluorochloroacetone and water in a mol ratio of 1.07:1, corresponding substantially to the monohydrate, CF COCF Cl.H 0, This material was found to have a melting point 3 « 2 of 26.Ο - 26.5°C. The neck of the flask was connected to a distillation coluran having a cooled head. On heating up the flask contents to a little below about 105°C., the solids melted at a little above 26-27°C, and there was distilled over a gas which, when condensed in a dry-ice trap, gave about 112 g. of water-white liquid* Infrared analysis of the latter showed the C=0 group and otherwise known pattern of pentafluorochloroacetone, and the material boiled at the +8°C, the b.p. of anhydrous pentafluorochloroacetone. When discharge of gas from the top of the distillation column ceased, the latter was put on reflux maintained at about 105-106°C. On take- off of further vaporous product from the column, the temperature, including the pot temperature remained at about 105-106°C. during distillation until the pot was substantially dry and empty. In the course of the distillation there was produced an off-gas which, when condensed at about room temperature, gave about 8l g, of water-white liquid. On the basis that the initial addition of water to the pentafluorochloroacetone formed pentafluorochloroacetone monohydrate, "which during heating and distillation was disproportionated to pentafluorochloroacetone and its trihydrate, the recovery of 112 g. of pentafluorochloroacetone compared with the theoretical recovery of 121 g. indicating a sraall loss of ketone. On the basis of" the water charged, the liquor of constant boiling point 105-106°C. would be CF COCF„C1 , 2.βΗ\ 0. Instrumental NMR analysis for fluorine 3 2 2 of the constant boiling liquor showed 39 »8% by weight as compared with the 40.2½ required for CF COCF CI ,3H 0. Based on material balance, fluorine analysis and constant boiling characteristic- the final EXAMPLE D About 36 g. (2.0 mol.) of water and about 400 g. ( 2.2 mol.) of pentafluorochloroacetone were reacted in substantially the same manner as in Bxample 0, There was formed in the flask a slightly moist mass of solid crystals, substantially the same as in Example 0, having an m.p. of about 26°C. , and containing pentafluorochloroacetone and water in a mol ratio of about 1.1:1, corresponding substantially to OF^QOOF^Ol^E^O, This mass was subjected to heating and distillation substantiall as in Exmple @., and there were recovered about 260.8 of material boiling at +8°C, i.e. pentafluorochloroacetone, and about 163 g. of material boiling at 105.5°G. during recovery of the last fraction the pot temperature stayed constantly a about 105°C. , the material was stable throughout the distillation, which was continued until the pot was substantially dry and empty. On the basis of the water and pentafluorochloroacetone initially charged, the 261 g. of the fraction boiling at +8°0. recovered compares with the theoretical recovery of pentafluorochloroacetone of about 279 g. $he trihydrate is misclble with water i all proportions, and has a specific gravity at 25° . of about 1.63, and a melting point 'of about -5°0.

About 23*5 g» (-0.1 mol.) of the pentafluoromono-c loroacetone trihydrate product of Example D (b.p. 105°C ) was introduced into a flask cooled in wet ice. About 41 g. (0.23 aol.) of gaseous pentafluorochloroacetone were bubbled into the liquid trihydrate. On cessation of feed of pentafluorochloroacetone, the contents of the flask comprised a sli^itly moist mass, substantially the same as in Example 3), containing pentafluorochloroacetone and water in a mol ratio of 0.33:0.30. ihe resulting mass was heated gently at less than about 0 and there were vapo ised off and recovered about 7.5 of material identified by infrared analysis as pentaflueroohloroaoetone. fte residue recovered in the flask was a relatively dry white crystalline solid saterial in amount 57 g», the amount ©f peatafl¾or©ehlorpaoetone sonO-hydrate theoretically recoverable was about 60 g. 3?he melting point of the solid ra& erial me about 26.5%. iilM|,M »iM> ° - n f| »■ ' ■ ·■ ■ " ■· ■ " r 1 111 M i mi l .. I u p .» f4 tl|i i1 m p Jlli1 "J Infrared analysis and material balance establish the product to be pentafluorochloroacetone monohydrate.

As already indicated, the present invention comprises the use of the above While they are useful as selective herbicides, the herbicidal compositions of the invention are dominantly useful as non-selective herbicides for control of established broad-leaf or dicotyledonous varieties of plants such as smartweed, rape, lambs-quarters, bindweed, horsenettle, Canada thistle, and broad-leaf plantain; control of established more pernicuous monocotyledonous plants and grasses such as ryegrass, foxtail, crabgrass and nutgrass, Johnson grass, orchard grass, meadow grass and panicum species; and most particularly for non-selective defoliation or kill of brush and trees. They are also useful to provide complimentary rapid herbicidal action when used in combination with slower acting herbicides.

Although the liquid trihydrates may be applied directly, as by spraying, to the area to be treated, for reasons of economy and uniformity of application they are preferably formulated with a suitable dispersion medium prior to application. Dispersion media may be liquids or pulverulent solids. The trihydrates are miscible with water in all proportions, and this property affords the economic advantages of permitting ready make-up of aqueous spray solutions of any desired concentration without the use of emulsifiers, agitated mixing equipment, etc., and application to the locus to be treated ' in the form of easily handleable aqueous solutions which may be applied by use of the simplest types of spray apparatus. Surface active agents nay be used to enhance the wetting, spreading and penetration properties of the sprays, and thus the herbicidal effects. While water is the preferred liquid dispersion medium, other liquid carriers such for example as acetone and glycols may be employed, Dispersants such as the latter may be used for dormant winter application on brush. The solutions or liquid dispersions may contain trihydrate, preferably hexafluoroacetone trihydrate, in amount as little as about 0.3 g. per litre, depending upon the particular use.

Alternatively each of the trihydrates may be impregnated on a solid pulverulent dispersion medium, preferably of a type which is capable of absorbing a substantial amount of liquid and yet appearing sensibly dry. Typical solid diluents, which may be in finely divided or granular form, include diatomaceous earth, wood flours, silica gels, corn cob grits and vermiculite, to which wetting, dispersing or suspending agents may be added if desired. Thus, the trihydrate herbicidal material may be used as dusts which may contain as little as about 0.25%, more usually 5% to 20%, by weight of the trihydrate* The monohydrates also may be employed in solid form, as the compounds per se or in mixtures with solid diluents or dispersion media in substantially, the same way as the trihydrates. Any of the known types of spraying or dusting apparatus may be used for applying the herbicide to the soil or vegetation to be treated, a primary consideration being uniformity of application.

The monohydrates also may be employed as herbicidal compositions in the form of liquid dispersions such as aqueous solutions As noted, the monohydrates are normally crystalline solids. Addition to a solid monohydrate, e.g. hexafluoroacetone monohydrate, of water in amount about 0.4 raol per mol of hexafluoroacetone (reckoned as anhydrous) results in the formation of a mass which is definitely liquid in the usual sense of the term, but is probably an indefinite mixture* Addition -of further water up to an amount sufficient to provide 3 mols total water per mol of hexafluoroacetone effects formation of a definite distillable ρ.ηη-mimri heyaf1 nornar.atnne trihydrate of boiling point 105°C. Further addition of water to provide more than mols total water is believed to form a solution of hexafluoroacetone trihydrate in water; The terra "solution" is employed herein to indicate the compositions obtained in this way, without implying that the hexafluoroacetone or pentafluorochloroacetone has or has not undergone any particular chemical transformation, since the exact chemical forms taken by the hexafluoroacetone trihydrate and/or monohydrate when added to water in quantity to provide spray solutions are not definitely known or understood. It has been established that when either the monohydrate or the trihydrate is associated with more than 3 mols of water, the only compound separable from the aqueous solution is the trihydrate which may be recovered as a still bottom in a distillation operated at a pot temperature of about 105°C. Hence, although hexafluoroacetone monohydrate and trihydrate may lose their identities as such on addition to water, nonetheless the monohydrate affords a liquid herbicidal composition when water is added to the solid in amount to provide at least about 1,4 mols of water per raol of hexafluoroacetone . This likewise applies to pentafluorochloroacetone monohydrate. Quantities of monohydrates employed may be similar to those of the trihydrates.

Whether used for selective or non-selective control, the herbicides of the invention may be applied to the vegetation to be treated in amounts (kg. per hectare) sufficient to afford the degree of control of vegetation desired in the given area. Application to vegetation includes application to vegetation per se and to the locus in the case of pre-eraergence use. Optimum intensity of the area; degree of permanency of plant eradication desired; type of plants growing in the area and climatic conditions; and whether the objective is non-selective or selective control. In most instances, pre-emergence control, and control of e.g. germinating weed seeds and small weed seedlings may be had by applying the hydrate at a rate of 2.25 kg ./hectare and upwards, more usually 2.25-4.5 kg./hectare. Where prolonged non-selective control of established vegetation is desired, particularly in the defoliation and killing of dense under-growth , greater dosages up to about 28 kg./hectare may be employed. Depending mostly upon local conditions and the overall results required, the choice of precise dosages and hydrate concentrations in sprays and dusts are within the skill of the art.

The following Examples illustrate the invention.

EXAMPLE 1 A complex of established broadleaf weeds, grasses and woody plants (spurge, broad- and narrow-leaf plantain, bladder campion, dandelion, bunch grass, running blackberry, poison ivy, wild carrot, meadow grass, mullein, wild daisy, goldenrod, ragweed, Canada thistle and wild strawberry) was sprayed with 6.25, 12.5 and 28 kg./hectare of hexafluoroacetone trihydrate as water solutions applied at the rate of 945 litres/hectare on a June 26th. Periodic observations up to the following September on topgrowth "brown-out" were then made with the results as follows: CF COCF 3H 0 % Topgrowth Browned Out 3 3 Per Hectare June 28th July 25th Aug. 7th Aug. 21st Sept. 24th 6.25 kg. 5 75 75 6 40 12.5 kg. 5 90 95 95 80 28 kg. 10 98 99 99 95 EXAMPLE 2 diluted 1 : 50 , 1 : 100 , 1 : 200 and 1:400 by volume with water and applied as a foliage spray to run-off on small dogwood, birch, poplar, maple, sumac, elm and mock orange trees. The 1 : 50 dilution was applied on an August 1 st , and the other dilutions on the following August 15th . Effects on foliage were as follows: Percent 'of Foliage Tri- Browned Out Defoliated hyd-rate Species Aug.6th Sept.10th Oct.11th Aug.1 th Sept.10th Oct .11th 2% Dogwood 100 100 100 95 100 100 2% Birch 100 100 100 100 100 100 2% Poplar 95 100 100 80 100 100 2% Maple 95 100 100 99 100 100 2% Sumac 95 100 100 100 100 100 2% Cattails 90 100 100 - - - Aug.23rd Sept.10th Oct.11th Aug.23rd. Sept.10th Oct.11th 1% Dogwood 70 100 100 35 100 100 1% Elm 60 100 100 50 99 100 1% Poplar 95 100 100 75 100 100 1% Sumac 85 100 100 - 100 100 1% . Mock Orange 95 100 100 80 95 85 0.5% Dogwood 40 100 100 100 100 0.5% Birch - 70 100 - 40 100 0.5% Poplar , 30 - 98 - - 98 0.5% Maple 50 90 100 - 50 100 0.5% Sumac 35 100 100 - 100 100 0.5% Mock Orange 95 90 70 - 80 70 0.25% • Dogwood 25 25 85 — 15 85 0.25% Poplar 10 10 95 - 10 95 0.25% Elm ' 20 95 100 - 80 100 0.25% Sumac 30 70 100 - 60 100 0.25% Mock Orange 20 100 85 - 30 85 Additional observations showed that terminal buds were killed by the 2% and 1% sprays. The only regrowth of leaves which occurred in the year of the tests was on mock orange trees where the compound was applied at less than 2%.

EXAMPLE 3 The results below were obtained in pre-emergence greenhouse tests carried out by the macro-screening technique described The quantities of hexafluoroacetone trihydrate indicated were made up to about 38Ο litres of water solutions per hectare for spraying purposes. Test plot crops were maize, cotton, ryegrass (considered representatative of grassy weed) and rape (representative of broadleaf weeds) Dosage kg,/hectare 2*25 4,5 Maize Injury Rating 1 3 % Height Reduction 2 33 % Plant Kill 0 0 Cotton Injury Rating 2 3 % Height Reduction l8 25 % Plant Kill 0 0 Ryegr ss Injury Rating 4 6 % Height Reduction 40 60 Rape Injury Rating 3 5 % Plant Kill 30 5 Injury Rating; 0 = none, 1-3 = slight, 4-6 = moderate, 7-9 = severe, 10 = kill.

In corresponding acetone and untreated checks, all of the above values were zero, EXAMPLE 4 In pre-emergence tests substantially the same as Example 3, the quantities of pentafluorochloroacetone trihydrate used were 7«26 kg, made up to 375 litres of acetone solution per hectare for spraying purposes. Test plot crops were maize, wheat, soybeans, ryegrass and rape.

Maize Injury Rating 1 % Height Reduction 3 % Plant Kill 6 Wheat Injury Rating 1 % Height Reduction 4 % Plant Kill 0 Soybeans Injury Rating 1 % Height Reduction 9 % Plant Kill 0 Ryegrass Injury Rating 5 % Plant Kill 45 Rape Injury Rating 5 % Plant Kill 5 In corresponding acetone and untreated checks, all the above values were zero.

EXAMPLE 5 In post-emergence greenhouse tests the quantities of pentafluorochloroacetone trihydrate used were 7*26 kg. made up to about 380 litres of acetone solution per hectare for spraying purposes Test plot crops were maize, wheat, and rape. Injury ratings, taken 10 days after application, were - maize, zero; wheat, 3» and rape, 8, In corresponding acetone and untreated checks all the foregoing values were zero.

In all embodiments of the invention, no matter how used, the herbicide is pentafluorochloroacetone or hexafluoroacetone associated with water in amount at least equivalent to the mono-hydrate. Where the solid monohydrates are used directly, i.e. as dusts, the water associated with the ketone is water of constitution. Similarly, where the liquid trihydrates are utilized in the form of a phytotoxic amount impregnated upon a solid pulverulent dispersion medium, the water is likewise water of constitution of the trihydrates. When the liquid trihydrates per se are used directly, as in sprays consisting of the liquid trihydrates, the water associated with the ketone is water of constitution. When, as in the more usual operations, the solid monohydrates or the liquid trihydrates are added to a liquid dispersion medium e.g. water, and applied as an aqueous spray, the water associated with the ketone is water of constitution plus other water. Thus, in customary practice using liquid spray solutions of relatively high dilutions it will be appreciated that when any mono-or trihydrate is added to water, for example, to form a herbicidal composition comprising and usually consisting of a relatively dilute spray solution containing added hydrate in phytotoxic amount, the ketone component of the added hydrate is associated with water in amount much more than that equivalent to the trihydrate.

The hydrates of hexafluoroacetone and pentafluorochloro- 2Ο8 3 acetone are the subject of our Application No. "

Claims (10)

HAVING NOW particularly described and ascertained the nattire of our said invention and what manner the same is to be performed, we declare that what we claim is:

1. * Process for controlling growth of or destroying vegetation, which comprises applying thereto, or to the locus in which it is growing or is to grow, the monohydrate or trihydrate of pentafluorochloroacetone or hexafluoroacetone.

2. Process according to claim 1, wherein the said compound is associated with a dispersion medium.

3. Process according to claim 2, wherein the said compound is in solution in an aqueous liquid.

4. Process according to' claim 2, wherein the said compound is mixed with or absorbed on a pulverulent solid.

5. Process according ^to any one of the preceding claims, wherein the said compound is associated with a surface active agent.

6. Process for controlling or destroying vegetation according to claim 1 substantially as hereinbefore described.

7. A herbicidal composition comprising the monohydrate or trihydrate of pentafluorochloroacetone or hexafluoroacetone and a dispersion medium.

8. A herbicidal composition according tc claim 7» wherein the dispersion medium is an aqueous liquid.

9. · A herbicidal composition according to claim 7? wherein the dispersion medium is a pulverulent solid.

10. A herbicidal composition according to any one of claims 7-9» containing also a surface active agent. 11, A herbxcidal composition according to claim 7 substantially as hereinbefore described. Dated this 6th day of August,1964 For the Applicants DR. REIHSOLD COSH & CQ By: