US2366534A - Production of long-chain tertiary amines - Google Patents

Description

Patented Jan. 2, i945 areas b raonuc'r'rouormouo-cnamraa'rmar ames James Ehltirbyrwilmington, DeL, assignor to :E. L du Pont de Nemours 8: Company, Wilmington, D'eL, a corporation-of Delaware No nmvm. Application July so, 1941,

l Serial No. 404.617

6 Claims. (oi. zoo-sea) i 1: relatesitothe production of amine an or cularlyit relatestoaprocroductionfof long-chain tertiary caily, this invention relates ring iong chain alkyl N- naturaljsou'rcesihave'for-many years been recogriiz'jedas valuable" intermediates for the synthesis offtextile Compounds containing rromgiz gtpia .car

ain aliphatic l compounds derived from a his have been found to variety f productsproduced from amides, esters,

in thisrange are how commercially available for use jas,.textil'e reagents." "More recently, longmout wash amm d importance, not only as intermediates for the manufacture of textile treating agents, but'for many other uses. Among textile chemicals prepareditrom amines, those derived from long-chain tertiary amines have show "outstandingiyflattractive properties from the. inn ierfcial poin er view, but unfortunately, development alpngthesejlines has been hampered seriously 'by thellack ofeconomically sound and practicable 1 methods .for thesynthesis of suitable tertiary. jhas! been proposed in the literature to prepare'long-chain alkyl N -dimethyl amines byQreactiiig lQng-Chain allwl halides or alcohols with. dimethyflamine, by methylatins lougichainj amines with methanol in the presence of mineral-acid catalysts, and by reducing ;l9n85chaincarboxylic amides. All of these proposed. processes; arecharacterized by a deficiency in yield performance, by the formation of diflicultly separable mixtures of products, and by excessive costs for, manufacturing N-dimethyl long chain, aliryl on, a practical commercialise-ale, l o

Thisinve'ntion has as an objectto develop a process for the production of? long-chain tertiary amines. Another obiect is to provide a process for the: production or} long -chain N-dimethyl amines. Still another object. is to provide a smooth and low cost process for the production of long chain tertiary high yields. Other; objects be apparent, from the followihgdescriptionof; theinventlom. l

biectsareac plishedbythe following invention, which comprises reducing, a mixa or ms ehv a n S d from thewlassqc m ti s-fi l nwhai P me and long- -chain at a temperature between about 251;, about, 10020. The rea m: medium i mom a the embodiments of this invention, the synthesis of N-dimethyl long-chain alkyl amines is accomplished by treating mixtures of 12 to 18 carbon primary amines and formaldehyde in molecular ratios of less than 1:2 with formic acid at temperatures between about 25 C. and about 100 C. Long-chain alkyi aminesare converted to the corresponding N-dimethyl amines by reduction possess especial iitilityjiri this field. and a wide with formic acid according to the following procedure. One mol of long-chain amine is charged in a suitable reaction vessel equipped with an emcient agitator, and approximately five mole of formic acid (90% aqueous solution) is added slowly at a rate insuiiicient to bring about a rise in temperature above about C. The resulting solution is cooled to approximately room temperature and about 2.2 mols of formaldehyde (37% formalin) added without especial precautions. The mixture is then slowly heated with stirring to a temperature of approximately 35 to 38 C. to initiate the evolution of carbon dioxide, The reaction is slightly exothermic and proceeds without further application of heat for a period of Ito 2 hours during which time approximately 60% of the theoretical quantity of carbon dioxide is evolved. At this stage of the reaction, the evolution of gas is accompanied by severe foaming and extreme care must be exercised in adjusting the temperature to avoid loss of product. Subsequently, the temperature of.

Example I Ninety-five parts of commercial formic acid was placed in a reaction vessel provided with an efllcient agitator and cooled to about 10 C. in an ice bath. One hundred parts of technical stearyl amine containing approximately equal parts of n-hexadecyl and n-octadecyl amines was melted and added slowly to the formic acid to produce a thick slurry of the corresponding salts. After stirring for a brief period, the reaction mixture was allowed to warm up to room temperature and 71 parts of formalin solution containing 37% by weight of formaldehyde added rapidly. At room temperature evidence of reaction was slight, but on heating slowly to about 35 0., evolution of carbon dioxide began at a steady rate. This was accompanied by the formation of a thick head of viscous ioam onthe surface of the reaction mixture, audit was necessary to exercise extreme care in adjusting the temperature and trample III 1500 parts of crude, technical stearylamine containing approximately 90% or n-hexadecyl and rate of stirring to avoid losing the product. By 1 operating between about 40 and about 43 (2..

approximately 60% of the theoretical quantity of 1 carbon dioxide was evolved during about 2 hours.

by the quantity of gas evolved, the mixture was brought to the boiling point (94 C.) and the re-' action completed by refluxing for a period of 1 t 1.5 hours. The resulting product consisted of a thick syrupy liquid, which was transferred to an evaporation pan, treated with'a slight excess of concentrated hydrochloric acid to decompose amine-formic acid salts, and evaporated to a thick paste, to remove unreacted formaldehyde and formic acid. The-residue was then taken up in hot water and treated with an excess of caustic alkali solution. The liberated amines were separated by extraction with benzene. Fractional distillation of the benzene extract gave 41.5 parts of N-dimethylhexadeeylamine, B. P. 175' /6 mm.; 14.8 parts of mixture of N-dimethylhexadecyl and N-dimethyloctadecyl amines; 30.2 parts of N-dimethyloctadecylamine, B. P. 194 C. at 6 mm.; and 10.8 parts of high boiling residue. The

combined yield of N-dimethyl long-chain alkyl amines was about 80% of theory.

Example 11 Six hundred forty parts of 90% formic acid solution was added slowly with stirring to 465 arts of pure n-dodecylamine. The neutralization was accompanied by the evolution of considerable heat, and the rate of addition was controlled to avoid exceeding a temperature of about 65 C. The resulting mixture was cooled to below 30 C. and 446 parts of 37% formalin solution added rapidly. Only a slight thermal efiect was noted and the mixture'was heated cautiously to approximately 35C. At this temperature an exothermic reaction set in, and the evolution of carbon dioxid began at a steady rate. The reaction continued without iurther application of heat for about 1 to 1.5 hours, during which time the temperature remained at 42 to 44 C. and the amount of gas given off was 60% to 65% of theory. During this period foaming was severe, but the tenacity of the foam was somewhat less than in the case of the higher members of the series. The reaction was completed by boiling under reflux for an additional period of about 3 hours until th evolution of carbon dioxide had essentially stopped. The

syrupy product was treated with a slight excess of concentrated hydrochloric acid, evaporated overnight to eliminate'unreacted formic acid and formaldehyde, and finally made strongly alkaline to liberate the free amines. The oily prodnot was separated from the aqueous solution by extracting thoroughly with successive portions of benzene. Fractional distillation of the combined benzene extracts gave 460- parts of pure N-dimethyldodecylamine, B. P. 121 to 122' C. at mm. The molecular yield was 86.5% of-theory.

n-octadecylamines and 7% to 10% of the corresponding secondary amines were treated with 1425 parts, of 90% formic Q1d8-933 parts of 37% formalinaccordingito the procedure of Example II. On working up the product by vacuum fractional distillation there were obtained 59.7 parts. of lower N-dimethyl alkyl amines, B. P. 105 to 173 C. at 5 mmi; 440 parts of N-dimethyl cetylamine, B. P. 173 to 175 C. at 5 mm.: 66.6 parts of an intermediate fraction, B. P. 175 to 4190" c. at? 5 mm.; 538.2 parts of N-dimethyloctadecylamine,B. P. 190" C. at 5 mm., and 338 h parts oif high boiling residual products.

Example 1V One hundred parts of 7-aminoheptadecane was charged into a suitable corrosion-resistant reaction vessel equipped with an emcient agitator.

' with vigorous stirring, 100 parts of 90% formic acid was added to the amine'at a rate adiusted to avoid an exothermic temperature rise above C. The resulting mixture was cooled to room temperature and parts of 37% formalin solution added. On warming to about 35 to 38' C. reduction began as evidenced by the evolution of carbon dioxide. The temperature of the mixture was raised gradually during a period of about 3 hours, care being taken to avoid overheating and excessive foaming. The reaction was completed by boiling the solution under reilux for one hour. 'On'w'orking up the product according to the procedure of Example "I there was obtained 100.1 parts of 7-dimethylaminoheptadecane, B. P. 164 to' 166 Cxat 4 mm. The molecularyi'eld was 90.2%.

Example V Three hundred sixty grams of dodecylamine was placed in a 12 liter flask fitted with a stirrer and thermometer. With vigorous stirring oi the amine paraformaldehyde was gradually added over a period of V hour. During this addition the temperature rose from about 28 toabout 69 C. While controlling the temperature between 43 and 67 C., 257 grams of formic acid-was added dropwise over a period ofabout l-hour and 55 minutes. Ether was addedto the fla'sk in such quantities as to keep the reaction-from foaming so violently due to the evolution of carbon dioxide that the reaction mixture would be lost. After all the formic acid had been addedthe reaction mixture was heated on a steam bath for 2 hours and 10 minutes and then allowed to remain at room temperature for 16 hours. The reaction mixture was then diluted with water, treated with 280 grams of sodium hydroxide and extracted with ether. The resulting product was then dried over potassium hydroxide. 'Analyti-' cal distillation indicated that a, yield of about 90% N-dimethyl dodecylamine was obtained, B. P. C. at8mm. a

In the reduction of long-chain primary amines according to the process of this invention, it is essential to maintain an excess of the reducing agent in the reaction mixture at all times. With formic acid, the minimum amount required is at least two mols per mol of primary amine, and th reduction is preferably carried out with an excess of. formic acid amounting to at least iive mols per mol of amine. The excess functions primarily as a solvent for the reaction andserves to lower. the viscosity of the solution. In.-

the absence of such an xcess, the reaction mixture becomes extremely viscous, dlflicult to stir, and is likely to go out of control during the period of eifervescence owing to the inherent surface active properties and tendency to foam of materials in the 12 to 18 carbon range. In'order to avoid excessive foaming there may be added to the reactants an anti-foaming agent such as ether. As mentioned in the above examples, the use of a solvent or anti-foaming agent does not completely avoid th danger of product losses through foaming, and extreme care must be exercised in adjusting the temperature of the reaction. In most instances, the reductio starts at temperatures ranging from room temperature to about 35 C., and thenceforth is exothermic until approximately 55% to 65% of the theoretical amount of CO2 has been evolved; This is usually accompanied by a temperature rise to 42 to 45 C., and further application by heat is seldom necessary until the danger of foaming over has passed. Thereafter, raising the temperature of the reaction mixture to the atmospheric pressure boiling point offers but few difficulties.

The reaction may be carried out under superit is usually preferably and more convenient to employ commercial formalin solutions containing about 37% by weight of formaldehyde. In

conducting the reduction process, the preferred proportions of formaldehyd and primary amine are at least two mols of formaldehyde per mol of amine, and it is usually desirable to use approximately 10% excess of formaldehyde.

In a broad sense, this invention contemplates the conversion to N-dimethyl amines of longchain primary amines in which the amino group is attached to an aliphatic hydrocarbon radical containing at least twelve carbon atoms. The hydrocarbon radicals may be straight chain or branched chain, and the amino group may be attached either to'a terminal carbon atom or to a secondary or tertiary carbon at some intermediate point in the hydrocarbon residue. Typical examples of primary and secondary amines com? ing within the scope of the invention are octylamine, decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, 'I-aminoheptadecane, S-amincdodecane, 8-aminohexadecane, 2-methyl-3-aminopentadecane, 8-amino pentadecane, 12-aminooctadecane, dioctylamine, didodecylamine, octyldodecylamine, ditetradecylamine, dihexadecylamine, etc. It will be recognized that, in general, primary and secondary amines coming within the scope of the invention are those'containing hydrocarbon radicals which tend to confer surface active properties such as wetting power, detergency and the like on any solubilized organic derivative containing them. Sodium dodecyl sulfate is, for example, a familiar synthetic detergent.

The process of this invention provides a convenient and practical method for the synthesis of valuable long-chain N-methyl or N-dimethyl long-chain tertiary amines. The outstanding advantages of the process are convenience and ease of handling on a commercial scale, high yields, and economy. These characteristics are in marked contrast to methods of the prior art referred to above which are known to possess many practical disadvantages from the standpoint of commercial operation.

The long-chain N -methyl and N-dimethyl amines of the invention are valuable articles of commerce and may be employed as intermediates for the preparation of textile reagents, insecticide compositions, moth-proofing agents, and many other materials useful in the arts.

Having described in detail the objectives and preferred embodiments of my invention, it is to be understood that I do not limit myself to the specific disclosures thereof except as defined in the following claims.

I claim:

1. A process for the production of long-chain tertiary amines which comprises reducing a mixture of formaldehyde and an amine selected from the class consisting of long-chain primary and long-chain secondary amines with formic acid at a temperature between about 25 C. and about 100-Q, said formic acid being present in a molar amount equivalent to at least twice the amount of amine being treated.

2. A process for the preparation of N-dimethyl long-chain alkyl amines which comprises treating a mixture of formaldehyde and a. long-chain primary amine having from 12 to 18 carbon atoms in the chain with formic acid ata temperature between about 25 C. and about 100 C.

3. A process for the preparation of N-dimethyl long-chain alkyl amines which comprises bringing into admixture a primary amine having between 12 and 18 carbon atoms and formic acid in molecular excess of at least 5 times that of said amine under such condition; that the temperature of the mixture does not exceed 60 C., cooling said mixture to room temperature and adding formaldehyde, then gradually increasing the temperature of the mixture until the evolution of carbon dioxide is complete, and recovering an N-dimethyl alkyl amine from the reaction product. 4. The process in accordance with claim 1 characterized in that the formaldehyde is present in a molar amount equivalent to at least twice the amount of amine beingtreated.

5. A process for the preparation of N-dimethyl long-chain alkyl amines which comprises treating a mixture of formaldehyde and a long-chain primary amine having from 12 to 18 carbon atoms in the chain with formic acid at a temperature between about 25 C. and about 100 C., said formic acid being present in a molar amount equivalent to at least twice the amount of amine being treated.

6. The process in accordance with claim 5 characterized in that the formaldehyde is present in a molar amount equivalent to at least twice the amount of amine being treated.

JAMES E. KIRBY.