A millipede produces hydrogen cyanide (HCN) as a defense mechanism. In this work we show the science behind why the polydesmoid millipede can use benzoyl cyanide (PhCOCN) to very quickly produce HCN in a low energy barrier reaction. Cyanide is a very highly active leaving group. Using Arrhenius plots, we first obtained the rates of reaction for PhCOCN in 39 pure and mixed aqueous organic solvents of ethanol (EtOH), methanol (MeOH), acetone (Me2CO), dioxane, 2,2,2- trifluoroethanol (TFE) and in TFE-EtOH (T-E) mixtures at 25 °C. For all of the Arrhenius plots, the R2 values ranged from 0.9937 to 1.0000. To elucidate the reaction transition state, the two-tern Grunwald-Winstein (G-W) equation was then utilized. Second or third degree polynomial equations were used to calculate any missing NT, and YCl values. In 32 solvents (20-90% EtOH, 30-90% MeOH, 20-80% Me2CO, 10-30% dioxane, 10T-90E, 20T-80E, 30T-70E, 40T-60E, 50T-50E, and 70T-30E), we obtained, R = 0.988, F-test = 595, l = 1.54 ± 0.11, m = 0.74 ± 0.03 and c = 0.13 ± 0.04. These l and m values are consistent with an addition-elimination mechanism. For the seven highly ionizing aqueous TFE mixtures, the two-term G-W analysis resulted in, R = 0.999, F-test = 763, l = 0.25 ± 0.031, m = 0.42 ± 0.03, and c = -0.13 ± 0.14. Here, the dissociative SN1 process is clearly dominant.

Use of polynomial regression techniques to predict solvent mechanisms for benzoyl cyanide

253rd National Meeting (2017)

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