GB2165244A - Halogenation composition - Google Patents

Abstract

Compositions comprising a N-halodialkylamine as defined in the specification and an inorganic oxide are useful as halogenating agents for phenolic compounds, and are milder than halogens or hydrogen halides. N-chlorobis (2-chloroethyl)amine and N-chlorodiethyl amine, with silica, are exemplified.

Description

SPECIFICATION Chemical composition and use thereof The present invention relates to inorganic oxide derived compositions and to their use as halogenating agents for organic compounds, especially phenolic compounds.

Chlorinated phenols, for example, are valuable industrial products having a variety of uses, which include their use as intermediates in the manufacture of dyestuffs, preservatives, disinfectants, germicides, insecticides and antifungal agents.

Chlorinations of phenolic compounds have been carried out with a variety of chlorinating agents, catalysts and reaction conditions too numerous to mention in detail. Thus chlorophenols are obtained with chlorinating agents such as chlorine, chlorine oxide, SO2CI2, NaOCI, tertiary butyl hypochlorite etc.

The ortho/para ratio is very dependent upon the nature of the chlorinating agents and the conditions.

For example, the chlorination of phenol with tertiary butyl hypochlorite in CC14 gives an ortho:para ratio of 1.04 (cf. D.R. Harvey and R.O.C. Norman, J. Chem.

Soc., 1961,3604) and this ratio also depends on the concentration of phenol (cf. W.D. Watson, J. Org.

Chem., 1974,39, 1160). Likewise, the chlorination of phenol with Chlorine in CC14 gives an ortho:para ratio of 2.85 (cf. Y. Ogata et al, J. Chem Soc. Perkin Trans 11., 1984,451).

We have recently described in our published UK Patent Specification No. 2155009, the use of novel halogenation compositions comprising an inorganic solid and one or more organic halogen-containing compounds, which halogenate aromatic substrates such astoluene under mild conditions and avoid the use of corrosive halogen or hydrogen halide.

We have now found that compositions containing an N-halodialkylamine compound (cf. J.R. Lindsay Smith and L.C. McKeer, Tet. Letters, 1983,3117), such as for example N-chloropiperidine, and an inorganic oxide, such as for example silica gel, alumina or an aluminosilicate are highly effective halogenating agents and are especially useful for the halogenation of phenolic compounds.

Accordingly, the present invention provides a composition for use as a halogenating agent which comprises at least one N-halodialkylamine and at least one inorganic oxide.

By the term 'N-halodialkylamine' is meant here and throughout the specification that the nitrogen atom in the compound is linked directly to (a) at least two separate hydrocarbyl units which may themselves be substituted by other groups andlor which may together form a heterocyclic ring with the nitrogen being the hetero atom, and (b) a halogen atom.

A wide range of N-halodialkylamines may be employed including iodine-containing compounds, although chlorine- and bromine- containing compounds are preferred. Typical of the N-halodialkylamines which may be used in the composition of the present invention are N-chloropiperidine, Nchlorodiisopropylamine, N-chloromorpholine, N,Ndichloropiperazine, N-chlorobis(2-methoxyethyl)amine, N-chlorobis(2-chloroethyl)amine and Nchlorodiethylamine. It should be noted that Nchlorobis(2-methoxyethyl)amine and N-chlorobis(2chloroethyl)amine may have explosive properties when in their neat state and they should be handled with care. They may be handled with safety in the form of solutions or suspensions in appropriate solvents. These can be prepared in situ by reacting in aqueous solution the parent dialkylamines, e.g.

bis(2-methoxyethyl)amine and bis(2chloroethyl)amine respectively with sodium hyprochlorite. For further details on the preparation of N-halodialkylamines, the reader is referred to J.Am.

Chem. Soc., 1933, 55,3001 by G.H. Coleman and Can. J. Chem., 1970,48,546 by K.U. Ingold. The aqueous reaction mixture may then be stirred in carbon tetrachloride dichloromethane or hydrocarbon solvents so as to extract the N-halodialkylamine directly into the organic solvent of choice.

The inorganic oxides which may be employed include one or more of silica, alumina, silica/alumina, titania, zirconia and both natural and synthetic aluminosilicates.

In the compositions of the present invention the amount of N-halodialkylamine to inorganic oxide may vary over a wide range. The rate of halogenation reaction will vary with the relative proportion of the two components. Typically, the composition may contain 0.2 to 10 moles, preferably 0.5 to 5 moles of the N-halodialkylamine per kilogram of the inorganic oxide.

For example, in the case of a commercial silica (e.g. ex-British Drug Houses) a maximum rate of halogenation is achieved when using 0.65 mole of the N-halodialkylamine per kilogram of the silica.

The halogentating properties of the resulting compositions are quite different from those of the individual components. Many of the compositions falling within the scope of the invention will also tolerate the presence of water.

Such compositions are not only halogenating agents but also have the added advantage of preferentially forming the orthohalogenated isomer in the product during halogenation of phenols. Thus, for example chlorination of 2-methylphenol in carbon tetrachloride at 25"C with a slight excess of N-chlorobis(2-chloroethyl)amine can give a 94% yield of chloro-2-methylphenols in the proportions 6-chloro-2methylphenol (81%),4-chloro-2- methylphenol (10%), 2,4-dichloro-2methylphenol (9%) [ratio of ortho substituted : para substituted = 8:1]. Chlorination of phenol under the same conditions as above gives an ortho:para ratio of about 15:1.Ortho:para ratios in the product may be varied by varying the phenolic reactant to halogenating agent ratios, the concentration of the reactant(s), the reaction medium, e.g. solvent or the reaction conditions.

Although the compositions are especially useful for the halogenation of simple or substituted phenols e.g. phenol, ortho-chlorophenol, parachlorophenol, ortho-cresol and meta-cresol, they may also be used for the halogenation of other organic compounds, for example other aromatic compounds.

The components in the composition may be used as a preformed physical admixture or may be added sequentially to the halogenation reaction.

The relative proportions of the halogenating composition and the phenolic compound may be varied over a wide range depending on the level of chlorination required. However, molar ratios ofthe phenolic compound: N-halodialkylamine in the range 3:1 to 1:3 are preferred.

The halogenation reactions may be carried out over a range of temperatures, typically 0-80 C, but are most conveniently carried out at 15-40"C. Similarly, the most convenient pressure is atmospheric pressure, but sub-atmospheric or elevated pressures may be employed.

Although the reactions are conveniently carried out in the presence of a solvent, this is not essential.

The N-halodialkylamine may initially be deposited on the inorganic solid (with removal of any solvent employed for this purpose), and the reactant may be brought into contact with the supported halogenating agent in a gas flow, as a neat liquid or in solution.

Solid-phase reactions are also possible.

The invention will now be further illustrated by reference to the following Examples.

Example 1 Silica (3 g, 60-120 BSS mesh), carbon tetrachloride (10 ml), phenol (2.5 mmol) and N-chlorobis(2chloroethyl)amine (2.63 mmol) were gently stirred together at 25"C for 24 hours. The reaction mixture was filtered and the solid was washed with a little extra carbon tetrachloride and some methanol to give a filtrate containing ortho-chlorophenol (47%), 2,6-dichlorophenol (10%), 2,4-dichlorophenol (5%), para-chlorophenol (3%) and unreacted phenol (34%), as estimated by gas chromatography.

Example 2 The procedure of Example 1 was repeated except that the reactant was p-chlorophenol instead of phenol. The filtrate obtained contained 2,4dichlorophenol (55%), 2,4,6-trichlorophenol (16%) and unreacted para-chlorophenol (29%), as estimated by gas chromatography.

Example 3 The procedure of Example 1 was repeated except that ortho-chlorophenol was the reactant (instead of phenol), the reaction period was increased to 48 hours and the reagent used was Nchlorodiethylamine. The filtrate obtained contained 2,6-dichlorophenol (32%), 2,4-dichlorophenol (22%), 2,4,6-trichlorophenol (18%) and unreacted orthochlorophenol (28%), as estimted by gas chromatography.

Example 4 The procedure of Example 1 was repeated except that the reactant was ortho-chlorophenol (instead of phenol) and the reaction period was increased to 48 hours. The filtrate obtained contained 2,6dichlorophenol (41%), 2,4-dichlorophenol (8.5%), 2,4,6-trichlorophenol (12.5%) and unreacted orthochlorophenol (38%), as estimated by gas chromatography.

Example 5 The procedure of Example 1 was repeated except that the reactant was ortho-cresol instead of phenol and the reaction period was increased to 48 hours.

The filtrate obtained contained 6-chloro-2methyl phenol (76%), 4-chloro-2-methylphenol (9.5%), 4-6-dichloro-2-methylphenol (8.5%) and unreacted 2-methylphenol (6%), as estimated by gas chromatography.

Claims (7)

1. A composition for use as a halogenating agent which comprises at least one N-halodialkylamine as hereinbefore defined and at least one inorganic oxide.

2. A composition according to claim 1 wherein the N-halodialkylamine is selected from Nchloropiperidine, N-chlorodiisopropyl amine, Nchloromorpholine, N,N-dichloropiperazine, N chlorobis(2-methoxyethyl) amine, N-chlorobis(2chloroethyl) amine and N-chlorodiethyl amine.

3. A composition according to claim 1 wherein the inorganic oxide is selected from silica, alumina, silica/alumina, titania, zirconia, natural aluminosilicates, synthetic aluminosilicates and mixtures thereof.

4. A composition according to any one of the preceding claims wherein the composition contains 0.2 to 10 moles of the N-halodialkylamine per kilogram of the inorganic oxide.

5. A process for the halogenation of phenols said process comprising reacting a simple or substituted phenol with a composition comprising at least one N-halodialkyl amine as hereinbefore defined and at least one inorganic oxide.

6. A process according to claim 5 wherein the reactant phenol is selected from phenol, orthochlorophenol, para-chlorophenol, ortho-cresol and meta-cresol.

7. A process according to claims 5 or 6 wherein the molar ratio of the phenolic compound to Nhalodialkylamine is in the range 3:1 to 1:3.