The Halogenation of Amidines. I. Synthesis of 3-Haloand Other Negatively Substituted Diazirines1 Sir:Syntheses of diazirine and a variety of its alkyl de-rivatives have been carried out successfully for several years.2 However, the only reported 3-halodiazirine derivative is difluorodiazirine.3We have found that halogenation of alkylor arylamidines and isoureas in aqueous dimethyl sulfoxide (DMSO) solution affords the corresponding alkyl-, aryl-, or alkoxy-3-halodiazirine (I) in practical yields.

Proton and 13C chemical shift assignments are reported for the neuropeptide Met-enkephalin (ME) in both aqueous solution and in the presence of 50 mM sodium dodecyl sulfate (SDS). Rotating frame nuclear Overhauser enhancement spectroscopy was used to qualitatively describe interproton distances. These distances were then used as restraints in the distance geometry based molecular modeling program Dspace, developed by Hare Research to generate sets of conformations of ME. The resulting aqueous solution conformations of ME were determined to exhibit characteristic of an extended random-coil polypeptide with no distinguishable secondary structure. The resulting set of solution conformations of ME in the presence of 50 mM SDS exhibited characteristics of an amphiphilic type IV beta turn that are stabilized by hydrophobic aromatic-aromatic interactions between the side chains of Tyr1 and Phe4.

The transformation of metolachlor [2-chloro-N-(2-ethyl-6methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] and alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl)acetamide] in aquatic systems was investigated using outdoor tank mesocosms. Metolachlor and alachlor levels and their ethane sulfonic acid (ESA) and oxanillic acid breakdown products were monitored over time under five experimental treatments (each in quadruplicate). Background water conditions were identical in all treatments with each treatment differing based on the level and type-(s) of herbicide present. Treatments included a noherbicide control, 10 µg/L metolachlor, 25 µg/L metolachlor, 25 µg/L alachlor, and 25 µg/L alachlor plus 25 µg/L metolachlor in combination. The experiment was initiated by adding herbicide(s) to the units to the target concentrations; herbicide and breakdown product levels and other chemical parameters were then monitored for 85 days. In general, metolachlor half-lives were longer than alachlor half-lives under all treatments, although the differences were not statistically significant. Metolachlor halflives ((95% confidence limits) ranged from 33.0 d ((14.1 d) to 46.2 d ((40.0 d), whereas alachlor half-lives ranged from 18.7 d ((3.5 d) to 21.0 d ((6.5 d) for different treatments. Formation patterns of ESA were similar in all treatments, whereas oxanillic acid formation differed for the two herbicides. Alachlor oxanillic acid was produced in larger quantities than metolachlor oxanillic acid and either ESA under equivalent conditions. Our results suggest that the transformation pathways for alachlor and metolachlor in aquatic systems are similar and resemble the acetochlor pathway in soils proposed by Feng (Pestic. Biochem. Physiol. 1991, 34, 136); however, the oxanillic acid branch of the pathway is favored for alachlor as compared with metolachlor.

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