Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Reexamination Certificate
1998-03-30
2001-04-24
McKane, Joseph K. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
Reexamination Certificate
active
06222058
ABSTRACT:
This invention pertains to a process for the production of cyclopropanecarbonitrile (CPCN). More specifically, this invention pertains to the production of CPCN by feeding concurrently cyclopropanecarboxaldehyde (CPCA) and hydroxylamine aqueous solution to a reaction zone which contains formic acid. The process avoids the formation and accumulation of large amounts CPCA oxime intermediates which exhibit a very high energy release upon thermal decomposition. Additional embodiments of the invention comprise the steps of (1) synthesizing CPCN by feeding concurrently CPCA and hydroxylamine aqueous solution to a reaction zone containing formic acid to form a reaction product mixture comprising CPCN and (2) isolating and recovery the CPCN.
CPCN has proven to be a valuable as well as versatile compound. For example, it is an important synthetic building block for introducing the cyclopropane ring into agricultural chemicals such as N-cycloalkyl anilines, whose performance characteristics are substantially improved by the presence of the cyclopropyl group.
Prior art methods for preparing CPCN have involved reacting, in general, a halobutyronitrile with a base such as alkali metal hydroxide (
J. Am. Chem. Soc
., 1927, 49, 2068 and
J. Am. Chem. Soc
., 1929, 51, 1174) or sodium amide (
J. Am. Chem. Soc
., 1941, 63, 1734). However, certain problems have been encountered with these prior art procedures. For example, high temperatures normally are required for these reactions. Furthermore, substandard yields of product frequently have been obtained due to troublesome side reactions and difficult and prolonged distillation procedures.
U.S. Pat. No. 3,853,942 describes a process for the preparation of CPCN by reacting halobutyronitrile with an alkali metal alkoxide in an inert solvent at elevated temperatures and removing the alcohol formed. However, the alkali metal alkoxide is a relatively expensive reactant, which also is difficult to handle. U.S. Pat. No. 4,205,009 and GB 1,570,319 describe a similar process using alkali metal hydroxide instead of alkoxide in the presence of an anionic surfactant and an inert organic solvent. However, for better control of this phase-transfer reaction, environmentally unfriendly solvents such as benzene or dichloromethane are required. Furthermore, 4-halobutyronitrile (4-chloro- and 4-bromo-butyroniutile in particular) is used as the starting materials. Methods for preparing such nitrites are described in the
J. Am. Chem. Soc
. articles and U.S. Pat. No. 3,853,942 noted hereinabove. These nitriles typically are prepared by the anhydrous, free radical reaction of allyl chloride and hydrogen halide in the presence of benzoyl peroxide followed by the reaction of the resulting trimenthylenechlorohalide, in 500% excess, with sodium cyanide in ethanol-water medium. This method of preparing nitrites suffers from a number of disadvantages such as the handling of a corrosive hydrogen halide and highly toxic metal cyanide and difficult product isolation due to the formation of regeoisomers.
Additional procedures for the synthesis of CPCN on a laboratory scale involve a carbene insertion or Simmons-Smith reaction with acrylonitrile (see, for example, M. Mitain et al.,
J. Chem. Soc., Chem Commun
., 1983, 1446; H. Kanai et al.
Bull. Chem. Soc. Jpn
. 1983 56, 1025) or the dehydration of cyclopropanecarboxamide with the liquid “diphosgene”, trichloromethyl chloroformate as dehydrating agent (K. Mai and G. P Atil,
Tetrahedron Lett
., 1986, 27, 2203). While convenient for laboratory use, these procedures present serious safety concerns and/or require the use of expensive reagents when utilized on a commercial scale.
Prior art methods for preparing carbonitriles from aldehydes have involved, in general, (a) dehydration of aldoximes using diclohexylcarbodiimide, N,N′-carbonyl-diimidazole, N,N-imethyldichloromethaniminmium chloride, phosphonitrile dichloride, phenylchlorosulfite or selenium dioxide; (b) 1,2-elimination of reactions of O-substituted aldoximes; (c) 1,2-elimination reactions of aldehyde trimethylhydrazonium iodides and aldehyde N-tosylimines using base; (d) conversion of aldehydes to nitrites using ammonialsodium methoxide in methanol containing iodine or using an amine imide as an oxidizing agent. Again, while convenient for laboratory use, these methods are not suitable for large-scale commercial use due to safety concerns and/or use of expensive reagents.
Aldehydes having the formula of R-CHO have been converted to nitriles having the formula to R-CN wherein R is aryl or acyclic alkyl, using hydroxylamine chloride with large quantity of formic acid as solvent in the presence or absence of sodium formate. These methods generally give reasonable yields and less side reactions when R is an aromatic moiety or a long aliphatic chain (Cn where n=/>4). For example, T. ven Es (
J. Chem. Soc
. 1965, 1564) describes a procedure of using 1.15 equivalents of hydroxylamine and excess sodium formate (2 equivalents) with large amounts of formic acid (33 equivalents) to give good yields of aromatic nitriles. However, the procedure gives poor yields (30%) of n-propanecarbonitrile. Preparation of CPCN is not mentioned. G. A. Olah and T. Keumi (
Synthesis
1979, 112) describe a similar procedure (except no sodium formate is used) for the synthesis of aromatic nitriles and selected alkyl nitriles. In order to dissolve the hydroxylamine salt completely and to minimize side reactions, large amounts, e.g., 22 equivalents, of formic acid are required. It is very difficult, if not impossible, to isolate lower alkyl nitrites, e.g., nitrites containing a total of 2 to 4 carbon atoms, from formic acid either by extraction or distillation (formation of an azeotrope). Neutralization with a base (5% aqueous sodium hydroxide solution), as described in the procedure, will generate more than 20 equivalents of salts as wastes. Very intensive extractions are required for the product recovery of aliphatic nitrites. It is apparent that the commercial-scale use of the procedure described by Olah et al. would present serious problems.
Finally, U.S. Pat. No. 5,502,234 describes a process for the production of CPCN from CPCA in high selectivity and yield and for the recovery of the nitrile product. The process involves three steps comprising: (1) reacting CPCA with hydroxylamine base in the presence of water to obtain CPCA oxime; (2) contacting the CPCA oxime of step (1) with formic acid to obtain CPCN; and (3) contacting the mixture comprising CPCN formed in step (2) with a base to obtain a mixture comprising an organic phase containing CPCN and an aqueous phase. Although this process is useful for the preparation of CPCN, it presents safety problems due to the formation and accumulation of a large quantity of CPCA oxime intermediates. The CPCA oxime intermediates comprise the E and Z oxime isomers and, possibly, formate esters thereof It has been found that the CPCA oxime intermediates formed from in the process have a very high energy release upon thermal decomposition (1684 J/g with an onset temperature of 91° C. for E/Z isomers of 1:1 ratio). In the presence of formic acid, the onset temperatures are even lower (31-42° depending on the concentrations). The release of such large amounts of energy upon decomposition at relatively low initiation temperatures presents serious safety problems. For example, in commercial-scale operations, the loss of means of cooling and/or agitation could result in an explosive release of energy. Most organic oximes decompose exothermically with the release of large amounts of energy. For example, propionaldehyde oxime has a thermal decomposition energy of 2058 J/g with an onset temperature of 202° C. It has been reported (T. Ando at al.,
J. Hazardous Materials
, 1991, 28, 251-280) that DSC testing has shown that 16 out of 18 organic oximes have an average energy release upon thermal decomposition of about 2000 J/g with an average onset temperature of 220° C. The release of large amounts of energy from thermal decomposition presents serious sa
Blake Michael J.
Eastman Chemical Company
Gwinnell Harry J.
McKane Joseph K.
Murray Joseph
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