User:Benjah-bmm27/degree/3/GCLJ1

Mechanisms, GCLJ1

• Reaction mechanisms
• Molecularity
• Order of reaction
• Elementary reaction
• Concerted reaction
• Stepwise reaction
• Bodenstein approximation

The philosophy behind reaction mechanism determination

According to Buskirk and Baradaran: Yet textbooks continue to teach that mechanisms can only be proven false... Chemists should be free to use evidence to either support or disprove mechanistic hypotheses... Mechanisms can be proven on a practical basis to the same extent as other scientific theories can be. The article's reviewers were divided on whether this is true, and most of them have published their views alongside the article itself "Can Reaction Mechanisms Be Proven?", J. Chem. Ed. (2009) 86, 551–558

See User:Benjah-bmm27/degree/hps.

Isotopic labelling

• Solvolysis of phenethyl tosylate, Ph-CH₂-CH₂-OTs, to phenethyl acetate with acetic acid
  • Simple S_N2 with EWGs in the para position on the benzene ring (e.g. p-NO₂): ρ ≈ −1.5 (no significant accumulation of charge)
  • EDGs allow a symmetrical phenonium ion intermediate to form: ρ ≈ −1.5 (no significant accumulation of charge)
  • So-called assisted S_N1
  • Evidence for symmetrical intermediate comes from scrambling of ¹³C label (C) on the α-carbon of phenethyl tosylate:

Ar-CH₂-CH₂-OTs → Ar-CH₂-CH₂-OAc + Ar-CH₂-CH₂-OTs