PENTAHYDROPERFLUOROALKYLAMINE N-OXIDES

Abstract: Amine N-oxides represented by the formula: wherein R f is C₃-C₂₀ perfluoroalkyl; R is H or alkanoyl containing 1-4 carbons; R¹ and R² are the same or different C₁-C₆ alkyl or C₁-C₆ hydroxyalkyl, or together with the N atom to which they are bonded form a piperidine, morpho­ line or N-alkyl (C₁-C₄) piperazine ring; or R¹ is C₁-C₆ alkyl or C₁-C₆ hydroxyalkyl and R² is R³ is C₁-C₆ alkyl or C₁-C₆ hydroxyalkyl; and n is an integer from 1-8; and mixtures thereof. The amine N-oxides are highly effective in reducing the surface tension of aqueous systems and as aqueous foaming agents. They are prepared by oxidizing the amine repre­ sented by the formula:

Description: TITLE PENTAHYDROPEBLUOROALKYLAMINE N-OXIDES BACKGROUND OF THE INVENTION This invention relates to 1,1,2,3,3-pentahydroperfluoroalkylamine N-oxides having a 2-hydroxy or acyloxy substituent and processes for making and using the same as surfactants and foaming agents. Richter, in U.S. Patent No. 4,283,533, discloses amphoteric N-type betaines of 2-hydroxy-l,l,2,3,3-pentahydroperfluoroalkylamines and their use as surfactants. Krahler et al., in U.S. Patent Application Serial No. 454,589 filed December 30, 1982, disclose amphoteric N-type betaines of 2-acyloxy-1,1,2,3,3-pentahydro- perfluoroalkylamines and their use as surfactants. Katsushima et al., in U.S. Patent No. 4,165,338, disclose various hydroxy compounds including ones having the formula: EMI1.1 wherein R1 and R2 are each hydrogen or a hydrocarbon group, including CF3(CF2)6CH2CH(OH)CH2N(C2H5)2 and CF3(CF2)6CH2CH(OH)CH2N (CH3)2, among others. Katsushima et al. disclose acid addition salts of their compounds. Minnesota Mining and Manufacturing Company, in British Patent No. 1 302 612, discloses fluorinated amine N-oxide surfactants, some of which can be represented by the formula: EMI1.2 wherein n is 1-3. Amongst others, data are provided as to the foaming characteristics of the amine N-oxides. The compounds of the present invention overcome a number of disadvantages associated with the compounds of Richter, Krahler et al. and Katsushima et al. In order to prepare their betaines, both Richter and Krahler et al. react a tertiary amine, or mixture of tertiary amines, with an alkali metal salt of a monochloro or monobromo alkanoic acid. That type of reaction is much more difficult to perform effectively than any of the oxidation techniques described herein. Katsushima et al. report their compounds are oleophobic, not surface active. The compounds of the present invention are more effective in reducing surface tension of aqueous solutions at low concentrations than those of the Minnesota Mining and Manufacturing Company British Patent. Moreover, the amine N-oxides of the present invention are markedly superior aqueous foaming agents when compared with the amine oxides disclosed by Minnesota Mining and Manufacturing Company in the British patent. Moreover, the amine oxides of the Minnesota Mining and Manufacturing Company British patent are much more difficult to prepare than those of the present invention. DETAILED DESCRIPTION OF THE INVENTION The amine N-oxides of this invention can be represented by the formula: EMI2.1 wherein Rf is C3-C20 perfluoroalkyl; R is H or alkanoyl containing 1-4 carbons; R1 and R2 are the same or different C1-C6 alkyl or C1-C6 hydroxyalkyl, or together with the N atom to which they are bonded form a piperidine, morpholine or N-alkyl(C1-C4)piperazine ring; or EMI3.1 R3 is C1-C6 alkyl or C1-C6 hydroxyalkyl; and n is an integer from 1-8; and mixtures thereof. The amine N-oxides of this invention are highly effective in reducing the surface tension of water and of aqueous solutions of inorganic electrolytes. Because they are essentially nonionic, they can be used in environments in which ionic surfactants may fail, e.g., highly acidic oil well applications. The amine N-oxides of this invention are useful also as aqueous foaming agents. They may therefore find use in foam fracturing of pertroleum-bearing formations and in fire extinguisher compositions, particularly those used for extinguishing petroleum fires. Moreover, compositions containing them exhibit improved insecticidal properties, e.g., against German cockroaches. This invention contemplates single compounds represented by the foregoing formula as well as mixtures thereof; preferably the latter are prepared and used, because the starting materials which provide the perfluoroalkyl portion of the molecule are most commonly available commercially as mixtures. The usual commercial mixture will contain small amounts (less than 5% by weight) on both ends of the foregoing carbon chain length range, with 80-90% of the chains containing 6-12 carbons, preferably 6-10 carbons, with an average in the mixture between 6 and 8 carbons. The amine N-oxides of this invention can be prepared by reacting the appropriate 2-hydroxy or 2-acyloxy tertiary amine (or mixture of 2-hydroxyamines and/or 2-acyloxyamines) with an oxidizing agent. For example, one can react the amine or mixture of amines with hydrogen peroxide or peracetic acid in an alcohol or aqueous alcoholic solvent, such as methanol, ethanol, 1-propanol, 2-propanol, l-butanol, 2-methyl-2-propanol and mixtures thereof. Preferably, the oxidizing agent is peracetic acid, and the oxidation reaction is run in 2-propanol. The acyloxy tertiary amines can be prepared by reacting the corresponding 2-hydroxy tertiary amine with any appropriate acylating agent. While an acid anhydride is preferred, other acylating agents, such as acids and acid halides, may be used. The acylating reaction can be run neat or in a suitable nonpolar solvent or aprotic polar solvent, e.g., ketones such as methyl ethyl ketone; aromatic hydrocarbons such as toluene and benzene; diethyl ether; pyridine; alkanoic acids such as acetic, propanoic, butanoic or pentanoic acid; and the like. In a preferred embodiment, the acylation reaction is run in the absence of any reaction medium other than the amine and the acylating agent. The reaction product, in some instances, is reacted with the oxidizing agent without recovery of the acylation reaction product; in others, the reaction product is purified before it is oxidized, preferably the former. Some of the 2-hydroxyamines, from which some of the 2-hydroxyamine N-oxides and 2-acyloxyamine N-oxides are prepared, are disclosed by Richter and Katsushima et al., supra. Those 2-hydroxyamines, as well as the others which serve as starting materials for the amine N-oxides of this invention, can be prepared by the reaction: EMI5.1 The epoxide starting material for the foregoing reaction can be prepared by reacting an alkali metal hydroxide with 3-perfluoroalkylpropylene iodohydrin, having the formula: EMI5.2 Some of the iodohydrins are known compounds; Richter and Katasushima et al., supra, disclose some of them and their preparation. Moreover, they can be prepared, as is more particularly described hereinbelow by reacting the appropriate perfluoroalkyl iodide with triallyl borate in the presence of a free radical initiator, following which the resulting borate is hydrolyzed to the iodohydrin. The preparation of triallyl borate is described by Richter, supra. The following examples are given by way of illustration not limitation. Unless specified otherwise, all parts and percentages are by weight, and temperatures are in degrees Celsius. Surface tension data are given in Table I. The Ross-Miles Foam Test to which reference is made in the Examples is described in OIL AND SOAP, XVIII No. 1, 99-102 (1941). For purposes of the Examples herein, the Ross-Miles Foam Test has been modified in that deionized water is used at ambient temperature rather than distilled water at about 430C. I. The following preparation of 3-perfluoroalkyliodohydrins was made for Example 1, and it is typical of preparations made for Examples 2-5. Preparation of 3-Perfluoroalkyliodohydrins A mixture of perfluoroalkyl iodides was used which had the characteristics given below. The mixture was analyzed by gas chromatography, using a Perkin-Elmer Model 3920 flame ionization gas chromatograph, a 12' X 1/8" stainless steel column packed with 20% GE SE-30 silicone on 80/100 Chromosorb W-HP and a program of heating from 500C to 2600C at 160C/minute. The homolog distribution was expressed as area g and the average molecular weight calculated therefrom to give the following: : C4FgI - trace C6F13I - 51.36% C8F171 - 34.24* C10F211 - 9 948 C12F25I - 3.68% C14F29I - 0.72% C16F331 - 0.05% Non-iodides - 0.01% Average molecular weight as RfI = 528.6. A mixture of 1420 lbs (2.83 lb-mols) of the above-described Rff and 304 lbs of triallyl borate {85% purity; 1.81 lb-mols) was heated to 67 + 30C and Via zoo 64 azobisisobutyronitrile (3.0 lbs; 0.0183 lb-mol) added, resulting in a gentle exotherm lasting approximately 2 hours. The charge was held under agitation at 67 + 30C for 3 hours, after which another 3.0 lb increment of of 64 was added. The charge was agitated at 67 + 30C for 3 hours, after which increments of Vazob 64 were added as follows: 3.0 libs; 3 hours later 3.0 libs; 3 hours later 3.0 lbs; 3 hours later 3.0 lbs. After a total of 27 hours, the charge was sampled and the sample hydrolyzed with aqueous acetone and the hydrolyzed sample extracted into eF-113" 1,1,2-trichloro1,2,2-trifluoroethane. Gas chromatographic analysis of the "F-113" layer showed a > 99.5% conversion of RfI to 3-perfluoroalkylpropylene iodohydrins. To the charge was added 1000 lbs of 5% sodium chloride brine; the mixture was distilled to a head temperature of 980C (pot temperature 1020C) to remove unreacted allyl alcohol and the major portions of the toluene and unreacted RfI. The two-phase still residue was separated at 83 + 30C, the lower (product) layer being drummed and the upper (aqueous brine) layer being discarded, to yield 1540 lbs (97.2%) of a yellow-orange oil which solidified on cooling. Analysis (area % and mol. wt. calculated therefrom): C4F9CH2CHICH2OH - 1.20% C6F13CH2CHICH2OH - 48.41% C8F17CH2CHICH2OH - 31.98% C10F21CH2CHICH2OH - 9.61t C12F25CHICH2OH - 1.54* C14F29CHICH2OH - 1.18% Non- iodohydr ins - 6.08% Average molecular weight as RfCH2CHICH2OH = 592.1 EXAMPLE 1 N,N-Dimethyl(3-Perfluoroalkyl2-Hydroxypropyl)Amine N-Oxides Isopropyl alcohol, anhydrous (1335 lb) was warmed to 400, and the above-described mixture of perfluoroalkylpropylene iodohydrins (1022 Ib, 1.73 lb-mol) was added. The resultant solution was then cooled to 15 + 50, and sodium chloride (240 lbs) was added. Cooling was applied to the reaction vessel as aqueous sodium hydroxide (50%, 125 lbs, 1.56 lb-mol) was added over a 30-45 minute period. The resultant mass was stirred at 5 + 50 for 4 hours. Dimethyl amine (40% aqueous solution, 300 lbs, 2.66 Ib-mol) was added, with concomitant cooling of the reaction vessel, and the charge was stirred for an additional 4 hours at 5 + 5#. While maintaining a temperature of 5 + 5 , aqueous sodium hydroxide (50%, 14 Ibs, 0.175 lb-mol) was added slowly. The charge was stirred for 8 hours at 5 + 5 , 4 hours at 25 + 5 , and 80 + 2a for 4 hours. The charge was then diluted with 2335 Ibs of water. Next, heating was applied to effect the distillation of isopropanol at a head temperature of 93 + 10 and a pot temperature of 101-20, After distillation was complete, the charge was cooled to 55 +50. Agitation was stopped and the layers were allowed to separate. The lower (product) layer, 816 lbs of a dark amber oil, was drawn off. Analysis of the product by gas chromatography revealed the following composition: EMI8.1 <tb> RfCH2CH1#CH2N <SEP> (CH3)2 <tb> <SEP> OH <SEP> Area <SEP> % <tb> Rf <SEP> =C4Fg <SEP> 1.8 <tb> <SEP> C6F13 <SEP> 51.4 <tb> <SEP> C8F17 <SEP> 29.8 <tb> <SEP> C1OF21 <SEP> 10.6 <tb> <SEP> Cl2F25 <SEP> 1.8 <tb> <SEP> C14F29 <SEP> 0.4 <tb> <SEP> Unknowns <SEP> 3.8 <tb> By amine titration the amine product had an apparent molecular weight of 537.6. To 215 g (0.4 mol) of the mixture of N,N-dimethyl(3-perfluoroalkyl-2hydroxypropyl) amines were added g of isopropyl alcohol. Peracetic 9 g of isopropyl alcohol. Peracetic acid, 40% solution (83.6 g; 0.44 mol), was added dropwise to the isopropyl alcohol-amine solution while cooling in a cold water bath to prevent the exothermic reaction from going above 350C. After about one-half of the peracetic acid had been added, the reaction mass tended to foam. The foam was broken by warming to 40 to 450C, and the remaining peracetic acid was added, allowing the temperature to rise to 50#C. The pale yellow solution was heated for an additional 2 hours at SOOC. The reaction was diluted with 70 g of ethylene glycol and bottled. The calculated concentration of amine oxides in solution was 43%. In the Ross-Miles foam test, at 0.1% concentration of the amine N-oxide product in deionized water at 250C, foam was generated to a height of 140 mm and remained at that height for a 10-minute period. EXAMPLE 2 N,N-Dimethyl(3-Perfluoro2-Acetoxypropyl)Amine N-Oxides To 1080 g (2.00 mols) of a mixture of N,N-dimethyl(3-perfluoroalkyl-2-hydroxypropyldimethyl)amines were added 510 g (5.00 mols) of acetic anhydride. The exothermic reaction caused the temperature to rise to 70 to 730C. The temperature was increased to 75 to 800C and held for 2 hours to complete the reaction. The reaction mass was cooled to about 250C and added to 2 liters of cold water. The solution was neutralized to pH 7.0 + 0.1 by the addition of 30% sodium hydroxide solution (1008 g; 7.58 mols). Ice was added as needed to keep the temperature in the range of 20 to 300C. The heavy oil product was allowed to separate and the top water layer was siphoned off. The product was washed twice with 1.5 liters of water and finally separated in a separatory funnel to obtain 1078 g of product (apparent average molecular weight by amine titration was 592). To a solution mix of 178 g (0.3 mol) of the mixture of N,N-dimethyl(3-perfluoroalkyl-2 acetoxypropyl)amines and 89 g of isopropyl alcohol were added dropwise 62.7 g (0.33 mol) of 40% peracetic acid solution. The reaction temperature was maintained during the addition at less than 350C by cooling in a cold water bath. The reaction temperature was thereafter increased to 500C and held for 2 hours at that temperature. The solution was diluted with 90 g ethylene glycol and bottled. The calculated amine oxide concentration of the solution was 43.4%. In the Ross-Miles foam test, at 0.18 concentration of the amine N-oxide product in deionized water at 250C, foam was generated to a height of 190 mm which persisted for a 10-minute period. EXAMPLE 3 N,N-Diethyl(3-Perfluoroalkyl2-Acetoxypropyl)Amine N-Oxides Diethylamine (14.6 g; 0.2 mol) was reacted with 3-perfluoroalkylpropylene oxide (60 g; about 0.1 mol) by heating initially for one hour at 70 to 750C. The reaction temperature was gradually increased to 93 to 950C and held for 6 hours. The product was then extracted with 5% brine solution (100 cc) at 60 to 700C to remove excess diethylamine from the product. The extraction was repeated 3 more times. The final product weighed 58 g. Analysis: For N,N-diethyl(3-perfluoroalkyl2-hydroxypropyl)amines with theoretical average molecular weight of 485, milliequivalents amine/g: Calculated: 2.06 Found: 1.75 Thus, the apparent purity was 84.88 and the apparent average molecular weight was 571. The above hydroxy amines (28.6 g; 0.05 mol) were acetylated with acetic anhydride (10.2 g; 0.1 mol) by heating at 85 to 900C for one hour and 15 minutes. Without isolation of the acetoxy derivative, the reaction mass was cooled and diluted with isopropyl alcohol (12 g) and reacted with hydrogen peroxide 30% solution (7.4 g; 0.065 mol). The initial exothermic reaction to 550C was continued at 70 to 750C for 5 hours to complete the oxidation. EXAMPLE 4 N-Butyl-N-Methyl(3-Perfluoroalkyl2-Acetoxypropyl) Amine N-Oxides The process of Example 3 was repeated using N-methyl-N-butylamine (17.4 g; 0.2 mol). The product was extracted hot with 5% brine acidified to pH 5.7 with hydrochloric acid to remove excess N-methyl-N-butylamine. The preparation of a mixture of acetoxy derivatives without isolation and its oxidation with hydrogen peroxide to the amine N-oxide solution was carried out by the same procedure as in Example 3. EXAMPLE 5 N- (3-Perfluoroalkyl2-Acetoxypropyl)Piperidine N-Oxides The reaction of 3-perfluoroalkylpropylene oxides (60 g; ca. 0.1 mol) with piperidine (11 g; 0.13 mol) was carried out in a manner similar to that for Example 3. Excess piperidine was removed by extraction with 100 cc water at about 600C. The extraction was repeated 2 more times. The product (63.5 g) was a solid at room temperature. Analysis: For a mixture of telomers: EMI12.1 derived from a mixture of perfluoroalkyl iodides similar to that described above but with the average molecular weight of 511 the milliequivalents of amine/g: Calculated: 1.96 Found: 1.70 Therefore, the purity was 87% and the apparent average molecular weight was 588. Acetylation of the N-(3-perfluoroalkyl2-hydroxypropyl)piperidines (60.2 g; 0.102 mol) with acetic anhydride (20.5 g; 0.201 mol) was carried out at 80 to 850C for one hour. The reaction mass was drowned in water, neutralized with caustic soda and isolated by the general procedure of Example 2. Analysis: Milliequivalents amine/g: Calculated: 1.81 Found: 1.62 Therefore, the apparent purity was 89.6t. N- (3-perfluoroalkyl-2-acetoxypropyl) piper- idines (24.7 g; 0.04 mol) in isopropyl alcohol (20 g) were oxidized with 30% hydrogen peroxide (5.4 g; 0.048 mol) at 70 to 750C for 3 hours. The calculated content of amine N-oxides was 50.7%. II. The following preparation of 3-perfluoroalkylpropylene oxide was made for Example 6, and it is typical of preparations made for Examples 7-9. The iodohydrin starting material was prepared by a procedure similar to that disclosed hereinabove as well as to that disclosed by Richter. 3-Perfluoroalkylpropylene Oxide To isopropyl alcohol (544 g) was added a mixture of 3-perfluoroalkyl iodohydrins (400 g; 0.677 mol), and the mixture was heated to 45 to 500c to dissolve the iodohydrin. The solution was then cooled in an ice bath to 7 to 100C and 92.4 g (0.69 mol) of 30% sodium hydroxide solution were added gradually over a 4-hour period. The reaction mass was cooled to 2 to 50C during the addition of the caustic solution and that temperature range was maintained for an additional 16 hours after the caustic soda had been added. The reaction temperature was then increased to 10 to 150C and 8.3 g (0.06 mol) of monobasic sodium phosphate were added to neutralize excess caustic soda. The reaction mass was diluted with 800 cc water and the mixture, having a pH of 6.5, was warmed to 40 to 450C. The heavy light brown oil product was drawn off in a separatory funnel. The product (325 g) was analyzed by gas chromatography and found to contain 12.2 area % isopropyl alcohol and had the following distribution of 3-perfluoroalkylpropylene oxides (on a solvent-free basis): EMI14.1 <tb> <SEP> Area <SEP> i <tb> C4F9CH2C <SEP> 1.0 <tb> <SEP> 0 <tb> C(;F13CH2CCfCH2 <SEP> 3 <SEP> 7. <SEP> 2 <tb> C8Fl7CH2C\ <SEP> ZCH2 <SEP> 3 <SEP> 2. <SEP> 5 <tb> <SEP> 0 <tb> CloF2lCH2C\gCH2 <SEP> 17. <SEP> 6 <tb> Cl2F2 <SEP> 5CH2CH-CH2 <SEP> 6.2 <tb> <SEP> 0 <tb> Cl4F2 <SEP> 9CH2C\H#/CH2 <SEP> 1.5 <tb> <SEP> 0 <tb> Cl6F3 <SEP> 3CH2CX <SEP> ZCH2 <SEP> 0.6 <tb> <SEP> 0 <tb> Unknowns <SEP> 3.4 <tb> The calculated average apparent molecular weight of the product based upon the GC data was 470. On standing at room temperature, the product solidified partially. EXAMPLE 6 N,N-Diethyl(3-Perfluoroalkyl2-Acetoxypropyl)Amine N-Oxides A portion (292 g; 0.527 mol) of the crude epoxide product was reacted with diethylamine (66 g; 0.90 mol) initially at 70 to 750C. The reaction temperature was increased gradually to 80 to 840C over about a period of one hour and held in that temperature range for 9 hours. Water (400 cc) was added and the reaction mass subjected to distillation until the head temperature was 99 C, thereby removing excess diethylamine and isopropyl alcohol carried over from the epoxide preparation. The product, a light brown oil (283 g), was separated from the aqueous phase in a separatory funnel. Analysis: For a mixture of telomers: EMI15.1 with a calculated average molecular weight of 543 the milliequivalents of amine/g: Calculated: 1.84 Found: 1.71 Thus, amine product had an apparent purity of 92.4% and an apparent average molecular weight of 585. Since analysis by gas chromatography of the product appeared to give an incorrect distribution of the higher molecular weight components, a small sample was treated with acetic anhydride to convert it to the corresponding 2-acetoxy derivative. The composition by gas chromatography now appeared reasonable and was as follows: EMI15.2 <tb> RfCH2C1H-CH2N <SEP> (C2H5) <SEP> 2 <tb> <SEP> OCCH <tb> <SEP> 11 <SEP> 3 <tb> <SEP> O <SEP> Area <SEP> % <tb> Rf <SEP> = <SEP> C4Fg <SEP> 1.3 <tb> <SEP> 6F13 <SEP> 39.4 <tb> <SEP> C8Fl7 <SEP> 31.8 <tb> <SEP> C1 <SEP> oF2 <SEP> 1 <SEP> 15.4 <tb> <SEP> Cl <SEP> 2F2 <SEP> 5 <SEP> 5.6 <tb> <SEP> C14F29 <SEP> 1.5 <tb> <SEP> C16F3 <SEP> 3 <SEP> 0.4 <tb> <SEP> C18F3 <SEP> 0.1 <tb> <SEP> Unknowns <SEP> 4.5 <tb> The calculated average molecular weight of the perfluoroalkyl-2-hydroxypropyldiethylamines was 547. The N,N-diethyl-3-perfluoroalkyl-2-hydroxypropylamines (176 g; 0.3 mol) were acetylated with acetic anhydride (76.5 g; 0.75 mol) by a process similar to that of Example 2, resulting in 182 g of product. Analysis: 1.53 milliequivalents amine/g and apparent molecular weight of 653.6. Thirty-three grams (0.05 mol) of the foregoing amines were diluted with 15 g isopropyl alcohol. Peracetic acid 40% solution (10.5 g; 0.055 mol) was added gradually to the amine solution while cooling in a cold water bath. The solution was then warmed to 50 to 530C and held for 2 hours. The solution product was diluted with 20 g ethylene glycol and bottled. The calculated amine N-oxide content of the solution was 398. EXAMPLE 7 N- (3-Perfluoroalkyl 2-Acetoxypropyl) Piperidine N-Oxides The intermediate 3-perfluoroalkylpropylene oxides were prepared similarly to those described above; however, without isolation, they were reacted with piperidine (86.9 g; 1.02 mols) by heating the reaction mass at 84 + 20C for 4 hours. The product was worked up by diluting the reaction mass with 1.5 liters of water and then cooling to precipitate the product as a grained solid. The product settled rapidly, was washed two times by decantation, reslurrying each time in fresh water. The product was isolated by filtration and dried in air at room temperature. The dry weight was 338 g. Analysis: For a mixture of telomers: EMI16.1 with a calculated average molecular weight of 556 the milliequivalents of amine/g: Calculated: 1.80 Found: 1.69 Thus the apparent purity was 93.9% and the yield was 85.58 of theory. The 3-perfluoroalkyl-2-hydroxypropylpiper- idines (237 g; 0.4 mol) were reacted with acetic anhydride (81.6 g; 0.8 mol) by heating 2-1/2 hours at 84 + 3 C. The reaction mass was drowned into water and neutralized with caustic soda by the general procedure given as Example 2 to recover 253 g of an oil product. Analysis: For a calculated average molecular weight of 598 the milliequivalents of amine/g: Calculated: 1.67 Found: 1.55 Thus the yield was 94% of theory and the apparent purity was 92.8%. To a solution mix of N-(3-perfluoroalkyl2-acetoxypropyl)piperidines (61 g; 0.095 mol) and isopropyl alcohol (40 g) was added gradually peracetic acid 40% solution (21 g; 0.11 mol). The exothermic reaction increased the temperature of the solution mix to 550C. The reaction was further heated at 53 + 30C for 3 hours. The product was a light yellow, slightly cloudy viscous liquid. The calculated amine N-oxide content of the solution was about 47%. EXAMPLE 8 N,N-Dimethyl(3-Perfluoroalkyl2-Acetoxypropyl)Amine N-Oxides The general procedure for preparing the subject dimethylamine derivatives from iodohydrins (500 g; 0.83 mol) followed closely Example 7 in which the intermediate propylene oxide was not isolated. The amine product was isolated initially by diluting the final reaction mass with water (1200 cc) to obtain a heavy product layer containing some isopropyl alcohol which was separated in a separatory funnel to obtain 648 g of crude product. The crude product was subjected to distillation to maximum pot temperature of 1400C at atmospheric pressure, using a slow stream of nitrogen, to strip off excess dimethyl amine and isopropyl alcohol. The final product weight was 387. The product became a soft pasty solid on standing at room temperature. Analysis: For a mixture of Telomers: EMI18.1 with a theoretical average molecular weight of 518 the milliequivalents of amine/g: Calculated: 1.93 Found: 1.68 Thus, the apparent purity was 87% and the yield was 78.3% of theory based upon the starting iodohydrin. The N,N-dimethyl(3-perfluoro-2-hydroxypropyl)amines (376 g; 0.63 mol) were acetylated with acetic anhydride by the procedure of Example 2. The oil product (398 g) became a soft paste on standing at room temperature. The titration for milliequivalents/gram was 1.56 indicating an apparent average molecular weight of 641 and a yield recovery of 98.6%. A solution of N,N-dimethyl(3-perfluoroalkyl-2-acetoxypropyl)amines (32 g; 0.05 mol) and isopropyl alcohol (25 g) was treated with peracetic acid 40% solution (10.5 g; 0.055 mol) at 57 + 30C for 2 hours. The calculated amine N-oxide content of the solution was 42.7%. EXAMPLE 9 N,N-Bis(Hydroxyethyl) (3-Perfluoroalkyl- 2-Hydroxypropyl)Amine N-Oxides A mixture of 3-perfluoroalkylpropylene oxides (111 g; ca. 0.2 mol) was reacted with diethanolamine (42 g; 0.4 mol) by heating at 900C for 12 hours. The initial two-phase emulsion became a homogeneous light yellow, clear, thick liquid at the end of the heating period. Excess diethanolamine was removed by extracting the reaction mass two times as 60 to 700C with water containing approximately 10% isopropyl alcohol to aid in breaking gel formation. The crude product weight was 155.5 g. Analysis: For N,N-bis(hydroxyethyl) (3-perfluoroalkyl-2-hydroxypropyl)amines with a calculated average molecular weight of 575 the milliequivalents of amine/g: Calculated: 1.74 Found: 1.23 indicating a purity of 70.7%. The product yield, based upon the amine titration, was 95.6%. To a solution mix of the N,N-bis(hydroxy ethyl) (3-perfluoroalkyl-2-hydroxypropyl)amines (40 g; 0.049 mol) and isopropyl alcohol (40 g) was added a 30% hydrogen peroxide solution (7.0 g; 0.062 mol). The reaction mixture was heated 6 hours at 73 + 30C. The calculated concentration of amine N-oxide in the solution was 34%. EXAMPLE 10 N,N-Dimethyl(3-Perfluorohexyl2-Acetoxypropyl)Amine N-Oxide N,N-Dimethyl(3-perfluorohexyl-2-hydroxypropyl)amine (156 g; 0.35 mol) was obtained at about 958 purity by vacuum distillation and fractionation of N ,N-dimethyl (3-pe rfluoroalkyl-2-hydroxypropyl) - amines which had been prepared substantially as described in Example 1. The resulting amine was reacted with acetic anhydride (51 g; 0.5 mol) for 3 hours at 800C. The reaction solution was drowned into 600 cc cold water and neutralized to pH 7.2 with 30% sodium hydroxide solution to cause the acetoxy derivative to separate. The product was separated in a separatory funnel, washed once with 5% brine solution and again separated. The recovered weight was 167 g. Analysis: Titration for milliequivalents amine/g: Calculated: 2.06 Found: 2.00 Thus, the indicated purity was 97.1% and the yield was 95.4% theory. To a solution of N,N-dimethyl(3-perfluorohexyl-2-acetoxypropyl)amine (49 g; 0.103 mol) and isopropyl alcohol (20 g) was added gradually peracetic acid 40% solution (21 g; 0.11 mol). The heat of reaction raised the temperature to 550C. The solution mixture was then held at 600C for 1-1/2 hours, cooled and bottled. The calculated active ingredient of the solution was 55.8%. EXAMPLE 11 N,N-Diethyl(3-Perfluorohexyl2-Acetoxypropyl) Amine N-Oxide 3-Perfluorohexylpropylene oxide (38 g; 0.1 mol) which had been obtained from pure 3-perfluorohexyl iodide via the iodohydrin and then purified by vacuum distillation was reacted with diethylamine (8.0 g; 0.11 mol) for 7 hours at 70 to 750C and then 5 hours at 90 to 950C. Gas chromatographic analysis still showed the presence of 2.4% of the unreacted starting propylene oxide. Without isolation, the product was acetylated with acetic anhydride (11.2 g; 0.11 mol) by heating at 80 to 850C for 30 minutes. The solution was cooled to 60 to 650C and then diluted with isopropyl alcohol (16 g). Hydrogen peroxide 30% solution (13.6 g; 0.12 mol) was added and the solution then heated 7 hours at 70 to 750C. The calculated amine oxide content of the solution was 53.7%. EXAMPLE 12 N-Butyl-N-Methyl(3-Perfluorohexyl2-Acetoxypropyl)Amine N-Oxide The reaction procedure of Example 11 was repeated using N-methyl-N-butylamine instead of diethylamine. EXAMPLE 13 N,N-Bis(Hydroxyethyl) (3-Perfluorohexyl- 2-HydroxYpropyl)Amine N-Oxide 3-Perfluorohexylpropylene oxide (38 g; 0.1 mol) was reacted with diethanolamine (11.6 g; 0.11 mol) in the presence of isopropyl alcohol (8 g) at 55 to 600C for about 5 hours. The product was isolated by drowning into 5% brine solution and the product separated at about 50 C. A gas chromatographic analysis showed the presence of unreacted starting propylene oxide; however, the product apparently did not elute from the column and thus a quantitative determination was not made. Titration for milliequivalents of amine/g gave 1.67 while theory was 2.08 and thus showed a purity of 80.38. This material (30 g; 0.05 mol) was diluted with isopropyl alcohol (25 g) and oxidized with peracetic acid 40% solution (10.5 g; 0.055 mol) for 2 hours at 500C. An amine titration for product gave an amine N-oxide content of 37.3i. The Ross-Miles foam test on the product at 0.1% concentration in deionized water at 250C gave 280 mm of foam which persisted for 10 minutes. Thus, the product has excellent foaming properties in water. EXAMPLE 14 N,N-Dimethyl(3-Perfluorooctyl2-Hydroxypropyl)Amine N-Oxide The amine for this example was obtained at about 90% purity by vacuum fractional distillation of the N,N-dimethyl(3-perfluoroalkyl-2-hydroxypropyl)amines which had been prepared substantially as described in Example 1. To a solution mix of that amine (27 g; 0.05 mol) in isopropyl alcohol (25 g) at 45 to 500C was added peracetic acid 40% solution (10.5 g; 0.055 mol). The solution was then heated 2 hours longer at 50 + 30C. The calculated amine N-oxide content of this solution was 438. EXAMPLE 15 N,N-Dimethyl(3-Perfluorooctyl 2-AcetoxYpropyl)Amine N-Oxide N,N-Dimethyl(3-perfluorooctyl-2-hydroxypropyl)amine corresponding to that used in Example 14 was acetylated with acetic anhydride by the procedure of Example 2 and then vacuum distilled (75 to 800C at 0.4-0.5 mm) to obtain material of about 94% purity as the perfluorooctyl derivative and 6% as perfluorohexyl derivative. To a solution of N,N-dimethyl(3-perfluorooctyl-2-acetoxypropyl)amine (47.5 g; 0.08 mol) in isopropyl alcohol (20 g) was added gradually peracetic acid 40% solution (17 g; 0.09 mol) while maintaining the temperature at 50 C. Heating at 500C was continued for 2 hours. The colorless solution was cooled and bottled. The calculated amine N-oxide content of the solution was 54.8z. Surface tension data recorded in Table I show the product has outstanding properties. EXAMPLE 16 N- (3-Perfluorooctyl- 2-Hydroxypropyl)Piperidine N-Oxide The general procedure of Example 7 was followed, starting with 3-perfluorooctylpropylene iodohydrin. The product was isolated as a solid and air dried. Based upon titration for amine the purity was 94.4% and the yield of product was 89% of theory. To the hydroxy derivative (89 g; 0.15 mol) was added acetic anhydride (30.8 g; 0.30 mol). After allowing the initial exothermic reaction to subside, the reaction was heated for 2 hours at BOOC. The reaction mass was drowned in cold water, neutralized with caustic soda to pH 7.5 and separated in the separatory funnel as a hot melt. The product crystallized on standing and cooling. To a solution of N-(3-perfluorooctyl2-acetoxypropyl)piperidine (26.3 g; 0.04 mol) and isopropyl alcohol (25 g) was added peracetic acid 40% solution (8.4 g; 0.044 mol). The reaction mass was heated 2 hours at 53 + 30C to complete the oxidation. The calculated amine N-oxide content of the solution was 45.1t. EXAMPLE 17 N,N0-Bis(3-Perfluorohexyl-2-Acetoxypropyl)- N ,N'-Dime thyihexame thylenediamine-N ,N '-Dioxide In accordance with the general reaction procedure of Example 11, 3-perfluorohexylpropylene oxide (38 g; 0.1 mol) was reacted for 7-1/2 hours at 95 + 3 0C with N,N'-dimethylhexame thylenediamine (7.5 g; 0.05 mol). This reaction was followed by acetylation with acetic anhydride (0.095 mol), dilution with isopropyl alcohol and reaction with hydrogen peroxide 30% solution (12.5 g; 0.11 mol). EXAMPLE 18 N,N'-Bis(3-Perfluorohexyl-2-Acetoxypropyl)- N,N'-Diethylhexamethylenediaimine-N,N'-Dioxide Following the general procedure of Example 11, 3-perfluorohexylpropylene oxide (38 g; 0.1 mol) was reacted 9 hours at 95 + 30C with N,N'-diethylhexamethylenediamine (9.0 g; 0.05 mol). After acetylation the oxidation was carried out using peracetic acid 40% solution (21 g; 0.11 mol) at 500C for 2 hours. TABLE I Surface Tension of Amine Oxide Fluorosurfactants Surface Tension (Dynes/cm) at Concentrations (%) Example ermine Oxide 0.1 0.01 0.001 1. N,N-Dimethyl(3-Perfluoroalkyl- 17.3 18.4 36.1 2-Hydroxypropyl)Amine N-Oxides 2. N,N-Dimethyl(3-Perfluoro-2- 17.0 18.8 25.3 #etoxypropy1)Amine N-Oxides 3. N,N-Diethyl(3-Perfluoroalkyl- 16 .b 17.3 21.5 2-Acetoxypropyl)Amine N-Oxides 4. N-Butyl-N-Methyl(3-Perfluoro- 17.2 17.5 23.9 alkyl-2-Acetoxypropyl)Pçnine N-Oxides 5. N-(3-Perfluoroalkyl-2-Acetoxy- 17.1 21.0 31.7 propyl)Piperidine N-Oxides 6. N,N-Diethyl(3-Perfluoroalkyl- 17.8 18.5 21.6 2-Acetoxypropyl)Amine N-Oxides 7. N-(3-Perfluoroalkyl-2-Acetoxy- 17.8 18.5 20.7 propyl)Piperidine N-Oxides 8. N,N-Dimethyl(3-Perfluoroalkyl- 18.1 19.3 26.0 2-Acetoxypropyl)Amine N-Oxides 9. N,N-Bis(Hydroxyethyl) (3-Per- 16.8 17.5 24.9 fluoroalkyl-2-Hydroxypropyl) Amine N-Oxides 10. N,N-Dimethyl(3-Pefluorohexyl- 16.4 18.1 44.6 2-Acetoxypropyl)Amine N-Oxide 11. N,N-Diethyl(3-Perfluorohexyl- 16.4 20.7 45.6 2-Acetoxypropyl)Amine N-Oxide 12. N Cutyl-N-Methylt3-Perfluoro- 16.9 21.6 41.7 hexyl-2-Acetoxypropy1)Pmine N-Oxide 13. N,N-Bis(Hydroxyethyl) (3-Per- 15.7 29.7 57.2 fluorohexyl-2-Hydroxypropyl)- Amine N-Oxide 14. <RTI ID=25.18> N,N-Djmethyl(3-Perfluoro- 16.6 17.5 21.1 octyl-2-Hydroxypropyl)Amine N-Oxide 15. N,N-Dimethyl(3-Perfluorooctyl- 16.2 16.4 17.5 2-Acetoxypropyl)Amine N-Oxide TABLE I (cont.) Surface Tension of Amine Oxide Fluorosurfactants Surface Tension (Dynes/cm) at Concentrations (t} Example Amine Oxide 0.1 0.01 0.001 16. N-(3-Perfluorooctyl-2-Hydroxy- 18.0 18.2 22.0 propyl) Piperidine N-Oxide 17. N,N'-Bis(3-Perfluorohexyl- 17.0 18.4 21.1 2-Acetoxypropyl)-N,N'-Dimethyl- hexamethy lenediamine- N,N1-Dioxide 18. N,N'-Bis(3-Perfluorobexyl- 17.5 17.5 25.3 2-Acetoxypropyl)-N,N'-Diethyl- hexamethylenediamine N,N'-Iioxide

Claims: CLAIMS 1. A 1,1,2,3, 3-pentahydroperfluoroalkylamine N-oxide represented by the formula: EMI27.1 wherein Rf is C3-C20 perfluroalkyl; R is H or alkanoyl containing 1-4 carbons; R1 and R2 are the same or different C1-C6 alkyl or C1-C6 hydroxyalkyl, or together with the N atom to which they are bonded form a piperidine, morpholine or N-alkyl(C1-C4) piperazine ring; or R1 is C1-C6 alkyl or C1-C6 hydroxyalkyl and R2 is EMI27.2 R3 is C1-C6 alkyl or C1-C6 hydroxyalkyl; and n is an integer from 1-8; and mixtures thereof. 2. Mixtures of amine N-oxides as claimed in claim 1 wherein 80-90% of the Rf groups contain 6-12 carbons. 3. Mixtures of amine N-oxides as claimed in claim 2 wherein said Rf groups contain 6-10 carbon atoms. 4. Mixtures of amine N-oxides as claimed in claim 1, 2 or 3 wherein the average of the chain lengths in the Rf groups is 6-8 carbons. 5. An amine N-oxide or mixtures of amine Noxides as claimed in any one of the preceding claims wherein R is acetyl. 6. A process for reducing surface tension in an aqueous system comprising adding thereto an effective amount of an amine N-oxide or mixture of amine N-oxides as claimed in any of the preceding claims. 7. A process for generating foam in an aqueous system comprising adding thereto an effective amount of an amine N-oxide or mixture or amine N-oxides as claimed in any one of claims 1 to 5 and agitating the same. 8. A process for preparing an amine N-oxide or mixtures of amine N-oxides as defined in any of claims 1 to 5, which comprises reacting an oxidizing agent with an amine or mixture of amines represented by the formula: EMI28.1 wherein Rf, R, R1 and R2 are as defined in claim 1. 9. A process according to claim 8, wherein said oxidizing agent is peracetic acid. 10. A process according to claim 8, wherein said oxidizing agent is hydrogen peroxide.

Inventors: CLARKE, RAY ALLEN, CORDS, DONALD PHILIP
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1984
Main classification: C07C135
IPC codes: C07C291, B01F17, B01D19, C11D1, C07D295