DE939869C - Process for the preparation of 2, 2, 4-trimethylpentane-1, 3-diol - Google Patents

Description

Process for the preparation of 2, 2, 4-trimethylp, entane-1, 3-diol article of the present invention is a process for converting 5, 5-dimethyl-a, q.-di-isopropyl-6-oxy-1, 3-dioxane (isobutyraldoxane) in 2, 2, q.-trimethylpentane-1, 3-diod.

According to the invention, isobutyraldoxane is in the liquid phase and at moderately elevated temperatures. from 3o to 1300 in the presence of Raney-N nickel treated with hydrogen as a hydrogenation catalyst under weakly acidic conditions, where 2, 2, 4-trimethylpentane-1, 3-diol and is-obu tanol obtained in good yields will.

It is difficult to find a practically pure isobutyraldoxane which is can be used to carry out the process according to the invention, free from isobutyraldol to obtain which the latter is formed during the condensation of isobutyraldehyde. However, it is a special feature of this invention, a crude isobutyraldoxane, as is the case with the alkali-catalyzed condensation of isobutyra1, dehyde, without prior purification of unchanged isobutyraldehyde or isobutyraldehyde, l to use.

If the used I.sobutyrüldoxane does not react acidic in and of itself, becomes weakly acidic. Reaction condition brought about by the fact that one low Amounts of a weak acid such as acetic acid, propionic acid, butyric acid, Isobutyric acid, succinic acid, malonic acid or adipic acid added. Strong acids, such as phosphoric acid or trichlorosetic acid, must be avoided as they are common adversely affect the catalyst. Formic acid is also. to avoid, there their influence on the catalyst is also detrimental. The required weak acidity Reaction can also be achieved by adding salts of weak bases with strong acids, such as B. of salts of alkaline earths with hydrohalic acids. When using a crude isobutyraldoxane, which over anhydrous calcium chloride has been dried, the product often has sufficient acidity for the named Purpose.

Since the reaction is carried out in a non-aqueous medium, can be a range for the pH value within which the most favorable working conditions are not specified. It should be noted, however, that it is only weakly acidic Conditions are required and that these, as described above, are brought about can be ..

The reaction proceeds easily with neat isobutyraldoxane; but thinners can be used. Suitable diluents are for example ethyl alcohol, propyl alcohol, isoprapyl alcohol and isobutyl alcohol. .

Temperatures used are between 30 and 130 degrees, and the preferred range is 50 to too degrees. Temperatures higher than 130 ° should be avoided, since isohutyraldoxane tends to decompose into isobutyraldehyde under these conditions.

The pressure in the hydrogenation apparatus is not a critical characteristic the invention. As a result, atmospheric pressure or positive pressure can be applied will.

The 2, 2, 4-trimethylpentane-1, 3-diol can from the reaction mixture obtained by any known procedure, preferably by distillation of the crude product under reduced pressure.

The parts given in the following examples are parts by weight. Example r A mixture of 282 parts of crude isoibutyraldoxane, 50 parts of a 500 / oigen Raney nickel paste in isopropyl alcohol and 5 parts of glacial acetic acid was made in a hydrogen atmosphere Stirred for 8 hours, the temperature being gradually increased from 5o to 85 °. During this time approximately 4.5 parts of hydrogen were absorbed. distillation of the crude product gave a yield of 2, 2, 4-trimethylpentane-1, 3-diel of -8oo / 0. The boiling point - at a pressure of 20 mm of mercury "was 1221, the melting point 32 to 33 °: After recrystallization from aqueous alcohol, the melting point was this dial 51 °.

If you used the same starting material and the same catalyst, however, in the absence of glacial acetic acid, the reaction was very slow, only 0.42 parts of hydrogen were absorbed in minutes. After this time the absorption stopped at a measurable rate. After the addition of acid began the hydrogen uptake immediately anew.

Example e 272 parts of crude isobutyraldoxane, which before removal the solvent had been dried over anhydrous calcium chloride, was -As described in Example 1, treated with hydrogen without that in this case acid was added. About 4.3 parts of hydrogen were used recorded in 45 hours. During work-up, yields of Diel, of, 710/0 obtain.

An important advantage of the method of the invention is that it represents a convenient method for the production of the diol, which one in the Hydrogenation of Isoibutyraldo: l normally could have expected. This last connection however, it cannot easily be obtained in pure form, it would have to be that isobutyraldoxane is distilled in the presence of acids. This is a difficult one Method., And as a result, isohutyraldol is expensive and not easily available Material.

Claims (2)

PATENT CLAIMS: 1. A process for the preparation of 2 "2, 4-trimethylpentari-1,3-diol, characterized in that 5, 5-dim: ethyl-2,4-di-isopropyl-6-oxy-1,3 -dioxane (isobutyraldoxane) treated with hydrogen as the hydrogenation catalyst in the liquid phase at moderately elevated temperatures of 30 to 130 °, expediently 50 to 10o °, under mildly sauna conditions and in the presence of Raney nickel as a hydrogenation catalyst , characterized in that crude isobutyraldoxane is used as starting material 3. Process according to Claims 1 and 2, characterized in that a crude isobutyraldoxane dried over anhydrous calcium chloride is used 4. Process according to Claim 1 -bit 3, characterized that the hydrogenation is carried out with the addition of a diluent, such as ethyl alcohol, propyl alcohol, isopropyl alcohol or is, o: bwtylalkolil. Cited publications: German patent specification No. 548 814; USA patent specification No. 2,334,761; reports from the deu Chen Chemischen Gesellschaft, Vol. 76 (1943), p. 1196 Ws. 12o8; Journal of the American Chemical Society, 1943 pp. 1715-1717; Encyclopedia of Chemical Teahnology, 1948, Vol. 1, p.41 and Val. 2, p.69_1; Annual Repärt an, the Progress of Chernisüry for 1944 vol. 41 (1945) pp. 144 and 145.