2,913,481 United States Patent Office Patented Nov. 17, 1959 arimanoramitroverwar 2 the solvent at low temperature or by crystallisation at 2,913,481 low temperature. The pure hyponitrous esters are how ever dangerous detonating explosives and isolation is ESTERS OF HYPONTROUSACD usually avoided. Hyponitries can be prepared from un John Wooley Batty, Arthur Lambert, and Gerald Scott, 5 stable halides which can be generated in situ. Blackley, Manchester, and Leslie Seed, Northwich, Eng The yield of the new hyponitrites is greater than the land, assignors to Imperial Chemical Industries Lim: yield of alkyl hyponitrites described in the prior art when ited, Milburne, London, England, a corporation of prepared by the same general reaction. Thus, for ex Great Britain ample, whereas the yield of isobutyl hyponitrite by inter No Drawing. Application April 29, 1957 0 action between silver hyponitrite and isobutyl iodide is Serial No. 655,478 about 10%, the yield of methoxymethylhyponitrite from chloromethyl ether under similar conditions is about 95%. Claims priority, application Great Britain May 2, 1956 Other hyponitrites included within the general class 8 Claims. (CI. 260-466) provided by this invention include esters (which may be 5 polymeric) of the general structure This invention relates to esters and more particularly to hyponitrous esters especially useful as catalysts for X-O-CHY-O-N-N-O-CHY-O-X the polymerisation of ethylenically unsaturated com wherein X may be alkyl, alkoxyalkyl, cycloalkyl or aryl pounds. and Y may be hydrogen, alkyl, cycloalkyl, aryl, alkoxy, This application is a continuation-in-part of our appli 20 alkoxyalkyl or may form part of a ring with X. cation Serial No. 607,559, filed September 4, 1956, and Those hyponitrites are preferred which contain the now abandoned. structure R'-O-CH2-O-N FN-O-CH-O-R' It has already been proposed, in specification Ser. No. wherein R' stands for ethyl, n- or isopropyl, n-, iso- or 618,168, now Patent Number 2,809,787, to use for ex sec-butyl, iso-amyl, n- or sec-octyl, 2:4:4-trimethylpentan ample alkyl, allyl or benzyl hyponitrites as catalysts for 25 2-yl, 3:5:5-trimethyl-hexan-1-yl, dodecyl, cyclohexyl, etc., the polymerisation of ethylenically unsaturated com or stands for a difunctional group containing for example pounds. other or the same O-alkoxyalkyl hyponitrite groups, ox Of these hyponitrites, which have been prepared by chloroether groups, etc.; examples of such hyponitrites interaction between silver hyponitrite and alkyl, allyl or are those obtained from bis(halogenomethyl) ethers, etc. benzyl iodide, bis-benzyl and allyl hyponitrites are very 30 Also within this preferred class are tetrahydropyranyl and inefficient initiators, particularly in the case of the less tetrahydrofuranyl hyponitrites. - reactive monomers such as vinyl acetate or ethylene. The invention is illustrated but not limited by the Alkyl hyponitrites are more efficient initiators, but are not following examples in which parts and percentages, are obtained in good yield by this method. We have now by weight. found that when there is used, in place of an alkyl iodide, 35 Example. I an organic halide which may be a dihalide in which the organic residue contains at least one ether oxygen atom, 27.6 parts of silver hyponitrite and 22.2 parts of mono the organic hyponitrites so obtained are also valuable chloromethyl ether are cooled in ice and are mixed to catalysts for the polymerisation of ethylenically unsatu gether in 200 parts of white spirit and the mixture is rated compounds, and in particular for the polymerisation 40 stirred for 16 hours at 0° C. At the end of this time, the of such unreactive monomers as ethylene and vinyl silver chloride is removed by filtration at 0°C. and bis acetate. methoxymethyl hyponitrite is obtained as a solution in Thus according to the present invention we provide new white spirit. The yield of bis-methoxymethyl hyponitrite esters of hyponitrous acid wherein the organic residue con may be determined by adding 5 parts of an 80/20 ethanol tains at least one ether oxygen atom, preferably on an 45 water mixture to 1 part of the solution thereof first ob alpha carbon atom. tained, followed by warming to 50° C. and measurement The new organic hyponitrites have the formula of the volume of nitrogen, evolved. The yield so deter R-O-N FN-O-R' wherein R and R stand for mined is about 70% based on silver hyponitrite and the organic radicals containing at least one ether oxygen atom, concentration of the ester in-the-white spiritis about 5.3%. preferably on the alpha carbon atom. Furthermore, R Example 2 and R', and optionally the hyponitrous acid residue may 2.08 parts of silver hyponitrite and 25 parts of the form part of a ring system. diethyl ether of diethylene glycol are stirred at -10 C. The new organic hyponitrites may be prepared by inter whilst 1.27 parts of monochloromethyl ether are slowly action between silver hyponitrite or other metal hypo added. The solution is stirred for 12 hours at -10° C. nitrite and a halide R-Hal (when monomeric compounds and is then filtered at 0° C. from the precipitated silver are obtained) or Hal-R-Hal (when polymeric com chloride and the precipitate is washed with two portions of pounds may be obtained) wherein R has the significance 0.9 part of the diethyl ether of diethylene glycol. The stated above, preferably in solution in an inert hydro solution so obtained has a concentration of approximately carbon solvent, for example white spirit, ethers or aro 22% of bis-methoxymethyl hyponitrite as determined by matic hydrocarbons. Other solvents that may be used 60 the nitrogen evolution method of Example. 1. The yield include readily volatile compounds and liquefied gases of bis-methoxymethyl hyponitrite is 90-95% of the including ethylene and also other polymerisable mono theoretical. mers that are to be polymerised by means of the hypo nitrite. The reaction is controlled by external cooling of Example 3 the reaction mixture usually to a temperature of -20 65 1.04; parts of silver hyponitrite and 5.0 parts of dify C. to 10° C., preferably to below -10° C. When the ether are stirred at -10° C. whilst 0.635 part of mono reaction is finished, the silver halide may be removed by chloromethyl ether is slowly added. The solution is filtration. The so-obtained solution of the hyponitrite stirred for a further 12 hours at 0° C. and is then filtered may be used as such, for example in the polymerization of at 0 C. and the residual silver chloride is washed with ethylenically unsaturated compounds, or the hyponitrite two portions of 1.5 parts of ether. The ether solution may be isolated therefrom, for example by evaporation of is evaporated in a slow stream of dry air whilst maintain 2,913,481 3 4 ing the temperature at 0° C. Bis-methoxymethyl hy uct are melting point 3–6. C., nitrogen 12.1% (theory ponitrite is obtained as a pale yellow oil; the oil is a 12.0%). detonating explosive sensitive to friction, shock or Sudden 0.102 gm. of the crystallised isobutoxymethyl hypo temperature change. nitrite is dissolved in 2 ml. of white spirit and is heated - Example 4 to 60° C. The gas evolved is collected over white Spirit in a gas burette and the volume is measured at the same 2.08 parts of silver hyponitrite and 2.5 parts of the di temperature (21 C.) as that of the cooled spent solution. ethyl ether of diethylene glycol are stirred at -10 C. 96.2 mls. of gas (98.6% theory) substantially nitrogen, whilst 1.84 parts of chloromethyl isobutyl ether are slow are evolved. The experiment is repeated; the gas is co ly added. The solution is stirred for 12 hours at 0°C. 10 lected over mercury and analysed. No gases other than and is then filtered from the precipitated silver chloride nitrogen and about 2% of hydrogen are detected. CO2, and the precipitate is washed with two portions of 1 part oxygen, CH4 and hydrocarbon gases are shown specifical of the diethyl ether of diethylene glycol. The solution ly to be absent by vapour phase chromatography. has a concentration of approximately 25% of isobutoxy A similar yield of gas, but this time containing about methylhyponitrite, as determined by the nitrogen evolu 5 5% hydrogen, is obtained when the pure hyponitrite is tion of Example 1. The yield of isobutoxymethyl hy dissolved in purified diethyl oxalate. ponitrite is approximately 70% of the theoretical. The pure hyponitrite is soluble to the extent of 24% Example 5 in white spirit at -14 C. and 5% at -36 C.; that 27.6 parts of silver hyponitrite and 100 parts of the solution exhibits absorption in the infra red region which diethyl ether of diethylene glycol are mixed and stirred 20 is characteristic and is predominantly at 973 and 984 at -15° C. and 24.2 parts of 2-chlorotetrahydropyran are cm. l. slowly added. The mixture is stirred at -15° C. for 12 Example 8 hours and then the silver chloride is removed by filtra The process of Example 7 is repeated using 5.38 parts tion at 0 and is washed twice with 50 parts of the di of cyclohexyloxymethyl chloride (99.5%) and 5.5 parts ethyl ether of diethylene glycol. A portion of the solu 25 of silver hyponitrite. A yield of 70% of the ester is tion is estimated by the method of Example 1 and the obtained.