Atomic similarities

Consideration of stereochem-iitry. The parity or handedness - R/S or chjirans - of a stcreoccnter can be obtained by considering the sequence of the Morgan numbers of die atoms, similarly to CIP. Then the number of pairwise interclianges is counted until the numbers arc in ascending order (see Section 2,8,5). 

While neat-resonant light exerts both scattering forces and dipole forces on single atoms, similar forces ate also exerted on larger dielectric objects. 

The reaction of benzyl radicals wdth several heterocyclic compounds W as more extensively studied by Waters and Watson, " - who generated benzyl radicals by decomposing di-tert-butyl peroxide in boiling toluene. The products of the reaction with acridine, 5-phenyl-acridine, 1 2- and 3 4-benzacridine, and phenazine were studied. Acridine gives a mixture of 9-benzylacridine (17%) (28) and 5,10-dibenzylacridan (18%) (29) but ho biacridan, w hereas anthracene gives a mixture of 9,10-dibenzyl-9,10-dihydroanthracene and 9,9 -dibenzyl-9,9, 10,10 -tetrahydrobianthryl. This indicates that initial addition must occur at the meso-carbon and not at the nitrogen atom. (Similar conclusions were reached on the basis of methylations discussed in Section III,C.) That this is the position of attack is further supported by the fact that the reaction of benzyl radicals with 5-... 

Alpha hydrogen atoms of carbonyl compounds are weakly acidic and can be removed by strong bases, such as lithium diisopropylamide (LDA), to yield nucleophilic enolate ions. The most important reaction of enolate ions is their Sn2 alkylation with alkyl halides. The malonic ester synthesis converts an alkyl halide into a carboxylic acid with the addition of two carbon atoms. Similarly, the acetoacetic ester synthesis converts an alkyl halide into a methyl ketone. In addition, many carbonyl compounds, including ketones, esters, and nitriles, can be directly alkylated by treatment with LDA and an alkyl halide. 

In many metals each atom is attached to some of its neighbors by strong bonds and to others by much weaker bonds. An extreme case is, 8-tungsten, in which there are straight strings of strongly bonded atoms. Similar strings are also present in the a-uranium structure. 

It contains a Hg atom bridging two Co atoms. Similarly, [Tj -Cp(CO)3MoMoHg]4 forms by reduction of [Mo(CO)3Cp-Tj ]2 by Na/Hg in the presence of 2-chlorobutene and THF. The central metal atoms are arranged in a cubane structure... 

From all of the cases above (oxygen, nitrogen, carbon), you can see why you have to know how many lone pairs there are on an atom in order to figure out the formal charge on that atom. Similarly, you have to know the formal charge to figure out how many lone pairs there are on an atom. Take the case below with the nitrogen atom shown ... 

Each line in a structural formula represents one pair of shared electrons, but atoms can share more than one pair of electrons. When two atoms share one pair of electrons, the bond is called a single bond, and the structural formula shows a single line. When two atoms share four electrons, the bond is called a double bond, and the structural formula shows two lines between the atoms. Similarly, when two atoms share six electrons, the bond is called a triple bond, and the stmctural formula shows three lines between the atoms. Two carbon atoms can bond to each other through any of these three kinds of bonds, as the compounds in Figure illustrate. 

O-atoms. Similar situation has also been shown for adsorption of nitrogen atoms [38]. In this case the equation (3.11) holds over wider time interval and for higher volume concentrations of active particles. 

Allowing for the fact that the secondary electron current is in proportion to the concentration of metastable atoms in gaseous phase [62], one may infer that the Au/ZnO structures are highly sensitive proportional sensors of helium metastable atoms. Similar results were obtained for other rare gases. 

The chlorine atom of 43 may be displaced readily by carbon-based nucleophiles with predominant overall retention of configuration at the phosphorus atom, similar to that observed in pentacoordinated analogues [37, 38], In some reactions, unselective substitution was observed [39], This approach was successfully applied for the... 

Hampden-Smith and co-workers have prepared [Zn(SEt)Et]10 (Figure 30) by the insertion of sulfur into the Zn—C bond of diethylzinc. 7 Although this decameric thiolate possesses an arrangement of zinc and sulfur atoms similar to that found in wurtzite, pyrolysis of the material at 250 °C led to predominantly cubic ZnS. Cubic ZnS was also formed when the precursor is used in a spray CVD process. 

The chemical properties of trichalcogen dications are, in many ways, analogous to the properties of dichalcogen dications, but are considerably less studied. Hydrolysis of chalcogenurane dications occurs preferentially at the onium chalcogen atom. Similar to the usual dichalcogen dications, trichalcogen dications also display oxidative properties. For example, reduction of selenu-rane dication 135 (X = Y = Se) is observed in reactions with Sm(II) salts, triphenylphosphine or thiophenol (Scheme 54).135... 

This compound can be considered as a derivative of the hydrolysis product, [(H20)3Be(0H)Be(H20)3]3+, in which the bidentate 3-methyl-salicylate ligands each replace two water molecules, the other two water molecules being replaced by a carbonate ion bridging between two beryllium atoms. Similar carbonate bridges have been proposed previously (132). 

The Sn-Cl distances in the SnCl2 dumb-bell as opposite to the Sn(P)-Cl tin centers differ by 0.3 A, which has been explained by the higher coordination of the SnCl2 tin atom. Similar complexes between cyclodiazastannanediyls with SnX2 have been reported (53). 

Cioslowski et al. used fragment similarity indices to compute the degree of similarity between atoms of the same element in different molecules, where the atoms were those derived from Bader s atoms in molecules theory [68,69]. They introduced a novel atomic similarity index for atom A in molecule X and atom B in molecule Y defined as [70]... 

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