Lithium 2- ethyl

At higher temperatures the reaction between ethyl bromide and ethyl-lithium ("Wurz coupling") becomes significant. 

A mixture of 0.40 mol of propargyl chloride and 150ml of dry diethyl ether was cooled at -90°C (liquid nitrogen bath) and a solution of 0.40 mol of ethyl-lithium (note 1) in about 350 ml of diethyl ether (see Exp. 1) was added with vigorous stirring and occasional cooling (note 2). The temperature of the reaction mixture was kept between -70 and -90°C. The formation of the lithium derivative proceeded almost instantaneously, so that the solution obtained could be used directly after the addition of the ethyl 1ithium, which was carried out in 15-20 min. This lithium acetylide solution is very unstable and must be kept below -60°C. 

To absolution of 1.00 mol of ethyl lithium in 800-900 ml of diethyl ether (see Chapter II, Exp. 1) was added, with cooling between -20 and -10°C, 0.50 nol of dry propargyl alcohol, dissolved in 100 ml of diethyl ether. Subsequently 1.1 mol of trimethylchlorosilane was introduced over a period of 25 min with cooling between -15 and +5°C. After stirring for an additional 2 h at about 30°C the suspension was poured into a solution of 30 g of acetic acid in 150 ml of water. After stirring for 1 h at room temperature the layers were separated and the aqueous layer v/as extracted four times with diethyl ether. The combined ethereal solutions were washed with sodium hydrogen carbonate solution in order to neutralize acetic acid, and were then dried over magnesium sulfate. The diethyl ether was removed by evaporation in a water-pump vacuum and the residue distilled... 

The effect of penultimate units on the rate constants of anionic propagation is observed also in other systems. For example, the addition of styrene to the lithium salt of 1-phenyl-n-hexyl anion is 4 times faster than to polystyryl lithium 51). Similarly, the addition of monomer to the lithium salt of 1,1-diphenyl-n-hexyl lithium is faster than the addition to 1,1,3-triphenyl-n-octyl lithium or 2-poly-sty ry 1-1,1-diphenyl ethyl lithium, the latter two salts having comparable reactivities52 . See also Ref.53)... 

Dyashkovskii and Shilov [Kinetics and Catalysis, 4 (808), 1963] have studied the kinetics of the reaction between ethyl lithium and ethyl iodide in decalin solution. 

The following data are typical of those observed by these authors at 20 °C. They correspond to initial ethyl lithium and ethyl iodide concentrations of 2.0 and 1.0 kmoles/m3, respectively. 

From equation 10 with phenyl lithium as the benchmark species, RLi, and the hydrocarbon compounds, R H, in their reference gaseous states, the derived enthalpies of formation of allyl, ii-l-propenyl, 2-propenyl and ethyl lithium, are —12.8, —7.3, 54.3 and —58.3 kJmoP, respectively. The first and last of these are remarkably consistent with the values in Table 1. 

Unfortunately, we lack measured enthalpy of formation values for most organic iodides of interest here except for ethyl, n-propyl and phenyl iodides. From equation 14 and with phenyl iodide in its reference liquid state and with ethyl and propyl iodides in their reference gaseous states, the enthalpies of formation of ethyl lithium and of n-propyl lithium are calculated to be ca —54 and —74 klmoP, respectively. The former value is the same as those from Table 1 and the latter is compatible with one of the other values for n-propyl lithium derived in earlier sections. 

The occurrence of such equilibria may also account for the fact that deprotonation of l,3-Sg(NH)2 with ethyl-lithium and reaction of the resulting anion with methyl iodide produces S NMe but no alkylated derivatives of the diimide... 

The crude, alkylated product mixture can be either hydrolyzed with acid to give nonracemic 2-alkylalkanoic acids 5 of good optical purities (as80% ee) or reacted with methyl- or ethyl-lithium to furnish the corresponding 3-substituted 2-alkanones and 4-substituted 3-alkanones 6, respectively, in moderate yield and enantiomeric excess2. 

Efficient synthesis of 2-chlorofuran is best achieved by decarboxylation of 2-chlorofuran-5-carboxylic acid (63JGU1397) or via the lithium derivative of furan. When furan or 3-bromofuran were treated in turn with ethyl-lithium and hexachloroethane, 2-chlorofuran (48%) or 3-chlorofuran (54%) was formed, uncontaminated by any polychlorinated products (73SC213). Chlorodesilylation of ethyl 5-trimethylsilyl-2-furoate with sul-furyl chloride in acetonitrile gave the 5-chloro ester in —85% yield (91MI4). 

Another complication introduced by the associative properties of organolithium solutions in non-polar solvents is the fact that the alkyllithium initiators are themselves associated and can be expected to "cross associate" with the active polymer chain ends. Thus some of our studies (26) on the effect of added ethyl lithium on the viscosity o -polyisoprenyl lithium solutions in n-hexane support the following association equilibrium... 

Lithium triethylcarboxide 3-Pentanol, 3-ethyl-, lithium salt (8,9), (32777-93-8). 

Triethylsilanetellurol, when added gradually to ethyl lithium in pentane, caused precipitation of lithium triethylsilanetellurolate. Recrystallization from hexane gave the pure compound [m.p. 122° (dec)] in 22% yield5. 

Lithium triethylsilanetellurolate, prepared from bisftriethylsilyl] tellurium and ethyl lithium, reacted with an excess of chlorobutane to form butyl triethylsilyl tellurium2. 

The Lewis acidity of organoaluminium compounds is the reason of their association. The association of alkylaluminium molecules and aluminium hydrides proceeds by way of electron-deficient bonds [143a], The associates of dimethylberyllium, dimethyl- and diethylmagnesium, methyl- and ethyl-lithium are of the same type each alkyl group is simultaneously bound to two or three metal atoms [143b],... 

FIG. 10. Temperature-dependent Li NMR spectra of a mixture of ethyl-lithium and methyl-lithium in ether (EtLi MeLi = 1 L55). The least shielded lithium is the one having three adjacent methyls. (89)... 

---