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Contributing structures of the carbonate ion. In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, [1] also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory.
Ru(PPh 3) 2 (CO) 3 + (SCN) 2 → Ru(NCS) 2 (PPh 3) 2 (CO) 2 + CO, where Ph = C 6 H 5. Even though the reaction involves cleavage of the S-S bond in thiocyanogen, the product is the Ru-NCS linkage isomer. In another unusual method, thiocyanate functions as both a ligand and as a reductant in its reaction with dichromate to give [Cr(NCS) 4 (NH 3 ...
The effect is used in a qualitative way and describes the electron withdrawing or releasing properties of substituents based on relevant resonance structures and is symbolized by the letter M. [2] The mesomeric effect is negative ( –M ) when the substituent is an electron-withdrawing group , and the effect is positive ( +M ) when the ...
Such a resonance structure is called a Clar structure. In other words, a polycyclic aromatic hydrocarbon with a given number of π-sextets is more stable than its isomers with fewer π-sextets. [1] [2] In 1984, Glidewell and Lloyd provided an extension of Clar's rule to polycyclic aromatic hydrocarbons containing rings of any size. [3]
If R 1 and R 2 (note equation at top of page) are different substituents, there is a new stereocenter formed at the alpha position when an enol converts to its keto form. Depending on the nature of the three R groups, the resulting products in this situation would be diastereomers or enantiomers .
In resonance structures, major and minor contributing structures may exist. For amides, for example, NBO calculations show that the structure with a carbonyl double bond is the dominant Lewis structure. However, in NBO calculations, "covalent-ionic resonance" is not needed due to the inclusion of bond-polarity effects in the resonance ...
Structure of [Co 2 (OH 2) 10] 4+ color code: red = O, white = H, blue = Co. In the binuclear ion [Co 2 (OH 2) 10] 4+ each bridging water molecule donates one pair of electrons to one cobalt ion and another pair to the other cobalt ion. The Co-O (bridging) bond lengths are 213 picometers, and the Co-O (terminal) bond lengths are 10 pm shorter.
Tautomers are distinct chemical species that can be distinguished by their differing atomic connectivities, molecular geometries, and physicochemical and spectroscopic properties, [6] whereas resonance forms are merely alternative Lewis structure (valence bond theory) depictions of a single chemical species, whose true structure is a quantum ...