US2494650A - Production of n-(hydroxy-aryl) aspartic acid diesters - Google Patents

Description

water.

Patented Jan. 17, 1950 UNITED STATES PATENT OFFICE PRODUCTION OF N- (HYDROXY-ARYL) ASPARTIC ACID DIESTERS Lawrence'H. Flett, Scarsdale, and Leon W. Seigle, Bronxville, N. Y., assignors to Allied Chemical & Dye Corporation, New York, N. Y., a corporation of New York No Drawing. Application January 11, 1945,

' Serial No. 572,432

COIHbUStiOHTITlOtOIS must possess a combination of several properties. Itmust be effective for inhibitinggum formation :at such. small concentrationth'atith'e quantity of inhibitor added to the fuel doesinott alter the performance :of. the fuel. It must be s'ufliciently volatile'to avoid the formation" or. deposits in thecarburetting system. It must besuflicie'ntly stable to retain its effectiveness upon stor'age of the fuel, and sufficiently inert andzinsoluble'in water to avoid substantial destruction or removal of the inhibitor upon contact of the fuel with containers andwith water as the fuel'is stored: and-handled- Furthermore, a satisfactory gum inhibitor must be so1ub1em the fuel to-ber stabilized in the small concentrations at which it is used for inhibiting'gum formation and must not alter the appearance" of the fuel in such a wayas to make the stabilized fuel commercially unacceptable: gasoline or other clear distillate whichis made' turbid and'darkcolored upon addition of a stabilizer, for example,is not generally acceptable in commerce;

As pointed: out in. ListonPatent 2,207,063 of J uly 9, 1940 theN- (hydroxy-aryl') and N- (aminoary'l) aspartic acid diester's have particular merit as guminhibitors"for 'fuels for internal combustion motors. These compoundsgive satisfactory stabillation' in" relatively low concentrations, do notforni depositsincarburetting'systems, are not only" stable upon storage and handlingof'the fuel, but are even improved in effectiveness with suchstorage and handling in the presence of It has been found, however, that the N:- (hydr'oxy-aryl) aspartic acid diester inhibitors made as described in this patent have the disadvantage of imparting a. pronounced cloudiness to theafuelsirrwhich they are used. Such cloudinessi does not'interfere with the effectiveness of the compounds: in preventing gum formation but does-make the compoun'ds unacceptable in commerce;

We have now discovered a new method of preparing N-(hydroxy aryl) aspartic acid diester antioxidants which, when added to a motor fuel such as gasoline in sufficient concentration for inhibitingv gum formation, impart no haze or cloudinesseto the fuel; Our new method of preparing these compounds involves condensing a, diester ofmaleic. or fumaric acid'with a hydroxyaryl amine in the presence of a monohydric alcohol having an appreciable water solubility, i. e. soluble in water to the extent of at least 0.5% and preferably, at least about,5% by weight at room temperature (25 C.). Water is also preferably present in the condensation reaction mixture and.

the condensation is preferably carried out in the presence of a small amount of an alkaline material. The reaction should be carried out at a temperature below 150 (3., preferably below 100 C., and most advantageously in the range to C.

One possible explanation which may be ad vanced for the fact that the process of this invention produces an N-(hydroxy-aryl) aspartic acid diester which, when added to motor fuel such as gasoline, gives clear solutions, whereas such diesters made in the absence of a diluent alcohol give highly turbid solutions, is that the process of this invention results in the production of a product substantially free, or containing a substantially smaller amount, of constituentssuch as para-aminophenols, amidesand acids, which are'believed to impart haze and turbidity to the motor fuel. Another factor is believed to be an alcoholysis reaction that takes place at the same time as the condensation, whereby radicals from the diluent alcohol are substituted to some extent for the radicals of the diester employed in the condensation reaction, forming a complex mix ture of aspartic acid diesters. Thus, when condensing diisobutyl maleate and para-aminopheno] in the presence of ethy1 alcohol, it has been found that ethy1 groups are substituted for the isobutyl groups in the final aspartic acid diester to the extent of about 15%, robably forming minor amounts of both a diethyl aspartate and an ethylisobutyl' aspartate, in addition to the predominant diisobutyl aspartate.

The composition that is produced when the diluent alcohol contains different radicals than those present in themaleic or fumaric diester, we have found, is a particularly advantageous gum inhibitor. This new compositionis a mixture of two or more diesters of the above-described N-substituted aspartic acid, in which, on the average, radicals derived from the diluent alcohol makeupfrom about 5 to 50 mol of the alcohol radicals inv the N-substituted aspartic diesters.

In a preferred method of preparing N-'(hydroxy-aryl) aspartic acid diesters in accordance with the process of our invention, the reactants are mixed and the mixture is heated under reflux at the temperature indicated, at atmospheric pressure, or, if desired, at higher or lower pressures. until the reaction is substantially complete or reaches a point when substantially no further reaction takes place. This may require from 2 to 120 hours depending on the temperature. Completion of the reaction is determined by analyzing a sample of the reaction mixture for unreacted aminophenol.

The diester of maleic or fumaric acid employed in the reaction may be any mixed or symmetric diester, but it is preferably one in which the alcohol radicals are alkoxy or aralkoxy; i. e. the diester reactant is preferably a dialkyl (including dicycloalkyl) or a diaralkyl maleate or fumarate, the two alcohol radicals being either the same or dissimilar. Examples of suitable esters include: dimethyl, diethyl, diisopropyl, diisobutyl, di-secondary butyl, di-(2-ethyl-hexyl), dilauryl, dibenzyl, dicyclohexyl, di-tetrahydroiurfuryl, cet-yl isobutyl,

ethyl isobutyl, methyl ethyl and ethyl isopropyl I maleate or fumarate. Such diesters may conveniently be prepared just prior to carrying out the condensation reaction of the invention by refluxing maleic anhydride or maleic or fumaric acid with the desired alcohol or alcohols for esterifying the acid 01' anhydride. A dialkylmaleate or fumarate in which each alkyl group contains no more than 5 carbon atoms is particularly suitable.

The hydroxy-aryl amine condensed with the maleic or fumaric ester may be a hydroxy-amino derivative of benzene, naphthalene, diphenyl, or the like, but is preferably a mononuclear aminophenol. This amine reactant is preferably employed in about equimolecular proportion to the fumaric or maleic ester, but either of the reactthe condensation in accordance with our new process as above stated are the monohydric alcohols having appreciable water solubility, i. e. soluble in water to the extent of at least 0.5% and preferably at least about 5% by weight. These include: methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, the various butyl alcohols, the amyl alcohols (e. g. normal amyl alcohol, methyl-n-propyl carbinol, etc.), Cellosolve (beta-ethoxy ethyl alcohol), Methyl Cellosolve (beta-methoxy ethyl alcohol), Butyl Cellosolve, Carbitol (monoethyl ether of diethylene glycol). These alcohols may be employed in the condensation reaction mixture with or without water but are preferably used with water; i. e. the diluent for the condensation reaction may range from a substantially anhydrous alcohol to a dilute aqueous alcohol solution containing, for example, as little as about 5% alcohol, and the alcohol present will still exert its ameliorating effect on the reaction. Preferably, an aqueous alcohol diluent should contain not less than by weight of alcohol. The alcohol (or aqueous alcohol solution) should make up at least 15% by weight of the condensation reaction mixture and may be present to the extent of of the reaction mixture. Preferably, the anhydrous or aqueous alcohol is present to the extent of from one-half to five times the weight of maleic or fumaric diester reactant. Our preferred alcohol diluent is an aqueous solution of an alcohol of not more than 5 carbon atoms, advantageously ethyl alcohol, most advantageously a solution of about 40% to 60% concentration. This ethyl alcohol solution most advantageously makes up from about 40% to 60% of the condensation reaction mixture.

The alkalies'suitable for addition to the condensation reaction mixture of our invention in clude particularly the tertiary nitrogen bases and organic ammonium compounds which are inert towards the reactants, e. g. pyridine, quinoline, dimethylaniline and triethylamine, and inorganic alkaline salts such as sodium carbonate and bicarbonate, trisodium phosphate. Such alkaline materials are preferably added in amount from 0.4% to 4% of the weight of the maleic or fumaric diester; i. e. preferably make up from 0.1% to 1% of the condensation reaction mixture.

The products of the present invention may be employed as gum inhibitors for motor fuels derived from cracked hydrocarbon distillates in general and particularly for internal combustion motor fuels such as gasoiines that contain appreciable amounts of unsaturated compounds that tend to polymerize t0 gums. For accomplishing its inhibiting action, the compound of our invention is added to the motor fuel in only a small amount, preferably to yield a. concentration between 0.001% and 0.1% by weight of the mixture. The solid compounds may be added directly to the gasoline or may first be dissolved or suspended in a diluent miscible with the gasoline, for example, in anhydrous ethyl alcohol, butyl alcohol or propyl alcohol or any other suitable alcohol. We have found it is quite advantageous either to add the solid inhibitor directly to gasoline or to dissolve it first in ethyl alcohol and add this solution to the gasoline.

As above pointed out, inhibitor compounds prepared in accordance with our invention have the important advantage of not appreciably altering the appearance of the gasoline; i. e., although some gasoiines stabilized by compounds prepared in accordance with our invention may show a faint haze in a cone of strong light directed through the gasoline, they do not show the undesirable haze or opacity visible to the naked eye under normal lighting conditions that results from using as gum inhibitors compounds of the same class prepared by carrying out the condensation in the absence oi an alcohol diluent as above described.

The following examples are illustrative of our invention. All parts are by weight.

Example 1. A mixture of 98 parts of maleic anhydride, 156 parts of isobutyl alcohol, 17.3 parts of toluene and 0.25 part of p-toluene-sulfonic acid was heated to boiling in glass apparatus and refluxed until esterification was complete, as indicated when no further water was distilled from the mass. The reaction mixture was cooled to about room temperature after which 158 parts of 2B ethyl alcohol (96% alcohol denatured with /2 gallon of benzene per 100 gallons of ethyl alcohol in accordance with the specifications for 213 ethyl alcohol: U. S. Treasury Dept, Bur. of Internal Rem, Appendix to Reglns. #3. Formulae for completely and specially denatured alcohols, 1942, page 14), 200 parts of water, 1 part of pyridine and 109 parts of p-aminophenol were added-A, Theimixturea thus obtained: zwasfirefluxed (temperatures Bit-86% C.) with 1 agitation on: av

steam: bathfor172 hours, after which it wascooled to :50-'C.. .andrisludge -filtered to remove. insoluble particles; The-iflltrate was-mixed withza solu-. tion 'of .200 -partsr:by volume of ZB'et-hyl alcohol andszbomartsr byv-volume of water; and-the re.- sultingo agitated emulsion: was" cooled-:1 to room'- temperature :and 'zstirreduntil the' emulsion was broken." andzifines particles of tan crystals 2 were formed; The: mass was agitated for abut' /2 hour-. torcomplete thecrystallization of the solid; which was washed with a solution of IOOwparts by=volume:of 2B ethyl alcohol and :100 :pprtscby volume of water; thenz'wi-th-about 6000 partsof waten'andrdried.at.40 -50 C. in vacuo toyield a flnely dlvideddlight tan solid; The productwas a mixture of ethyliand isobutyl esters of N=(phydroxyphenyl'). aspartic acid', probably ae'mix ture of N (p-thydroxy=phenyl) diethyl aspartate, N=(pehydi:oxy-phenyl) diisobutyl aspartatev and N-(p-hydroxy-phenyl') monoet-hyl monoisobutyl aspartate in unknown proportions. On the averagepethyl'radicals constituted about 15 -mol per cent of therester forming radicals. and isobutyl radicals aboutaimolper cent (the mol' per cent referring'tosmolsof corresponding alcohol). The meltlngrpoint lot the. product over a" number of runs varied slightly between the 'temperaturesof 65 'and-*80-".'-'C. The product was appreciably lighten-in" color 'than the' product resulting from the practice of "a process'which differs from'that ofthis example inthat nodiluent'alcoholwas used. The yield ranged from abcut'70% to 80% of" theory" calculated. as N-(p hydroxy-phenyl) diisobutyl "aspartate.

In twoparallel tests, the product thus obtained and aproduct prepared by a process which-difiers-from EXample 1, above, chiefly inthat-no diluent alcoholwas used, which latter product ishereafter-referred to as Prior Product, were eaehadded to separate samples of the same gasoline; This-was accomplished by dissolving .1335 gramsofeach gum inhibitor in sufiicient anhydrous 2B ethyl alcohol to give a Volume of cos. and adding 0.01 cc. of each solution to 50 cc; of Skellysolve '-C (a water-white low-boiling hydro-- carbon" material consisting essentially of parat finic' hydrocarbons) The'solution-of Skellysolve C, prepared as described abovefrom the product obtained as describedby-the'process of our'invention, was completely-clear=to the naked eye at ordinary tom peraturesand under normal lighting conditions and'showed onlya slight'Tyndall effect when illuminated by a'coneof light. The Skellysolve C solution-ofthe PriorProduct appeared consider ably-turbid under normal lighting conditions; Both thepresent product and the Prior Product possessed the same efilci'encywhen tested as gasol'ine guminhibitors.

Erta'mpte 2.'--'1his example illustrates the use of "aqueous ethyl alcohol of 90%, 70% and 30% volume concentration as diluent.

114' parts' of diisobutyl maleate, 54.5 parts of para-aminophenoly and about 155 parts of the 2B ethyl alcohol; 10 parts of water, and 015' part pyridine werecharged to a stillequipped with an agitator and a'refiux condenser. Themixture'was a'gitatedand:refluxed for '72 hours, thus bringing? about the desired condensation in the presenceofabout'90 volume per cent'aquecus ethyl alcohol. The 'reaction'mixture was-allowed to'cool somewhat and a solution ofan additional oven at room temperature.

190 parts otzwater andrz8rparmsof ther2B3etliyl aloohclrwereeaddedl Thiszdilutionzgaveiapprox'ie mately (imparts of a;. .50% .by; volume aqueous alcohol.ffrom which'to isolate .theaproduct. The mixtures-was filtered; and t the filtrate: was: agie tatedrrapidly and cooled. A solidseparatedsin rather large pellets; This-product: was'fi'ltered off 'andzwashed. with aboutz200'parts of the aqueous: ethyl alcohol. The solid. was then re--= slurriediirr 500 partsof :water; filtered and washed with'zfiooapartsot water. Theaproduct wasdried' ati40fi 50fi Cain: a: vacuum ovenproduct were thus obtained.

This procedure. was: repeated, in: one case carryingout the condensation in .the presence of an aqueous alcohol solution containing, about%l by volumeof alcohol and in another case. in the presence: of: aqueous alcohol solution containingrabout 30% by =volume ethyl alcohol. Reaction" in lthese solvents gave .150 parts and 132 parts of product, respectively.

Each otthese three products, when-added to gasoline, as described in Example 1, gave'substantially less: haze than the Prior Product.

Example: 3.' -Isopropyl alcohol was substituted for the ethyl alcohol in our preferred method or preparation, as described in Examples 1 and 2, above.-

114 parts of diisobutyl maleate, 54.5 partsof para-aminophenol, about partsof isopropyl alcohol, parts of water, and 0.5part of pyridine were refiuxed ior '72 hours.- The reaction mixture was allowed-to cool slightly and was then filtered-. The filtrate was diluted with 200 parts- 0f :approximately 50% I aqueousethyl alco= hol, agitated and cooled. The-light yellow solid which: separated .wasfiltered ofi and washed with 200*parts of I approximately 60% aqueous ethyl alcohol and- 2500 partsof water and was then driedin a -vacuum oven at -50 60' C. The result ing pr oduct obtainedina yield of 124 parts was employed as a gum inhibitor for gasoline as above. described and the gasoline showed I sub"- stan:tially=--l'ess haze when a conical beam of light was: directed therethrough than the Prior Product. Example 4.-This example illustrates the use of anhydrous methyl alcohol as diluent.

5 1 parts of diisobutyl maleate and 2712 parts of para-aminophenol were refluxed in about 1 60 partsof methyl alcohol for 96-hours; The reaction mixture was filtered and the filtrate was drowned in 2000vparts of cold water. The solid which formed was filtered off and dried: in' a vacuum Thisproduct, when addedrfto gasoline; gave substantially less'haze than the Prior Product,

Emamp1e-5.-This exampleillustrates the use of aimixture-"of "Cel los'olve, ethyl alcohol and water as-diluent.

About 57 parts of diisobutyl maleate', 272 parts of para-am'inophenol, 100 parts of Cellosolve, 102 parfs'0f-2Bethy1 alcohol and 69' parts ofwater were: mixed; warmed slightly and agitated until a homogeneous solution was obtained. Thesolu tion'was stoppered and allowed to stand at room temperaturefor about 69 '-days- At theend of thattime; thes mixture was chilled and-the -in-. soluble-material was removed-by filtration.- The filtrate wasdrowned in 1500 parts of water. A light tan soli'd: was: isolated, washed with about 200 parts 'ofazvolati'le-parafilnic hydrocarbon sol vent and dried at room temperature 'in a-vacuum oven Thee product: gave substantially no haze when incorporated in gasolineas wgum inhibitor.

, Various N-(hydroxyl-aryl) aspartic acid diesters may each be prepared by procedures such as those described in the above examples, by employing in each case a diluent alcohol containing the same radicals as the diester, and although the chemical composition of the compound obtained will apparently be substantially the same as the compounds of said Patent 2,207 ,064, nevertheless a gasoline containing the ester prepared in accordance with our invention in the concentration proper for inhibiting gum formation, is substantially clear under normal lighting conditions, whereas the compound, nominally the same, prepared without the diluent alcohol gives an undesirable cloudy gasoline. The compounds listed below are typical gum inhibitors that may be thus prepared by the process of our invention:

N-(p-hydroxy-phenyl) diethyl aspartate N-(p-hydroxy-phenyl) diisopropyl aspartate N-(p-hydroxy-phenyl) di-secondary butyl aspartate N- (p-hydroxy-phenyl) aspartate N- (p-hydroxy-phenyl) dilauryl aspartate N-(p-hydroxy-phenyl) cetyl isobutyl aspartate N-(p-hydroxy-phenyl) dibenzyl aspartate N-(p-hydroxy-phenyl) dicyclohexyl aspartate di- (2'-ethyl-hexyl) N-(p-hydroxy-phenyl) ditetrahydrofurfuryl aspartate By carrying out the process of our invention as described in the above examples employing a diluent alcohol containing radicals dissimilar to the alcohol radicals of the maleic or fumaric diester, particularly advantageous gum inhibitor compositions may be obtained, as above pointed out, that are mixtures of two or more N -substituted aspar tic acid diesters. Such mixtures, as above stated, may contain two difierent symmetrical diesters and may also contain the unsymmetrical diester; i. e., the diester containing in the same molecule one alcohol radical from the diluent alcohol and one alcohol radical from the maleic or fumaric diester. Examples of such gum inhibitor compositions are:

Mixed methyl and ethyl esters of N -(p-hydroxyphenyl) aspartic acid Mixed methyl and isobutyl esters of N-(p-hydroxy-phenyl) aspartic acid Mixed ethyl and lauryl esters of N-(p-hydroxy phenyl) aspartic acid Mixed ethyl and isobutyl esters of N- (p-hydroxyphenyl) aspartic acid Since certain changes in carrying out the above process, and certain modifications in the composition which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. In the production of an N- (p-hydroxy-aryl) aspartic acid diester by condensation of an unsaturated diester selected from the group consisting of maleic and fumaric diesters with a mononuclear aminophenol, the step that comprises bringing about such condensation by interaction between the unsaturated diester and the mononuclear aminophenol at a temperature of at least room temperature but under 150 C., in a liquid reaction medium containing as active ingredient at least 5% of a 1-5 carbon alkanol that is soluble at C. in water to the extent of at least 0.5% by weight.

2. In the production of an N-(hydroxy-aryl) aspartic acid diester by condensation of an unsaturated diester selected from the group consisting of maleic and fumaric diesters with a mononuclear aminophenol, the step that comprises bringing about such condensation by interaction between the unsaturated diester and the mononuclear aminophenol, at a temperature of at least room temperature but under C., in a liquid reaction medium containing as active ingredient at least 5% of a l-5 carbon alkanol that is soluble at 25 C. in water to the extent of at least 0.5% by weight.

3. In the production of an N-(hydroxy-aryl) aspartic acid diester by condensation of an unsaturated diester selected from the group consisting of maleic and'fumaric diesters with a hydroxy-aryl amine, the step that comprises bringing about such condensation by heating, at a temperature of at least room temperature but below about C., a mixture of said diester. said amine, an aqueous solution of a 1-5 carbon alkanol that is soluble at 25 C. in water to the extent of at least 0.5% by weight said alkanol being present in amounts from one-half to five times the weight of said unsaturated diester, and about 0.4% to 4% by weight on the diester of an alkaline material substantially inert toward the reactants.

4. In the production of an N-(hydroxy-aryl) aspartic acid diester by condensation of an unsaturated diester selected from the group consisting of maleic and fumaric diesters with a mononuclear aminophenol, the step that comprises bringing about such condensation by heating, at a temperature of at least room temperature but below about 100 C., a mixture of said diester, said aminophenol, a 1-5 carbon alkanol that is soluble at 25 C. in water to the extent of at least 5% by weight said alkanol being present in amounts from one-half to five times the weight of said unsaturated diester, and about 0.4% to 4% by weight on the diester of an alkaline material substantially inert toward the reactants.

5. In the production of an antioxidant consisting of an N-(hydroxy-aryl) aspartic acid diester by condensation of an unsaturated diester selected from the group consisting of maleic and fumaric diesters with para-aminophenol, the step that comprises bringing about such condensation by interaction between the unsaturated diester and the para-aminophenol at a temperature in the range of about 60 to 90 0., in about 15% to 70% by weight of the reaction mixture of an aqueous solution of at least 25% concentration by weight of a 1-5 carbon alkanol containing about 0.4% to 4% by weight on the diester of an alkaline material substantially inert toward the reactants.

6. In the production of an antioxidant oi the class of N-(hydroxy-aryl) aspartic acid diesters by condensation of an unsaturated diester selected from the group consistin of maleic and iumaric diesters with an aminophenol, the step that comprises bringing about such condensation by interaction between the unsaturated diester and the aminophenol at a temperature of at least room temperature but below about 150 C. in a liquid reaction medium containing as active ingredient at least 5% of a 1-5 carbon alkanol that is soluble at 25 C. in water to the extent of at least .5% by weight, in which alkanol the alcohol radical is diiferent from the alcohol radicals of the diester and by an alcoholysis reaction replaces to an extent of from 5% to 50% the original alcohol radicals of the diester with alcohol radicals derived from said alkanol.

7. A process as defined in claim 6 in which the unsaturated diester is a dialkyl fumarate.

8. A process as defined in claim 6 in which the unsaturated diester is a diaralkyl maleate.

9. In the production of an antioxidant comprising a mixture of N-(hydroxy-aryl) aspartic acid diesters by condensation of a dialkyl maleate in which the alkyl radicals contain no more than 5 carbon atoms, with para-aminophenol, the step that comprises bringing about such condensation by interaction between the dialkyl maleate and the para-aminophenol in 15-70% by weight of the reaction mixture of an aqueous solution of at least 25% concentration by weight of an alkanol in which the hydroxyl group is attached to an alkyl radical of not more than 5 carbon atoms, dissimilar to the alkyl radicals of said unsaturated ester, at a temperature of at least room temperature but below about 100 0., whereby said unsaturated diester condenses with said para-aminophenol and at the same time an alcoholysis reaction takes place to substitute alkyl radicals of the alcohol to an extent of from 5% to 50% for the alkyl radicals of the diester.

LAWRENCE H. FLETT. LEON W. SEIGLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,207,063 Liston Jul 9, 1940 2,324,712 Lynch July 20, 1943 OTHER REFERENCES Groggins, "Unit Processes in Organic Synthesis, page 559, McGraw-Hill, N. Y. (1938).

Certificate of Correction Patent No. 2,494,650 January 17, 1950 LAWRENCE H. FLETT ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 34, for stabiliation read stabilization; column 2, line 2, after the word having strike out an column 7, line 8, for the patent number 2,207 ,064 read 2,207,063 line 63, for N -(p-hydroxy-aryl) read N-(hydrozy-aryl); lines 67 and 70, for mononuclear aminophenol, each occurrence, read hydrozy-aryl amine; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 16th day of May, A. D. 1950.

[sml

THOMAS F. MURPHY,

Assistant Gonwniasz'oner of Patents.

Certificate of Correction Patent No. 2,494,650 January 17, 1950 LAWRENCE H. FLETT ET AL. It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 34, for stabilietion read stabilization; column 2, line 2, after the word havin strike out on; column 7, line 8, for the patent number 2,207 ,064

read 2,207,063; me 63, for N-(p-hydroxy-aryl) read N-(hydroxy-aryl); lines 67 and 70, for mononuclear aminophenol, each occurrence, read hydroasy-aryl amine;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 16th day of May, A. D. 1950.

[smnl THOMAS F. MURPHY,

Assistant Gam/miasioner of Patents.

Certificate of Correction Patent No. 2,494,650 January 17, 1950 LAWRENCE H. FLETT ET AL. It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 1, line 34, for stabiliation read stabilization; column 2, line 2, after the word having strike out an column 7, line 8, for the patent number 2,207 ,064 read 2,207,063; line 63, for N -(p-hydroxy-aryl) read N-(h'ydroxy-cryl); lines 67 and 70, for mononuclear aminophenol, each occurrence, read hydroazy-aryl amine; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of May, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Claims (1)

1. IN THE PRODUCTION OF AN N-(P-HYDROXY-ARYL) ASPARTIC ACID DIESTER BY CONDENSATION OF AN UNSATURATED DIESTER SELECTED FROM THE GROUP CONSISTING OF MALEIC AND FUMARIC DIESTERS WITH A MONONUCLEAR AMINOPHENOL, THE STEP THAT COMPRISES BRINGING ABOUT SUCH CONDENSATION BY INTERACTION BETWEEN THE UNSATURATED DIESTER AND THE MONONUCLEAR AMINOPHENOL AT A TEMPERATURE OF AT LEAST ROOM TEMPERATURE BUT UNDER 150*C., IN A LIQUID REACTION MEDIUM CONTAINING AS ACTIVE INGREDIENT AT LEAST 5% OF A 1-5 CARBON ALKANOL THAT IS SOLUBLE AT 25*C. IN WATER TO THE EXTENT OF AT LEAST 0.5% BY WEIGHT.