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The traditional laboratory of synthesis of banana oil via Fisher esterification was modified to provide a practical integration of green chemistry concepts and principles into undergraduate organic chemistry laboratory at Southern University and A&M College-Baton Rouge campus (SUBR). Besides the traditional method described in our laboratory manual, two more modified methods for the synthesis of banana oil were added. Six out of the 12 principles of green chemistry were introduced. This laboratory offered students an opportunity to do a comparative study of the greenness and efficiency of different synthetic methods for the synthesis of banana oil and practice applying green chemistry principles into organic synthesis. The modified method II was found to be the greenest and most efficient synthetic method with least waste produced, highest atom economy and yield, environmentally benign chemicals, reduced hazardous risk, improved energy efficiency and enhanced accident prevention. Calculations of E-factor and percent atom economy were introduced. The comparison of experimental percent atom economy and percent yield was also included. 

Abstract The development of stimuli‐responsive materials suitable for use in wearable sensors is a key unresolved challenge. Liquid crystals (LCs) are particularly promising, as they do not require power, are light‐weight, and can be tuned to respond to a range of targeted chemical stimuli. Here, an advance is reported in the design of LCs for chemical sensors with the discovery of LCs that assume parallel orientations at free surfaces and yet retain their chemoresponsiveness. The resulting LC‐based sensors are more sensitive and exhibit faster responses than previous LC sensor designs. 

Abstract Computational chemistry‐guided designs of chemoresponsive liquid crystals (LCs) with pyridine or pyrimidine groups that bind to metal‐cation‐functionalized surfaces to provide improved selective responses to targeted vapor species (dimethylmethylphosphonate (DMMP)) over nontargeted species (water) are reported. The LC designs against experiments are tested by synthesizing 4‐(4‐pentyl‐phenyl)‐pyridine and 5‐(4‐pentyl‐phenyl)‐pyrimidine and quantifying LC responses to DMMP and water. Consistent with the computations, pyridine‐containing LCs bind to metal‐cation‐functionalized surfaces too strongly to permit a response to either DMMP or water whereas pyrimidine‐containing LCs undergo a surface‐driven orientational transition in response to DMMP without interference from water. The computation predictions are not strongly dependent on assumptions regarding the degree of coordination of the metal ions but are limited in their ability to predict LC responses when using cations with mostly empty d orbitals. Overall, this work identifies a promising new class of chemoresponsive LCs based on pyrimidine that exhibits enhanced tolerance to water, a result that is important because water is a ubiquitous and particularly challenging chemical interferent in chemical sensing strategies based on LCs. The work also provides further evidence of the transformative utility of computational chemistry methods to design LC materials that exhibit selective orientational responses in specific chemical environments. 

Abstract Surface‐supported liquid crystals (LCs) that exhibit orientational and thus optical responses upon exposure to ppb concentrations of Cl₂gas are reported. Computations identified Mn cations as candidate surface binding sites that undergo redox‐triggered changes in the strength of binding to nitrogen‐based LCs upon exposure to Cl₂gas. Guided by these predictions, μm‐thick films of nitrile‐ or pyridine‐containing LCs were prepared on surfaces decorated with Mn²⁺binding sites as perchlorate salts. Following exposure to Cl₂, formation of Mn⁴⁺(in the form of MnO₂microparticles) was confirmed and an accompanying change in the orientation and optical appearance of the supported LC films was measured. In unoptimized systems, the LC orientational transitions provided the sensitivity and response times needed for monitoring human exposure to Cl₂gas. The response was also selective to Cl₂over other oxidizing agents such as air or NO₂and other chemical targets such as organophosphonates.