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The generic structure of a nitrene group. In chemistry, a nitrene or imene (R−:Ṅ·) is the nitrogen analogue of a carbene.The nitrogen atom is uncharged and monovalent, [1] so it has only 6 electrons in its valence level—two covalent bonded and four non-bonded electrons.
Molecular orbital diagram of dinitrogen. With nitrogen, we see the two molecular orbitals mixing and the energy repulsion. This is the reasoning for the rearrangement from a more familiar diagram. The σ from the 2p is more non-bonding due to mixing, and same with the 2s σ. This also causes a large jump in energy in the 2p σ* orbital.
Case 2: the single atom is the nitrogen atom in the diazenyl group (N=N), which ends up as dinitrogen (N≡N). The above are known as cheletropic eliminations because a small, stable molecule is given off in the reaction. [1] Case 3 & 4: the single atom is the sulfur in sulfur dioxide (SO 2), which joins the alkene chains to form a ring.
In organic chemistry, a rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. [1] Often a substituent moves from one atom to another atom in the same molecule, hence these reactions are usually intramolecular.
Alkyl and aryl terminal alkenes react with high regioselectivity to give 5-substituted isoxazolidines. This outcome is consistent with frontier molecular orbital (kinetic) control of the distribution of isomers: the nitrone oxygen, which possesses the largest orbital coefficient in the HOMO of the nitrone, forms a bond with the inner carbon of the alkene, which possesses the largest orbital ...
A sigmatropic rearrangement is a reaction in which a sigma bond moves across a conjugated pi system with a concomitant shift in the pi bonds. The shift in the sigma bond may be antarafacial or suprafacial.
Using FMO analysis, [1,j]-sigmatropic rearrangements are allowed if the transition state has constructive overlap between the migrating group and the accepting p orbital of the HOMO. In [1,j]-sigmatropic rearrangements if j + 1 = 4n, then supra/antara is thermally allowed, and if j + 1 = 4n + 2, then supra/supra or antara/antara is thermally ...
The carbene has six electrons - two each in the carbon-nitrogen single bonds, two in its sp 2-hybridized orbital, and an empty p-orbital. The sp 2 lone pair acts as an electron donor, whereas the empty p-orbital is capable as acting as an electron acceptor.