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Influence of the hydrocarbon rest upon reactivity

Influence of the hydrocarbon rest upon reactivity. Influence of the hydrocarbon rest upon reactivity Csp 2 – Csp 3 – X and Csp – Csp 3 - X. primary. secondary. tertiary. allyl halogen derivatives. very reactive halogen derivatives : prim. + sec. react via S N 1, but also by S N 2

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Influence of the hydrocarbon rest upon reactivity

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  1. Influence of the hydrocarbon rest upon reactivity

  2. Influence of the hydrocarbon rest upon reactivityCsp2 – Csp3 – X and Csp – Csp3 - X primary secondary tertiary allyl halogen derivatives very reactive halogen derivatives : prim. + sec. react via SN1, but also by SN2 tert. only by SN1 (steric reasons)

  3. Influence of the hydrocarbon rest upon reactivityCsp2 – Csp3 – X a Csp – Csp3 under SN1 conditions always expect allylic rearrangement

  4. Influence of the hydrocarbon rest upon reactivityCsp2 – Csp3 – Xa Csp – Csp2 - X under SN1 conditions always expect allylic rearrangement

  5. 1. elektrofilic addition (charcteristic reaction of alkenes), proceeds badly (decreased elektron density) 2. when at the double bond is more electrowithdrawing groups, we can expect rather nukleofilic additions 3. substitution is not realized very often, but then addtion - elimination mechanism is taking place Reaktivity of vinylhalogenides Csp2 - X

  6. The characteristic reactions for aromatic systems are elektrofilic aromatic substitution, they are realized at halogen substituted aromatic system to ortho- a para- position. Such an aromat has got lower electron density than unsubstituted benzene (it behaves as worse nucleophile) Reaktivity of aromatic halogen derivatives

  7. Nukleofilic substitution of halogen • at benzene ring is more difficult due to conjugation of free electron pairs of halogen with p-electrons of the benzene ring (the bond halogen – carbon is strengthen and at that carbon there is no sufficient electron gap for a nucleophile attack) • Nukleofilic substitutions proceeds only if the systém is activated and electron gap for entrance of nucleophile is realized by electronwithdrawing substituents in o- or in p- position(or better in both) this time by addition-elimination mechanism Reaktivity of aromatic halogen derivatives Meisenheimer complex

  8. 3. nucleophilic substitution at other aromatic halogen derivatives proceeds only when the system is treated by a strong base by elimination-addition mechanism(via benzyn intermediate) Reaktivity of aromatic halogen derivatives elimination addition

  9. Důkaz benzynu Reaktivity of aromatic halogen derivatives [4+2] cykloadice dokázala strukturu

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