United States Patent Office

Patented June 16, 1953 - - - - - 2,642.456 UNITED STATES PATENT OFFICE

N-CARBOXYALKYL-a-AMNO TOLUIC ACDS AND THEIR ALKYL ESTERs William S. Emerson, and Robert A. Heimsch, Dayton, Ohio, assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Dela ware No Drawing. Application April 25, 1950, Serial No. 158,074 8 Claims. (C. 260-471) 1. 2 This invention relates to new aralkyl amino in which R is as defined above. As illustrative dicarboxylic acids and esters of the Same. Of compounds having this structure may be men The new dicarboxylic compounds are N-car tioned N-carboxymethyl-N-methyl-a-amino-2, boxyalkyl-a-amino toluic acids and their alkyl 3- or 4-toluic acid, methyl N-carbomethoxy esters having the general structure: . . . . methyl-N-methyl-a-amino-4-toluate, butyl N 5 carbobutoxymethyl-N-methyl-a-amino-2-toluate, 2-ethylhexyl N-carbo (2-ethylhexyl)oxy-N-meth K C-CHN-Hcoor yl-a-amino-3-toluate, n octyl N-carbooctyloxy ROOC X Y. methyl-N-methyl-a-amino-4-toluate, isopropyl in which R is a member of the group consisting O N - carboisopropoxymethyl-N-methyl-a-amino-4- of hydrogen and alkyl groups of from 1 to 8 car tOluate, etc. bon atoms and X and Y are members of the Still another group of compounds provided by group consisting of hydrogen and alkyl groups of the present invention includes those obtainable from 1 to 4 carbon atoms. m - The present new aminodicarboxylic acids or by employing leucine or its alkyl esters as the their dialkyl esters are readily obtainable by con 5 amino acid compound and having the general tacting an a-halotoluic acid or an alkyl a-halo formula: . . . . . toluate with an a-amino acid or its ester, the reaction proceeding according to the scheme: X X-CHNHgico OR RO O.C. &HCHCH, & D-CH2 -- It cool a 20 (H, ROOC X in which R. is as defined above, e. g., N-(a-car boxy-at-isobutylmethyl)-a-amino-4-toluic acid. & D-chi-Hoo OR - HZ Depending upon the nature of the individual ROOC X Y. 25 reactants, the condensation may occur under in which Z is a member of the group consisting varying conditions of temperature and/or pres of chlorine, bromine and iodine, R is a member Sure. For optimum yields, however, it is advan of the group consisting of hydrogen and alkyl tageous to reflux the mixture of the toluic acid groups of from 1 to 8 carbon atoms, and X and Y Compound and the amino acid compound in a are members of the group consisting of hydrogen 30 Suitable Solvent. Also while the present amino and alkyl radicals of from 1 to 4 carbon atoms. dicarboxylic compounds are obtainable by con The toluic acid compounds which may be em ducting the reaction in the absence of any extra ployed include, e. g., a-chloro-4-toluic acid, a neous material, we have found that optimum bromo-2-toluic acid, a-iodo-3-toluic acid and yields are obtained by employing in the reaction alkyl esters of such acids in which the alkyl group 35 mixture a basically reacting material which serves has from 1 to 8 carbon atoms. As illustrative of to neutralize the hydrogen halide evolved during amino acid compounds which may be employed the condensation. Basically reacting materials may be mentioned glycine, sarcosine, a-alanine, Which may be employed include alkali and alkali leucine, isoleucine, norleucine, paline and esters. metal hydroxides, e. g., sodium, potassium, of the same with aliphatic alcohols of from 1 to 8 40 lithium, calcium, or magnesium hydroxide; basi cally reacting Salts. Such as sodium carbonate, carbonwhen atoms. employing glycine or its esters as the potassium acetate, etc. amino acid component there are obtained com As herein stated alkyl esters of the amino acids pounds having the general formula: may be used instead of the free... acids. Thus, reaction of an ester such as the ethyl ester of 45 Sarcosine With ethyl a-chloro-4-toluate will yield X X-CHNHOH.cook ethyl N-carboethoxymethyl-N-methyl-a-amino RO OC . . . in which R is a member of the group consisting 4-toluate, the methyl ester of sarcosline with a of hydrogen and alkyl radicals of from 1 to 8 bromo-3-toluic acid will yield N-carpomethoxy 50 methyl-N-methyl-a-amino-3-toluic acid, etc. carbon atoms, e.g., N-carboxymethyl-a-amino-4- Mixed esters are thus obtainable, e.g., condensa toluic acid, butyl N-carboxymethyl-a-amino-3- tion of the methyl ester of sarcosine with iso toluate, etc. propyl a-chloro-4-toluate will give isopropyl N with sarcosine or its esters, the compounds carbomethoxymethyl-N-methyl-a-amino-4- tol which are obtained have the general formula: uate. Dialkyl esters of the present dicarboxylic acids also are obtainable by esterifying the free acids ROOC X >-on H coor - With an unsubstituted, aliphatic saturated alcohol 2,642,456 3 4. of from 1 to 8 carbon atoms, preferably in the of elastomeric vinyl compositions. While many presence of an esterifying catalyst. The higher plasticizers will produce flexible compositions at alkyl esters, e. g., N-carboalkoxyalkyl-a-amino room temperature the flexibility of these com toluates in which the alkoxy group has from 4 to positions at low temperatures may vary consid 8 carbon atoms are more advantageously pre 5 erably, i. e., plasticized polyvinyl chloride com pared; however, by an interchange reaction positions that are flexible at room temperature Whereby a lower dialkyl ester of an N-carboxy-r often become very brittle and useless at low tem alkyl-a-aminotoluic acid, for example, the di peratures. Low temperature flexibility tests methyl ester is reacted with an unsubstituted, herein employed are according to the Clash-Berg aliphatic saturated alcohol of from 4 to 8 carbon method. This method determines the torsional atoms in the presence of an esterifying catalyst. flexibility of a plastic at various temperatures. Catalysts of general utility in the trans-esteri The temperature at which the vinyl chloride Com fication are basic materials, for example, potas position exhibits an arbitrarily established mini sium ethylate, metallic sodium, Sodium hydroxide, mum flexibility is defined as the Low Tempera Sodium methylate, etc. In both esterifying pro ture Flexibility of the composition. This value cedures, formation of the desired esters. Occurs to may also be defined as the lower temperature some extent at ordinary room temperatures; how limit of the plasticized composition's usefulness ever, in order to obtain good yields we prefer to as an elastomer. operate at refluxing temperatures while remov Water resistance.--The amount of water ing from the reaction zone either the water which 20 absorption and the amount of leaching that takes is given off during the direct esterification or the place when the piasticized composition is im lower alcohol generated in the interchange reac mersed in distilled water for 24 hours is deter tion. w mined. The present N-carboxyalkyl-a-aminotoluic The invention is further illustrated, but not acids and their lower alkyl esters are solids, or 25 limited, by the following examples: stable, highly boiling, viscous liquids, which may Eacomple 1 be advantageously employed in the chemical and allied industries for a wide variety of purposes. A Two hundred eight grams (1.1 moles of a number of the free acids, e. g., the N-carboxy chloro-4-toluyl chloride was hydrolyzed by heat methyl-N-methyl-a-amino-2-, 3- or 4-toluic acids ing with a mixture of 1500 cc. of water and 45 g. and the dialkyl esters thereof may serve as in of sodium hydroxide. To the resulting hydroly termediates in the production of synthetic fibers sis product (comprising a-chloro-4-toluic acid in of the polycarboxylamide type, and in the pro an aqueous solution of sodium chloride) there duction of non-ionic wetting-out and detersive was added a solution of 150 g. (1.2 moles) of agents. Sarcosine hydrochloride, 140 g. of . Sodium hy Dialkyl esters of the present N-carboxyalkyl droxide and 500 cc. of water, and the whole was a-aminotoluic acids in which the -alkyl groups refluxed for a time of 18 hours. At the end of have from 4 to 8 carbon atoms are highly efficient that time the reaction mixture was filtered and plasticizers for vinyl chloride polymers. A wide the filtrate was acidified with hydrochloric acid variety of plasticizers has been employed for the 40 to a pH of 2. Solid material was recovered by purpose of improving the physical properties of repeated subsequent filtration and evaporation vinyl chloride polymers. Particular attention has followed by filtration. When the volume of the been given to the improvement of flexibility and filtrate was reduced to about 200 cc. it was treat heat and light stability of Such plasticized com ed with an equal volume of acetone and filtered. positions. We have found that very good low All of the solids thus obtained were combined temperature flexibility is imparted to vinyl chlo and dried, a total of 507 g. of solids being ob ride polymers When the present esters are emi tained in this manner. The Solid product, thus ployed as plasticizers for Such polymers. obtained comprised a mixture of N-carboxy The present esters are valuable plasticizers for methyl-N-methyl-a-amino-4-toluic acid, sodium polyvinyl chloride and copolymers of at least 70 50 chloride and probably some sodium hydroxide. per cent by weight of vinyl chloride and up to 30 Methyl N-carbomethoxymethyl-N-methyl-a- per cent by Weight of an unsaturated monomer amino-4-toluate was prepared by refluxing the copolymerized therewith, for example vinyl ace 507 g. of solids with 2.5 liters of methanol and 50 - tate, Vinylidene chloride, etc. - cc. of sulfuric acid for 17 hours. At the end of We have found these esters serve not only to 55 that time the entire reaction mixture was sub soften vinyl chloride polymers, but also to im mitted to distillation under reduced pressure un part simultaneously a high degree of low tem til its volume had been reduced to approximate perature flexibility, very good temperature sta y One liter. This residue Was then treated with bility and great mechanical strength to thiese one liter of water and extracted 5 times - each polymers. The esters are compatible with vinyl 60 with 75 cc. of benzene. The behzene extracts chloride polymers and show no exudation of were combined, neutralized and washed twice plasticizer even at plasticizer content of up to 50 with 50 cc. of water. After drying over calcium. per cent. Although the quantity of plasticizer chloride the combined extracts were distilled at Will depend upon the particular polymer to be reduced pressure to yield 179.0 g (64.8 per cent plasticized and upon its molecular weight, it is 65 theoretical yield) of methyl N-carbomethoxy generally found that compositions having from 5 methyl-N-methyl-a-amino-4-toluate,B, P.1639. C. per cent to 50 per cent by weight of plasticizer to 177° C./1.2 to 1.4 mm. of Hg, n.25-1.5245. Will, in most cases, be satisfactory for general utility. The good flexibility of the plasticized Eacample 2 - compositions increases with increasing plasticizer 70 This example shows the preparation of 2-ethyl-, Concentration. - - hexyl N-carbo (2-ethylhexyl)oxy-N-methyl-a- In evaluating plasticizer efficiency use is made amino-4-toluate from the methyl ester of the of the following empirical testing procedures: preceding example. L020 temperature flecibility-Low temperature A mixture consisting of 37 g. (0.147 mole) of flexibility is one of the most important properties 75 methyl N - carbomethoxymethyl- N - methyl

2,642,456 5 6 a-amino-4-toluate, 65. g. (0.5 mole) of 2-ethyl amino-4-toluic acid or of N-carboxymethyl-a- hexanol and 1.0 g. of sodium methylate was placed amino-2-toluic acid with 60 parts by weight of in a flask fitted with a 24 inch Wigreux" column polyvinyl chloride or with 60 parts by weight of and refuXed for 58 hours under slightly reduced a vinyl chloride-vinyl acetate copolymer known preSSure With the pot temperature being from 5 to the trade as "Vinylite,' there may be obtained 145 to 155°. C. During the refluxing, methanol clear, colorless compositions of very good flex Was removed as it was formed, and an additional ibility and stability. 3.0 g. Of Sodium methylate WaS added in portions While the above examples illustrate a com at intervals during the refluxing. The reaction position in which the ratio of plasticizer to poly. mixture was then washed with water to dissolve O ner content is 40:60, this ratio being employed the catalyst (sodium methylate), then with 50 in Order to get comparable efficiencies, the con cc. of 5 per cent aqueous acetic acid and sub tent of ester to polyvinyl chloride may be widely sequently with 25 cc. of 1 per cent aqueous so Varied, depending upon the properties desired in dium bicarbonate for neutralization. The whole the final product. For many purposes a plas was then washed 3 times with 50 cc. of water, 5 ticizer content of, say, from only 10 per cent to 1 g. of charcoal (Norite) was added, and the 20 per cent is preferred. The present esters are solvent and unreacted 2-ethylhexanol were dis compatible with polyvinyl chloride over a wide tilled off. The residue was then heated at a range of Concentrations, up to 50 per cent of temperature of 165° C./0.25 mm. of Hg for a esters based on the total weight of the plas time of 1.5 hours in Order to drive off OW-boil 20 ticizer composition yielding desirable products. ing materials. Filtration of the product to re Although the invention has been described par move the charcoal gave 35 g. Of 2-ethylhexyl N ticularly with reference to the use of the present carbo. - (2 - ethylhexyl)oxymethyl-N-methyl-a- aralkyl amino dicarboxylates as plasticizers for amino - 4-toluate, molecular refraction 131.7 polyvinyl chloride, these esters may be advan (calcd. 130.73), and analyzing as follows: ageously employed also as plasticizers for copoly mers of vinyl chloride, for example, the copoly Calcd. for CH15ON Found mers of vinyl chloride with vinyl acetate, vinyl idene chloride, methyl methacrylate, acryloni Percent C: 72.48------73.00 trile, butadiene, or styrene. Preferably, such co Percent H:10.06------: 9.72 polymers have a high vinyl chloride content, i.e., a vinyl chloride content of at least 70 per cent The reaction of other alcohols of from 4 to 8 by Weight of Vinyl chloride and up to 30 per cent carbon atons, instead of 2-ethylhexanol, With by weight of the copolymerizable monomer. nethyl N - carbomethoxymethyl - N - methyl The plasticized polyvinyl halide compositions a-amino-4-toluate may be effected Similarly, for 35 of the present invention have good thermal sta example, with n-hexanol and the dinnethyl ester bility; however, for many purposes it may be ad to yield n-hexyl N-carbo-n-hexyloxymethyl-N- Vantageous to use known stabilizers in the plas methyl-a-amino-4-toluate, and With isobutanol ticized compositions. Inasmuch as the present to yield isobutyl N-carboisobutoxymethyl-N- esters are Substantially unreactive With the com methyl-a-amino-4-toluate, etc. When Working 40 mercially available heat and light stabilizers With the higher alcohols, the diethyl ester in which are commonly employed with polyvinyl stead of the dimethyl ester may be used for the chloride or copolymers thereof, the presence of interchange reaction. Also, instead of using the Such additions in the plasticized materials does 4-isomers, the 2- or 3-isoner may be employed, not impair the valuable properties of the present i. e., the dimethyl or diethyl esters of N-car 45 esters. The present esters are of general utility boxymethyl-N-methyl-a-amino-2 or 3-toluic acid in softening vinyl chloride polymers. They may may be employed to give the higher dialkyl esters be used as the Only plasticizing component in a of these acids. compounded vinyl chloride polymer or they may Eacample 3 be used in conjunction. With other plasticizers. Sixty parts of polyvinyl chloride and 40 parts 50 What We claim is: by weight of 2-ethylhexyl N-carbo (2-ethyl 1. Compounds having the general structure hexyl)oxymethyl - N - methyl - a - amino - 4 toluate were mixed on a rolling mill to a homo CHNGHC OOR geneous blend. During the milling there WaS ROOC k observed Substantially no fuming and discolora 55 tion. A molded sheet of the mixture was clear in which R, is a member of the group consisting and transparent and substantially colorleSS. of hydrogen and alkyl radicals of from 1 to 8 car Testing of the molded sheet for low temperature bon atoms, X is a member of the group consist flexibility, according to the testing procedure de ing of hydrogen and the methyl radical and Y 60 is a member of the group consisting of hydrogen scribed above, gave a value of minus 34° C. When and alkyl groups of from 1 to 4 carbon atoms. subjected to heat at a temperature of 325 F. for 2. N-carboxymethyl - N - methyl-a-amino-4- a period of 30 minutes the clarity and color of toluic acid. the molded sheet Were Substantially unchanged. 3. Methyl N-carbomethoxymethyl-N-methyl Tests of the water-resistance properties of the 65 a-amino-4-toluate. plasticized material employing the test procedure 4. 2. - ethylhexyl carbo (2 - ethylhexyl)oxy described above showed a Solids-loSS of 0.14 per methyl-N-methyl-a-amino-4-toluate. cent and an 0.70 per cent Water absorption value. 5. The proceSS which comprises contacting an Instead of the ester employed in the example amino compound having the general formula, above, other esters of the present N-carboxyal O kyl-a-aminotoluic acids may be used to give sin NECEICO OR ilarly valuable plasticized polyvinyl chloride : y compositions. Thus, by employing 40 parts by in which X is a member of the group consisting weight of di-n-octyl, di-isoamyl, di-n-hexyl or of hydrogen and the methyl radical and Y is a dibutyl esters of N-carboxymethyl-N-methyl-ar 75 member of the group consisting of hydrogen and 2,642,458 7 8 alkyl radicals of from 1 to 4 carbon atoms, and in which R is a member of the group consisting R is a member of the group consisting of hy of hydrogen and alkyl groups of from 1 to 8 drogen and alkyl radicals of from 1 to 8 carbon carbon atoms which comprises contacting, in the atoms, with a toluic acid compound having the presence of a basically reacting agent, an amino general formula, 5 compound selected from the group consisting of sarcosine. and alkyl esters of sarcosine in which the alkyl group has from 1 to 8 carbon atoms with a compound having the general formula RO OC in which R is a member of the group consisting O of hydrogen and alkyl radicals of from 1 to 8 ROOC carbon atoms and Z is a member of the group in which R is an alkyl group of from 1 to 8 car consisting of chlorine, bromine and iodine, and bon atoms and Z is a member of the group con recovering from the reaction product a dicar sisting of chlorine, bromine and iodine. boxylic compound having the general formula. 5. 8. The process of producing N-carboxymethyl N-methyl-a-amino-4-toluic acid which com CHNHgh coo R prises contacting Sarcosine with a-chloro-4- ROOC X Y. toluic acid in the presence of a basically react ing agent. in which R is a member of the group consisting 20. of hydrogen and alkyl radicals of from 1 to 8 WILLIAM. S. EMERSON. carbon atoms, is a member of the group consist ROBERT A. HEIMSCH. ing of hydrogen and the methyl radical and Y is a member of the group consisting of hydrogen References Cited in the file of this patent and alkyl radicals of from 1 to 4 carbon atoms. 25 UNITED STATES PATENTS 6. The process claimed in claim 5 further de Number Name. , Date fined in that said amino compound is contacted 647,263 Heymann ------Apr. 10, 1900 with said toluic acid compound in the presence 2,413,856 BerSWorth ------Jan. 7, 1947, of a basically reacting agent. - 2,450,435. McGillicuddy et al. - Oct. 5, 1948 7. The process of preparing compounds hav- 30 2,518.525 Curtis ------Aug. 15, 1950 ing the general formula, X D-chi, CHCOOR ROOC CH