Bond , 16-25 with carbon double

Similar prediction can be made for larger molecules. It must be pointed out that the contributions of excited structures become important for bonds with small double bond character, inasmuch as in conjugated systems excited structures alone may lead to as much as 20% double bond character it is probable that the maximum carbon-carbon bond distance in aromatic hydrocarbons is about 1.46 A., the minimum being the double bond distance 1.38 A. 

Reactions of Titanium Carbene Complexes with Carbon -Double Bonds 487 -Oxygen... 

For double bond of 2P1-orbital the carbon atom has PE-parameter - (8.5043 eV) - similar to PE-parameter of hydrogen atom (table 1). Therefore one of the freed hydrogen atoms join the double bond C=C available in NADPN with the formation of single bond with carbon atom [9],... 

In the case of the formaldehyde molecule, you have to create a double bond between carbon and one of the outer atoms. Oxygen is the only choice for a double-bond partner, because each hydrogen can accommodate only two electrons in its shell. So use two of the electrons assigned to oxygen to create a second bond with carbon. 

Whereas carbon is able to form stable (p-p) double and triple bonds with carbon itself, nitrogen and oxygen, leading to coordination numbers 2 and 3 at the carbon atom, silicon cannot build up such bonds (compare Table 2). Although the existence of monomeric species such as SiO and SiNH has been established under specific conditions, and (p-p)ff bonded intermediates have been postulated in a number of... 

Citric acid (CgHsOj) contains seven oxygen atoms, each of which has two electron lone pairs. Three of the oxygens form double bonds with carbon. 

The formal double bond in carbene complexes may be compared with the double bond in alkenes. In the case of a carbene complex, the metal must use a d orbital (rather than a p orbital) to form the tt bond with carbon, as illustrated in Figure 13-40. 

ALIPHATIC Open chains, straight or branched, of carbon atoms bonded with single, double or triple bounds or combinations of them. 

The simplified SNC 80 structure 17 was further modified by replacement of the N-l of the piperazine with carbon double bond, leading to a new series of diarylalk-enylpiperidines [49]. These new compounds were evaluated for their affinity for all three human opioid receptors and their agonist activity was determined using the... 

To picture what polymers are, it is helpful to start with small synthetic polymers. You use such polymers every day. Plastics, synthetic fabrics, and nonstick surfaces on cookware are polymers. The unsaturated hydrocarbon ethylene, C2H4, is the monomer of a common polymer used often in plastic bags. The monomers are bonded together in a chemical reaction called polymerization (puh lih muh ruh ZAY shun). As you can see in Figure 15, the double bond breaks in each ethylene molecule. The two carbon atoms then form new bonds with carbon atoms in other ethylene molecules. This process is repeated many times and results in a much larger molecule called polyethylene. A polyethylene molecule can contain 10,000 ethylene units. 

It is commercially available and is used as starting material for the chemical vapor deposition of tungsten (see Sections 5.6.3. and 5.7.5) and for the preparation of metathesis catalysts which form double and triple bonds with carbon (see Chapter 10). 

An alkoxy or glycoxy anion is more easily eliminated by the ionized enediol than is a hydroxyl ion, and the pyranose rings of the released glycoxy anions will open readily because of the tendency of negatively charged oxygen to form a double bond with carbon. 

Congugated double bonds with carbon, nitrogen, and oxygen atoms... 

In addition to activated olefins, other double-bond substrates, such as carbonyl and thiocarbonyl compounds and azomethines have been used ( ). Likewise, heterocumulenes, such as carbon disulfide, isocyanates, isothiocyanates, carbodiimides, and N-sulfinylamines have been added to nitrile imides ( ). While usually reaction occurs across one of the cumulative double bonds, with carbon disulfide only the bis-adduct LVIII could be isolated ( ). 

Similar behavior is also observed with carbon double bonds ... 

Arylaminopyrylium salts are readily converted into 2-pyridones, whereas the corresponding thiopyrylium salts give thiopyranimines only (20). This is another example showing the reluctance of divalent sulfur to form a double bond with carbon. 

The structure of the benzene molecule was determined by the electron diffraction method in 1929 and the following years. It is a planar hexagon with carbon-carbon bond length 140 pm (C—H bond length 106 pm). This value for a bond with 50% double-bond character is reasonable in comparison with the values 154 pm for C—C, 133 pm for C=C, and 142 pm for 33j% double-bond character (graphite). The planar configuration is required by the properties of the double bond (Section 6-5). 

Furthermore, the next element after nitrogen capable of being inserted in such structure is that of oxygen, while contributing by its double bond with carbon to fixing the carbon chain form. 

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