CS217697B1 - Method of chlorination of the 2-methylpyridine in the gaseous phase - Google Patents

Abstract

The process of chlorination of 2-methylpyridine in the gas phase

Description

The present invention relates to a process for the gas-phase chlorination of 2-methylpyridine which is used to prepare chlorinated pyridines of the formula

wherein Z is chlorine or hydrogen and Y is chloromethyl, dichloromethyl and trichloromethyl. A compound wherein Z is chlorine and Y is trichloromethyl is used as an inhibitor of the growth of nitrifying organisms in the soil (Goring CA Soil Science 93 211-218 (1962) Goring CA Soil Science 93 431-39 (1962)), where it acts very favorably to increase nitrogen utilization from fertilizers by plants, thereby increasing crop yields without increasing fertilization requirements.

Moreover, the compounds of the present invention can be used as precursors for the synthesis of 2-chloro-6-trichloromethylpyridine, or for the synthesis of 2-6-disubstituted, otherwise difficult to obtain, pyridine derivatives, such as e.g. 6-chloro-pyridin-2-karboldehydu.

So far the! these compounds were prepared by chlorination of 2-picoline hydrochloride at high temperature with chlorine gas (Taplin H. W. US Pat. 3424754 CA 70 77806 1969). Chlorination of 2-picoline in a mixture with an inert solvent (Taplin HW US Pat. 6420 833 CA 71 3279 1969), optionally by chlorination of 2-trichloromethylpyridine under UV catalysis (Kosorol VI el. Al. Khim. Vysk. Energ. 12 81-3 1978) ).

The present invention describes a gas-phase chlorination method for 2-methylpyridine, the principle being that 2-methylpyridine, water and chlorine vapors are fed in a continuous chlorinator so that the molar ratio of chlorine to 2-methylpyridine is 6: 1 to 19: 1 preferably 10: 1 and the molar ratio of water vapor to 2-methylpyridine is 20: 1, at a temperature of 390 to 500 ° C, preferably 460 to 490 ° C.

An advantage of the process according to the invention is the possibility to vary the composition of the chlorination mixture by varying the temperature and the ratio of chlorine to 2-picoline over a wide range and to prepare very easily in one step with good yield of 6-chloro-2-trichloromethylpyridine. In the following, the invention is illustrated by way of example without being limited thereto.

Example 1

106 ml of 2-methylpyridine was mixed with 394 ml of distilled water to give an aqueous solution of 2-methylpyridine in which the concentration of 2-methylpyridine was 5 mol%. The 2-methylpyridine solution was pumped into the evaporator at a rate of 0.195 Μ. In an evaporator heated to 350-400 ° C, the aqueous solution was evaporated immediately. The resulting vapors of water and 2-methylpyridine were fed to a mixing nozzle where central chlorine was fed into the vapor stream for best mixing, chlorine being fed at a rate of 1.66 M / h. The ratio of chlorine to 2-methylpyridine used is 8.48: 1. Behind the mixer was the actual chlorination reactor, consisting of a heated quartz tube with a volume of 62 cm ³ . The gases passed through the chlorinator were cooled in a condenser and the chlorinated pyridines were obtained by extraction with chloroform from the neutralized aqueous phase. The chloroform extracts were concentrated and analyzed by gas chromatography on an OV 17 column using a heat program. The temperature of the chlorination reactor varied between 440-490 ° C.

Temperature ° C 2-chloro-6-chloro- metylpyridxn (% by weight) 2-dichlormetylpyridín (% by weight) 2-trichloromethylpyridine (% by weight) 2-chloro-6-dichloro- methylpyridine (° / mass) 2-chloro-6-trichloro methylpyridine (% by weight) Conversion of pyridine <%) 440 21.4 18.2 27.5 25.9 5.8 48 470 0 3.5 20.9 18.9 54.6 75 490 0 2.2 17.8 1.8 67.0 85

Example 2

106 ml of 2-methylpyridine was mixed with 394 ml of distilled water to obtain an aqueous solution of 2-methylpyridine with water in a molar ratio of 1:20, the solution thus prepared was pumped to the evaporator at a rate of 0.127 M 2-methylpyridine / h, where evaporator of 350-400 ° C almost instantaneously evaporated. The resulting 2-methylpyridine / water vapors were mixed with chlorine in the mixing head just in front of the chlorinator itself, which was fed to the reactor at a rate of 2.045 M / h, so that the ratio of chlorine to 2-methylpyridine used was 16: 1. The chlorinator consisted of a heated quartz tube. After passing the vapor through the chlorinator, these were condensed in the condenser and the chlorinated pyridines were recovered from the aqueous phase by extraction with chloroform. The chloroform extracts were concentrated and analyzed by gas chromatography on an OV-17 column using a thermal program. The temperature of the chlorinator varied between 425 and 457 ° C.

Temperature ° C 2-chloro-6-chloromethylpyridine (wt.%) Ό £ and 8 o .o «5, 2-Trichloromethylpyridine (wt.%) 2-chloro-6-dichloromethylpyridine (wt.%) 2-chloro-6-trichloromethylpyridine (wt.%) Pyridine Conversion (%) 425 16.2 37.4 21.7 23 0 35 435 17.6 32.6 22.1 24.7 1.5 38 440 10.7 29.8 24.2 29.2 5.6 40 452 2.9 23.6 16.8 42.7 14.11 52 457 1.2 14.1 9.3 52.7 22.7 70

Example 3

A 1:20 molar ratio of 2-methylpyridine with water was dosed analogously to Example 1 into the evaporator at a rate of 0.195 M / h. 2-methylpyridine and the vapors thus formed were dosed with chlorine at a rate of 2.96 M / h. The ratio of chlorine to 2-methylpyridine used is 15.2: 1. After treatment of the condenser analogously to Examples 1 and 2, the obtained mixture was analyzed by gas chromatography on an O 17 column using a heat program. The temperature of the chlorination reactor varied between 395 and 445 ° C.

Temperature ° C 2-chloro-6-chloromethylpyridine (wt.%) 2-Dichloromethylpyridine (% by weight) 2-Trichloromethylpyridine (wt.%) 2-chloro-6-dichloromethylpyridine (wt.%) 2-chloro-6-trichloromethylpyridine (wt.%) Conversion of pyridine <70> 395 7.8 20.7 32.8 21.8 11.2 38 412 21.6 28.5 22.0 16.6 6.0 41 434 2.1 18.0 10.1 32.6 34.9 48 445 0.5 12.3 7.4 29.0 45.8 54

Example 4

A 1:20 molar ratio of 2-methylpyridine with water was charged to the evaporator at a rate of 0.112 M / h of 2-methylpyridine. Analogous to Examples 1 and 2, chlorine was admixed to the resulting vapors of water and 2-methylpyridine at a rate of 1.18 M / h. The ratio of chlorine to 2-methylpyridine used is 10.5: 1. After working up the condensate as in Examples 1 and 2, this was analyzed by gas chromatography. The temperature of the chlorination reactor varied between 465-485 ° C.

Temperature “C 2-chloro-6-chloro- methylpyridine (° / mass) C 'rt t-t and 1) o o 3 fi W Λ X5 o i ! 2-trichloromethylpyridine (% by weight) 2-chloro-6-dichloro- methylpyridine (% by weight) 2-chloro-6-trichloro methylpyridine (0 / mass) Conversion of pyridine (%) 470 - - 6.1 22.7 71.2 41 475 - - - 12.1 82.0 54 480 - - - 7.65 79.6 59 485 - - - 1.25 71.5 63

Example 5

A 1:20 molar ratio of 2-methylpyridine in distilled water was charged to the evaporator at a rate of 0.112-0.196 M / h and chlorine was added to the vapors at a rate of 1.18 M / h to 2.17 M / h. The chlorination was carried out analogously to Examples 1 and 2 and the chlorinated pyridine mixture was analyzed by gas chromatography after separation. The temperature of the chlorination reactor was maintained at 470-475 ° C.

Fiction Ό & CM »rt at 2-Dichloromethylpyridine methylpyridine (wt.%) 2-Trichloromethylpyridine (wt.%) 2-chloro-6-dichloromethylpyridine (wt.%) 2-chloro-6-trichloro methylpyridine (O / O mass) conversion 2-methylpyridine (%) 6: 1 7.2 31.6 29.5 29 43 8: 1 10.3 17.0 71.5 49 10.5: 1 - 1.0 12.0 82.1 54 17: l - 2.6 28.6 68.0 26 19: 1 - 6.88 29.3 63.2 31

OBJECT OF THE INVENTION

Claims (1)

OBJECT OF THE INVENTION Process for gas-phase chlorination of 2-methylpyridine characterized in that vapors of 2-methylpyridine, water and chlorine are passed in a continuous stream in a continuous chlorinator such that the molar ratio of chlorine to 2-methylpyridine is 6: 1 to 19: 1, preferably 10: 1 and a molar ratio of water vapor to 2-methylpyridine of 20: 1, at a temperature of 390 to 500 ° C, preferably 460 to 490 ° C.