For many years, a controversy raged concerning the structures of so-called electron-deficient molecules; that is, molecules with

For many years, a controversy raged concerning the structures of so-called €œelectron-deficient€ molecules; that is, molecules with insufficient electrons to make normal two-atom, two-electron bonds. Typical is ethyl cation, C₂H₅⁺, formed from protonation of ethene.

Is it best represented as an open Lewis structure with a full positive charge on one of the carbons, or as a hydrogen-bridged structure in which the charge is dispersed onto several atoms?

Is it best represented as an open Lewis structure with a full positive charge on one of the carbons, or as a hydrogen-bridged structure in which the charge is dispersed onto several atoms? Build both open and hydrogen-bridged structures for ethyl cation. Optimize the geometry of each using the B3LYP/6-31G* model and calculate vibrational frequencies. Which structure is lower in energy, the open or hydrogen-bridged structure? Is the higher energy structure an energy minimum? Explain your answer.

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Н Н н c- н7 Н н hн, н Н Open Нydrogen bridged