Methyl anion, electronic structure

Before we move on from the hybrid orbitals of carbon, we should take a look at the electronic structure of important reactive species that will figure prominently in our consideration of chemical reactions. First, let us consider carbanions and carbocations. We shall consider the simplest examples, the methyl anion CHs and the methyl cation CH3+, though these are not going to be typical of the carbanions and carbocations we shall be meeting, in that they lack features to enhance their stability and utility. 

Since the methylation of 60 under the same conditions but in the presence of 5-15% crown ether gave the ot-syn disubstituted product only in axial position (83% yield), the reason for the stereoselectivity probably lies in the electronic structure of the evolved anion, and not in the formation of a chelate. The stereoselectivity arises from the regioselectivity for the following reasons ... 

Early quantum chemical calculations on ionic liquids were focused towards the haloaluminate, and related metal- (Au and Fe) containing melts, these are examined in the foUovying subsection. As the field has developed, this focus has shifted towards imidazolium-based ionic liquids because of their lower melting points and more fevorable physical properties. Imidazolium-based ionic liquids are discussed in the third subsection which examines imidazolium cations with small alkyl chains (methyl, ethyl and butyl). The ionic liquids which can be formed from imidazolium cations and small anions such as halides or [PFe]" are then discussed, mention is also made of calculations carried out on a few more diverse systems. The electronic structure of the imidazolium-based ionic liquids is the focus of the fourth and final subsection. 

The employment of photoelectronic spectroscopy in conjunction with results from ab initio MO calculations has provided a valence orbitals description of the structure of the neutral and anionic forms of the nucleotide (143), the simplest among all the common nucleotides occurring in DNA and RNA <90JA538>. The electronic structure enables conclusions to be drawn about the distribution of the products in the electrophilic attack of nucleotides. This is supported by alkylation patterns in methylation and ethylation of DNA and RNA. 

Borbulevych et obtained an experimental charge density of the Meisen-heimer complex of potassium 3-methyl-5, 7 -dinitro-5, 8 -dihydrospiro(l,3-oxazo-lidine-2,8 -quinolmide) and compared it to computed densities. The influence of the cation on the electronic structure of the anion in the crystalline phase is the most probable cause for the differences detected between the two charge densities. To better understand this effect, ab initio calculations of different anion-K+ systems were performed and an AIM analysis was carried out. 

Electronic structure calculations have been carried out on organobismuth species [C4H4Bi-, C4H4Bi, C4H4BiH and (C4H4Bi)2] using effective core potentials and relativistically parametrized semi-empiral M.O. methods. Calculations (at the PM3 SCF level) have also been made on the molecular and electronic structures of neutral, cationic and anionic methyl-arsines, -stibines and -bismuthines. ... 

Methyl methacrylate, the monomer used in super glue, polymerizes by an anionic mechanism. Its structure is typical of such monomers and consists of two electron-withdrawing groups that facilitate reactions with relatively weak nucleophiles such as the —OH groups found in cellulose through the formation of a strong polymer... 

Draw Lewis structures for methyl anion, ammonia and hydronium cation. How many electrons are left over in each after all bonds have been made Display and compare electron density surfaces for methyl anion, ammonia and hydronium cation. Which is the smallest molecule Which is the largest Rationalize your observation. (Hint Compare the number of electrons in each molecule, and the nuclear charge on the central atom in each molecule.)... 

There have been no reports of complexes of " JV-substituted thiosemicarbazones derived from 2-formylpyridine, but 2-acetylpyridine JV-methyl-thiosemicarbazone, 3a, formed [Fe(3a-H)2]C104 and [Fe(3a-H)2]FeCl4 [117]. The nature of these two species was established by partial elemental analyses, molar conductivities, magnetic moments, electronic, infrared, mass and electron spin resonance spectra. A crystal structure of a related selenosemicarbazone complex confirmed the presence of a distorted octahedral iron(III) cation coordinated by two deprotonated anions so that each ligand is essentially planar and the azomethine nitrogens are trans to each other the pyridyl nitrogen and selenium donors are both cis. 

N-Alkylhydroxamic acid hydrolysis Methyl Violet + OH" Cl C12H25S03Na + H30+, CTABr + OH". An attempt made to separate electronic and hydrophobic effects on the micellar reaction Anionic and cationic micelles. Effect of surfactant structure examined Berndt el at., 1984 Malaviya and Katiyar, 1984... 

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