Single bonds carbon-oxygen

Arguably the most challenging aspect for the preparation of 1 was construction of the unsymmetrically substituted sec-sec chiral bis(trifluoromethyl)benzylic ether functionality with careful control of the relative and absolute stereochemistry [21], The original chemistry route to ether intermediate 18 involved an unselective etherification of chiral alcohol 10 with racemic imidate 17 and separation of a nearly 1 1 mixture of diastereomers, as shown in Scheme 7.3. Carbon-oxygen single bond forming reactions leading directly to chiral acyclic sec-sec ethers are particularly rare since known reactions are typically nonstereospecific. While notable exceptions have surfaced [22], each method provides ethers with particular substitution patterns which are not broadly applicable. 

The formation of carbon-oxygen single bonds via the attack of an alkoxide on an alkyl halide, (Williamson ether synthesis) is an extremely important reaction that... 

However, we must recognize that the large driving force for this reaction comes from two sources (1) the formation of the carbon-oxygen single bond—Reaction 1—which is exothermic by about 28 kcal. This initially... 

Similar constancy is shown by other covalent bond distances (with certain exceptions that will be discussed later). For the carbon— oxygen single bond, for example, the value 1.43 A has been reported for methanol,4 ethanol, ethylene glycol, dimethyl ether, paraldehyde, metaldehyde, and many other molecules this value is accepted as standard for the C—O bond. 

The 1,2-migration of a silicon moiety to the oxygen anion of a carbon-oxygen single bond produced by nucleophilic addition to a carbonyl group (Brook... 

Unsymmetrical alkyl phenyl tellurium derivatives were prepared in good yields from phenyl trimethylsilyl tellurium and epoxides, carboxylic acid esters, and linear or cyclic ethers under very mild conditions. In these reactions, which proceed in dichloromethane in the presence of a catalytic amount of zinc iodide, a carbon-oxygen single bond is cleaved. The highly nucleophilic benzenetellurolate binds to the carbon fragment, whereas the trimethylsilyl group becomes linked to the oxygen. 

AH = -83 kj The carbon-oxygen double bond is stronger than two carbon-oxygen single bonds hence C02 and H20 are more stable than H2C03. 63. Three resonance structures can be drawn... 

Actual measurement shows that all the carbon-oxygen bonds in CaC03 have the same length, 1.31 A, as compared with a usual length of about 1.36 A for a carbon-oxygen single bond and about 1,23 A for a carbon-oxygen double bond. What is a better representation of the CO3" ion ... 

In the ketone there is a carbon/oxygen double bond, three C-H bonds from an sp carbon and one carbon/carbon single bond. In the enol tautomer, in contrast, there are two C-H bonds from an sp2 carbon, a carbon/carbon double bond, a carbon/oxygen single bond and an O-H bond. This may be simplified by assuming that a C-H bond from an sp carbon is about as stable as a C-H bond from an sp carbon. Now one is looking at the difference between one carbon/oxygen double bond plus one C C bond and plus one C-H bond for the ketone, and one carbon/carbon double bond plus one C-0 bond and plus one O-H bond for the enol tautomer. 

At 122 pm, the carbon-oxygen double bond distance in aldehydes and ketones is significantly shorter than the typical carbon-oxygen single bond distance of 141 pm in alcohols and ethers. 

Notice that this reaction is another example of a hydrogenation reaction. As the hydrogens are added to the carbon-oxygen double bond, it is converted to a carbon-oxygen single bond, as the carbonyl oxygen becomes a hydroxyl group. 

The bond energy of the carbon-oxygen double bond is more than twice that of the carbon-oxygen single bond, while the energy of the carbon-carbon double bond is less than twice that of the carbon-carbon single bond. 

Which is longer, the carbon-oxygen single bond in a carboxylic acid or the carbon-oxygen bond in an alcohol Why ... 

The sharp absorption at approximately 1070 should be indicative of the carbon-oxygen single bond stretch. The weak doublet at 3400 would be indicative of a double bond. The medium peak at 830 could be indicative of a parasub-stituted benzene the presence of benzene is indicated by the weak finger-like absorptions between 1700 and 2000 cm . The absence of a sharp absorption at 1700 cm would be indicative of the absence of a carbonyl group, while the absorption at approximately 1380 would indicate the presence of a methyl, isopropyl, ethyl or t-butyl... 

Tables 3.15 and 3.16 list the R—OOX, RO—OX and ROO—X (X = CH3 or H) bond energies for the different peroxides. The CdOO—C energies for all species listed in Table 3.15, are lower than the corresponding CdOO—bond strengths by ca. 17 kcal mof This is consistent with data for alcohols where carbon - oxygen single bonds are typically -13.5 kcal mof lower than hydrogen-oxygen bonds. The bond energy in CdO—OC is about 5 kcal mof weaker than the bond in CdO—OH, for all peroxides reported in Table 3.15.

Osmium-mediated hydroxylation of carbon-carbon double bonds has been known about for many years. However, using OSO4, two alternative mechanisms which lead to the first stable product — an osmium complex with two carbon-oxygen single bonds — are still under scrutiny. As shown in Scheme 45, in one possible mechanism a concerted cycloaddition forms the two new bonds simultaneously, while in another the two new bonds are formed... 

As before, R indicates that the two R groups can be the same or different. The process of ester formation is called esterification, and the carbonyl carbon-oxygen single bond of the ester group is called the ester linkage ... 

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