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Die NO‐katalysierte Isomerisierung von 2,6‐Dimethyl‐1, trans ‐3,6‐heptatrien in der Gasphase
Author(s) -
Egger Kurt W.
Publication year - 1968
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19680510305
Subject(s) - chemistry , isomerization , cis–trans isomerism , intramolecular force , reaction rate constant , catalysis , kinetics , medicinal chemistry , photochemistry , stereochemistry , organic chemistry , physics , quantum mechanics
The nitric oxide catalyzed isomerization of 2,6‐dimethyl‐1, trans ‐3,6‐heptatriene has been measured for temperatures ranging between 209.1 and 311.4°C. The reaction follows second order kinetics and appears to be truly homogeneous. The main products are 1.5.5‐trimethyl‐1.3‐cyclohexadiene (1,5,5‐TCHD), 2.6.6‐trimethyl‐1.3‐cyclohexadiene (2,6,6‐TCHD) and 2.6‐dimethyl‐1, trans ‐3.5‐heptatriene. Only traces of the cisoid structures of the linear trienes are detected, in equilibrium with the trans ‐isomers, which is attributed primarily to a loss of conjugation energy in the cis ‐isomer. The least squares regression analysis yields for the overall rate constants the A RRHENIUS equation log k (1/mole‐s) = (7.78 ± 0.14) − (25340 ± 350) /2.303 RT (°K). The analysis of the rate data shows that the reaction proceeds via a NO catalyzed geometrical isomerization followed by a thermal intramolecular 1,5‐hydrogen transfer and subsequent cyclization of the 1, cis ‐3. 5‐triene structure. No competition with abstraction of the «triallylic» hydrogen by NO is observed.