Resonance structure electronegative

Chapter 10, Properties of Solids and Liquids, introduces electron-dot formulas for molecules and ions with single and multiple bonds as well as resonance structures. Electronegativity leads to a discussion of the polarity of bonds and molecules. Electron-dot formulas and VSEPR theory illustrate covalent bonding and the three-dimensional shapes of molecules and ions. The attractive forces between particles and their impact on states of matter and changes of state are described. Combining Ideas from Chapters 8, 9, and 10 follows as an interchapter problem set. 

The structure of the conjugate base is more like resonance structure B than A because the nega tive charge is on the more electronegative atom (O versus S)... 

Aldiough diese structures have a positive charge on a more electronegative atom, diey benefit from an additional bond which satisfies file octet requirement of the tricoordinate carbon. These carbocations are well represented by file doubly bonded resonance structures. One indication of file participation of adjacent oxygen substituents is file existence of a barrier to rotation about the C—O bonds in this type of carbocation. 

Both compounds have a pi bond between a carbon atom and an electronegative atom (C=0), and both compounds have a lone pair next to the pi bond. So we would expect their resonance structures to be similar, and we would expect these compounds to have the same number of significant resonance structures. But they do not. Let s see why. Let s start by drawing the resonance structures of the first compound ... 

When a resonance structure has a positive charge on an electronegative atom, that resonance structure wiU only be significant if the electronegative atom has an octet. If it does not have an octet, the resonance structure will not be significant. For example, consider the following ... 

Multiple bonds between atoms with different electronegativities such as the C=0 and S=0 bonds, are also necessarily polar. This polarity is frequently represented by resonance structures such as... 

Structures such as these imply that the bonds are polar, which is consistent with ligands that are more electronegative than the central atom, as is often the case. When resonance structures are written in this way, it is assumed that the bond lines represent fully covalent... 

An extension of the above method was developed for conjugated it-systems Partial Equalization of Pi-Electronegativity (PEPE)47,48). After calculation of the charge distribution in the a-skeleton, the various resonance structures of a it-system are generated. The 7t-charge distribution is obtained by assigning weights to these... 

And what about an alternative product There are two lines of thought, and the most obvious is that the reaction is repeated, since we are using a dibromide as substrate. Alternatively, we could consider one of the other resonance forms of the phenolate anion as nucleophile. This would generate a C-alkylated phenol. In the majority of cases, C-alkylation is not observed, in that the preferred resonance structure has charge on the electronegative oxygen. 

Idle exponent, m, in the electrostatic attraction term, was taken as unity This value of m is in agreement with, resonance structure II where the two electronegative atoms carry partial charges. The two remaining parameters A and b can be evaluated using Eq. (24) which defines A in terms of b and i 0. The hydrogen bond potential function... 

As another example, the resonance structure for N2O that places the formal negative charge on the more electronegative oxygen atom rather than on the less electronegative nitrogen atom is probably a more accurate representation of the molecule. 

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