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Home , Vinyl group

Patented Aug. 21, 1951 2,554,760

UNITED STATES PATENTpQFFlCE

2,564,’? 60 PROCESS FOR MAKING ALKOXYACETALS Raymond I. Hoaglin, Charleston, W. Va., and Samuel Clark, Oxford, Miss., assignors, by mesne assignments, to Union Carbide and Car bon Corporation, a corporation of New York N 0 Drawing. Application October 26, 1946, Serial No. 706,052 '7 Claims. (Cl. 260—615) 1 2 The present invention relates to a process for dialkyl , the ethylenic group adds across making alkoxyacetals. one of the linkages of the , as before, It has already been proposed in U. S. Patent forming a compound ‘having a'branched-chain No. 2,185,962 to form alkylidene diethers by re skeleton. This reaction may be illus acting vinyl others with acetalclehyde acetals. trated as follows: The general reaction proposed in this patent B. 0R2 is as follows: Dialkyl acetal OR? OR; / / CH2=CH + onion ___-» CH3—CH——CHZCH 10 Unsaturated ether

R1, R2 and R3 being , aralkyl or aryl radi~ oals. We have found that, in fact, the acetal l does not unite with the vinyl other by addition 15 to the double bond, as indicated in this patent, R1 OH; Alkoxyacetal and that the equation corresponds to the prod ucts actually formed only in the special instance where R1, R2 and R3 are identical radicals. where R1 is hydrogen or an'alkyl, aryl or aralkyl We have found that of alpha, beta ‘radical, and R2 and R3 are alkyl radicals, such as unsaturated react with dialkyl acetals 20 methyl, ethyl, propyL'butyl, amyl, hexyl, heptyl of , the sum of the carbon atoms in the ‘or octyl radicals. unsaturated and the being at More than one mole of the vinyl ethers may least ?ve, by addition across one of the ether add in step-wise fashion to the dialkyl acetal linkages of the acetal. ‘This ether linkage then to form a compound having an extended carbon breaks to give the alkoxyacetal. Thus, when 25 ‘chain to which is attached a plurality of alkoxy vinyl ethers are added to acetals of those alde groups. This step-wise or reac hydes containing at least three carbon atoms to tion maybe represented as follows: .the aldehyde molecule, the carbon atoms of the C. 0R2 alkylidene group of the acetal unite With those ———0 R2 Dialkyl acetal of the vinyl group to form a straight chain, 30 rather than a branched chain, as would be the case if addition to the Z-carbon atom of the Vinyl other acetal occurred. The reaction which takes place in this instance may be represented as follows: A. 0 R2 35 0 R2 R10 Hz (‘1H 0 R2 Dialkyl acetal Polyalkoxyacetal R\ /

40 where R1 is an alkyl, aryl or aralkyl radical, R2 is an alkyl radical, and n is a Whole number from 2 to 20, for instance. These polymeric deriva tives are readily formed by charging a molar ex (I)Rz I 0 R2 R1 CH2 CH CH2 Cg Alkoxyacetal cess of the vinyl ether over the dialkyl acetal to 45 the reaction vessel. In fact, if the lower molecu lar weight addition products are desired in good where R1 is an alkyl, aryl or aralkyl radical and yields, it is preferable to charge a considerable Re is an alkyl radical, such as a methyl, ethyl, molar excess of the dialkyl acetal, as shown in propyl, butyl, amyl, hexyl, heptyl or octyl radi the examples. cal. " 50 Several experiments were carried out to dem When the ethers of those alpha, beta-unsat onstrate the addition of ethers of alpha, beta urated alcohols containing at least three carbon unsaturated alcohols to dialkyl acetals. In one atoms to the alcohol molecule are reacted with of these experiments, vinyl ethyl ether was added 2,564,760 4 to diethyl butyral in accordance with the follow Thus dibutyl acetal may react with vinyl ethyl insr reaction: ether and/or vinyl butyl ether and l-ethoxy OC2H5 l-butoxyethane may also react with vinyl ethyl ether and/or vinyl butyl ether according to the CHQCHZCHZC + CH2=CHOC2H5 —-> 5 mechanism herein explained to give a complex O C2115 mixture of ethoxy- and butoxyacetals. 0 02115 The addition reactions of this invention are CH3CH2CH2CH(O C2115) CHZCH preferably carried out at temperatures of 25° to 75° C. in the presence of a boron trifluoride OCzH5 10 catalyst. Our preferred catalyst is the complex The addition product was simultaneously hydro compound of boron tri?uoride and diethyl ether. lyzed and de-ethanolated to form an unsaturated The amount of the catalyst may be between 0.01 aldehyde. This aldehyde was identi?ed as and 0.5% of the reactants. The reaction may 2-hexenal, CH3CH2CH2CH=CHCHO. From the be carried out by simple mixing of the reactants position of the ethylenic linkage in the aldehyde, accompanied by external cooling. The tempera and from the fact that the unsaturated aldehyde ture may also be controlled by slow addition of was a straight chain compound, it is concluded the unsaturated ether to the dialkyl acetal ac that the addition product was 1,1,3-triethoxy companied by vigorous stirring. After comple hexane. Such a compound could be formed only tion of the reaction, the catalyst is neutralized by the addition reaction shown immediately 20 with an alkaline reagent, such as sodium hydrox above, because, if reaction had occurred by ad ide, sodium carbonate, or sodium bicarbonate. dition of the_2-carbon atom of the acetal to the The mixture is then distilled to recover the un vinyl group, the unsaturated aldehyde corre~ changed dialkyl acetals, and to isolate the higher sponding to the alkoxyacetal would have been boiling alkoxyacetals. 2-ethyl-2-butenal or a-ethylcrotonaldehyde, The alkoxyacetals are valuable as solvents and H3O 011:0 CHO plasticizers and as chemical intermediates. The 02115 alkoxyacetals are readily converted to unsatu rated aldehydes which may be reduced to satu In another experiment, diethyl acetal was rated alcohols. The alkoxyacetals may also be added to ethyl 1-butenyl_ether according to the ; hydrolyzed to alkoxyaldehydes which may be following reaction: reduced or oxidized to the corresponding alkoxy 0 CzH5 alcohols or alkoxyacids. Hydrogenolysis of the CHgCH + CH3CHzCH==CHOCzH5 —» acetal group of the alkoxyacetal may also be carried out, in which event alkyl ethers of poly O CzHs hydric alcohols are obtained. Thus, the reac C2115 O C2H5 tion of this invention is a very valuable tool for CHSOHJNJHCH the industrial organic chemist in building up higher molecular weight compounds starting C2135 O CzH5 with simple, readily available compounds. In The alkoxyacetal formed according to the reac 40 industrial practice, the initial raw material may tion was simultaneously hydrolyzed and de be any of the cheap, readily available alcohols, ethanolated to form an unsaturated aldehyde. such as and butanol. The alcohols may This aldehyde was identi?ed as a-ethylcrotonal be oxidized to aldehydes, and the dialkyl acetals dehyde, proving that the alkoxyacetal formed may be formed from the alcohols and the alde was 1,1,3-triethoxy-2-ethylbutane. This com hydes. The alpha, beta-unsaturated ethers are pound could not have been formed if the l-carbon readily formed by passing the dialkyl acetals over atom of the unsaturated ether had added to the appropriate catalysts. 2-carbon atom of the acetal. The following examples will illustrate the prep In reactions A, B and C designated above, the aration of various alkoxyacetals. special case where the R2 radicals are identical has been represented. This is the preferred Example 1.--The reaction of vinyl ethyl ether embodiment of the invention, because easily iso and diethyl butyral lated products are obtained. However, the re Four hundred and ?fty-nine (459) grams (6.37 action may be carried out with acetals and un moles) of vinyl ethyl ether were added by means saturated ethers in which the alkoxy radicals of of a dropping funnel to 4,650 grams (31.85 moles) the acetal and ether linkages are’ different. In of diethyl butyral containing 4 cc. of a diethyl this instance, a number of co-reactions may oc ether solution of boron tri?uoride-diethyl ether cur. For example, dibutyl acetal was reacted complex (35% boron tri?uoride). The mixture with vinyl ethyl ether to yield a mixture of prod was stirred constantly during the addition of ucts, only two of which, 1,1,3-tributoxybutane the ether and the temperature was maintained and l-ethoxy-‘l-butoxyethane were isolated in at 43 to 51° C. by means of external cooling and the pure state. It is assumed that these products regulation of the flow of vinyl ethyl ether. After were formed as a result of the following equi all the ether had been added stirring was con librium which may be established: tinued until the temperature dropped to that 65 of the room. Then the catalyst was neutralized 0 04119 with an excess of solid sodium carbonate, and CHJC + CH2=OHOC2H5 (-2 stirring was continued about two hours. The O C4H9 reaction product was distilled, and the unreacted Dibutyl acetal Vinyl ethyl ether diethyl butyral was recovered. A compound boil 70 ing at 185° at 5 mm. (speci?c gravity 0.874 at 0 C2115 20°/20° C.) was obtained in 69.5% yield based on C1130 -|- CH2=CHOC4Hn vinyl ethyl ether. This compound was identi?ed O C4139 as 1,1,3-triethoxyhexane by hydrolysis to the un 8 Vinyl butyl ether saturated aldehyde, 2-hexenal. The remaining 75 portion of the vinyl ethyl ether which reacted 2,564,760 5 was recovered as a mixture of condensation Alkyl ethers of alpha, beta-unsaturated alco products of diethylbutyral containing more than hols other than those shown in the foregoing ex one mole of vinyl ethyl ether. amples may be reacted with dialkyl acetals to Example 2.—The reaction of diethyl Z-ethylhewal form a series of useful compounds. When ethers and vinyl ethyl ether of vinyl alcohol are employed, the invention pro vides a means of increasing the carbon length of A mixture of 5357 grams (26.4 moles) of diethyl the augend compound by units of two, depend 2-ethylhexal and 7 cc. of a diethyl ether solu ing on the number of moles of the vinyl ether tion of boron tri?uoride-diethyl ether complex added. Thus, by starting with an acetal of an (35% boron tri?uoride=0.05% BF: based on the 10 aldehyde having an odd number of carbon atoms, weight of the acetal) was stirred and warmed for instance diethyl propional, and adding one to 45° C. To this mixture was added with good mole of vinyl ethyl ether, it is possible to form an agitation 494 grams (6.6 moles) of vinyl ethyl alkoxyacetal having a straight carbon chain of ether (96.2% vinyl ethyl ether, 3.8% diethyl ?ve carbon atoms. From this alkoxyacetal the ether). The rate of addition was regulated, so 15 corresponding normal alkanol, pentanol, may that by cooling with water a reaction tempera readily be derived as a commercial product. In ture of 45 to 47° C. was maintained. The addi this respect, our reaction is not analogous to the tion of the vinyl ethyl ether required 20 minutes, known reaction of diethyl acetal and vinyl ethyl after which the mixture was stirred an additional ether, as the predicted compound based on prior two hours and was then neutralized with 14 20 art teachings would have been, in the case above, grams of sodium carbonate. The reaction prod an alkoxyacetal having a branched-carbon chain, uct was distilled under vacuum to recover un from which only a branched chain ?ve carbon reacted diethyl 2-ethylhexal and the product, atom alcohol could be obtained. Thus, our in 1,1,3-triethoxy-4-ethyloctane. The yield of the vention may provide a cheap method for making latter compound was 66.5%, based on the vinyl 25 pure, normal amyl alcohol of a grade superior to ethyl ether. 1,1,3-triethoxy-4-ethyloctane has a that of the impure product derived from fusel boiling point of approximately 94° C. (1 mm. oil. Hg), sp. gr. (20/20° C.) 0.873 and refractive in Subject matter disclosed in this application is dex (NDm) 1.4277. Higher boiling products were claimed in our continuation-in-part application, obtained, but not isolated as pure compounds. 30 Serial No. 35,968, ?led June 29, 1948, entitled Example 3.-The reaction of diethyl acetal and “Process for Making Branched-Chain Alkoxy ethyl I-butenyl ether acetals.” We claim: A mixture of 1062 grams (9 moles) of diethyl 1. 1,1,3-trialkoxy containing at least acetal and 1 cc. of a diethyl ether solution of 35 5 carbon atoms. boron trifluoride-diethyl ether complex (35% 2. Alkoxyacetals of the formula: boron tri?uoride-approximately 0.04% ' BFs R1_CH—(CH2—'CH)1|_0R2 based on the weight of the acetal) was stirred and warmed to 475° C. Ethyl 'l-butenyl ether R2 R2 (300 grams, 3 moles) was added from a dropping wherein R1 is an alkyl radical containing at least funnel in a period of 10 minutes. The reaction two carbon atoms, the groups R2 are lower alkyl was essentially complete within 20 minutes after radicals, and n is an integer. / I all the unsaturated ether was added. 'The mix 3. 1,‘1,3-trialkoxy hexanes. ture was stirred an additional two hours and 4. Ethoxyacetals of the formula: then the catalyst was neutralized by agitation OOzHn with 5 grams of sodium carbonate. After re RqCHCHzC covering the unreacted diethyl acetal by vacuum distillation, a product identi?ed as 1,1,3-tri 02115 002115 ethoxy-2-ethy1butane was obtained in 48.1% wherein R1 is an alkyl radical containing from 3 yield, based on the ethyl l-butenyl ether charged. 50 to 7 carbon atoms. 1,1,3-triethoxy-2-ethylbutane has a boiling point 5. 1,1,3-triethoxyhexane. of about 76° C. (5 mm. Hg), sp. gr. (20/20° C.) 6. 1,1,3-triethoxy-4-ethyloctane. 0.881 and refractive index (NDW) 1.4172. No 7. 1,1,3-triethoxyoctane. higher boiling ethoxyacetals were isolated as pure RAYMOND I. HOAGLIN. compounds. 55 SAMUEL F. CLARK. Example 4.—The reaction of vinyl ethyl ether REFERENCES CITED and diethyl hexal The following references are of record in the Vinyl ethyl ether (1 mole) was reacted with 5 file of this patent: moles of diethyl hexal in the manner described 60 in the foregoing examples. 1,1,3-triethoxyoctane UNITED STATES PATENTS was obtained in a yield of 57.4% based on the Number Name Date vinyl ethyl ether. 2,165,962 Cunradi et a1. ____ ..- July 11, 1939