Ethers, 738 table

Aliphatic Halogen Compounds, Table III, 42 Aromatic Halogen Compounds, Table IV, 28. Aliphatic Ethers, Table III, 60. 

Polyether Polyols. Polyether polyols are addition products derived from cyclic ethers (Table 4). The alkylene oxide polymerisation is usually initiated by alkah hydroxides, especially potassium hydroxide. In the base-catalysed polymerisation of propylene oxide, some rearrangement occurs to give aHyl alcohol. Further reaction of aHyl alcohol with propylene oxide produces a monofunctional alcohol. Therefore, polyether polyols derived from propylene oxide are not truly diftmctional. By using sine hexacyano cobaltate as catalyst, a more diftmctional polyol is obtained (20). Olin has introduced the diftmctional polyether polyols under the trade name POLY-L. Trichlorobutylene oxide-derived polyether polyols are useful as reactive fire retardants. Poly(tetramethylene glycol) (PTMG) is produced in the acid-catalysed homopolymerisation of tetrahydrofuran. Copolymers derived from tetrahydrofuran and ethylene oxide are also produced. 

Simple alkyl radicals such as methyl are considered to be nonnucleophilic. Methyl radicals are somewhat more reactive toward alkenes bearing electron-withdrawing substituents than towards those with electron-releasing substituents. However, much of this effect can be attributed to the stabilizing effect that these substiments have on the product radical. There is a strong correlation of reaction rate with the overall exothermicity of the reaction. Hydroxymethyl and 2-hydroxy-2-propyl radicals show nucleophilic character. The hydroxymethyl radical shows a slightly enhanced reactivity toward acrylonitrile and acrolein, but a sharply decreased reactivity toward ethyl vinyl ether. Table 12.9 gives some of the reactivity data. 

Several experiments were repeated starting from the corresponding dimethyl or ethylidene ketals as well as the corresponding enol ethers (Table 11, entries 2,... 

The reaction enthalpy is known as a very important factor that determines the reactivity of reactants in free radical abstraction reactions [71]. The IPM method helps to calculate the increment of AEfi that enthalpy determines in the activation energy of the individual reaction. This increment can be estimated within the scope of IPM through the comparison of activation energy Ee of the chosen reaction and activation energy of the thermoneutral reaction Ee0 (see Equation [6.18] in Chapter 6). This increment was calculated for several reactions of different peroxyl radicals with ethers (Table 7.19). 

If the reaction rates of a specific carbene with various quenchers are studied in the same solvent, and with small concentrations of Q, K will be constant. Relative reactivities for the singlet state of a spin-equilibrated carbene can thus be derived. However, few researchers have varied the acidity of ROH, estimated kinetic isotope effects, and compared alcohols with ethers (Table 4). The data indicate proton transfer to diarylcarbenes (139d, 139k, 205, 206)112-117 and diadamantylcarbene (207).118... 

A number of publications purport to give values for the absolute propagation rate constant kp for the polymerization of isobutyl vinyl ether (Table 2). The values of Okamura et ah, are derived by techniques and arguments which are of doubtful validity [54a] and they seem much too small. Eley s value, derived from an analysis of non-stationary kinetics, is four orders of magnitude smaller than the kp deduced from studies of radiation... 

Whereas deprotonation and halogen-lithium exchange represent the most common methods to access allenic and propargylic lithium intermediates, several less direct routes to more functionalized analogues have also been reported. Additions of various lithium acetylides to acylsilanes followed by Mel or EtI afforded alkylated allenyl silyl ethers (Table 9.4) [10]. The adducts were analyzed after hydrolysis to the related enones. 

Allenylsilanes react with acetals to afford homopropargylic ethers (Table 9.37) [61]. These reactions are promoted by silyl and carbocation species. A variation of this conversion involves in situ formation of the acetal from an aldehyde and Me3SiOMe (Eq. 9.55). The success of this method indicates that conversion of the aldehyde to the acetal and its subsequent reaction with the silane must be faster than direct reaction of the aldehyde with the silane. 

Martin, Castro and Martin 22> found increases in for two chloromethyl ethers (Table 4) which are in agreement with the Watts and Goldstein data. Cox and Smith 23> examined 1/13c H, 1/13c 19p and 2/H F in difluoro-and trifluoro-methane (Table 5). The results for the I3C-H coupling are in accord with those... 

Example The El mass spectra of 1-hexanol, Mj = 102, and 1-hexene, Mr = 84, show close similarity because the molecular ion peak is absent in the mass spectrum of hexanol (Fig. 6.40). However, a more careful examination of the hexanol spectrum reveals peaks at m/z 18, 19, 31, and 45 that are absent in the hexene spectrum. These are due to H20, HsO and to oxonium ions (H2C=OH and H3CCH=0H in this case) which are reliable indicators of aliphatic alcohols and ethers (Table 6.8). 

The procedure is very easy to reproduce and to scale up. Bioconversion products can be easily isolated by evaporation of the extraction solvent (e.g. tert-butyl methyl ether). Table 12.4 summarizes the product concentrations, molecular conversion yields and enantioselectivities obtained during linalool biotransformation with C. cassiicola DSM 62475. 

Phenols show a two-electron oxidation wave on cyclic voltammetry in acetonitrile at a less positive potential than for the con-esponding methyl ether (Table 6.5) or a related hydrocarbon. Phenol radical-cation is a strong acid with pKg ca. -5 in water [93], so the two-electron oxidation wave for phenols is due to formation of a phenoxonium ion such as 13, where the complete oxidation process is illustrated for 2,4,6-tri-tt rf-butylphenol. Phenoxide ions are oxidised at considerably less positive potentials than the conesponding phenol. They give rise to a one-electron wave on cyclic voltammetry in aqueous acetonitrile or in aqueous ethanol containing potassium hydroxide. 2,4,6-Tri-/ert-butyiphenoxide ion is reversibly oxidised to the radical in a one-electron proces.s with E° = -0.09 V V5. see. The radical undergoes a further irreversible one-electron oxidation with Ep = 1.05 V vs. see on cyclic voltammetry forming the phenoxonium ion which reacts with water [94J. 

Whenever possible, alkyllithiums should be prepared from chloroalkanes in paraffinic media for reasons of economy. As a 1930 landmark study has revealed, both bromoalkanes and iodoalkanes react rapidly with butyllithium in benzene and extremely rapidly in diethyl ether (Table 7) producing butane, 1-butene, 2-butene, octane and possibly also methylcyclopropane. 

UV Absorptions of (32 R = H) in ether (Table 5) <85ZAAC(525)ll2> bear little resemblance to UV spectra of amino analogues (32 R = NHj, NMej, NHC02Et) either in acid or in basic solutions. Absorption bands for the dithiazole cation (31 R = R = NMcj) <87BCJ2686> are markedly shifted relative to bands of the unsubstituted diamino cation in ethanol (31 R = R = NH2) <84CHEC-I(6)897>. UV spectral comparison of (34 X = O, R = N=CHPh, R = Ph) with the other two derivatives (34 X = O) in Table 5 was used in structural assignment <91JHC1957>. 

SCHEME 12. Synthesis of hydroperoxides from silyl enol ethers TABLE 3. Preparation of alkyl hydroperoxides via singlet oxygen oxygenation... 

Silyl alkyl and silyl aryl peroxides 7 are prepared by reaction of alkyl, aryl or aralkyl hydroperoxides with halosilanes (equation 12). Such reactions are carried out in an inert solvent in the presence of an acid acceptor, such as pyridine, ammonia or a tertiary amine in ether or petroleum ether (Table 3) . ... 

Plenio and Diodone have also reported fluorocrown ethers (Table 5), which exhibit chemical shift response upon binding Ca + [314]. Of course, calcium could potentially be analyzed directly by " Ca NMR, however, its natural abundance is <0.2%, its sensitivity is <1% that of H, and being quadrupolar, it is liable to extensive line broadening [59]. Thus, the application of F NMR with appropriately designed reporter molecules gives insight into cytosolic [Ca +]. 

Asymmetric ring opening of achiral monocyclic, bicyclic and tricyclic anhydrides under formation of the corresponding chiral monoesters can be accomplished in high yield with modest enantioselectivity with methanol in the presence of less than stoichiometric amounts of cinchona alkaloids in toluene or diethyl ether (Table 9)91 94. As expected the use of cinchonine A or quinidine C, and of cinchonidine B or quinine D gives opposite enantiomers. Recrystallization of the monoesters and lactones affords material of considerably higher enantiomeric purity (Table 9, entries 15, 16, 21, and 23). 

The following findings point to the harmful effect of air on the stability of green nitrocellulose powder, i.e. freshly pressed and containing a considerable quantity of solvent (alcohol and ether) (Table 171). 

Uranium(VI) fluoride can react35 as a Lewis acid or an oxidizing agent with alcohols. In the vapor phase at 80 °C (note that this is considerably lower than the temperatures used in the examples given vide supra) it behaves as a Lewis acid and gives35 mixtures of the corresponding fluorides, alkenes and ethers (Table 1). 

Near a critical temperature, however, solubility often decreases with rising temperature, so that there may actually be no CST at all—for example, see the systems of aniline with methane, ethane, or propane (Table I). One phase reaches its critical temperature below the CST. A few such critical temperatures of the upper layer are listed—e.g., for carbon dioxide, ethane, and ethyl ether (Table I). 

BUTYL CELLOSOLVE (ETHYLENE GLYCOL MONOBUTYL ETHER, Table VIII)... 

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