B. -3-Ethoxy-2-methylcyclohexene (0.18 mol) was treated as described above, yielding 6.6 g (38%) of mixed dienes. Glpc analysis yielded 41% 6, 35% 7, 22% 8, and 2% 9.C. -3-Ethoxy-l-methylcyclohexene (0.18 mol) was treated as above yielding 7.0 g (41%) of mixed dienes. Glpc analysis yielded 18% 5,18% 6, 46% 7,14% 8, and 2% 9.Thermal Isomerization Reactions. General Procedure.-Mixtures of the three isomeric methyl-1,3-cyclohexadienes of known composition were added dropwise through a 22-mm Pyrex tube packed to a depth of 12 in. with Win. Pyrex helices and externally heated at either 300, 325, or 350°as in the above elimination studies. The thermolysis products were isolated in a similar manner (90-95% recovery) and submitted to glpc analys is (Table II). Addition of 3-methylenecyclohexene did not affect the above reactions, and 8 survived quantitatively in all cases. Alumina studies were carried out under identical conditions of temperature and flow rate.
For unsymmetrical molecules and for those in which the inherent thermal motions introduce large fluctuations in the internuclear separations, gas-phase electron diffraction data alone cannot provide unique parameter assignments. We propose to separate the data reduction step that leads to an ltj } matrix, which accurately represents the diffraction data, from the structure interpretation step which requires the exploration of the shape of the potential energy surface in the vicinity of its minima. The procedure is particularly applicable to molecules in which the internal motions are highly anharmonic and the root-mean-square amplitudes are large. Four examples are presented. These include two cases with single rotators (trifluoronitrosomethane and perfiuoroethyl iodide) and two with two rotators (perfluoroisopropyl iodide and acetone). New diffraction data for trifluoronitrosomethane gave the following rg parameters: (C-F) = 1,326 ± 0.003 A;
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