United States Patent 19 11 4,414,419 Weber et al. 45) Nov. 8, 1983

(54). STABILIZATION OF ALDEHYDES 3,257,162 6/1966 Cox...... 568/421 75) Inventors: Jirgen Weber, Oberhausen; Volker 3,562,344 2/1971 Berkowitz et al ... 568/421 Falk, Voerde; Claus Kniep, 3,849,498 11/1974 Sato et al...... 568/421 Oberhausen, all of Fed. Rep. of OTHER PUBLICATIONS Germany Bogert et al., "Drugs and Cosmetic Industry' Apr. 73) Assignee: Ruhrchemie Aktiengesellschaft, Fed. 1933, pp. 312 and 332–338. Rep. of Germany Bogert et al., "Drug and Cosmetic Industry', Jun. 1933, pp. 513 and 533–540. 21 Appl. No.: 115,781 Fiore et al., "The American Perfume and Essential Oil 22 Filed: Jan. 28, 1980 Review” Jul. 1944, pp. 33–35. (30) Foreign Application Priority Data Primary Examiner-Werren B. Lone Feb. 12, 1979 IDE Fed. Rep. of Germany ...... 2905267 Attorney, Agent, or Firm-Jordan B. Bierman; Linda May 3, 1979 IDE Fed. Rep. of Germany ...... 2917789 Bierman 5) Int. Cl...... C07C47/058; C07C 47/02 57 ABSTRACT 52 U.S.C...... 568/421 58) Field of Search ...... 568/421, 304, 422, 423; Aldehydes having 3 to 14 carbon atoms are stabilized 260/601 R against polymerization and autocondensation by the addition thereto of triethanolamine or dimethyle (56) References Cited thanolamine in an amount at least 10 ppm (based on the U.S. PATENT DOCUMENTS amount of aldehyde) and preferably 20 to. 100 ppm. 2,237,092 4/1941 Swain et al...... 568/422 3,168,573 2/1965 Butter ...... 568/422 15 Claims, No Drawings 4,414,419 1. 2 hyde. Polymerization and autocondensation reactions STABILIZATION OF ALDEHYDES can be prevented by the addition of suitable substances. In practice these substances are subject to a whole This application claims the priority of German appli range of requirements that have to be satisfied if the cation Nos. P 2905 267.3 and P 29 17789.7 filed Feb. aldehyde is to be used without any restriction in a very 12, 1979 and May 3, 1979, respectively. wide variety of applications. One such requirement is The invention relates to the stabilization of aldehydes that the substance in question must be effective for a having 3 to 14 carbon atoms against polymerization and long period of time in low concentrations and further autocondensation. more must not interfere in the processing of the alde Such aldehydes have a tendency to spontaneously 10 hyde by chemical conversions. undergo polymerization and autocondensation. They Mercaptobenzimidazole and 2,2-methylene-di-(4- have a tendency to form a cyclic trimeraldehyde (trialk methyl-6-tert-butylphenol) have been described as sta yltrioxane) of the general formula bilizers for isobutyraldehyde. It has been found, how ever, that both of these stabilizers are not active for a H R 15 N / sufficient length of time. C An object of the invention is to provide stabilizers / N that prevent, even in low concentration, polymerization and autocondensation reactions of aldehydes for as long R-CH CH-R a period of time as possible. N / 20 O It has now surprisingly been found that aldehydes with up to 14 carbon atoms can be effectively stabilized (where RCHO is the formula of the initial aldehyde and against polymerization and autocondensation by adding R represents an alkyl radical), and to form aldol con triethanolamine or dimethylethanolamine to them. Ac densation products by autocondensation. The ring cordingly, the present invention provides a process for forming polymerization of isobutyraldehyde mainly 25 stabilizing an aldehyde having 3 to 14 carbon atoms produces 2,4,6-triisopropyl-1,3,5-trioxane. The auto against polymerization and autocondensation compris condensation of isobutyraldehyde leads to the aldol ing adding triethanolamine or dimethylethanolamine to condensation product 2,6-diisopropyl-5,5-dimethyl-1,3- the aldehyde, dioxan-4-ol. The ring-forming polymerization of alde The invention also provides a composition compris hydes is catalyzed by various acid reagents such as 30 ing an aldehyde having 3 to 14 carbon atoms and trieth sulphuric acid, hydrochloric acid, hydrogen fluoride, anolamine or dimethylethanolamine, the aldehyde boron trifluoride and aluminum chloride. Under the being stabilized against polymerization and autoconden action of such acidic compounds the polymerization of sation by the triethanolamine or dimethylethanolamine. the aldehydes occurs spontaneously and leads within a Examples of aldehydes of the aforementioned molec few minutes to crystalline trimeraldehydes. Even the 35 ular size are: propanal, isobutyraldehyde, n-pentanal, small amounts of carboxylic acids formed by the oxida and dimethylhexanal. Further examples are, in particu tion of the aldehydes in the presence of atmospheric lar, higher aldehydes containing 8 to 14 carbon atoms, oxygen are sufficient for catalyzing the trimer forma such as n-octylaldehyde, n-nonyl-aldehyde, n tion. The trimerization of isobutyraldehyde is catalyzed decylaldehyde, undecylaldehyde, lauraldehyde, me particularly by chlorine, bromine, phosphorus pentox thylnonylacetaldehyde (MNA), tridecylaldehyde, and ide, hydrogen chloride, oxygen and zinc chloride. myristylaldehyde, which are used on a large scale in the Trimerization of isobutyraldehyde also occurs under preparation of synthetic perfumes and fragrances. In the action of UV light. Also in the presence of alkali, derived for example from the containers in which the this connection, it is therefore important that the sub isobutyraldehyde is stored, autocondensation of isobu 45 stances added to prevent polymerization are not only tyraldehyde to form 2,6-diisopropyl-5,5-dimethyl-1,3- highly effective, but also do not have any negative dioxan-4-ol occurs even at 5 to 10° C. In addition, low effect on the nature or character of the perfumes pre temperatures, i.e. temperatures of about 0° C. and be pared therefrom. It has surprisingly been found that low, promote the polymerization of aliphatic aldehydes. triethanolamine and dimethylethanolamine are highly On account of its conversion into higher molecular 50 effective and meet these requirements in an outstanding weight compounds, in particular under the action of manner. Neither amine interferes in the further process oxygen or UV light or alkaline-reacting substances, ing of the aldehydes to form secondary products. It isobutyraldehyde cannot be stored for an indefinite should be noted in particular that triethanolamine and period of time. Although in fact the polymerization and dimethylethanolamine, although they react in an alka autocondensation products of isobutyraldehyde decom 55 line manner, do not catalyze the aldol condensation of pose further at elevated temperature, their formation the aldehydes. nevertheless prevents the unlimited technical use of the These stabilizers are effective even in very low con aldehyde. centrations. As little as 10 ppm (based on the aldehyde) Trimerization and autocondensation of aldehydes can of the amines prevent the formation of high molecular be prevented for a limited period of time if the alde 60 weight compounds over a period of at least several hydes are highly pure. The purification operations re weeks, e.g., in the case of isobutyraldehyde under the quired are however so costly that they are not practica action of oxygen, for a period of 30 weeks. In general, ble for the commercial preparation of aldehydes. Also, it is preferred that the stabilizers be used in amounts of addition of a solution of diphenylamine in ethanol to 20 to 100 ppm (based on the aldehyde). In such a con aldehydes suppresses polymerization but is not reliable 65 centration, the stabilizers prevent the formation of the for this purpose over a prolonged period of time. trimer or autocondensation aldol product during stor Attempts have been made to prevent the formation of age of the aldehyde, even at low temperatures, without higher molecular weight products from isobutyralde any further measures or precautions and for a period of 4,414,419 3 4. at least several months, depending on the aldehyde, and What we claim is as follows: one year in the case of isobutyraldehyde. 1. A process for stabilizing a saturated aliphatic alde Triethanolamine and dimethylethanolamine are solu hyde having 3 to 14 carbon atoms against polymeriza ble in the aforementioned aldehydes and can, thus be tion and autocondensation comprising adding an effec used without solvents. The amines are preferably added tive amount of triethanolamine or dimethylethanola in specified amounts while stirring and at such a rate mine to said aldehyde. that no local overheating occurs. The following exam 2. A process according to claim 1 wherein said trieth ples are intended to illustrate the present invention in anolamine or dimethylethanolamine is added to said greater detail. aldehyde in an amount of at least 10 ppm based on said 10 aldehyde. 3. A process according to claim 2 wherein said EXAMPLE 1 amount is 20 to 100 ppm. ------Tests on the stabilization of isobutyraldehyde were 4. A process according to claim 1 wherein said alde carried out in polyethylene-lined containers. The con hyde is isobutyraldehyde. tainers were stored in the open and thus subjected to 15 5. A process according to claim 1 wherein said alde variable temperatures. As stabilizer, either triethanol hyde has 8 to 14 carbon atoms. amine or dimethylethanolamine in a concentration of 20 6. A process according to claim 1 wherein said alde to 100 ppm was used. The polymer content was deter hyde is n-octylaldehyde, n-nonylaldehyde, n-decylalde mined by gas chromatography every 4 weeks. Errors hyde, undecylaldehyde, lauraldehyde, methyl were excluded by a system of double determinations. nonylacetaldehyde, tridecylaldehyde or myristylalde The results are given in the Table 1 below. hyde. Trimer content (%) as a function of the storage time under comparable conditions --- Amount of 5 weeks 10 weeks 20 weeks 30 weeks 40 weeks 50 weeks 60 weeks Stabilizer material storage storage storage storage storage storage storage (concentration) used time time time time time time time Mercaptobenzimidazol (100 ppm) 0.02 0.36 0.59 - - - - - Dimethylethanolamine (100 ppm) 0.02 0.02 0.02 0.02 0.03 0.04 0.07 0.10 Dimethylethanolamine (20 ppm) 0.02 0.02 0.02 0.02 0.04 0.06 0.10 0.17 Triethanolamine (100 ppm) 0.02 0.02 0.02 0.02 0.02 0.02 0.05 0.09 Triethanolamine (20 ppm) 0.02 0.02 0.02 0.02 0.02 0.02 0.06 0,12 No stabiliser 0.02 0.86 2.60 4.80 7.00 7.60 7.70 9.00

EXAMPLE 2 7. A composition comprising a saturated, aliphatic aldehyde having 3 to 14 carbon atoms and an effective 20 ppm (based on the aldehyde) of triethanolamine or amount of triethanolamine or dimethylethanolamine, diphenylamine was added to n-dodecanal (lauralde 40 the aldehyde being stabilized against polymerization hyde) and the aldehyde was stored in aluminum con and autocondensation by the triethanolamine or dime tainers some of which were kept at 0° C. and some of thylethanolamine. which were kept at 20° C. 8. A composition according to claim 7 comprising at The aldehyde content was monitored by determining 45 least 10 ppm of the triethanolamine or dimethyle the carbonyl number (CON) after 1, 3, 6, 9 and 14 thanolamine based on said aldehyde. weeks. Errors were eliminated by a system of double 9. A composition according to claim 8 comprising 20 determinations. The results are given in Table 2. to 100 ppm of the triethanolamine or dimethylethanola mine based on said aldehyde. TABLE 2 10. A composition according to claim 7 consisting CON 50 essentially of said triethanolamine or dimethylethanola Start of After 1. After 3. After 6. After 9. After 14 mine and said aldehydes. Stabilizer Test weeks weeks weeks weeks weeks 11. A composition according to claim 7 wherein said Temperature: aldehyde is isobutyraldehyde. O C. 55 12. A composition according to claim 7 wherein said None 288 198 12 73 50 33 aldehyde has 8 to 14 carbon atoms. Diphenyl 13. A composition according to claim 12 wherein said amine in aldehyde is n-octylaldehyde, n-nonylaldehyde, n ethanol 288 282 270 230 148 100 decylaldehyde, undecylaldehyde, lauraldehyde, me Tri ethanolamine 288 287 286 286 284 273 60 thylnonylacetaldehyde, tridecylaldehyde or myris Temperature: tylaldehyde. 20° C. 14. A process according to claim 1 wherein said None 288 286 284 275 275 270 amount is at least 20 ppm based on said aldehyde. Diphenyl amine in 15. A composition according to claim 7 wherein said ethanol 288 287 283 282 282 274 65 amount is at least 20 ppm based on said aldehyde. Tri ethanolamine 288 287 287 - 286 283 281 k k it k .