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The light-harvesting system of PSI uses multiple copies of the same transmembrane proteins used by PSII. The energy of absorbed light (in the form of delocalized, high-energy electrons) is funneled into the reaction center, where it excites special chlorophyll molecules (P700, with maximum light absorption at 700 nm) to a higher energy level.
In graphite, each carbon atom uses only 3 of its 4 outer energy level electrons in covalently bonding to three other carbon atoms in a plane. Each carbon atom contributes one electron to a delocalized system of electrons that is also a part of the chemical bonding. The delocalized electrons are free to move throughout the plane.
Although the energy difference between coplanar anisole and its isomer is quite large, the rotation between the O–CH 3 bond becomes favorable when the electronic properties of methoxy group on aromatic rings need to be altered to stabilize an unusual intermediate or a transition state. In the following reaction, the regioselectivity could be ...
In the electron-donating case, the SOMO interacts with the lower energy lone pair to form a new, lower-energy, filled, delocalized bond orbital and a new, higher-energy antibonding SOMO (in net, a three-electron bond). Because the new bonding orbital contains more electrons than the SOMO, the resulting electronic state reduces molecular energy.
Cinnamaldehyde is a naturally-occurring compound that has a conjugated system penta-1,3-diene is a molecule with a conjugated system Diazomethane conjugated pi-system. In theoretical chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability.
The theory predicts two energy levels for ethylene with its two π electrons filling the low-energy HOMO and the high energy LUMO remaining empty. In butadiene the 4 π-electrons occupy 2 low energy molecular orbitals, out of a total of 4, and for benzene 6 energy levels are predicted, two of them degenerate.
Carbon nanotubes are metallic or semiconducting, based upon delocalized electrons occupying a 1-D density of states. However, any covalent bond on SWNT sidewall causes localization of these electrons. In the vicinity of localized electrons, the SWNT can no longer be described using a band model that assumes delocalized electrons moving in a ...
Cyclobutadiene, for example, rapidly dimerizes with no potential energy barrier via a 2 + 2 cycloaddition reaction to form tricyclooctadiene. [14] While the antiaromatic character of cyclobutadiene is the subject of debate, the relief of antiaromaticity is usually invoked as the driving force of this reaction. Dimerization of cyclobutadiene