Diethyl ether structure

Hate 3. All glassware used for the work-up and distillation must be rinsed with a dilute solution of triethylamine in diethyl ether or acetone in order to be sure that traces of acids on the glass walls have been neutralized. Allenic sulfides with the structure C=C=C(SR)-CH- isomerize under the influence of acids to give conjugated dienes, C=C-C(SR)=C. 

Reaction of ethyl iodide with triethylamine [(CH3CH2)3N ] yields a crystalline compound CgH2oNI in high yield This compound is soluble in polar solvents such as water but insoluble in nonpolar ones such as diethyl ether It does not melt below about 200°C Suggest a reasonable structure for this product... 

Typical carbon-oxygen bond distances m ethers are similar to those of alcohols (—142 pm) and are shorter than carbon-carbon bond distances m alkanes (—153 pm) An ether oxygen affects the conformation of a molecule m much the same way that a CH2 unit does The most stable conformation of diethyl ether is the all staggered anti conformation Tetrahydropyran is most stable m the chair conformation—a fact that has an important bearing on the structures of many carbohydrates... 

Lipids differ from the other classes of naturally occurring biomolecules (carbohy drates proteins and nucleic acids) in that they are more soluble m nonpolar to weakly polar solvents (diethyl ether hexane dichloromethane) than they are m water They include a variety of structural types a collection of which is introduced m this chapter... 

Protonation of the anion [SN2] by acetic acid in diethyl ether produces the thermally unstable sulfur diimide S(NH)2. Like all sulfur diimides, the parent compound S(NH)2 can exist as three isomers (Scheme 5.5). Ab initio molecular orbital calculations indicate that the (cis,cis) configuration is somewhat more stable than the (cis,trans) isomer, while the (trans,trans) isomer is expected to possess considerably higher energy. The alternative syn,anti or E,Z nomenclatures may also be used to describe these isomers. The structures of organic derivatives S(NR)2 (R = alkyl, aryl) are discussed in Section 10.4.2. 

What effect does the solvent have on the structure, charges and reactivity of Grignards Compare geometries, atomic charges and electrostatic potential maps of the diethyl ether complex to that of methylmagnesium chloride itself. How does solvent-magnesium bond formation affect the reactivity of the methyl group Explain. 

The K-R reaction has also been useful for structural confirmation of natural products such as tambulin (71), a flavonoid isolated from the seeds of Xanthoxylum acanthopodium In the critical reaction (O-ethoxyphloroacetophenone (72) was allowed to react with anisic anhydride (38b) in the presence of sodium anisate (73) at 170 C to deliver flavone 74 in 65% yield. Flavone 74 was then converted after multiple steps to diethyl ether 75 which corresponded to the diethyl ether of tambulin (71). 

Enantioselectivities were found to change sharply depending upon the reaction conditions including catalyst structure, reaction temperature, solvent, and additives. Some representative examples of such selectivity dependence are listed in Scheme 7.42. The thiol adduct was formed with 79% ee (81% yield) when the reaction was catalyzed by the J ,J -DBFOX/Ph aqua nickel(II) complex at room temperature in dichloromethane. Reactions using either the anhydrous complex or the aqua complex with MS 4 A gave a racemic adduct, however, indicating that the aqua complex should be more favored than the anhydrous complex in thiol conjugate additions. Slow addition of thiophenol to the dichloromethane solution of 3-crotonoyl-2-oxazolidinone was ineffective for enantioselectivity. Enantioselectivity was dramatically lowered and reversed to -17% ee in the reaction at -78 °C. A similar tendency was observed in the reactions in diethyl ether and THF. For example, a satisfactory enantioselectivity (80% ee) was observed in the reaction in THF at room temperature, while the selectivity almost disappeared (7% ee) at 0°C. 

By reaction of an a-halo ester 1 with zinc metal in an inert solvent such as diethyl ether, tetrahydrofuran or dioxane, an organozinc compound 2 is formed (a Grignard reagent-like species). Some of these organozinc compounds are quite stable even a structure elucidation by x-ray analysis is possible in certain cases ... 

The pharmaceutical interest in the tricyclic structure of dibenz[6,/]oxepins with various side chains in position 10(11) stimulated a search for a convenient method for the introduction of functional groups into this position. It has been shown that nucleophilic attack at the carbonyl group in the 10-position of the dibenzoxepin structure renders the system susceptible to water elimination. Formally, the hydroxy group in the enol form is replaced by nucleophiles such as amines or thiols. The Lewis acids boron trifluoride-diethyl ether complex and titanium(IV) chloride have been used as catalysts. 

A 300 ml three-neck flask equipped with condenser, stirrer, dropping funnel, dry nitrogen inlet tube, and containing 5.5 g (0.145 mol) lithium aluminum hydride LAH suspension in 100 ml anhydrous diethyl ether, was placed in an ice bath. Over a period of 25 min 30 ml (0.123 mol) 1 was added dropwise into the stirred suspension. The mixture was stirred for an additional hour at 0 °C, then poured over a mixture of 50 ml ether, 100 g crushed ice, and 50 ml ice water with stirring. When necessary more crushed ice was added to cool the mixture. The layers were separated, and the organic layer was concentrated first by distillation over calcium hydride, then by vacuum distillation over calcium hydride. The yield of 4 was 22.5 g (86%). Bp. 78-9 °C, 0.4 mm. The product was stored in a freezer. The structure of 4 was confirmed by its H NMR spectrum as shown in Fig. 4. 

L9.67 (a) Write the structural formulas of diethyl ether and 1-butanol (note that they are isomers), (b) The boiling point of L-butanol is 117°C, higher than that of diethyl ether (35°C), yet the solubility of both compounds in water is about 8 g per 100 mL. Account for these observations. 

Diethyl ether, (CH3CH2)20, has the greater standard molar entropy because its molecular structure consists of more atoms than dimethyl ether. (CH3)20. 

ABA type poly(hydroxyethyl methacrylate) (HEMA) and PDMS copolymers were synthesized by the coupling reactions of preformed a,co-isocyanate terminated PDMS oligomers and amine-terminated HEMA macromonomers312). Polymerization reactions were conducted in DMF solution at 0 °C. Products were purified by precipitation in diethyl ether to remove unreacted PDMS oligomers. After dissolving in DMF/toluene mixture, copolymers were reprecipitated in methanol/water mixture to remove unreacted HEMA oligomers. Microphase separated structures were observed under transmission electron microscope, using osmium tetroxide stained thin copolymer films. 

Equation (3) shows that when tri(2-pyridyl)phosphane 9 [44] is treated directly with trimethyl aluminum in diethyl ether the adduct complex Me3Al(/r-Py)PPy2 10 is obtained which has structurally been characterised,... 

Aqueous solutions are not suitable solvents for esterifications and transesterifications, and these reactions are carried out in organic solvents of low polarity [9-12]. However, enzymes are surrounded by a hydration shell or bound water that is required for the retention of structure and catalytic activity [13]. Polar hydrophilic solvents such as DMF, DMSO, acetone, and alcohols (log P<0, where P is the partition coefficient between octanol and water) are incompatible and lead to rapid denaturation. Common solvents for esterifications and transesterifications include alkanes (hexane/log P=3.5), aromatics (toluene/2.5, benzene/2), haloalkanes (CHCI3/2, CH2CI2/I.4), and ethers (diisopropyl ether/1.9, terf-butylmethyl ether/ 0.94, diethyl ether/0.85). Exceptionally stable enzymes such as Candida antarctica lipase B (CAL-B) have been used in more polar solvents (tetrahydrofuran/0.49, acetonitrile/—0.33). Room-temperature ionic liquids [14—17] and supercritical fluids [18] are also good media for a wide range of biotransformations. 

Fig. 1.6. Crystal structure of dimer of lithium salt of N-phenylimine of methyl -butyl ketone. Two molecules of diethyl ether are present. Reproduced from J. Am. Chem. Soc., 108, 2462 (1986), by permission of the American Chemical Society. 

The LiC104-diethyl ether system shows a considerable dependency on concentration, with the maximal effect around 5 M, which may be due to the detailed structure of LiC104 in ether. The optimum reactivity may be associated with a monosolvate. Dilute solutions have more of the dietherate, whereas in more concentrated solution LiC104 may form less reactive aggregates.35 LiN(S02SCF3)2 has been recommended as an alternative to avoid the use of a perchlorate salt.36... 

Again, weak coordination is expected for ether ligands to zinc, however, the larger number of structurally characterized examples is at least partially attributable to the frequent use of solvents such as diethyl ether or tetrahydrofuran which may provide additional ligands to the metal center. 

There are a reasonable number of structurally characterized zinc compounds with bound THF molecules. For example, a six-coordinate zinc porphyrin complex with axial THF donors and a four-coordinate zinc center with two THF ligands and two phenolate ligands.341,357 Although less common there are other structural examples of ether solvents, such as diethyl ether, coordinated.358 The X-ray structure of zinc chloride with 1,4-dioxane ligands shows a monomeric four-coordinate zinc center with two 1,4-dioxane ligands.359... 

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