Abstract:
It has been surprisingly discovered in accordance with the present invention that when 1,3-dioxolane is reacted with formaldehyde in the presence of an organic peroxide and an ionizable, at least sparingly soluble metal salt, the reaction preferentially involves an addition of the formaldehyde to the 2-methylene group of the 1,3-dioxolane with only minor reaction with the 4-methylene and 5-methylene groups of the 1,3-dioxolane whereby the reaction product that is formed contains significant quantities of 2-hydroxyalkyl-1,3-dioxolanes. 2-Hydroxyalkyl-1,3-dioxolanes are hydrolyzed with comparative ease to ethylene glycol and the corresponding glycol aldehyde (CHO--CH 2  --OH). The glycol aldehyde in turn can be catalytically hydrogenated to form additional quantities of ethylene glycol.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     This invention relates to the manufacture of 2-substituted-1,3-dioxolanes. More particularly, this invention relates to a method wherein 1,3-dioxolane is reacted with formaldehyde in the presence of an organic peroxide and an ionizable, at least sparingly soluble metal salt initiator under non-acidic conditions to provide 2-hydroxymethyl-1,3-dioxolane and 2-hydroxymethyl-oxymethylene-1,3-dioxolanes. The 2-hydroxymethyl-1,3-dioxolane is useful as a raw material for the manufacture of ethylene glycol. The hydroperoxide is prepared from the 1,3-dioxolane in accordance with a preferred form of the present invention. 
     2. Prior Art 
     Kollar U.S. Pat. No. 4,337,371 discloses a method for the preparation of ethylene glycol wherein methanol and formaldehyde are reacted in the presence of an organic peroxide and water to provide ethylene glycol. In a technical article Oyama discloses the free-radical reaction of primary and secondary alcohols such as methanol, 2-propanol, ethanol, 2-butanol and 3-methyl-2-butanol with formaldehyde, and t-butyl peroxide to provide glycols (J. Org. Chem., 30, 2429 (1965). Watanabe et al. in an article in Bull. Chem. Soc. Jpn., 56, 1428-1430 (1983), Vol. 56, No. 5 disclose the reaction of 1,3-dioxolane with electron-deficient alkenes such as diethyl maleate, maleic anhydride, etc. Russian Author&#39;s Certificate No. 975,704 (Imashev et al.) discloses a method wherein 1,3-dioxolane is oxidized with molecular oxygen at a temperature of about 10° to 60° C. to provide ethylene glycol monoformate as a principle reaction product. 
     RELATED COPENDING PATENT APPLICATIONS 
     Copending coassigned Sanderson et al. U.S. patent application Ser. No. 06/683,441, filed Dec. 19, 1984 (filed of an even date herewith), discloses a method wherein 1,3-dioxolane is reacted with formaldehyde under non-acidic conditions to provide 2-hydroxymethyl-1,3-dioxolane. 
     Copending coassigned Sanderson et al. U.S. patent application Ser. No. 06/683,549, filed Dec. 19, 1984 (filed of an even date herewith), discloses the air oxidation of 1,3-dioxolane in the presence of an initiator to provide 2-hydroperoxy-1,3-dioxolane. 
     Copending coassigned Yeakey et al. U.S. patent application Ser. No. 06/683,546, filed Dec. 19, 1984 (of an even date herewith), discloses a method wherein dimethoxymethane is reacted with paraformaldehyde in the presence of an organic peroxide to provide an ethylene glycol precursor. 
     SUMMARY OF THE INVENTION 
     It has been surprisingly discovered in accordance with the present invention that when 1,3-dioxolane is reacted with formaldehyde under non-acidic conditions in the presence of an organic peroxide initiator and an ionizable, at least sparingly soluble metal salt, the reaction preferentially involves an addition of the formaldehyde to the 2-methylene group of the 1,3-dioxolane with only minor reaction with the 4-methylene and 5-methylene groups of the 1,3-dioxolane whereby the reaction product that is formed contains significant quantities of 2-hydroxyalkyl-1,3-dioxolanes, such as 2-hydroxymethyl-1,3-dioxolane. The dioxolanes are hydrolyzed with comparative ease to ethylene glycol and the corresponding glycol aldehyde (CHO--CH 2  --OH). The glycol aldehyde in turn can be catalytically hydrogenated to form additional quantities of ethylene glycol. 
     In accordance with a preferred embodiment of the present invention, 1,3-dioxolane is oxidized to form the corresponding hydroperoxide, which is then used, in conjunction with a metal salt, to initiate the reaction of 1,3-dioxolane with formaldehyde to form the 2-hydroxyalkyl-1,3-dioxolane, which, in turn, is hydrolyzed to form ethylene glycol and the corresponding glycol aldehyde. The glycol aldehyde, in its turn, is hydrogenated to form an additional quantity of ethylene glycol. 
     The overall sequence is illustrated by the following equations wherein the 1,3-dioxolane nucleus is schematically indicated, i.e.: ##STR1## 
     DETAILED DESCRIPTION OF THE INVENTION 
     Starting Materials 
     The starting materials for the present invention are 1,3-dioxolane, formaldehyde, an organic peroxide and a metal salt. 
     Formaldehyde may be employed in its conventional form, as an aqueous formalin solution, in &#34;inhibited&#34; methanol solution as paraformaldehyde, or as trioxane. 
     The organic peroxide employed in the process of the present invention is preferably 2-hydroperoxy-1,3-dioxolane. The 2-hydroperoxy-1,3-dioxolane can be prepared in the manner disclosed in copending Sanderson et al. application Ser. No. 06/683,549, filed Dec. 19, 1984 (of an even date herewith) and entitled &#34;Production of 2-Hydroperoxy-1,3-Dioxolane&#34;. However, other organic hydroperoxides can be used, if desired, such as tert.-butyl hydroperoxide, ethylbenzyl hydroperoxide, cumyl hydroperoxide, etc. Suitably, from about 0.1 wt.% to about 10 wt.% of the hydroperoxide is used, based on the weight of the dioxolane feed. 
     The ionizable, at least sparingly soluble metal salt is used as an initiator. It is suitably a metal salt of an inorganic acid or an organic carboxylic acid, such as a salt of a heavy metal, preferably a group VIIIb heavy metal. Still more preferably, the salt is an ionizable, at least sparingly soluble cobalt II salt of an organic compound, such as cobalt nitrate, cobalt chloride, cobalt hexanoate, cobalt benzoate, cobalt cyclohexane butyrate, cobalt oxalate, cobalt octoate, cobalt acetate, cobalt naphthenate, cobalt acetylacetonate, etc. However, other metal salts may be used, if desired, such as for example, chromium acetate, iron acetylacetonate, iron nitrate, diammonium azium nitrate, nickel acetylacetonate, etc. From about 0.0001 to about 5.0 wt.% of metal salt is preferably used, based on the 1,3-dioxolane feedstock. 
     Reaction Conditions 
     The desired products of the present invention, 2-hydroxyalkyl-1,3-dioxolanes, are an equimolar addition product of formaldehyde and 1,3-dioxolane. However, a molar excess of either of the reactants may be used, if desired. Preferably, formalin is used, and is used in a molar excess (e.g., from about 1 to about 5 moles of formaldehyde per mole of 1,3-dioxolane). 
     The organic peroxide is suitably used in an amount ranging from about 0.1 to about 10 wt.%, based on the 1,3-dioxolane. More preferably, from about 2 to about 5 wt.% of the organic peroxide is used. 
     The reaction is suitably conducted at a temperature within the range of about 80° to about 250° C., and more preferably, within the range of about 80° to about 150° C. 
     The reaction is preferably conducted at atmospheric pressure. Superatmospheric or subatmospheric pressures may be used if desired, but there is no particular advantage in doing so. 
     Reaction times of from about 0.5 to about 10 hours may be employed with satisfactory results. More preferably, the reaction time will be within the range of about 1 to about 5 hours. 
     The reaction can be conducted in inert solvent solution with a solvent such as acetonitrile, t-butyl alcohol, monochlorobenzene, benzene, etc. but there is no particular advantage in doing so. 
     At the end of the reaction, the reaction mixture may be separated into components by any suitable technique such as filtration, distillation, solvent extraction, etc. 
     As indicated earlier, the 2-hydroxymethyl-1,3-dioxolane can be hydrolyzed to provide ethylene glycol and glycolaldehyde under conditions as disclosed, for example in J. D. Roberts, M. C. Caserio, &#34;Basic Principles of Organic Chemistry&#34;, W. A. Benjamin, Inc., New York, 1965. See page 443. The glycolaldehyde may also be catalytically hydrogenated to form additional quantities of ethylene glycol under conditions of the type disclosed by H. O. House, &#34;Modern Synthetic Reactions&#34;, 2nd Ed., W. A. Benjamin, Inc., 1972. See Chapter 1 and references therein. 
    
    
     SPECIFIC EXAMPLES 
     Example 1 
     A 250 ml flask equipped with water-cooled condenser, magnetic stirrer, heating mantle, thermometer (Thermo-O-Watch), and dropping funnel was charged with 50 ml 1,3-dioxolane, 50 g paraformaldehyde and additive. The mixture was heated to a gentle reflux and a hydroperoxide/dioxolane mixture added over several hours. [The hydroperoxide/dioxolane mixture was prepared by oxidizing the dioxolane with air under various conditions.] At the end of the reaction, the mixture was cooled to ambient temperature and the solid paraformaldehyde filtered off. The products were determined by GC. The results are summarized in the following tables. A comparison example is included. 
     
                                           TABLE I__________________________________________________________________________Reaction of 1,3-Dioxolane with Formaldehyde               2-HydroperoxyNotebook 1,3-Dioxolane        Paraformal-               1,3-dioxolaneNumber (ml)   dehyde (g)               conc. (wt. %)                      (ml)                         Catlayst (g)__________________________________________________________________________5831-66 65     5.0    3.73   15 Co(oct.).sub.2                                  0.245831-65 65     5.0    6.77   15 Fe(NO.sub.3).sub.3                                  0.105831-64 65     5.0    6.77   15 Co(oct.).sub.2                                  0.245831-63 65     5.0    6.77   15 Co(oct.).sub.2                                  0.245831-62 65     5.0    6.77   15 Fe(NO.sub.3).sub.3                                  0.105831-52 50     5.0    3.50   30 Fe(NO.sub.3).sub.3                                  0.125831-51 50     5.0    3.50   30 Co(oct.).sub.2                                  0.125831-49 50     5.0    4.38   30 Co(oct.).sub.2                                  0.125831-48 65     5.0    4.38   15 Co(oct.).sub.2                                  0.125831-47  0     5.0    0.33   50 Co(oct.).sub.2                                  0.125831-41 30     5.0    3.89   50 Co(oct.).sub.2                                  0.125831-40 30     5.0    1.0    50 Co(oct.).sub.2                                  0.125831-67 65     5.0    3.73   15 Ce(NH.sub.4).sub.2 (NO.sub.3).sub.6                                  0.215831-69 65     5.0    3.73   15 Co(oct.).sub.2                                  0.245831-70 65     5.0    3.73   15 Ni(OAc).sub.2                                  0.25__________________________________________________________________________ 
    
     
                                           TABLE II__________________________________________________________________________Reaction of 1,3-Dioxolane with Formaldehyde        Products, (Area %)Notebook Time    Temp        Ethyl             Ethylene                  2-Hydroxy    EthyleneNumber (Hr)    (°C.)        Formate             Glycol                  1,3-dioxolane                         A  B  Carbonate__________________________________________________________________________5831-66 5.5    60  0.455             0.098                  4.450  2.219                            0.124                               0.8425831-65 6.5    50-55        0.007             0.008                  4.687  0.096                            -- 0.4235831-64 6.5    60-65        0.601             0.100                  4.582  2.315                            0.179                               0.9695831-63 6.1    55  0.492             0.079                  7.063  1.737                            -- 1.2375831-62 6.1    60  0.013             0.005                  4.762  0.386                            -- 0.3135831-52 8.0    75  0.869             0.009                  6.843  4.143                            0.617                               1.3385831-51 8.0    75  0.031             0.079                  5.487  0.148                            -- 0.6435831-49 8.0    75  0.961             0.035                  7.358  3.423                            0.393                               1.5865831-48 6.0    75  0.653             0.172                  4.262  2.827                            0.366                               0.9715831-47 6.0    75  --   0.021                  0.651  0.082                            -- 1.4655831-41 8.0    75  0.006             0.142                  6.966  0.794                            -- 1.0345831-40 3.0    75  0.013             0.070                  7.730  0.953                            -- 1.1635831-67 5.5    60  0.020             0.006                  3.794  0.052                            -- 0.5035831-69 6.5    60  0.349             0.094                  4.138  1.903                            0.030                               0.8675831-70 6.5    60  0.083             0.135                  4.876  0.067                            0.032                               0.948__________________________________________________________________________ ##STR2## ##STR3## 
    
     The data shown in Table I and Table II illustrate the reaction of 1,3-dioxolane with formaldehyde under various conditions: temperature, initiator (hydroperoxide), and metal salt concentration and different metal salts. Ce and Ni salts do not appear to be as effective as some of the other metal salts. 
     Example 2 
     1,3-Dioxolane (80 ml), paraformaldehyde (10 g) and di-tert-butyl peroxide (3.00 ml) were charged to a 300 cc. stainless steel autoclave equipped with a magne drive stirrer. The autoclave was heated slowly (over one hour) to the desired temperature and held at this temperature for the desired time. The autoclave was cooled to ambient temperature and the solid paraformaldehyde filtered from the reaction mixture. The reaction conditions, etc., are shown in Table III. 
     
                                           TABLE III__________________________________________________________________________1,3-DIOXOLANE WITH FORMALDEHYDE       Products, (Area %).sup.c NumberNotebook  Time (Hr)        Temp (°C.)              Ethanol                   Ethyl Formate                           AcetatesGlycol Ether                                  ##STR4##                                             ##STR5##__________________________________________________________________________5807-85 2     180   4.14 16.60   1.44    8.98      3.855807-84 3     160   3.39 17.52   1.67    9.97      4.245807-83 5     140   1.46 16.16   2.09   12.10      4.075807-48 2     130   --   --      --     --         -- 2     140   1.48 12.11   2.17   13.94      5.06__________________________________________________________________________ .sup.c =  Products determined on sample after solid paraformaldehyde had been removed. .sup.d =  n = 2-5 
    
     As will be seen from Table III, moderate yields of 2-hydroxymethyl-1,3-dioxolane were obtained in all of the runs, but moderate yields of ethyl formate were also obtained thus lowering the selectivity to the desired products. 
     Example 3 
     Procedure 
     A 250 ml flask equipped with water-cooled condenser, magnetic stirrer, heating mantle, thermometer (Therm-O-Watch), and dropping funnel was charged with 50 ml, 1,3-dioxolane, 10 g paraformaldehyde and additive. The mixture was heated to a gentle reflux and a TBHP/dioxolane mixture added over several hours. [The TBHP/dioxolane mixture was prepared by adding 3.00 ml 65% TBHP/TBA to 30 ml 1,3-dioxolane]. At the end of the reaction, the mixture was cooled to ambient temperature and the solid paraformaldehyde filtered off. The products were determined by GC. The results are summarized in the following Tables IV and V. A comparison example is included. 
     
                                           TABLE IV__________________________________________________________________________Reaction of 1,3-Dioxolane with FormaldehydeNotebook 1,3-Dioxolane        Paraformal-               TBHP.sup.a     Time                                 TempNumber (ml)   dehyde (g)               (ml 65%)                    Additive  (Hr)                                 (°C.)__________________________________________________________________________5831-6 50 (+30)        10.0   3.00 cobalt octate                              7  75                    (5 d)5831-10 50 (+30)        10.0   3.00 Fe complex (0.05 g)                              6  755831-12 50 (+30)        10.0   3.00 cobalt octate                              7  75                    (10 d)5831-22 50 (+30)        10.0   3.00 Fe(AcAc).sub.3 (0.05)                              5  755831-24 50 (+30)        10.0   .sup. 3.00.sup.d                    cobalt octate                              8  75                    (10 d)5831-25 50 (+30)        10.0   3.00 chromium acetate                              7  75                    (0.05 g)5831-27 50 (+30)        10.0   6.00 cobalt octate                              7  75                    (10 d)__________________________________________________________________________ 
    
     
                                           TABLE V__________________________________________________________________________Reaction of 1,3-Dioxolane with FormaldehydeProducts, (Area %) Notebook  TBA      Ethyl Formate              AcetatesGlycol Ether                     1,3-dioxolane2-Hydroxy-methyl-                               ##STR6##__________________________________________________________________________5831-6 3.16     Trace   1.69   4.08      0.945831-10 3.39     sh.sup.b             1.67   2.72      1.505831-12 3.13     0.64    1.54   9.60      1.665831-22 3.42     --      0.86   0.38      --5831-24 3.04     0.41    1.64   4.04      0.645831-25 2.23     0.28    0.58   2.76      0.435831-27 4.66     0.76    2.27   6.18      1.28__________________________________________________________________________ .sup.a TBHP = tertbutylhydroperoxide; DTBP = ditert-butylperoxide .sup.b shoulder on tertbutylalcohol peak .sup.c n = 2-5? .sup.d added all at once 
    
     Note from Tables IV and V that the formation of ethyl formate by-products was virtually eliminated when the reaction was catalyzed with tert-butyl hydroperoxide promoted with cobalt octate. In contrast, the results from Table III show that the yield of ethyl formate was significant. 
     The foregoing examples are given by way of illustration and are not intended as limitations on the scope of the present invention, which is defined by the appended claims.