Unimolecular reaction

Japanese: 一分子反応 - いちぶんしはんのう（英語表記）unimolecular reaction

When classifying chemical reactions by the number of molecules involved, this refers to an elementary reaction A → B (B is the product) in which only one molecule A is involved. It is also called a unimolecular reaction. The reaction proceeds by a mechanism in which A is activated and then decomposes independently to become B. Therefore, the reaction rate equation is v = k [A], that is, first order with respect to A. Typical unimolecular reactions include the thermal decomposition of peroxides and the ring-opening of cyclopropane. (CH ₃ ) ₃ C-O-O-C(CH ₃ ) ₃ - → 2(CH ₃ ) ₂ CO + C ₂ H ₆ In organic chemistry reactions, unimolecular reaction is used almost interchangeably with first order reaction.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

反応の分子数で化学反応を分類するとき，1個の分子Aだけが関係する形式の素反応A→B(Bは生成物)をさす。単分子反応ともいう。反応は，Aが活性化され，それが単独に分解してBになる機構で進む。したがって反応速度式はv＝k[A]，すなわちAについて一次になる。典型的な一分子反応には，過酸化物の熱分解やシクロプロパンの開環などがある。　(CH₃)₃C－O－O－C(CH₃)₃―→2(CH₃)₂CO＋C₂H₆有機化学反応では，一分子反応は一次反応とほとんど同じ意味に用いられる。

出典　株式会社平凡社世界大百科事典第２版について　情報

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