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| Telone (1,3-D) |
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Aniline
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| To understand the potential pathway of chemical degradation of 1,3-D in amended soil, the reaction of 1,3-D with aniline was determined at 25°C in solution. The NH2 group on aniline functions as a nucleophile, and was found to react readily with CH3Br and CH3I in a previous study (Gan and Yates, 1996). Water solution containing 5 mM aniline and 0.2 mM 1,3-D was prepared and transferred to 21-mL headspace vials, and the vials were immediately sealed. Disappearance of 1,3-D isomers from the solution was determined by periodically analyzing the ethyl acetate extract by GC-ECD. At the end of reaction, an aliquot of ethyl acetate extract was injected into an HP5890 GC in tandem with an HP5971 MSD to obtain mass spectra of the reaction products. The conditions were: RTX-624 or HP-5MS column (cross-linked 5% phenyl methyl silicone, 30 m × 0.25 mm × 0.25 μm, Hewlett Packard); 0.9 mL min-1 helium flow rate; 80°C initial oven temperature (2 min), ramping at 5°C min-1 to 200°C; 70 eV in EI mode; and 14 to 200 m/z scanning range. |
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Results |
| The possible involvement of SN2 mechanism was illustrated from the rapid disappearance of 1,3-D isomers in 5 mM aniline solution that was 5 times faster than that in water. As aniline was present in abundance to 1,3-D, the second-order reaction followed a pseudo first-order (r2 = 1.00). Compared to MeBr degradation under the same conditions (k = 0.24 d-1), disappearance of 1,3-D isomers (k = 0.55-0.59 d-1) was about 2.3 times as fast (Gan and Yates, 1996). GC/MS analysis of the ethyl acetate extract showed two peaks after aniline: peak 1 had a retention time of 25.7 min on the RTX-624 column and 16.4 min on the HP-5MS column, and peak 2 had respective retention times of 26.6 and 17.0 min. Both peaks on either column gave identical spectra, indicating that they were likely isomers to each other. From the spectrum, it was tentatively determined that the reaction products were isomers of 3-chloroallyl aniline (MW = 167), the product of SN2 substitution at the N position of aniline by chloride on C3 of the 1,3-dichloropropene molecule. |
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Last Modified: 10/20/2005
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