DE848649C - Process for the preparation of acetals of aliphatic ª,ª-acetylenic aldehydes - Google Patents

Description

Process for the production of acetals of aliphatic a, ß-acetylenic aldehydes The invention]> ezlelit is based on a process for Manufacture% -on Acctal (! N allphatIscher a, fl-acetNIle- iiisclici- Aldchyde and is of particular value at the production of acetals of the propargylalde- 11v (Ls, your lowest link in the hotnological series. lias \ 'learn is to express cleavage of hydrogen halide from acetals aliphatic a-balo-substituted olefinic Aldehydes tuiter formation of the corresponding acce- tylenic acetals, specially designed for the cleavage of Clilor \\ assei -, #, toti ans acetals of a-chloracrolein to the flvrstuliL111 " nozzle desired Acetals Init iiil, *) '<' ljcllzt g "eriti", ctl formation of Tars, resins or polymers or other tin-desired by-products.

According to the process of the invention, acetals aliphatic for acetylenic aldehydes are prepared by treating the corresponding acetals aliphatic for fl-olefinic aldehydes with an aqueous alkali solution under increased pressure and, if the temperature is above the boiling point of the solution at atmospheric pressure, obtaining the desired, acetylenic acetals from the reaction mixture. The method of the invention \ N ill z \\ according - ZCK-ni # running a resident of the way (let nian which is formed by elimination of hydrogen halide acetylenically # n aldehyde acetals in the vapor phase under superatmospheric pressure at a rate substantially equal to the rate of formation of Acetals, continuously withdraws.

The process of the invention is particularly advantageous because it enables the production of acetals des propargylaldiehy, d # 9 from acrolein, in a much improved manner. Prior to the invention, there was no useful known method for converting acetals from aliphatic α-halogen substituted. olefinic aldehydes, e.g. B. Acctalen "-one aC.hloracrolein" to the corresponding acetals of the acetylenic aldehyde. Accordingly, acetals of propargylal, d-ehyd- and certain higher hornologists, vein straight-chain series by bromination of z. B. acrolein with the formation of acroleindibromi, d produced, whereupon z. B. the acetal of the dibromoaldehyde is obtained by reacting with an ortho-antic acid ester. and 2 moles of hydrobromic acid are split off from the SCM. The direct production of the dibrornaldehyde acetal turned out to be quite unpleasant and only gives low yields of the desired product. Also are. the yields of acetylenic aldehyde acetals, very small in the elimination of hydrogen bromide from Dibromaldehydacetalen, since forms overall in the known methods of complex mixtures, materials, from which the desired acetylenic Aldchydacetal can be separated only with great difficulty.

Acetals of α-haloacrolein can easily and conveniently be prepared by Ualogenation of acrolein to L) ihalogenpropion.ald-ehyd according to known processes, which can be converted to α-haloecrolein by elimination of hydrogen halide, e.g. B. by adding to boiling water and distilling off the resulting azeotropic mixture of α-haloacrolein and) water. The acetals of the monohalosubstituted olefinic, ch-ene aldehydes can be prepared well and in excellent yield by reaction of the aldehyde with an alcohol at about room temperature, preferably in the presence of a trace of acidic catalyst. The fact that for the first time a useful method for the splitting off of the hydrogen halide from these monohalosubstituted olefinic acetals. is shown, the difficulties encountered in the known processes are avoided and acrolein is converted into propargylaldehyde acetals in an excellent manner with high overall yields of the desired product.

The method of the invention differs significantly before) the amount of C 1 Aisen, the proposed process for the preparation of acetals of Proparg, # -. IALD ehyd, consequently, an acetal of Dibrompropionaldehyd miit an alcoholic solution of potassium hydroxide is treated for removal of 2 molecules Hydrobromic acid from the acetal. The process proposed by Claisen has the disadvantage that, although the acroleindil) rom acetal is almost completely consumed, no less than about 400/0 is converted into products other than the desired propargylaldehyde acetal. In other words, the method of C 1 ais e ri. brings about a nonselective conversion of the di) romaldi.-hvdacetal into a mixture of products (it only contains a small amount of the desired acetylenic acetal. It has also been found that the treatment of acetals by aliphatis-clie. ri tiio # nolialog # - n-substituted aldehydes with an olefin bond in a, f-position, e.g. the dietary acetal of a-chloracrolein, with an alcoholic, caustic alkali solution at a temperature and a pressure in the range of temperatures and pressures Processes of the present invention are used, leads to almost complete conversion of the .11, cetal into products which are markedly different from those obtained according to the present invention without formation of the desired acetylenic acetal.

The elimination of hydrogen halide from the monohalogen-substituted one olefinic acetal by the treatment according to the method of the present invention with aqueous alkali solutions, as a result, brings substantial and unexpected Advantages over the elimination of hydrogen halide from dihalosubstituted ones saturated Aldebydac -, - talen by treatment with alcoholic, solutions of potassium hydroxide with himself. The advantages are based in part on the considerably increased ones to be maintained Yields of acetylenic, \ ld #, - h- "dacetals. In other words, the reactivity # the conversion has been compared to the knownerr process for the production of such Acetals significantly improved. Another advantage of the invention is that it is larger Ease and economy, with the elimination of hydrogen halide, can be carried out, especially with regard to the extraction and purification of the desired acetylenic acetal without separation of the acetal from one organic solvent is required. Furthermore, through the use of aqueous alkali solutions due to the presence of alcohol as a solvent Overtly favored excessive formation of undesired by-products avoided.

The alkalis to be used in the process are preferably alkaline compounds of alkali metals such as alkali carbonates or hydroxides and ammonia. The ""# for %% - endLing of caustic alkalis is preferred. It has been proposed by V 1 g uier to use potassium hydroxide in solid form for carrying out the 1-talog # .- n #, N-as # hydrogen elimination from the diethyl, acetal of the dibromobutyraldehyde; however, the results were not satisfactory, since a complex mixture of products was formed and the yield of the desired acetylenic acetal was very low. Even alcoholic solutions of Kal # iumliN-droxN-d lead to low and uneven yields and excessive formation of byproducts. their separation from the desired acetylenic product proves extremely difficult and proved time consuming. Unexpectedly revealed that the elimination of hydrogen halide from imii (-) Iialog-etisul) .stittii, ertcii olcfiii # isclizti acetals by treatment with aqueous, solutions of Alkalicii Schw:, eri-keten. out of the world overall by f, rzieliiii "l, lioll-er to the Endausheuten wishes a product and through considerable min, eration of gL # 1) II (1 "t (2ii by-products, which also easily separated \\ - being able to earth -, ii. The use of aqueous solutions \, oii sodium, hydroxide in the prefer the present invention; it can each- but also N \ zis-lerl, #, e solutions of other alkalis, such as Kalitiiiili #, dr (-) x #, cl, lithium hydroxide and also Ru- bidium- and (. "is; tiiiiIiN '(Iroxv (1 oder .- *" m-mon # ial "so- like \\ i. Lsseri "e U ') stingen der Erd-alkalihvdrox # -de and alkali carbonates such as 13th sodium carbonate are used will. 13, when carrying out the procedure of Invention contain the aqueous alkaline Solutions in the lZc "" el at the beginning of about 2 bis about g 30 (-ü% \ - iclitsl) rozütit, 3 preferably un- about 5 to about 30 (per weight alkali. The method of the invention can clisconically, continuously To be carried out lightly or continuously. at k-oiitlii # tilcrllclicr carrying out the procedure can additional alkali either in solid form or as concentrated solution, into the reaction svstem uitig,. # fiilirt # \ erd -, # ii, do (read at d "-m ver drive to replace alkali, or it can the solution (k # s alkali continuously or from time zu Z #! it au, # d #, # r kuaktionszone deducted and for the original alkali content be treated. The method of Ei fin, du: tig has the advantage that those caused by the reaction of the alkali with your ans your a-Iialog-uiistil) stittiicuteti oleCinic acetal free- set 1 l # il (-) geii \ # - assürstoti formed, halides Remain in the solution during the procedure can, en, The presence of the lialogeli # idK # in the solved State facilitates the ( iu # N # iiiiiiiiig of the desired Product -., S urli # cl) licli tti - "(1 continues to avoid the more expensive and 1, otni) llzlcrt #, 1- pre devices used to treat large quantities of donated or precipitated solids 1,- holding kvaktion, sinischut gLii, z. B. when using use of organic solvents as a reaction tionnieditiiii, n # otwen, dig warcii. The Ilalogenidü can be mixed with icilZvaction by peeling off the wassi-i-, en g Ustiiig 0 or a part of the continental Lich or from 7 to 7cit #% - 'iliren # d of the procedure and l # 'rs # etzcii (1, e-solution by eincii frisclil) ei-cit (#teii part or by treating the ab- drawn- "ii, #" ii part in a common known manner Separation (lK # i- I [al (i ", ciii (le from the alkali ciit- far away Those of the 1), ui your \ 'experienced used Alk-alll (* 3stiii #, does not need to be meticulously set to become; it is judocli to take into account that that Alkali (Inrelt the released during the reaction 1 [alo, # "etii \ # - 2is.sers, toff iietitralisiert and (let des- half the stoichiometric amount of alkali in relation to its purpose: 1), - becomes one mi z. I ', i o worked; vorzig's- l # wise, amounts of more than about 1 j acid equivalent of alkali per mole of this olefinic aldehyde acetal are used. Much larger amounts can also be used, a practical, but not theoretical, maximum being about 10% alkali per mole of the olefinic aldehyde acetal.

The process of the invention is carried out under positive pressure and at a temperature above the normal boiling point of the aqueous allali solution. The preferred pressure range is from about 3 to about 14 at Considerably higher pressures can be used when working in batches. Usually, however, the use of pressures significantly above approximately 1.4 at is not particularly advantageous. At pressures below 3 at, the conversion of the a-halogen occurs -sul) stittlated. o], efinian Aldchydac-etals essentially below the transformations which are obtained when working under higher pressures. The minimum of the pressure used is preferably not below iI at, since at pressures substantially below this limit the conversion of the α-halogen-substituted olefin, al, dehydoacetal to the desired triple unsaturated aldehyde acetal with one in practical processes. acceptable limit is reduced. The temperature used must be high enough to bring about the desired halogen-% -asserstotiabspalüuiig, but not so high that a heat decomposition of the olefinic or acetylenic acetal occurs. It was found. that for useful conversion processes with advantage temperatures of N% -en, usually about 10 ', preferably at least about 130', are used. The maximum of the temperature used is at the point at which the total vapor pressure of the reaction mixture is the same as that used; Pressure. Preferably, however, (1 final temperature is not above about igo ',', although slightly higher temperatures up to about 220 'can be used at times. Optimal results can be obtained within the temperature range of about 130 to about 170 ". The The pressure can easily be the vapor pressure of the reaction mixture at the temperature used; however, it may be desirable to work at pressures somewhat above the vapor pressure of the reaction mixture, in which case the pressure is increased by introducing an inert gas into the reaction zone ... , e.g. 13. Nitrogen, helium, methane or ethane, produced by KanTi. The elimination of hydrogen halide is initiated by bringing the α-halogen sulfide into place. Aldehyde vdacetals with the aqueous alkali solution under the conditions indicated below at elevated temperature and under excess pressure. If the process is carried out batchwise, the aqueous alkali solution and the halogen-substituted acetal are introduced into a pressure-tight reaction vessel and heated to the elevated temperature and under pressure for a sufficient time. If desired, the reaction mixture is vigorously stirred while heating. Response times of 1 to 6 hours are generally sufficient. It is advisable to avoid unnecessarily long reaction times because this would increase the possibility of excessive side reactions occurring. Real action times. of at most about 3 hours. are preferred.

When practicing the method of the invention continuously can be a mixture of the α-halogen-substituted olefinic aldehyde acetal and Aqueous Allzali, solution in the desired proportions by one or more Zolisen are passed through at the desired temperature and. the pressure held. will. According to a preferred embodiment, the acetylenic Acetal withdrawn in the vapor phase from the reaction mixture at a rate essentially the rate of formation of the acetal during the splitting off of hydrogen halide is the same, what is achieved by appropriate setting of, temperature and pressure can be,.

If the process is carried out continuously, the vapors of the acetylenic acetal can be separated off in one separation device or in several separation devices with partial separation in each of them. The vapors thus withdrawn are condensed to obtain the desired product; Any unreacted halogen-substituted acetal and / or water which have also passed over can be returned to the reaction zone. It can lead to the end and work up the entire Reaktionsgernisch to obtain the desired acetate also Halogünwasserstoffabspaltung before the separation of the desired acetal. For example, the mixture can be cooled in two phases to separate the layers: an aqueous phase and an organic phase containing the desired acetal, the two phases being e.g. B. separated by decantation and the organic phase z. B. is worked up by fractional distillation. Any unreacted α-halogen-substituted olefinic acetal and / or the aqueous alkali solution can be wholly or partly returned to the process, with additional alkali being added to the aqueous solution if necessary.

The following examples, in which the parts are parts by weight s), show preferred embodiments of the invention. Example I Acrolcine was chlorinated by passing a liquid stream of acrolein in an amount of about 4 moles per hour in countercurrent to a stream of gaseous chlorine flowing upward through a glass tube maintained at a temperature of about 25 ' . The proportions of the streams of aerosol and chlorine were chosen so that there was approximately 10/0 excess chlorine over the theoretically required M 7 range .

The a, fl-dichloropropionaldehyde thus formed was introduced directly from the lower end of the column into boiling water, the distilling azcotropic mixture of 'water and: a-chloroacrolein was condensed and then redistilled under a pressure of 30 mm of mercury, where' The fraction distilling over between 31 and 32 'was collected as the desired α-chloracrolein.

The dimethylacetal de-, 2-chloroacrolein was prepared by reacting the a-chloroacrolein with 1vIetliyI-alcohol in a l #, [olarverliält, n, is of i : .5 11., the reaction by adding - # en one (, 2-ring amount of anhydrous hydrochloric acid was catalyzed. After 3 hours, at 25 #, the acid was neutralized and the mixture of des 2-chloroacrolite was found to be between 38 and 39c obtained under a pressure of 20 mm of mercury distilling fraction. The yield of the acetal, based on the α-chloro # racrolein used, was 82% of theory.

For hydrogen chloride elimination of the dimethyl acetals of a-Chloracroleiii-z; A pressure-resistant reaction vessel, with a mechanical stirrer and means for heating the contents # -crs, ch, clir.-s, pressure-resistant reaction vessel was used. A steel deplegmator was attached directly to the vessel for the condensation of substances vaporising from the reaction mixture at the reaction pressure. The dephlegmator was surrounded by a jacket through which steam at atmospheric pressure flowed for cooling and which was provided with a suitable shutter and outlet valve for removing a desired fraction of the condensate from the system.

100 parts of the α-Cliloracroleitidiinethylacetals and 33o parts of a 1% by weight solution of sodium hydroxide in. Water were mixed in the reaction vessel. The vessel was then closed from the outside air and (the mixture was heated to a temperature of 146 'under a pressure of about 5.5 at and withdrawn from your system. The condensate was found to be composed of a mixture of essentially pure l'ropar ""# - Ialdehvddimetlivlac, etal and water. Heating was discontinued after 70 minutes . The collected product was for the recovery of the prol) arg #, laldeh #, dimetlivlacetal redistilled, which was obtained in a yield of 71%, based on the α-chloroacroleindlmeth, vlacetal consumed in the process, which shows the highly selective conversion of the halogen-substituted acetal to the acetal obtained. , 1, eii, is, cheli acetal shows. In this experiment, the conversion of the α-chloroacrolide dimethyl acetal to the propargy1-aldehyde acetal was inadequate for the amount used. extension of the reaction time or return of lillreactiert, ciii a-Cliloracrolein # dimethylacetal in the Process could be increased significantly. Example 11 1) .is 1) 1, # tli \, lacetal des 2-Cliloi-acrolein produced by adding α-chloracrolein init Ätli # -Ialk- (ili #) 1 in a similar way as in your previous At, # piel. The resulting halogen Substituted Acctal was using in an autoclave dC111 2,24f; ICIICII his weight of a nt weight j) rozetit, i "l, cit of '- \' atrluin-hyd-roxyd in Water mixed and the 'mixture for i hour under 1Ziilireii on ioo to 165 # under the steam pressure of the Geinisches heated. - \ at the end of this time was the car cooled oclavely and # the mixture -Vzog 11 under ri-, utiiitiii "in z, # \ - ci phases. The orga- e el niche phase -, -, was abandoned by the N #, - ässerigeti phase- divided and fractionally distilled. The diethyl acetal des trol) arg #, laicleli # l (ls was in a Today from about 70 0/0, based on the amount of the consumed a-Clilor # -tcroleiiidläthylacetals, he lialteii. One example of this was the conversion of the 2-Cliloracroleiiidl * 'itlivlacetals zu PropargyIaldehyd- acetal about 32 0/0. When repeating the \ 'cr s L i- ,; under X'.er \% - etidtitig the same condition-un- -c11, Cdoch with a reaction time of 2 hours was d-ic conversion to l'ropargylaldeli ## dacetal increased to approximately g ä _ # 90 / 'o without x% -significant changes- determination of the yield obtained, d. left without essential Changes in the selectivity of the procedure. In sp iel 111 1 ti the previous one. Examples were 14 to i s0 / t) solutions of caustic alkali used; it can - solutions with significantly higher concentrations are also tration can be applied, as in this experiment will be shown. 68 parts of the dimethylacetals α-Chloracroleins were mixed with igo parts a 23 weight percent. Solution of, sodium hydroxide in water, and the mixture was rciid 2 hours on i-io 'under the steam, pressure the M ischung heated. The resulting mixture became withdrawn from your IZ # 2aktiotisgef'iLl, the organic Pliase became like in your previous example separated and distilled. The Dimetlivlacetal des l'rol) arg #, lal (lellN, d- ,; was obtained in a yield of 70.5 0, "(), lwz0," tii on (read used a-Cliloracroltin- acetal, and in a comparative receive a convertible union agreement, 13 C i sp ie 1 1 V Aii StelIc dus in the previous examples Sodium hydroxide used can be similar to it l Results Kaliuni # liydrox #, dN-erwcti # detwerdün.Zurn Example can (read 1) imetliylacetal of a-chlorine acroleins in an autoclave with i, irnolar Equivalents of potassium hydroxide in the form of a i.5 weight percent solution mixed in water and the mixture under (learn its own vapor pressure Heated to i_3o 'for 2 hours. That resulting geniizcli contains after processing the # orh-er-Chen, the Heifen das Propargy1- aldehyde acetal in yields which correspond to those obtained in the previous experiments.

The invention has been described and clarified above with specific reference to the conversion of acetals, from α-chloroacrolein to acetals from propargylaldehyde; Acetals lioniologer aliphatisAer a, fl-acetv # len # isclier Aldeh, vde can also be prepared by the process of the invention from corresponding acetals of a-halogena. fl-olefinic aldehydes, e.g. B. acetalt of tetroaldehyde can be prepared from the corresponding acetals of α-chlorotonaldehyde, and acetals of higher aliphatic α, fl-acetylenic aldehydes can be prepared from the corresponding monohalogenubstituted olefinic acetals; getting produced. Although it is desirable for conventional purposes to use the u-chloro-substituted ofefinic aldehyde acetals, the process of the invention can also be used to convert the corresponding olefinic acetals into which a. halogen atom other than chlorine is bonded to the olefinic carbon atom adjacent to the acetal group. Thus, instead of a-chiloracrolein acetals, acetals of the a-bromine, a-iodine or a-fluoro derivative of acrolein or homologous, aliphatic a, fl-olefinic aldehydes can be used. The acetals can be those that result from the reaction of the free aldehyde with some c.invalent. or more, alcohol such as aliphatic, aromatic or cycloaliphatic alcohols are formed. For common purposes, however, it is usually desirable to use the acetals in which the acetal group is derived from a lower alcohol (such as meth. 1, ethyl, propyl, isopropyl, butyl, pentyly, or similar alcohols) Contains alkoxy groups.

Claims (2)

PATENT CLAIMS: i. Process for the production of. Acetals aliphatic ct, beta-acetylenic aldehydes, characterized in that A # acetals aliphatic, ischer a-halo-a, ß-colefinischer Aldehvd-e for the purpose of ex cleavage of aqueous solutions of an alkali Halogenwasserstodmit under elevated pressure and at a normal to the The boiling point of the aqueous alkali solutions lies in the temperature. 2. The method according to claim i, characterized in that the acetylenic Ald formed by the elimination of hydrogen halide, eh #, d # acetals from the reaction mixture, withdrawn at a rate which essentially corresponds to the image rate, we r the, 3. The method according to claim i and, 2, characterized in that aqueous alkaline solutions are used with a concentration of approximately 2 to 30 percent by weight, preferably of approximately 5 to 30 percent by weight. 4. Procedure. according to claims 1 to 3, characterized in that the aqueous alkaline solutions used are those of an alkali metal hydroxide, preferably sodium hydroxide. 5. The method according to claim i to 4, characterized in that the treatment at a temperature between iio and # 220 ', preferably between about 130 and 170', takes place. 6. The method according to claim i to 5, characterized in that the treatment is carried out at a pressure of approximately 3 to 14 atm. 7. The method according to claim i to 6, characterized in that an excess of. Alkali solutions are used, e.g. B, at least about iol / o, calculated on the amount of the halogenated water, toffs. 8. The method according to claim i to 7, characterized in that halogen-substituted olefinic aldehyde acetals of low molecular weight alcohols, preferably a-haloacrolein acetals, z. B. a-chloracrolein acetal, can be used,