Publikace detail

Kinetics and mechanism of the reaction of polarized ethylenes with hydrazines and anilines

Autoři: Hanusek Jiří | Tarabová Denisa | Milata Viktor

Rok: 2013

Druh publikace: ostatní - přednáška nebo poster

Strana od-do: nestránkováno

Tituly:

Jazyk	Název	Abstrakt	Klíčová slova
eng	Kinetics and mechanism of the reaction of polarized ethylenes with hydrazines and anilines	The kinetics and mechanism of the nucleophilic vinylic substitution of dialkyl (alkoxymethylidene)malonates (alkyl: methyl, ethyl) and (ethoxymethylidene)malononitrile with substituted hydrazines and anilines R1-NH2 (R1: (CH3)2N, CH3NH, NH2, C6H5NH, CH3CONH, 4-CH3C6H4SO2NH, 3- and 4-X-C6H4) were studied at 25 °C in methanol. It was found that the reactions with all hydrazines (the only exception was the reaction of (ethoxymethylidene)malononitrile with N,N-dimethylhydrazine) showed overall second-order kinetics and kobs were linearly dependent on the hydrazine concentration which is consistent with the rate-limiting attack of the hydrazine on the double bond of the substrate. Corresponding Bronsted plots are linear (without deviating N-methyl and N,N-dimethylhydrazine) and their slopes (beta-Nuc) gradually increase from 0.59 to 0.71 which reflects gradually increasing order of the C-N bond formed in the transition state. The deviation of both methylated hydrazines is probably caused by the different site of nucleophilicity/basicity in these compounds (tertiary/secondary vs. primary nitrogen). A somewhat different situation was observed with the anilines (and once with N,N-dimethylhydrazine) where parabolic dependences of the kinetics gradually changing to linear dependences as the concentration of nucleophile/base increases. The second-order term in the nucleophile indicates the presence of a steady-state intermediate - most probably T?. Br?nsted and Hammett plots gave ?Nuc = 1.08 and ? = ?3.7 which is consistent with a late transition state whose structure resembles T?.	Kinetics; mechanism; polarized ethylenes; hydrazines; anilines

Vyhledávání

Přihlášení pro studenty

Přihlášení pro zaměstnance

Publikace detail

Katedry

Ústavy a pracoviště

Jak nás najdete?

Služby

Často hledáte