Shigeyoshi Arai

Radiation Stability of Liquid Cyclooctatetraene

Cyclooctatetraene was irradiated at low pressure for several days with gamma rays from Co/sup 60/ at a dose rate of about 5300 r/min, total doses ranging from 30 to 50 mr. The H/sub 2/ and acetylene produced were identified and measured, and other products were measured after istilling the unreacted cyclooctatetraene out of the rection cell. It is evident that liquid cyclooctatetraene is one of the most radiation-stable organic liquids. (J.R.D.)

Mercury Photosensitized Reaction of Ethylene at High Temperature

The mercury photosensitized reaction of ethylene at high temperature was investigated using gas chromatographic technique. Hydrogen, methane, acetylene, propane, propylene, butane, butene‐1, and butene‐2 as well as the hydrocarbon products heavier than C4 were observed. Hydrogen and acetylene were formed by the intramolecular decomposition of excited ethylene. The dependence of hydrogen formation on ethylene pressure was in fair accordance with Cvetanovics relationship. The hydrocarbon products except acetylene were mainly produced by the thermal decomposition reactions of larger hydrocarbon radicals. The irradiation of mixtures of ethylene and nitric oxide showed that a part of butene‐1 was formed by the reaction of excited ethylene with ethylene. A reaction between excited ethylene and acetylene was also found to occur. In the cadmium photosensitized reaction of ethylene the same products were also observed. In this case a part of the hydrogen was presumably formed by the abstraction reactions of hydrogen atoms.

Mercury-Photosensitized Decomposition of Cyclohexane and Cyclopentane at High Temperatures.

350℃,400℃の高温でシクロヘキサンおよびシクロペンタンの水銀光増感反応を行なったところ,室温付近では認められなかった種々の開環分解生成物を見出した。すなわちシクロヘキサンについて室温付近での場合,生成物は水素,シクロヘキセンおよびジシクロヘキシルのみであるが,高温ではメタン,エタン,エチレン,プロパン,プロピレン,ブテンならびにブタジエン等が認められた。またシクロペンタンについても同様で,室温付近では水素,シクロペンテンおよびシクロペンチルシクロペンタンのみが生成するが,高温ではメタン,エタン,エチレン,プロパン,プロピレンならびにブテン等が見出された。これらの生成物は最初に生ずるシクロヘキシルおよびシクロペンチルラジカルの熱分解で生じたと考えられるが,さらに詳細に各生成物について生成速度と反応時間の関係を調べると,反応の初めから生じているものと,ある程度時間を軽て蓄積した不飽和炭化水素と水素原子との2次的反応で生じたものとに分けられる。このうち前者の化合物はシクロヘキシルおよびシクロペンチルラジカルからできたと考えられる直鎖状のラジカルCH2CH2CH2CH2CH=CH2およびCH2CH2CH2CH=CH2の異性化反応と分解反応で説明しうるが,この際の分解反応では直鎖状のラジカルの最も弱いとみなされるC-C結合の切れる反応がおもなものであると結論される。