Active Complex - Catalytic Complex

Also known as an activated complex. In a chemical reaction, when the atomic arrangement is rearranged from the original system to the product system while choosing the path with the lowest possible energy, this refers to the state that corresponds to the position with the highest free energy among the paths taken. This state corresponds to the so-called saddle point when considering the surface of the potential energy (or more accurately, the free energy) of the reaction system as a function of bond distance. An activated complex is a type of molecule that has degrees of freedom for translation, rotation, and vibration, but only vibration along the reaction coordinate axis causes decomposition into the original system and product system with equal probability. Transition state theory considers an activated complex in equilibrium with the original system, and evaluates the reaction rate based on its decomposition into the product system.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

活性錯合体ともいう．化学反応において，できるだけエネルギーの低い経路を選びつつ，原系から生成系へ向かって原子配置の組換えが行われる際，通る経路のなかで自由エネルギーの最高の位置に相当する状態をいう．この状態は，結合距離の関数として反応系のポテンシャルエネルギー(正確には自由エネルギー)の曲面を考えるときのいわゆる鞍点に相当する．活性錯体は並進，回転，振動の自由度をもつ一種の分子であるが，反応座標軸方向への振動のみが原系および生成系へ等しい確率で分解を引き起こす．遷移状態理論は原系と平衡にある活性錯体を考え，その生成系への分解をもって反応速度を評価する理論である．

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