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Dicamba, 3,6-dichloro-2-methoxybenzoic acid, has been used in agriculture as an herbicide for over fifty years, and has seen an increase in use in the past decade due to the development of glyphosate resistant weeds and soybeans genetically modified to resist dicamba. Despite the previous use of dicamba, many questions remain regarding its environmental fate, especially the new commercial formulations used on genetically modified crops. Here, the photolysis of dicamba, including the commercial formulation Diablo®, is examined in aqueous solutions of varying water quality and on the surface of corn epicuticular waxes. Dicamba is stable to hydrolysis but degrades under UV light. The photolytic half-life for dicamba photolysis in aqueous solutions at pH 7 irradiated with Rayonet UVB lamps (280–340 nm) was t 1/2 = 43.3 min (0.72 hours), in aqueous solutions at pH 7 in a Q-Sun solar simulator ( λ > 300 nm) was t 1/2 = 13.4 hours, and on epicuticular waxes irradiated in the Q-Sun solar simulator was t 1/2 = 105 hours. Experiments with adjuvants, compounds added into the commercial formulations of dicamba, led to increases in rate constants for both aqueous and wax experiments. In addition to kinetic rate constants, photoproducts were tentatively assigned for the aqueous solution experiments. This work deepens the knowledge of the environmental fate of dicamba including the role surfactants play in chemical reactions and in providing new applications of current methods to examine the photolysis of chemicals sorbed to surfaces. 

Abstract A new compound NaCd₄Sb₃(Rm,a=4.7013(1) Å,c=35.325(1), Å, Z=3,T=100 K) featuring the RbCd₄As₃structure type has been discovered in the Na−Cd−Sb system, in addition to the previously reported NaCdSb phase. NaCd₄Sb₃and NaCdSb were herein synthesized using sodium hydride as the source of sodium. The hydride method allows for targeted sample composition, improved precursor mixing, and an overall quicker synthesis time when compared to traditional methods using Na metal as a precursor. The NaCd₄Sb₃structure was determined from single‐crystal X‐ray diffraction and contained the splitting of a Cd site not seen in previous isostructural phases. NaCd₄Sb₃decomposes into NaCdSb plus melt at 766 K, as determined viain‐situhigh‐temperature PXRD. The electronic structure calculations predict the NaCd₄Sb₃phase to be semi‐metallic, which compliments the measured thermoelectric property data, indicative of ap‐type semi‐metallic material. The crystal structure, elemental analysis, thermal properties, and electronic structure are herein discussed in further detail.