Starting with formaldehyde-C14, 1,2-dibromocyclopentane-4-C14 (XI) was synthesized in eight steps. Conversion of XI to cyclopentadiene was accomplished in three different ways, namely: the dehydrobromination of XI with quinoline at 195–198 °C, the preparation of 1,2-bis-(trimethylammonium)-cyclopentane-4-C14 hydroxide from XI followed by thermal decomposition, and the conversion of XI to 3,5-dibromocyclopentene followed by reaction of the latter with magnesium in dry ether. Degradations of the samples of cyclopentadiene obtained by these three synthetic routes showed a completely randomized distribution of the C14 activity, with 20% of the total activity on each of the five carbon positions. These results led to the conclusion that these preparations of cyclopentadiene very likely involved ionization to the cyclopentadienyl anion. The randomized distribution of C14 in the resulting products thus furnishes a strong indication that all five carbon positions in the cyclopentadienyl anion are equivalent.
从
甲醛-C14开始,经过八个步骤合成了
1,2-二溴环戊烷-4-C14(XI)。将XI转化为
环戊二烯的方法有三种,分别是:在195-198℃下用
喹啉脱
溴制备XI,从XI制备1,2-双(三甲基
铵)-
环戊烷-4-C14羟化物后进行热分解,以及将XI转化为3,5-二
溴环戊烯,随后与干醚中的
镁反应。通过这三种合成路线得到的
环戊二烯样品的降解表明,C14活性的分布是完全随机的,总活性的20%分布在五个碳位置的每一个上。这些结果表明,这些
环戊二烯的制备很可能涉及到
环戊二烯基阴离子的电离。因此,所得产物中C14的随机分布表明
环戊二烯基阴离子中的五个碳位置是等价的。