C, bonding structure

Fig. 9.11 Spatially extended soliton (f = 7) on a polyacetylene chain centred on the 30th carbon atom, (a) variation in bond alternation parameter, (b) the electronic wavefunction and (c) bonding structure.

Number of C atoms Number of C=C bonds Structure Name Mp ro... 

Recently, Lewis et al. (18) measured the infrared spectra of a number of acetylacetonato complexes of Pt(II) and have shown that the 0-bonded (chelated) and C-bonded structures can be distinguished easily from their infrared and NMR spectra. We 24) have carried out normal coordinate analyses on both types of structures and have obtained the results shown in Table III. As is seen in this table, these two types of coordination exhibit very different spectra. 

A number of structure-sensitive reactions take place in the catalytic converter which, as expected, will be influenced by the noble metal dispersion. These include first of all the very important oxidation of saturated hydrocarbons. It is an accepted view that whenever the surface reaction involves the scission of a C-C bond structure-sensitivity is to be expected. There is ample evidence that oxidation of saturated hydrocarbons, especially those of short chain length, does not proceed readily on Pt catalysts with very high dispersion. 

The presence of two peaks in CV curves for DHB is a result of using 4-aminocatechol as a precursor, as it has two different ways of bonding with the carbon cloth, either through a C-C bond (Structure 1) or a C-N bond (Structure 2) (Fig. 28.7). 

In certain crystals, e.g. in quartz, there is chirality in the crystal structure. Molecular chirality is possible in compounds which have no chiral carbon atoms and yet possess non-superimposable mirror image structures. Restricted rotation about the C=C = C bonds in an allene abC = C = Cba causes chirality and the existence of two optically active forms (i)... 

As an example, let s analyse the synthesis of y-lactones (e.g. TM 334) and see how we may choose one of a number of strategies depending on the structure of the target molecule. We ll consider in turn each of the three C-C bond disconnections. The one with the most appeal is probably b complete the analysis for this approach. 

The first step of the reaction involves the formation of the S-C bond with the elimination of a molecule of ammonium salt. The fact that it has been possible to isolate the acyclic intermediate (176), R = Me or Ph, would confirm this hypothesis, particularly when the reaction is carried out for a short time in the cold in ethereal solution (27, 82). These intermediates (176) can be cyclized quantitatively on standing or on being treated by hydrochloric acid. However, no evidence has been advanced concerning their structures. 

With practice writing structural formulas for organic molecules soon becomes rou tine and can be simplified even more For example a chain of carbon atoms can be rep resented by drawing all of the C—C bonds while omitting individual carbons The result mg structural drawings can be simplified still more by stripping away the hydrogens... 

Structure. Ethylene is a planar molecule with a carbon—carbon bond distance of 0.134 nm, which is shorter than the C—C bond length of 0.153 nm found in ethane. The C—H bond distance is 0.110 nm, and the bond angles are [Pg.432]

Structure Bond lengths (A) a b c Bond angles (°) ca ab be CRSE (kJ mol ) Section number/ref. 

The main features of the effect of structure on the site of attack are summarized in Table 3, and can be understood in.terms of a borderline 5n2 (59CRV737) transition state (48) which somewhat resembles an 5n1 transition state in charge distribution because C—O bond breaking runs ahead of Nu—C bond making. 

Natural rubber is composed of polymerized isoprene units. When rubber is under tension, ozone attacks the carbon-carbon double bond, breaking the bond. The broken bond leaves adjacent C = C bonds under additional stress, eventually breaking and placing shll more stress on surrounding C = C bonds. This "domino" effect can be discerned from the structural formulas in Fig. 9-4. The number of cracks and the depth of the cracks in rubber under tension are related to ambient concentrations of ozone. 

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