. This graphic gives the chemical structure abamectin, a pesticide that is produ
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Question
.This graphic gives the chemical structure abamectin, a pesticide that is produced by fermentation action of the soil bacterium Streptomyces Avermitilis. (This makes in an “organic” pesticide). The bacterium produces two molecules, avermectin B1a and B1b, with the tiny difference shown in the graphic.
A. The two molecules are virtually identical. If you had a sample that was either pure avermectin B1a or pure avermectin B1b, and if you had only proton NMR available, propose a way to tell the difference between the two. Feel free to mention any difficulties you anticipate.
B. If you had carbon NMR available, propose a way to tell the difference between the two.
Explanation / Answer
Both avermectin B1a and B1b shows almost similar proton and carbon NMR but avermectin B1a shows two more sets of multiplets than avermectin B1b due to -CH2- and -CH3 protons in 1H NMR otherwise there would be only one peak due to R group(CH(CH3)2) in avermectin Ba1b.
Similarly in 13C NMR also avermectin B1a contain one more peak than avermectin B1b due to -CH2- carbon
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