Action of heat on pyrethrum extract: The isomerisation of pyrethrins to isopyrethrins

@inproceedings{Goldberg1965ActionOH,
  title={Action of heat on pyrethrum extract: The isomerisation of pyrethrins to isopyrethrins},
  author={Alan A. Goldberg and S. Head and P G B Johnston},
  year={1965}
}
The thermal isomerisation of the pyrethrins to isopyrethrins has been studied, the progress of the reaction being followed by the rise in optical density at 2700 A and the fall at 2300 A. The isomerisation is a first-order reaction with 106k equal to 4·58 and 481 at 125° and 195° respectively; these values give E* = 24,610 cal. mol.−1; log A = 8·17; ΔS* = −21·8 cal. deg.−1. In normal (unheated) pyrethrum extract the ratio of the optical densities at 2700 A and 2300 A is 0·08; in… CONTINUE READING

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