US2396330A - Process of nitrating alcohols - Google Patents

Description

Patented Mar. 12,1946

PROCESS OF NITRATING ALCOHOL James Edward Lufkin, Woodbury, N. 3., assignor to E. I. du Pont de Nemours & Company, Wilmington, Deb, a corporation of Delaware No Drawing. Application February 27, 1945,

Serial No. 580,080

7 Claims.

This invention relates to a process for preparing nitric esters of aliphatic and cycloaliphatic alcohols and more particularly to a nitration process whereby such nitric esters, particularly of secondary and tertiary alcohols, are obtained in good yields and under conditions favoring the main reaction and elimination of side reactions.

Alkyl nitrates have been made in the past by the action of nitric acid or mixtures of sulfuric and nitric acids on aliphatic alcohols. In the case of primary alcohols, the esterification has been carried out ordinarily without a great deal of difliculty, When attempts have been made to prepare secondary alkyl nitrates, however, results have been much less satisfactory and an undesirable formation of oxidation rather than esterification products has taken place.

An object of the present invention is a novel and improved method of preparing nitric esters of aliphatic alcohols, particularly of secondary and tertiary alcohols. A further object is such a method whereby the nitration reaction is better controlled, and greatly improved yields of the desired product are obtained. A still further object is a method of nitration of higher alcohols whereby oxidation reactions are largely eliminated. Additional objects will be disclosed as the invention is described more at length hereinafter.

I have found that the foregoing objects are accomplished, and the disadvantages of the methods of the prior art overcome, when I react a compound taken from the group consisting of the secondary and tertiary aliphatic alcohols with nitric acid in the presence of acetic anhydride. While varying strengths of nitric acid may be utilized, material of high strength will desirably be used, preferably over 95% strength, as concentration of nitric acid is more attractive economically than the use of increased amounts of acetic anhydride.

The following examples will serve as specific embodiments of procedures followed in carrying out my invention. It will be understood, however, that these are not to be taken as limiting the invention in any way.

Example I crude amyl nitrate product amounted to 1278 grams, a yield of 93.0%, based on the weight of alcohol used. The product had a specific gravity of 0.99 and a boiling range of 144-150 C.

Example II Again 908 grams of secondary amyl alcohol was caused to react in a similar manner with 796 grams of 98% nitric acid, the two materials being caused to flow at proportionate rates in separate streams into 1420 grams of acetic anhydride. The temperature was maintained between 20 and 33 C. After separation, washing and drying, 1293 grams of crude amyl nitrate was obtained, a yield of 94.2%. The product had a boiling range between 139 and 150 C.

In the addition of reactants, 5% of the total nitric acid was introduced at the start and the reactants were added at such a rate that 5% more of the nitric than of the alcohol had been added at all times. Subsequently it was found that a 15% lead of nitric acid was desirable.

Example III Example IV Twenty-two grams of diethyl carbinol and 20.8 grams of 98% nitric acid were caused to flow into 31.2 grams of acetic anhydride in the same manner as described in the previous examples, the temperature being maintained at 18-22" C. The crude nitrate, after drowning, separation, washing and drying amounted to 27.3 grams, a yield of 82.0%, The product had a specific gravity of 0.97 and a boiling point of around 140 C.

Example V Fifty grams of methyl isobutyl carbinol and 39.3 grams of 98% nitric acid were added gradually and simultaneously to 64 grams of acetic anhydride, the addition being such that always 5% more of the nitric acid had been introduced than of the alcohol. Cooling water was used, and a nitration temperature of 7-10 C. was maintained. The nitration mixture was allowed to cook for five minutes at the end of the feeding.

The mixture was drowned in cold water and the oil layer separated and neutralized. The product amounted to 69.0 grams, a yield of 95.7%, based on the alcohol used.

Example VI A small sample of tertiary amyl alcohol was reacted with 98% nitric acid in an acetic anhydride medium in the manner described in the preceding examples. The nitrated compound was obtained after separation of the product. Attempts to nitrate this tertiary alcohol by means or mixed sulfuric and nitric acids resulted in instantaneous fume-oils, even when the temperature was lowered to -18 C.

In the foregoing examples nitric acid has been used at a strength of 98% HNOa. High strength nitric acid is highly desirable, for example above amount of acetic anhydride will be required than if weaker nitric were used. I am not limited, however, to acid of the high strengths cited. In general, I prefer to use an excess of nitric acid over that theoretically required for the complealcohol, various secondary and tertiary amyl alcohols, and higher straight and branched chain secondary and tertiary alcohols.

In carrying out the process of the invention, I may, if desired, first mix the alcohol and acetic anhydride, and then add the nitric acid thereto. Preferably, however, I add the nitric acid and the alcohol simultaneously to the acetic anhydride. Better control of the reaction is thereby obtained and such a procedure is considered desirable from the safety viewpoint, as no intermediate formation of undesirable compounds results by this preferred procedure. While the nitric acid and alcohol may be said to be added simultaneously, I find it desirable to introduce a small percentage of the total nitric acid at the outset, for example 5-15%, and maintain this lead throughout the addition period, so that all times there is this excess of nitric acid present. While the examples have shown the procedure to comprise the introduction of nitric acid and alcohol into acetic anhydride, the three ingredients may allbe added simultaneously, with a Such compounds may be 95% strength, as this means" that a smaller controlled excess of acetic anhydride and nitric acid. A continuous process may be carried out in this manner.

The method of my invention is very advantageous, as it allows the preparation of nitrated compounds that would otherwise be impossible, or attainable only with great difficulty. when various secondary alcohols have been nitrated by means of a mixture of sulfuric and nitric acid, for example, sub-zero temperatures must be maintained ordecomposition or polymerization of'the product takes place, with resultant low yields. The present process allows the use of temperatures of 0 to 50 C., for example, and higher, with the attainment of excellent yields.

The invention has been described clearly in the foregoing. It will be understood, however, that many variations in details of procedure and "specific compounds treated may be introduced without departure from the scope of the invention; I intend to be limited, therefore, only by the following claims.

I claim:

1. A process for preparing aliphatic and cycloaliphatic nitrates which comprises reacting a compound taken from the group consisting of the secondary and tertiary aliphatic and cycloaliphatic alcohols with nitric acid in the presence of acetic anhydride.

2. A process for preparing aliphatic nitrates which comprises causing to pass simultaneously into acetic anhydride nitric acid and a compound taken from the group consisting of the secondary and tertiary aliphatic and cycloaliphatic alcohols, and bringing about reaction therein,

3. The process of claim 2, in which secondary butyl alcohol is reacted with nitric acid.

4. The process of claim 2, in which a secondary amyl alcohol is reacted with nitric acid.

5. A process for preparing aliphatic nitrates which comprises causing to pass simultaneously into acetic anhydride nitric acid of over strength, and a compound taken from the group consisting of the secondary and tertiary aliphatic and cycloaliphatic alcohols, and bringing about reaction therein,

6; The process of claim 5, in which an excess of nitric acid over the alcohol is maintained throughout the addition period.

7. A process for preparing aliphatic nitrates which comprises causing to flow in contact with one another and at predetermined rates acetic anhydride, nitric acid of over 95% strength and a compound taken from the group consisting of the secondary and tertiary aliphatic and cyclo-' aliphatic alcohols, and causing reaction to take place therebetween.

JAMES EDWARD LUFKIN.