Diethyl ether dimeric

However, in diethyl ether, dimeric or polymeric species are apparently present, except at low concentrations (below 0.1 M). 

Form Supplied in commercially available as approximately 1.6 M, 2.5 M, and 10.0 M solution in hexanes and in cyclohexane, approximately 2.0 M solution in pentane, and approximately 1.7 M, and 2.7 M solution in n-heptane. Hexameric in hydrocarbons tetrameric in diethyl ether dimer-tetramer equilibrium mixture in THF when used in combination with tertiary polyamines such as TMFDA and DABCO, reactivity is usually increased. ... 

Crystal stmctures of Grignard reagents do not necessarily correspond to their stmcture in solution. In general, the crystal stmctures (61—64) indicate the reagents are ligated with THF or diethyl ether and are frequentiy observed to be dimers. The Mg atoms in the dimers do not have a Mg—Mg bond instead the dimers are typically held together by a haUde bridge. 

The synthesis of thiepins 14 was unsuccessful in the case of R1 = i-Pr,79 but if the substituents in the ortho positions to sulfur arc /erf-butyl, then thiepin 14 (R1 = t-Bu R2 = Me) can be isolated in 99% yield.80 Rearrangement of diazo compound 13 (R1 = t-Bu R2 = H), which does not contain the methyl group in position 4, catalyzed by dimeric ( y3-allyl)chloropalladium gives, however, the corresponding e.w-methylene compound. The thiepin 14 (R1 = t-Bu, R2 = H) can be obtained in low yield (13 %) by treatment of the diazo compound with anhydrous hydrogen chloride in diethyl ether at — 20 C.13 In contrast, the ethyl thiepin-3,5-or -4,5-dicarboxylates can be prepared by the palladium catalysis method in satisfying yields.81... 

The second stable biradicaloid, l,3-diaza-2,4-distannacyclobutane-l,3-diyl, 54, was unexpectedly obtained by the reaction of chloro(amino)stannylene dimer [Sn N(SiMe3)2 (n-Cl)]2 and AgOCN in diethyl ether (Scheme 2.41). ... 

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 position of the equilibrium depends upon the solvent and the identity of the specific organic group, but in ether lies well to the left for simple aryl-, alkyl-, and alkenylmagnesium halides.21 Solutions of organomagnesium compounds in diethyl ether contain aggregated species.22 Dimers predominate in ether solutions of alkylmagnesium chlorides. 

Starting with l,l-bis(trimethylsilyl)ethylene (5) in hexane or diethyl ether as the solvent we obtained another dimeric product, a monolithiumorganic compound 8 which was shown not to be formed by lithium hydride elimination from the 1,4-dilithiobutane derivative 6, the only product in THF as the solvent. Obviously the vinyllithium derivative 7, primarily formed in the same manner as vinyllithium from ethylene [4], in contrast to vinyllithium [4] does not add further lithium atoms but adds itself to the starting material 5 yielding 8 ... 

Catalytic opening of diazabicyclohexane 331 in the presence of boron trifluoride-diethyl ether complex or concentrated hydrochloric acid leads to formation of a dimer 493 <1999RJO 44>, in contrast to the thermal process... 

Cycloadditions are in general an effective way of constructing cyclobutane rings. A wide variety of heterocyclic systems dimerize in this way. 1,3-Diacetylindole, for example, affords the head-to-tail dimer 242 on irradiation in ethanol.185 Ethyl 2-ethoxy-l,2-dihydroquinoline-l-carboxy-late is similarly converted in diethyl ether into the trans head-to-head dimer.186 Notable among many analogous photodimerizations are those reported in 1,4-dihydropyridines,187 in furo[3,2-b]pyridin-2(4//)-ones,188 in 8-methyl-s-triazolo[4,3-a]pyridine,189 and in 2H-2-benzazepine-1,3-diones.190 The [ 2 + 2] dimerization of amidopyrine is the first reported example of a photocycloaddition in a 4-pyrazolin-3-one.191... 

At concentrations of about 1 molal in tetrahydrofuran, C2HsMgBr exists almost entirely as the monomer. However, at a comparable concentration in diethyl ether, the dominant species is the dimer. Explain this... 

With the aid of 13C NMR, 6Li NMR and XH HOESY (heteronuclear Overhauser effect spectroscopy) NMR of a-lithiomethoxyallene (106) and l-lithio-l-ethoxy-3-J-butylallene (107) as well as by ab initio model calculations on monomeric and dimeric a-lithiohy-droxyallene, Schleyer and coworkers64 proved that 106 and 107 are dimeric in THF (106 forms a tetramer in diethyl ether) with a nonclassical 1,3-bridged structure. The 13C NMR spectrum of allenyllithium in THF is also in agreement with the allenic-type structure the chemical shift of C2 (196.4 ppm) resembles that of neutral allene (212.6 ppm), rather than C2 of propyne (82.4 ppm). 

The Ponzio reaction provides a useful route to gem-dinitro compounds and involves treating oximes with a solution of nitrogen dioxide or its dimer in diethyl ether or a chlorinated solvent. The Ponzio reaction works best for aromatic oximes where the synthesis of many substituted aryldinitromethanes have been reported. Compound (56), an isomer of TNT, is formed from the reaction of dinitrogen tetroxide with the oxime of benzaldehyde (55) followed by mononitration of the aromatic ring with mixed acid. Yields are usually much lower for aliphatic aldoximes and ketoximes. " The parent carbonyl compound of the oxime is usually the major by-product in these reactions. 

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