Thermal Rearrangements, XX<sup>[1]</sup> The Kinetics of Thermal Isomerisation of 4‐Methyl‐1,2,5‐hexatriene in the Gas Phase
書誌事項
- 公開日
- 1992-03
- 権利情報
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- http://onlinelibrary.wiley.com/termsAndConditions#vor
- DOI
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- 10.1002/cber.19921250326
- 公開者
- Wiley
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説明
<jats:p>4‐Methyl‐1,2,5‐hexatriene (<jats:bold>13</jats:bold>) has been prepared and subjected to gas‐phase pyrolysis. Above 220°C, <jats:bold>13</jats:bold> rearranges reversibly to both <jats:italic>trans</jats:italic>‐5‐hepten‐1‐yne (<jats:bold>14</jats:bold>) and its <jats:italic>cis</jats:italic>‐isomer <jats:bold>15</jats:bold>. Formation of <jats:bold>14</jats:bold> is faster than that of <jats:bold>15</jats:bold>. These isomerisations are accompanied by a slower irreversible rearrangement to 1‐methyl‐4‐methylene‐1‐cyclopentene (<jats:bold>16</jats:bold>) and 1‐methyl‐3‐methylene‐1‐cyclopentene (<jats:bold>17</jats:bold>). Rate constants and Arrhenius parameters have been obtained for all these reactions which were shown to be homogeneous and unimolecular. For the processes <jats:bold>13 ⇄ 14</jats:bold> and <jats:bold>13 ⇄ 15</jats:bold> the data are consistent with [3,3] Cope‐type sigmatropic rearrangements. For the process <jats:bold>13 → 16</jats:bold> + <jats:bold>17</jats:bold>, a rate‐determining formation of the 1‐methyl‐3‐methylenecyclopentane‐2,5‐diyl diradical is proposed. The rearrangements form a consistent pattern with other known examples. – The equilibrium data are shown to be in good agreement with thermodynamic estimates based on Group Additivity. The additivity scheme of Benson required extension to provide values for two new group contributions.</jats:p>
収録刊行物
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- Chemische Berichte
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Chemische Berichte 125 (3), 711-721, 1992-03
Wiley
