Nascent hydrogen

Nascent hydrogen is a concept that was once invoked to explain dissolving-metal reactions, such as the Clemmensen reduction and the Bouveault–Blanc reduction. Since organic compounds do not react with H2, a special state of hydrogen was postulated. It is now understood that dissolving-metal reactions occur at the metal surface, and the concept of nascent hydrogen is discounted, and even ridiculed.
History.
The idea of hydrogen in the nascent state having chemical properties different from those of molecular hydrogen was developed the mid-19th century. Alexander Williamson repeatedly refers to nascent hydrogen in his textbook "Chemistry for Students", for example writing of the substitution reaction of carbon tetrachloride with hydrogen to form products such as chloroform and dichloromethane that the "hydrogen must for this purpose be in the nascent state, as free hydrogen does not produce the effect". Williamson also describes the use of nascent hydrogen in describing earlier work of Marcellin Berthelot. Franchot published a paper on the concept in 1896, which drew a strongly worded response from Tommasi who pointed to his own work that concluded "nascent hydrogen is nothing else than H + "x" calories".
The term "nascent hydrogen" continued to be invoked into the 20th Century.