CA1152086A - Method for producing a di-acetal of sorbitol and an aromatic aldehyde - Google Patents
Method for producing a di-acetal of sorbitol and an aromatic aldehydeInfo
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- CA1152086A CA1152086A CA000354071A CA354071A CA1152086A CA 1152086 A CA1152086 A CA 1152086A CA 000354071 A CA000354071 A CA 000354071A CA 354071 A CA354071 A CA 354071A CA 1152086 A CA1152086 A CA 1152086A
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- acetal
- sorbitol
- aromatic aldehyde
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Abstract
METHOD FOR PRODUCING A DI-ACETAL
OF SORBITOL AND AN AROMATIC ALDEHYDE
Abstract of The Disclosure A method is provided for producing a di-acetal of sorbitol and an aromatic aldehyde wherein an aqueous solution containing a catalytic amount of a mineral acid and sorbitol is formed. There-after, an effective amount of an aromatic aldehyde such as benzaldehyde is incrementally admixed into the homogeneous aqueous admixture containing the sorbitol at a rate sufficient to allow a substantially spontaneous reaction to occur between the D-sorbitol and aromatic aldehyde; thus, forming an aqueous slurry containing crude di-acetal, e.g., dibenzylidene sorbitol. The amount of aromatic aldehyde employed is that amount sufficient to provide a molar ratio of D-sorbitol to aromatic aldehyde of from about 1:.75 to about 1:1.75. Thereafter, the aqueous slurry is neutralized, and crude di-acetal is removed from the liquid phase and washed with water to remove mono-acetal impurities, e.g., monobenzylidene sorbitol. The washed di-acetal may then be dried to provide dried di-acetal, and the dried di-acetal may be further purified by washing with a relatively non-polar solvent.
OF SORBITOL AND AN AROMATIC ALDEHYDE
Abstract of The Disclosure A method is provided for producing a di-acetal of sorbitol and an aromatic aldehyde wherein an aqueous solution containing a catalytic amount of a mineral acid and sorbitol is formed. There-after, an effective amount of an aromatic aldehyde such as benzaldehyde is incrementally admixed into the homogeneous aqueous admixture containing the sorbitol at a rate sufficient to allow a substantially spontaneous reaction to occur between the D-sorbitol and aromatic aldehyde; thus, forming an aqueous slurry containing crude di-acetal, e.g., dibenzylidene sorbitol. The amount of aromatic aldehyde employed is that amount sufficient to provide a molar ratio of D-sorbitol to aromatic aldehyde of from about 1:.75 to about 1:1.75. Thereafter, the aqueous slurry is neutralized, and crude di-acetal is removed from the liquid phase and washed with water to remove mono-acetal impurities, e.g., monobenzylidene sorbitol. The washed di-acetal may then be dried to provide dried di-acetal, and the dried di-acetal may be further purified by washing with a relatively non-polar solvent.
Description
iZ(~I 36 This invention relates to di-acetals of sorbitol and an aromatic aldehyde, e.g., dibenzylidene sorbitol. rn one aspect it relates to an improved method for the manufacture of di-acetals l~of sorbitol and an aromatic aldehyde.
¦ Di-acetals of sorbitol and aromatic aldehydes, such as, for instance, dibenzylidene sorbitol, have heretofore been known as polymer additives for imparting unique properties to ~certain polymers. For examPle, dibenzylidene sorb:itol has Ibeen employed as a clarifying agent for polyolefins" especiallv ¦polyethylene and polypropylene to improve the transparency of ¦films made from suc:h polyolefins. While the use o:E dibenzvlidene ¦~sorbitol for polymer additives has shown much prom:ise and utility, ¦~problems have nevertheless been encountered in providing l economical commercial methods for the manufacture of dibenzylidene !
¦ sorbitol having a degree of purity sufficient to justify its manufacture.
Therefore, an object of the present invention is to provide an improvecl method for the manufacture of cli-acetals i such as dibenzvlidene sorbitol by the condensation of sorbitol and ¦ aromatic aldehydes, Another object of the invention is to provicle an economical commercially feasible method for producing di-acetals of sorbitol and an aromatic aldehyde, such as dibenzylidene sorbitol, for use ¦las polymer additives.
1I These and other objects, advantages, and features of the ¦~present invention will be apparent to those skilled in the art i from a reading of the following detailed disclosure.
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1 115;21~86 According to the present invention, I have disco~ered a rnethod for producing di-acetals of sorbitol and an aromatic aldehyde which comprises admixing an effective amount of D-Isorbitol into an aqueous solution containing a catalytic amount of a mineral acid so as to form a homogeneous aqueous admixture containing the mineral acid. Thereafter, an effective amount of an aromatic aldehyde is incrementally admixed into the homogeneous aqueoùs admixture containing the D-sorbitol at a rate sufficient to allow a substantially spontaneolls reaction between the D-sorb:itol and the aromatic aldehyde, thereby re-sultiny in an aqueous slurry containing crude di-acetal. The aqueous slurry of the crude di-acetal is then neutralized and the crude di-acetal separated from the liquid phase of the neutralized aqueous slurry. The crude di-acetal is then washed with water to remove mono-acetal impurities present in the crude di-acetal product. The washed di-acetal is then dried to rennove sub-stantially all of the residual water and provide a purified, dry ~di-acetal product.
I ~t should be appreciated with regard to the di-acetals of ¦sorbltol and aromatic aldehyde nnade according to the process of ¦the ~resent invention that what is intended is the disubstituted compound, e.g., the sorbitol component will be substituted with two molecules of aromatic aldehyde, ra~her than one or three molecules. Thus, in the case of benzaldehyde, the condensation product will be dibenzylidene sorbitol rather than monobenzyli-dene sorbitol or tribenzylidene sorbitol, which la1:er compounds may have other utilities but are considered to be, and therefore 115Z~86 ¦lare defir)ed as ":i.m~urities" insofar as the r:)re~ent Invention i.s concer~ed~ Other examr~les of "cli.-aceta~s", as thi-~ t-er[n lS de-fined according to the present invention include, e.c3., di-(p-chlorobenzylidene) sorbitol, di(m-chlorobenzvliclene) sorbitol, di(methylbenzylidene) sorbitol, etc. I
It has been found that a mineral acid should be ~rovided in the aqueous solution to which the D-sorbitol is added. The ¦acid should be present in a catalytic amount which can vary ~widely and which may depend to a certain extent on the acid Istrength of the particular acid employed. Generally a catalyti.c amount is from about 10 to 75 weight percent, preferably from about 15 to 60 weight percent or even 3~ to 60 weight percent, based on the total amount of water present in the reaction mixture. The preferred mineral acids may be hydrochloric acid and sulphuric acid, although others, such as ortho~.hos~horic acid mav be employed. When the acid employed is hydrochloric, the preferred acid conc~ntration has been found to be f:rom about 10 to 25 weight percent, preferably 10 to 20 wei~ht pe.rcent. When ¦sul~hurlc acid is used the preferred concentration may be from about 30 to 60 weight ~ercent, ~reEerably 35 to 50 weit~ht ~ercent.
The amourlt of D-sorbitol admixed with the aqueous solution ¦
of the mineral acid to form a homogeneous aqueous admixture con-taininq the mineral acid can vary widely. However, the amoun-t of ¦
D-sorbitol. employed should not exceed the solubility characteris- I
l tics of D-sorbi.tol in tne aqueous solution of the mineral acid at !
the temperature at which the reaction between the D--sorbitol and laromatic al ehyde is carried out.
115;2~8~
Il Once the desired amount of D-sorbltol has been incorporated ¦¦i.nto the aqueous solution Or the mi.neral acid con-taining the ,amount of mineral acid as heretofore speclfied, an aromatic alde- .
~hyde lS incrementa:Lly added to the homogeneous aqueous admixture 5 ¦containing the D-sorbitol at a rate sufficient to aLlow a sub-stantially spontaneous reaction to occur between the D-sorbitol and the aromatic a:Ldehyde. Such incremental addition is generally achieved b~ very s:lowly adding the aromatic aldehyde to the aqueous admixture while maintaining the aqueous adm.ixture under agitation. Further, the amount of aromatic aldehyde added to the aqueous admixture containing the D-sorbitol is that amount sufficient to prov:ide a molar ratio of ~-sorbitol to aromatic aldehvde of from about 1:.75 to about 1:1.75, ~refe:rably about 1:1 to about 1:1.5, or even about 1:1.25 to about 1:1.75.
A wide variety of aromatic aldehydes and mixtures of aromatic aldehydes may be employed in the process o:E the in-Iven-tion. Examples oE such aromatic aldehydes include benzalde-¦hyde, ortho-, para- and meta-tolualdehvde, anisaldehyde and sub-stituted benzaldehydes having one to three substituents and wherein the substituents are sclected from lower al}cyl, methoxy, mono- and di-alkylamino, amino, nitro or halogen. E'referred aromatic aldehydes include benzaldeh~de, meta- and para-chlorobenzaldehyde, meta- and para-bromobenzaldehYde and meta-and para-tolualdehyde.
I The reaction between the D-sorbitol and aromatic aldehyde to form the desired condensation product can be carried out at various t mperatures. In the case of benzaldehyde, for instance, I
I I
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I
~it has been determined that such reaction may be desirably carriedl jou-t at ambient or room temperatures. In the case of other alde- ;
hydes temperatures above or even below ambient or room temperature~
l may be more suitab:Le.
¦ Once the aromatic aldehyde has been added to the aqueous admixture containing the D-sorbitol and the minera:L acid and an aqueous slurry results from the formation of the di-acetal, the aqueous slurry is neutralized with an alkali substance, such as sodium hydroxide, potassium hydroxide, sodium bicarbonate and the like. The amount of alkali material employed may vary widely.
It may be desirable in some applications that the amount of alkali material employed be slightly in excess of the amount required to neutralize the aqueous s~urry admixture, although large excesses of alkali should be avoided.
¦ After the aqueous slurry admixture has been neutraliæed, ¦the crude di-acetal which is the solid material of the aqueous ¦slurry admixture containin~ minor amounts of mono-acetal im-¦purities, such as monoben~ylidene sorbitol, is separated from the ¦liquid phase of the neutralized at~ueous slurry admixture. It may be desirable to include the step of washing the crude di-acetal with cool water to remove any residual salts formed as a result of the neutralization of the aqueous slurry and excess alkali material present in the wet, crude di-acetal product. When washing the wet, crude di-acetal product with cool water, the temperature of the water can vary widely. However, it is be-lieved that best r~sults will be obtained when the water is main-ained at a tem~erature of from about 20~C to about 40C. The , . I
I , I
~se~dra~ecl, wet, crllde condensation pro~uc-t ma~ thell bc~ washc~
¦again wi-th warm wa~er to remove the mono-acetal impurities. The temperature o~ the water employed to wash the crude di-acetal product to remove mono-acetal impurities can vary widely.
The washed product substantially free of the mono-acetal impurities may the~eafter be dried to remove residual water and provide purified, substantially dried di-aeetal product. Drying ean be aceomplished by any conventional method known in the art, such as use of a vacuum oven, eonveetion heat and the like. The drying temperature is not eritieal provided sueh is suffieient to ¦effeetively dry the material but not deeompose sam~e. Subsequent to drying the puriEied di-aeetal produet may be even further puri-fled by extraeting same with a relatively non-polar solvent as will be described hereinbelow in greater detail.
It may be desirable to operate the method for produein~
di-acetal in a continuous or semi-eontinuous method. In sueh instance, it is desirable that the erude di-aeetal produet be re-moved from the liquid phase of the aqueous slurry prior to neutralization so that the reeovered liquid phase can be recycled ¦
or employed ~or further makeup of the initial aqueous solution of the mineral aeid and the D-sorbitol. In sueh instanee, the erude solid di-acetal produe-t separated from the liquid phase ean be neutralized using an aqueous solution of an alkali material, such as those set forth hereinabove, and thereafter the neutral-ized produet may be washed using warm water or a eombination of cool water and warm water as reeited above.
1~ llSZ(~86 The separation of the crude di-acetal product fr~m the aqueous slurry containing same can be accomplished by any suitable¦
means well known in the art, such as filtration, centrifuging, and the like.
In order to further illustrate the present invention, the following examples are given. However, these examples are for illustrative purposes only and are not to be construed as unduly limiting the scope of the subject invention as set for~ in the claims hereafter.
EXAMPLES
. ., Procedure A
This procedure was employed for Examples 1-3 and 10-12 shown in Tables 1 and 2. A 70 percent aqueous solution of sorbitol (135 grams, 0.5 mole), the appropriate amount of benzal-dehyde to give the molar ratio of benzaldehyde to sorbit:ol shown in Tables 1 and 2, and the designated aqueous mineral ac:id solution [200 grams) of the concentration indicated, were placed in a l-liter vessel fitted with a Teflon*~addle stirrer. This reaction mixture was stirred at about 25C until the viscosity had risen to the point where stirring was no longer effective.
The acid was then ~eutralized to an extent of about 98 percent with a 10 percent aqueous solution of sodium hydroxide, and the reaction mixture finally brought to a pH of about 8 with 10 percent sodium car~onate. The white, solid product was filtered, washed thoroughly with water, and dried at 95C in a convection oven.
*Trademark ~1521~
~j High performance l.iquid chromatography was then used to determine the ratio of dibenzylidene sorbitol (DBS) to tri-,benzyl.idene sorbitol (TBS) in the product.
I Procedure B
l~ This procedure was similar to Procedure A except that the stated molar amount of benzaldehyde was added dropwise to the reaction mixture over a period of about 4 hours in -the following ¦manner first hour, 50 percent; second hour, 25 percent; third hour, 15 percent; fourth hour, 10 percent. The reaction was then continued for a short time to achieve the desired. h:igh viscosity, neutralized, and the product isolated as described llnder Pro-cedure A. I
Examples 1-6 l In Example 1 Procedure A was employed using a mole ratio Iof benzaldehyde to sorbitol that would be -theoretically requi.red to produce DBS (2:1 mole ratio). The product obtai:ned actually showed a DBS/TBS ratio of 75:25. By reducing the mole ratio of benzaldehyde to sorbitol, firstly to 1.5:1, and the:n to 1:1, in l Examples 2 and 3 respecti.vely, the DBS/TBS ratio in the product l steadi.ly increased to 83/17. A similar effect was observed in ¦~Examples 4 and 5, where a higher acid concentration was used. The results are summarized in Table 1.
1~ Examples 6-9 ¦1 In Examples 6-9 Procedure B was employed rather than Pro- ¦
cedure A and a lower mole ratio of benzaldehyde to .sorbitol was also employed resulting in a further increase in the DBS/TBS ratio, ¦¦reaching a maximum ratio of 91:9 in Example 9. The results are ¦Isummarized in Table 1.
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s~a~6 Examples 10-17 "
~, In Examples 10-17 generally similar effec-ts were observed with a sulfuric acid catalyst. The results are summarized in ,Table 2, where the Aiyher DBS/TBS ratio of 94/6 is observed in IlExample 17. Examples 10-17 and Table 2 also illustrate that the percentage yield of product, based on the benzaldehyde employed, rose very significantly as the mole ratio of benzaldehyde to sor-bitol is reduced. 'rhis is particularly illustrated by comparing Examples 12 and 16 with a 40 percent acid concentration.
Although the melting point of a mixture product tended to ¦be broad and somewhat erratic, it was clear from the results in Tables 1 and 2 that as the DBS/TBS ratio rose significantly, the melting point of the product also tended to rise as would be ex-l pected. Again, a comparison of Examples 12 and 16 shows this ¦ effect clearly.
Although the improvement of the DBS/TBS ratio as shown in Tables 1 and 2 is of great utility, there may still be a need in certain commercial applications for a product containing an even ~igher proportion o~ the DBS component. According to United States Patent 4,131,612, a crude DBS product, containing as impurities TBS and other compounds t may be purified by extracting it with a ~ower aliphatic alcohol, such as methanol, at elevated temperatures .
~his procedure described in the patent using methanol was applied ~¦to the product of Example 17 in Table 2, with the result shown in I,kable 3. It is seen that the content of DBS in the product actually declined, rather than increasing as would have been ex-~ected from the teachings of the abovementioned patent.
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., 1,l According to the present invention all or even a portion of -the TBS present in a di-acetal/tri-acetal pro~3uct may be re-`~lmoved to increase its di-acetal content by employing a rela-tively ~Inon-polar solvent. In Table 3 are also shown the results of , extracting DBS/TBS products with relatively non-polar solvents, viz: toluene and l.,l,l.-trichloroethane. A liquid-to-solid ratio ¦¦of 10:1 was employed as in the case of methanol described above.
¦¦A significant increase in the DBS content was achieved, especially l in the case of l,l,.l-trichlorethane. The recovery of desired ¦ product was also very high. In the case of the l,l,l-trichlorethan~, the liquid extract was concentrated to remove the solvent leavin~
a residue with DBS/TBS ratio of 8/92.
:Extraction DBS:TBS Ratio l Solvent ConditionsInitial FinalRecovery Methanol 1 Extraction 94:6 93:7 ~ 90%
r~'60~c Toluene 3 Extractions 92:8 95:5 v 85%
" ~J80C
l,l,l-Trichloro- 3 Extractions 92:8 98:2 ,~90 ethane ,~/70C
Example 18 I A 70~O aqueous D-sorbitol solution (52 grams, 0.2 mole ¦~orbitol) and 48~ sulfuric acid (87.1 grams) were placed in a flask¦
¦~ith stirrer. Benzaldehyde (31.5 grams, 0.3 mole) was then added ¦~ropwise with vigorous stirring over a period of 1 hour and 45 ¦~inutes. During the addition, the temperature of the reaction Il 1.
, , 1 115;;:(~86 , .
mixture rose from 24 to 28C, and a pale yellow solid was formed.
Continued stirring of the slurry for a further 1 hour and 30 llminutes. Poured the contents of the flask into 8% aqueous sodium jlhydroxide with vigorous stirring to neutralize the acid. Then l¦filtered off the solid, and washed i-t with cold water to a pH of 5.5. Slurried the solid product in water at 90C for 30 minutes, I
then filtered, and washed the material with more hot water. Dried ¦
the product in a vacuum oven to constant weight. Y:ield: 42 grams l (78% yield calculated as dibenzylidene sorbitol, and based on the weight of benzaldehyde employed.) The melting point of the off-white powder was 197-202C, versus the literature melting point for dibenzylidene sorbitol of 224C. Elemental analysis gave:
C, 68.7; H, 6.05~. (Calculated for C20H22O6: C, 67.0; H, 6.2%.) Example 19 ll The procedure used was essentially similar to that of llExample 18, except that the amount of benzaldehyde was increased ¦'(41 grams, 0.39 .nole). In this case, the yield of product was 50.8 grams (74% based on the benzaldehyde), but the melting point was lower, viz: 175-179C. ~Found: C, 69.1; H, 6.0) ¦ Example 20 Following a similar procedure to Example 18, but with a reduced amount of benzaldehvde (21.2 grams, 0.2 mole) the yield ~of solid product was 25.2 grams (70% based on the benzaldehyde).
I¦The melting point of this material was again lower: 173-177C.
Found: C, 67.5; H, 5.3) .
¦ Di-acetals of sorbitol and aromatic aldehydes, such as, for instance, dibenzylidene sorbitol, have heretofore been known as polymer additives for imparting unique properties to ~certain polymers. For examPle, dibenzylidene sorb:itol has Ibeen employed as a clarifying agent for polyolefins" especiallv ¦polyethylene and polypropylene to improve the transparency of ¦films made from suc:h polyolefins. While the use o:E dibenzvlidene ¦~sorbitol for polymer additives has shown much prom:ise and utility, ¦~problems have nevertheless been encountered in providing l economical commercial methods for the manufacture of dibenzylidene !
¦ sorbitol having a degree of purity sufficient to justify its manufacture.
Therefore, an object of the present invention is to provide an improvecl method for the manufacture of cli-acetals i such as dibenzvlidene sorbitol by the condensation of sorbitol and ¦ aromatic aldehydes, Another object of the invention is to provicle an economical commercially feasible method for producing di-acetals of sorbitol and an aromatic aldehyde, such as dibenzylidene sorbitol, for use ¦las polymer additives.
1I These and other objects, advantages, and features of the ¦~present invention will be apparent to those skilled in the art i from a reading of the following detailed disclosure.
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1 115;21~86 According to the present invention, I have disco~ered a rnethod for producing di-acetals of sorbitol and an aromatic aldehyde which comprises admixing an effective amount of D-Isorbitol into an aqueous solution containing a catalytic amount of a mineral acid so as to form a homogeneous aqueous admixture containing the mineral acid. Thereafter, an effective amount of an aromatic aldehyde is incrementally admixed into the homogeneous aqueoùs admixture containing the D-sorbitol at a rate sufficient to allow a substantially spontaneolls reaction between the D-sorb:itol and the aromatic aldehyde, thereby re-sultiny in an aqueous slurry containing crude di-acetal. The aqueous slurry of the crude di-acetal is then neutralized and the crude di-acetal separated from the liquid phase of the neutralized aqueous slurry. The crude di-acetal is then washed with water to remove mono-acetal impurities present in the crude di-acetal product. The washed di-acetal is then dried to rennove sub-stantially all of the residual water and provide a purified, dry ~di-acetal product.
I ~t should be appreciated with regard to the di-acetals of ¦sorbltol and aromatic aldehyde nnade according to the process of ¦the ~resent invention that what is intended is the disubstituted compound, e.g., the sorbitol component will be substituted with two molecules of aromatic aldehyde, ra~her than one or three molecules. Thus, in the case of benzaldehyde, the condensation product will be dibenzylidene sorbitol rather than monobenzyli-dene sorbitol or tribenzylidene sorbitol, which la1:er compounds may have other utilities but are considered to be, and therefore 115Z~86 ¦lare defir)ed as ":i.m~urities" insofar as the r:)re~ent Invention i.s concer~ed~ Other examr~les of "cli.-aceta~s", as thi-~ t-er[n lS de-fined according to the present invention include, e.c3., di-(p-chlorobenzylidene) sorbitol, di(m-chlorobenzvliclene) sorbitol, di(methylbenzylidene) sorbitol, etc. I
It has been found that a mineral acid should be ~rovided in the aqueous solution to which the D-sorbitol is added. The ¦acid should be present in a catalytic amount which can vary ~widely and which may depend to a certain extent on the acid Istrength of the particular acid employed. Generally a catalyti.c amount is from about 10 to 75 weight percent, preferably from about 15 to 60 weight percent or even 3~ to 60 weight percent, based on the total amount of water present in the reaction mixture. The preferred mineral acids may be hydrochloric acid and sulphuric acid, although others, such as ortho~.hos~horic acid mav be employed. When the acid employed is hydrochloric, the preferred acid conc~ntration has been found to be f:rom about 10 to 25 weight percent, preferably 10 to 20 wei~ht pe.rcent. When ¦sul~hurlc acid is used the preferred concentration may be from about 30 to 60 weight ~ercent, ~reEerably 35 to 50 weit~ht ~ercent.
The amourlt of D-sorbitol admixed with the aqueous solution ¦
of the mineral acid to form a homogeneous aqueous admixture con-taininq the mineral acid can vary widely. However, the amoun-t of ¦
D-sorbitol. employed should not exceed the solubility characteris- I
l tics of D-sorbi.tol in tne aqueous solution of the mineral acid at !
the temperature at which the reaction between the D--sorbitol and laromatic al ehyde is carried out.
115;2~8~
Il Once the desired amount of D-sorbltol has been incorporated ¦¦i.nto the aqueous solution Or the mi.neral acid con-taining the ,amount of mineral acid as heretofore speclfied, an aromatic alde- .
~hyde lS incrementa:Lly added to the homogeneous aqueous admixture 5 ¦containing the D-sorbitol at a rate sufficient to aLlow a sub-stantially spontaneous reaction to occur between the D-sorbitol and the aromatic a:Ldehyde. Such incremental addition is generally achieved b~ very s:lowly adding the aromatic aldehyde to the aqueous admixture while maintaining the aqueous adm.ixture under agitation. Further, the amount of aromatic aldehyde added to the aqueous admixture containing the D-sorbitol is that amount sufficient to prov:ide a molar ratio of ~-sorbitol to aromatic aldehvde of from about 1:.75 to about 1:1.75, ~refe:rably about 1:1 to about 1:1.5, or even about 1:1.25 to about 1:1.75.
A wide variety of aromatic aldehydes and mixtures of aromatic aldehydes may be employed in the process o:E the in-Iven-tion. Examples oE such aromatic aldehydes include benzalde-¦hyde, ortho-, para- and meta-tolualdehvde, anisaldehyde and sub-stituted benzaldehydes having one to three substituents and wherein the substituents are sclected from lower al}cyl, methoxy, mono- and di-alkylamino, amino, nitro or halogen. E'referred aromatic aldehydes include benzaldeh~de, meta- and para-chlorobenzaldehyde, meta- and para-bromobenzaldehYde and meta-and para-tolualdehyde.
I The reaction between the D-sorbitol and aromatic aldehyde to form the desired condensation product can be carried out at various t mperatures. In the case of benzaldehyde, for instance, I
I I
l, li~Z~
I
~it has been determined that such reaction may be desirably carriedl jou-t at ambient or room temperatures. In the case of other alde- ;
hydes temperatures above or even below ambient or room temperature~
l may be more suitab:Le.
¦ Once the aromatic aldehyde has been added to the aqueous admixture containing the D-sorbitol and the minera:L acid and an aqueous slurry results from the formation of the di-acetal, the aqueous slurry is neutralized with an alkali substance, such as sodium hydroxide, potassium hydroxide, sodium bicarbonate and the like. The amount of alkali material employed may vary widely.
It may be desirable in some applications that the amount of alkali material employed be slightly in excess of the amount required to neutralize the aqueous s~urry admixture, although large excesses of alkali should be avoided.
¦ After the aqueous slurry admixture has been neutraliæed, ¦the crude di-acetal which is the solid material of the aqueous ¦slurry admixture containin~ minor amounts of mono-acetal im-¦purities, such as monoben~ylidene sorbitol, is separated from the ¦liquid phase of the neutralized at~ueous slurry admixture. It may be desirable to include the step of washing the crude di-acetal with cool water to remove any residual salts formed as a result of the neutralization of the aqueous slurry and excess alkali material present in the wet, crude di-acetal product. When washing the wet, crude di-acetal product with cool water, the temperature of the water can vary widely. However, it is be-lieved that best r~sults will be obtained when the water is main-ained at a tem~erature of from about 20~C to about 40C. The , . I
I , I
~se~dra~ecl, wet, crllde condensation pro~uc-t ma~ thell bc~ washc~
¦again wi-th warm wa~er to remove the mono-acetal impurities. The temperature o~ the water employed to wash the crude di-acetal product to remove mono-acetal impurities can vary widely.
The washed product substantially free of the mono-acetal impurities may the~eafter be dried to remove residual water and provide purified, substantially dried di-aeetal product. Drying ean be aceomplished by any conventional method known in the art, such as use of a vacuum oven, eonveetion heat and the like. The drying temperature is not eritieal provided sueh is suffieient to ¦effeetively dry the material but not deeompose sam~e. Subsequent to drying the puriEied di-aeetal produet may be even further puri-fled by extraeting same with a relatively non-polar solvent as will be described hereinbelow in greater detail.
It may be desirable to operate the method for produein~
di-acetal in a continuous or semi-eontinuous method. In sueh instance, it is desirable that the erude di-aeetal produet be re-moved from the liquid phase of the aqueous slurry prior to neutralization so that the reeovered liquid phase can be recycled ¦
or employed ~or further makeup of the initial aqueous solution of the mineral aeid and the D-sorbitol. In sueh instanee, the erude solid di-acetal produe-t separated from the liquid phase ean be neutralized using an aqueous solution of an alkali material, such as those set forth hereinabove, and thereafter the neutral-ized produet may be washed using warm water or a eombination of cool water and warm water as reeited above.
1~ llSZ(~86 The separation of the crude di-acetal product fr~m the aqueous slurry containing same can be accomplished by any suitable¦
means well known in the art, such as filtration, centrifuging, and the like.
In order to further illustrate the present invention, the following examples are given. However, these examples are for illustrative purposes only and are not to be construed as unduly limiting the scope of the subject invention as set for~ in the claims hereafter.
EXAMPLES
. ., Procedure A
This procedure was employed for Examples 1-3 and 10-12 shown in Tables 1 and 2. A 70 percent aqueous solution of sorbitol (135 grams, 0.5 mole), the appropriate amount of benzal-dehyde to give the molar ratio of benzaldehyde to sorbit:ol shown in Tables 1 and 2, and the designated aqueous mineral ac:id solution [200 grams) of the concentration indicated, were placed in a l-liter vessel fitted with a Teflon*~addle stirrer. This reaction mixture was stirred at about 25C until the viscosity had risen to the point where stirring was no longer effective.
The acid was then ~eutralized to an extent of about 98 percent with a 10 percent aqueous solution of sodium hydroxide, and the reaction mixture finally brought to a pH of about 8 with 10 percent sodium car~onate. The white, solid product was filtered, washed thoroughly with water, and dried at 95C in a convection oven.
*Trademark ~1521~
~j High performance l.iquid chromatography was then used to determine the ratio of dibenzylidene sorbitol (DBS) to tri-,benzyl.idene sorbitol (TBS) in the product.
I Procedure B
l~ This procedure was similar to Procedure A except that the stated molar amount of benzaldehyde was added dropwise to the reaction mixture over a period of about 4 hours in -the following ¦manner first hour, 50 percent; second hour, 25 percent; third hour, 15 percent; fourth hour, 10 percent. The reaction was then continued for a short time to achieve the desired. h:igh viscosity, neutralized, and the product isolated as described llnder Pro-cedure A. I
Examples 1-6 l In Example 1 Procedure A was employed using a mole ratio Iof benzaldehyde to sorbitol that would be -theoretically requi.red to produce DBS (2:1 mole ratio). The product obtai:ned actually showed a DBS/TBS ratio of 75:25. By reducing the mole ratio of benzaldehyde to sorbitol, firstly to 1.5:1, and the:n to 1:1, in l Examples 2 and 3 respecti.vely, the DBS/TBS ratio in the product l steadi.ly increased to 83/17. A similar effect was observed in ¦~Examples 4 and 5, where a higher acid concentration was used. The results are summarized in Table 1.
1~ Examples 6-9 ¦1 In Examples 6-9 Procedure B was employed rather than Pro- ¦
cedure A and a lower mole ratio of benzaldehyde to .sorbitol was also employed resulting in a further increase in the DBS/TBS ratio, ¦¦reaching a maximum ratio of 91:9 in Example 9. The results are ¦Isummarized in Table 1.
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s~a~6 Examples 10-17 "
~, In Examples 10-17 generally similar effec-ts were observed with a sulfuric acid catalyst. The results are summarized in ,Table 2, where the Aiyher DBS/TBS ratio of 94/6 is observed in IlExample 17. Examples 10-17 and Table 2 also illustrate that the percentage yield of product, based on the benzaldehyde employed, rose very significantly as the mole ratio of benzaldehyde to sor-bitol is reduced. 'rhis is particularly illustrated by comparing Examples 12 and 16 with a 40 percent acid concentration.
Although the melting point of a mixture product tended to ¦be broad and somewhat erratic, it was clear from the results in Tables 1 and 2 that as the DBS/TBS ratio rose significantly, the melting point of the product also tended to rise as would be ex-l pected. Again, a comparison of Examples 12 and 16 shows this ¦ effect clearly.
Although the improvement of the DBS/TBS ratio as shown in Tables 1 and 2 is of great utility, there may still be a need in certain commercial applications for a product containing an even ~igher proportion o~ the DBS component. According to United States Patent 4,131,612, a crude DBS product, containing as impurities TBS and other compounds t may be purified by extracting it with a ~ower aliphatic alcohol, such as methanol, at elevated temperatures .
~his procedure described in the patent using methanol was applied ~¦to the product of Example 17 in Table 2, with the result shown in I,kable 3. It is seen that the content of DBS in the product actually declined, rather than increasing as would have been ex-~ected from the teachings of the abovementioned patent.
.
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., 1,l According to the present invention all or even a portion of -the TBS present in a di-acetal/tri-acetal pro~3uct may be re-`~lmoved to increase its di-acetal content by employing a rela-tively ~Inon-polar solvent. In Table 3 are also shown the results of , extracting DBS/TBS products with relatively non-polar solvents, viz: toluene and l.,l,l.-trichloroethane. A liquid-to-solid ratio ¦¦of 10:1 was employed as in the case of methanol described above.
¦¦A significant increase in the DBS content was achieved, especially l in the case of l,l,.l-trichlorethane. The recovery of desired ¦ product was also very high. In the case of the l,l,l-trichlorethan~, the liquid extract was concentrated to remove the solvent leavin~
a residue with DBS/TBS ratio of 8/92.
:Extraction DBS:TBS Ratio l Solvent ConditionsInitial FinalRecovery Methanol 1 Extraction 94:6 93:7 ~ 90%
r~'60~c Toluene 3 Extractions 92:8 95:5 v 85%
" ~J80C
l,l,l-Trichloro- 3 Extractions 92:8 98:2 ,~90 ethane ,~/70C
Example 18 I A 70~O aqueous D-sorbitol solution (52 grams, 0.2 mole ¦~orbitol) and 48~ sulfuric acid (87.1 grams) were placed in a flask¦
¦~ith stirrer. Benzaldehyde (31.5 grams, 0.3 mole) was then added ¦~ropwise with vigorous stirring over a period of 1 hour and 45 ¦~inutes. During the addition, the temperature of the reaction Il 1.
, , 1 115;;:(~86 , .
mixture rose from 24 to 28C, and a pale yellow solid was formed.
Continued stirring of the slurry for a further 1 hour and 30 llminutes. Poured the contents of the flask into 8% aqueous sodium jlhydroxide with vigorous stirring to neutralize the acid. Then l¦filtered off the solid, and washed i-t with cold water to a pH of 5.5. Slurried the solid product in water at 90C for 30 minutes, I
then filtered, and washed the material with more hot water. Dried ¦
the product in a vacuum oven to constant weight. Y:ield: 42 grams l (78% yield calculated as dibenzylidene sorbitol, and based on the weight of benzaldehyde employed.) The melting point of the off-white powder was 197-202C, versus the literature melting point for dibenzylidene sorbitol of 224C. Elemental analysis gave:
C, 68.7; H, 6.05~. (Calculated for C20H22O6: C, 67.0; H, 6.2%.) Example 19 ll The procedure used was essentially similar to that of llExample 18, except that the amount of benzaldehyde was increased ¦'(41 grams, 0.39 .nole). In this case, the yield of product was 50.8 grams (74% based on the benzaldehyde), but the melting point was lower, viz: 175-179C. ~Found: C, 69.1; H, 6.0) ¦ Example 20 Following a similar procedure to Example 18, but with a reduced amount of benzaldehvde (21.2 grams, 0.2 mole) the yield ~of solid product was 25.2 grams (70% based on the benzaldehyde).
I¦The melting point of this material was again lower: 173-177C.
Found: C, 67.5; H, 5.3) .
2~
!! Example 21 , i :
Again repeated the procedure of Exam~le 18, but lowered the concentration of the sulfuric acid from 48~; to 32% by weight.
IlAfter completion of the benzaldehyde addition and subsequent ¦Istirring period, there was relatively little solid present. Heate~
the reaction mixture to 70C for 1 hour, then cooled overnight, whereupon the reaction mass solidified. On working up the reaction as described there was obtained: 36.1 grarns of product (52% yield on the benzaldehyde); melting point 170-:L75C. (Found:~
C, 68.9; H, 6.2).
The above melting point data provided in Examoles 18 through 21 is believed to show the improved purity of dibenzyliden~
sorbitol employing the concept of the present lnvent:ion wherein l the amount of sorbitol to benzaldehyde is maintainecl in the ¦¦specified mole ratio and the benzaldehyde is contact:ed with the D-sorbitol in such a manner as to allow such reactants to react substantially simultaneously, thus preventing the formation of ,undesired side products.
'I ~
i, .
Il i
!! Example 21 , i :
Again repeated the procedure of Exam~le 18, but lowered the concentration of the sulfuric acid from 48~; to 32% by weight.
IlAfter completion of the benzaldehyde addition and subsequent ¦Istirring period, there was relatively little solid present. Heate~
the reaction mixture to 70C for 1 hour, then cooled overnight, whereupon the reaction mass solidified. On working up the reaction as described there was obtained: 36.1 grarns of product (52% yield on the benzaldehyde); melting point 170-:L75C. (Found:~
C, 68.9; H, 6.2).
The above melting point data provided in Examoles 18 through 21 is believed to show the improved purity of dibenzyliden~
sorbitol employing the concept of the present lnvent:ion wherein l the amount of sorbitol to benzaldehyde is maintainecl in the ¦¦specified mole ratio and the benzaldehyde is contact:ed with the D-sorbitol in such a manner as to allow such reactants to react substantially simultaneously, thus preventing the formation of ,undesired side products.
'I ~
i, .
Il i
Claims (12)
- THAT WHICH IS CLAIMED IS:
l. A method for producing a di-acetal of sorbitol and an aromatic aldehyde which comprises: admixing an effective amount of D-sorbitol into an aqueous solution of a mineral acid so as to form a homogeneous aqueous admixture containing a catalytic amount of said mineral acid; incrementally admixing an effective amount of an aromatic aldehyde into said homogeneous aqueous admixture at a rate sufficient to allow a substantially spontaneous reaction with said D-sorbitol so as to form an aqueous slurry containing crude di-acetal product, said effective amount of aromatic alde-hyde, being that amount sufficient to provide a ratio of D-sorbitol to aromatic aldehyde of from about 1:.75 to about 1:1.75;
neutralizing the aqueous slurry admixture; separating said crude di-acetal product from the liquid phase of the neutralized aqueous slurry; washing the separated crude di-acetal product with water to remove mono-acetal impurities present in said crude di-acetal product; drying the washed di-acetal product to remove sub-stantially all of the residual water; and recovering purified, substantially dry di-acetal product. - 2. The method of Claim 1 wherein said aromatic aldehyde is selected from benzaldehyde, ortho-, para- and meta-tolualdehyde, anisaldehyde and substituted benzaldehydes having l to 3 sub-stituents in their benzene nucleus wherein said substituents are selected from lower alkyl having fewer than five carbon atoms, methoxy, mono- and di-alkylamino, nitro and halogen.
- 3. The process of Claim 2 wherein said aromatic aldehyde is selected from benzaldehyde, meta- and para-tolualdehyde, meta-and para-chlorobenzaldehyde, and meta- and para-bromobenzaldehyde.
- 4. The method of Claim 1 which further includes the step of washing said separated crude di-acetal in two separate steps, in a first step with an effective amount of water maintained at a temperature of from about 20°C to about 40°C to remove any residual salts formed as a result of the neutralization of said aqueous slurry and in a second step at a higher temperature to remove other mono-acetal impurities present in said crude di-acetal.
- 5. The method of Claim 1 wherein said acid. is hydro-chloric acid, and the amount of acid present in said aqueous admixture is from about 10 to 25 weight percent based upon the total amount of water present in the reaction mixture.
- 6. The method of Claim 1 wherein said acid is sulphuric acid, and the amount of acid present in said aqueous admixture is from about 30 to 60 weight percent based on the total amount of water present in the reaction mixture.
- 7. The method of Claim 1 wherein the mole ratio of D-sorbitol to aromatic aldehyde is from about 1:1 to about 1:1.5.
- 8. The method of Claim 1 wherein said purified, sub-stantially dry di-acetal is even further purified by extracting it with a relatively non-polar solvent to remove tri-acetal impurities.
- 9. The method of Claim 8, wherein said relatively non-polar solvent is selected from toluene and 1,1,1-trichloroethane.
- 10. A method for producing a di-acetal which comprises:
admixing an effective amount of D-sorbitol into an aqueous solution of a mineral acid so as to form a resulting substantially homogeneous admixture containing a catalytic amount of said mineral acid; incrementally admixing an effective amount of an aromatic aldehyde into said homogeneous aqueous admixture at a rate sufficient to allow a substantially spontaneous reaction with said D-sorbitol so as to form an aqueous slurry containing crude di-acetal, said effective amount of aromatic aldehyde being that amount sufficient to provide a ratio of D-sorbitol to aromatic aldehyde of from about 1:.75 to about 1:1.75; separating said crude di-acetal from the liquid phase of the aqueous slurry;
neutralizing the separated crude di-acetal with an aqueous alkali admixture; washing the neutralized crude di-acetal with water to remove mono-acetal impurities present in said crude di-acetal;
drying the washed di-acetal to remove substantially all of the residual water; and further purifying said dried di-acetal product by extracting it with a relatively non-polar solvent to remove tri-acetal impurities; and recovering a highly purified, sub-stantially dry di-acetal product. - 11. The method of Claim 10 wherein said aromatic aldehyde is selected from benzaldehyde, ortho-, para- and meta-tolualdehyde anisaldehyde and substituted benzaldehydes having 1 to 3 sub-stituents in their benzene nucleus wherein said substituents are selected from lower alkyl having fewer than 5 carbon atoms, method mono- and di-alkylamino, nitro and halogen.
- 12. The process of Claim 11, wherein said aromatic alde-hyde is selected from benzaldehyde, meta- and para-tolualdehyde, meta- and para-chlorobenzaldehyde, and meta- and para-bromo-benzaldehyde.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000354071A CA1152086A (en) | 1980-06-16 | 1980-06-16 | Method for producing a di-acetal of sorbitol and an aromatic aldehyde |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000354071A CA1152086A (en) | 1980-06-16 | 1980-06-16 | Method for producing a di-acetal of sorbitol and an aromatic aldehyde |
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|---|---|
| CA1152086A true CA1152086A (en) | 1983-08-16 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3508522A4 (en) * | 2016-09-05 | 2020-10-14 | GCh Technology Co., Ltd. | Nucleating agent composition comprising trace amount of aromatic aldehyde, sorbitol diacetal and sorbitol triacetal |
| CN114933521A (en) * | 2022-06-01 | 2022-08-23 | 呈和科技股份有限公司 | Process method for recycling and regenerating aromatic aldehyde |
-
1980
- 1980-06-16 CA CA000354071A patent/CA1152086A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3508522A4 (en) * | 2016-09-05 | 2020-10-14 | GCh Technology Co., Ltd. | Nucleating agent composition comprising trace amount of aromatic aldehyde, sorbitol diacetal and sorbitol triacetal |
| CN114933521A (en) * | 2022-06-01 | 2022-08-23 | 呈和科技股份有限公司 | Process method for recycling and regenerating aromatic aldehyde |
| CN114933521B (en) * | 2022-06-01 | 2023-12-26 | 呈和科技股份有限公司 | Process method for recycling and reproducing aromatic aldehyde |
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