Delocalized tt bonding

Does the delocalized tt system of 1,3-pen tadiene stabilize the molecule relative to 1,4-pentadiene Each molecule reacts with two molecules of H2 to give a common product, pentane. Thus, a comparison of their energies of hydrogenation allows us to determine the relative stabilities of two delocalized tt bonds compared with two isolated tt bonds. The hydrogenation of 1,4-pentadiene releases 252 kJ/mol, but the hydrogenation of... 

The results are consistent with a [1.7] sigmatropic COCH3 rearrangement it is [1,7] and not [1.3] because the delocalized tt bonds in X -phosphorin must be taken into account. 

What is delocalized tt bonding and what does it explain Explain the delocalized TT bonding system in CgHg (benzene) and O3 (ozone). 

Localized electron model The central oxygen atom is sp hybridized, which is used to form the two cr bonds and hold the lone pair of electrons. An unchanged (unhybridized) p atomic orbital forms the tt bond with the neighboring oxygen atoms. The actual structure of O3 is an average of the two resonance structures. Molecular orbital model There are two localized cr bonds and a tt bond that is delocalized over the entire surface of the molecule. The delocalized TT bond results from overlap of a p atomic oribtal on each oxygen atom in O3. 59. 

Describe the bonding in the nitrate ion, NO3. Does this ion have delocalized tt bonds ... 

Analyze Given the chemical formula for a polyatomic anion, we arc asked to describe the bonding and determine whether the ion has delocalized tt bonds. 

Be able to explain the existence of delocalized tt bonds in molecules such as benzene. (Section 9.6)... 

FIGURE 24.10 Line formulas and common names of several aromatic compounds. The aromatic rings are represented by hexagons with a circle inscribed inside to denote delocalized tt bonds. Each corner represents a carbon atom. Each carbon is bound to three other atoms—either three carbons or two carbons and a hydrogen—so that each carbon has the requisite four bonds. 

In each structure, the electron-domain geometry at nitrogen is trigonal planar, which implies sp hybridization of the N atom. It is helpful when considering delocalized tt bonding to consider atoms with lone pairs that are bonded to the central atom to be sj hybridized as well. Thus, we can envision that each of the O atoms in the anion has three sj hybrid orbitals in the plane of the ion. Each of the four atoms has an unhybridized orbital oriented perpendicular to the plane of the ion. 

Alkanes contain only single C — C bonds. Alkenes, also known as olefins, contain at least one C = C double bond, and alkynes contain at least one C = C triple bond. In aromatic hydrocarbons the carbon atoms are connected in a planar ring structure, joined by both cr and delocalized tt bonds between carbon atoms, aao (Section 8.6) Benzene (C5H5) is the best-known example of an aromatic hydrocarbon. 

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