Ether and Ester Formation

These reactions are in equilibrium at any time. When the carbonylation reaction s rate is low, side reactions, e.g. ether and ester formation, can predominate. On the other hand a high carbonylation rate results in removing the available methanol from the reaction mixture and sub-... 

Oxidation of Monosaccharides Reducing Sugars 1117 23-11 Nonreducing Sugars Formation of Glycosides 1119 23-12 Ether and Ester Formation 1121... 

Halogenation and nitration of arenes, substitution reactions ofaliphatics Ether and ester formation, thiols from alcohols and H2S, amines from alcohols and NHj (mordenite, erionite)... 

Trifluoromethanesulfonic acid is miscible in all proportions with water and is soluble in many polar organic solvents such as dimethylformamide, dimethyl sulfoxide, and acetonitrile. In addition, it is soluble in alcohols, ketones, ethers, and esters, but these generally are not suitably inert solvents. The acid reacts with ethyl ether to give a colorless, Hquid oxonium complex, which on further heating gives the ethyl ester and ethylene. Reaction with ethanol gives the ester, but in addition dehydration and ether formation occurs. 

Synthesis of Silicone Monomers and Intermediates. Another important reaction for the formation of Si—C bonds, in addition to the direct process and the Grignard reaction, is hydrosdylation (eq. 3), which is used for the formation of monomers for producing a wide range of organomodified sihcones and for cross-linking sihcone polymers (8,52—58). Formation of ether and ester bonds at sihcon is important for the manufacture of curable sihcone materials. Alcoholysis of the Si—Cl bond (eq. 4) is a method for forming silyl ethers. HCl removal is typically accomphshed by the addition of tertiary amines or by using NaOR in place of R OH to form NaCl. 

TABLE 5. Enthalpies of formation for oxime ethers and esters (kJmol... 

In contrast, oxime ethers and esters are usually stable in solution but the E/Z isomerization can be induced by acids " or by irradiation ". Recently, Narasaka and colleagues"" "" studied the equilibration-isomerization of (E)-O-acyl oximes 239 in the presence of an acid in a nucleophilic solvent (equation 71). Isomerization probably proceeds via protonation of the oxime nitrogen followed by addition-elimination of a nucleophilic solvent until the equilibrium of E and Z isomers is achieved. The isomerization of the more labile 0-acyloximes occurs either by an Sjv2 substitution at the oxime nitrogen with acids and/or by acyl exchange through the formation of a mixed anhydride and the free oxime. 

Figure 4.50 Formation of ether and ester glucuronides of phenol and benzoic acid, respectively.

Williams83 has recently considered the possibility of ion molecule reactions in alcohols, ketones, ethers, and esters. He postulates that the primary reactions of the parent ion are the inter- or intra-molecular abstraction of a hydrogen atom and the formation of a x-bond between oxygen and the adjacent carbon atom after homolytic scission of a bond to that adjacent carbon atom. After examining some of the liquid phase data on the radiolysis of these oxygen compounds it was concluded that such ion molecule reactions may be of importance in these systems also. 

Alkyl and acyl hypohalites, when adding to carbon-carbon double bond, afford halohydrin ethers and esters, respectively.151 Regioselective and syn stereoselective addition of CF3OF, CF3CF2OF, and CF3COOF to stilbenes was reported.152-154 The stereochemistry was explained to originate from the formation and immediate... 

Formation of cellulose ethers and esters has shown that for every six carbon atoms contained in one C6H,0O5 group there are three free hydroxyl groups capable of undergoing esterification or forming ethers. It has also been established that the copper salts of Fehling s solution are reduced by cellulose only to a small extent. Those facts, supported by a series of studies devoted to the products of uncomplete hydrolysis of cellulose, for instance the isolation of cellotriose (Haworth, Hirst and H. A. Thomas [16]), provide suffident evidence that a molecule of cellulose... 

The intramolecular hydrogen abstraction has been largely developed for the case of the nitro group [22,37], and is well known for some derivatives of o-nitrotoluene, for o-nitrobenzyl alcohols, ethers and esters [38-40] as well as on the acetals of o-nitrobenzaldehyde [41], With these compounds, the nn (singlet or triplet) state abstracts a hydrogen and the biradical relaxes to the aci-nitro form (the first intermediate is actually observed in bicyclic systems where formation of the nitronic acid is sterically hindered) [41], which under basic conditions dissociates to the corresponding anion [42],... 

Macroscopic solvent effects can be described by the dielectric constant of a medium, whereas the effects of polarization, induced dipoles, and specific solvation are examples of microscopic solvent effects. Carbenium ions are very strong electrophiles that interact reversibly with several components of the reaction mixture in addition to undergoing initiation, propagation, transfer, and termination. These interactions may be relatively weak as in dispersive interactions, which last less than it takes for a bond vibration (<10 14 sec), and are thus considered to involve "sticky collisions. Stronger interactions lead to long-lived intermediates and/or complex formation, often with a change of hybridization. For example, onium ions are formed with -donors. Even stable trityl ions react very rapidly with amines to form ammonium ions [41], and with water, alcohol, ethers, and esters to form oxonium ions. Onium ion formation is reversible, with the equilibrium constant depending on the nucleophile, cation, solvent, and temperature (cf., Section IV.C.3). 

In the reaction of / -hydroxycarboxylic acids 20 and 21 with sulfur tetrafluoride, the formation of alkenes by elimination of hydrogen fluoride and of fluorinated ethers and esters by inter-molecular reaction is observed." Overall yields are low because of extensive resinification. 

Addition Reactions with Formation of Carbon-Halogen Bonds Table 1 Halogenation of Enol Ethers and Esters with Metallic Reagents... 

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