Lithium in benzene

Wyman, Allen and Altares (20) reported that the carbonation of poly-(styryl)lithium in benzene with gaseous carbon dioxide produced only a 60% yield of carboxylic acid the acid was contaminated with significant amounts of the corresponding ketone (dimer) and tertiary alcohol (trimer) as shown in eq. 6. A recent, careful, detailed investigation of the carbonation of polymeric organolithium compounds has... 

Poly(styryl)lithium. The calorimetric data obtained for the interaction of tetrahydrofuran (THF) and 2,5-dimethyltetra-hydrofuran (2,5-Me2THF) with 0.03M solutions of poly(styryl)-lithium in benzene as a function of R ([base]/[lithium atoms]) are shown in Figure 1. These data, as well as the corresponding data for poly(isoprenyl)lithium, are referred to dilute... 

Dicarbaundecaborane(13) is a white hygroscopic solid which is soluble in water, alcohols, and aromatic solvents. It is best stored cold in a dry, inert atmosphere. The proton-decoupled nB NMR spectrum (115 MHz, C6D6, referenced to external BF3OEt2) shows peaks at d 4.0 (2 B), - 4.4 (2 B), - 16.4 (1 B), - 17.0 (1 B), and - 27.4 (3 B). The complex is a diprotic acid with pK i of 2.98 and pKa2 of 14.25.6 Deprotonation of C2B9H13 with butyl lithium in benzene affords anhydrous Li2C2B9Hi... 

Initial enthalpies for addition of small amounts of bases to dilute solutions (0.2 M) of polymeric organolithiums at low R values ([base]/[Li]) provide direct information on the strength of the base interactions as well as the steric requirements of the bases. Data for initial enthalpies of interaction for a variety of bases with poly(styryl)lithium in benzene are listed in Table 8 88,89>. It is especially significant to note that the basicity order observed for poly(styryl)lithium (TMEDA > diglyme > THE > 2,5-Me2THF > dioxane > TMEDP > Et3P > EtzO = Et3N) is very similar to the order for simple alkyllithiums (see Tables 6 and 7) TMEDA > THF >... 

Milner and Young 181i have made a similar study of the influence of TMEDA upon the 1 H-NMR spectrum of poly(butadienyl)lithium in benzene at 30 °C. In the... 

The reactions of poly(styryl)lithium in benzene with an excess of diphenyl-ethylene 272) and bis[4-(l-phenylethenyl)phenyl]ether158) also were found to proceed by a first order process. However, the reactions of poly(styryl)lithium with the double diphenylethylenes l,4-bis(l-phenylethenyl)benzene and 4,4 bis(l-phenyl-ethenyl)l,l biphenyl gave l58) non-linear first order plots with the gradients decreasing with time. This curvature was attributed to departure from a geometric mean relationship between the three dimerization equilibrium constants (Ka, Kb and Kab). The respective concentrations of the various unassociated, self-associated and cross-associated aggregates involved in the systems described by Equations (49) to (51) are dependent upon the relative concentrations of the two active centers and the respective rate constants which govern the association-dissociation events. 

One cannot simply extrapolate results obtained for simple alkyllithiums to polymeric organolithiums since important factors such as the degree of association and diffusion rates are different. Thus, preliminary examination of the reaction of poly(butadienyl)-lithium in benzene with excess ethylene dibromide in benzene produced predominately the dimeric coupling product (Eq. (78)330)). 

EtsSiLi is formed along with EtLi, when the mercury compound EtHgSiEt3 is reacted with lithium in benzene (equation 10). However, when this reaction is performed in THF, EtsSiLi is obtained as sole lithiated compound (equation ll)17. 

Bachmann and Seebach [159] have reported the preparation and characterization of cyclic lactones (MeCHCH2C(0)0)n, where n = 4 and 8. The reaction product between butyl lithium in benzene and the solid polystyrene support PS-C6H4CH2NH2 leads to a lithiated species that can be represented as PS-Cfd bCI 12N11 Li(BuI i)x, where x 4 is active in the ring-opening of the cyclic esters L-lactide, rac-lactide, and 2,5-morpholinediones, leading to their respective cyclic oligoesters and cyclodepsipeptides (Fig. 49) [160]. The... 

Korotkov and Rakova (53) found that butadiene was more active in copolymerization with isoprene with lithium catalyst, although in homopolymerization isoprene is three times faster. Korotkov and Chesnokova (33) studied the copolymerization of butadiene and styrene with n-butyl lithium in benzene. Butadiene polymerized before much of the styrene was consumed. They claimed the formation of block polymers consisting initially of polybutadiene and the polystyrene chain attached. 

Figure 2. Variation of the propagation rate with concentration of polystyryl-lithium in benzene at 20° C., o—Worsfold and Bywater (27) —Morton and...

Polymerization of styrene initiated by n-butyl lithium in benzene was investigated by a spectrophotometric technique by Worsfold and Bywater156). Concentration of polysty-ryl anions was monitored by their absorbance at 334 nm, while the concentration of the unreacted styrene was determined by its absorbance at 291 nm. The results are shown graphically in Fig. 23. Concentration of polystyryl anions increases with time and eventually reaches its asymptotic value, being constant afterwards. This observation indicates the stability of these species. On the other hand, the concentration of styrene decays in sigmoidal fashion. This classic study unequivocally demonstrated the living character of the resulting polymers, and therefore it was justified to identify the rate of increase of the absorbance at 334 nm with the rate of initiation. 

The initiation of styrene polymerization by r-butyl lithium in benzene is an apparent exception. The rates were found to be proportional to the first power concentration of the lithium compound and independent of the monomer concentration which was varied from 0.1 to 10-3 M172). This strange behavior is illustrated by Fig. 26. The authors proposed that the dissociation of r-butyl lithium into smaller, active aggregates, dimers or monomers, is the rate determining step of this process. However, the rate of initiation of isoprene by r-butyllithium in benzene shows a more conventional behavior it increases with increasing concentration of the monomer, although again it is proportional to first power concentration of r-butyl lithium. 

Fig. 62 a. Plots of n of concentration of styrene or p-methyl styrene vs. time for a co-polymerization of those two monomers initiated by butyl lithium in benzene. Both monomers disappear in a pseudo-first order fashion. The pseudo-first order constants are A, and X2... 

The chemical reactivity of the thiocyano groups in these chelate rings has not been investigated, but the halogen atoms in the 3-halo metal acetylacetonates have been found to be quite inert and their behavior is different from that of aryl halides, since treatment of the tris(3-bromo-2,4-pentanediono)chromium(III) chelate with magnesium or lithium in benzene or tetrahydrofuran resulted in no reaction. Attempted nucleophilic displacement of the bromine atoms in this chelate by azide, acetate, nitrate, and iodide ions in hot dimethylformamide also failed. In most of these... 

Tetrabromo derivative (240) treated with methyl lithium in benzene or LAH in THF undergoes a dehalogenation reaction leading to (274). When the reaction with methyl hthium is performed in ether, a mixture of pyrroles (275) and (276) is formed (Scheme 51) <75JOC47>. 

The observation of concentration dependence of the reaction order (increasing from 0.25 to 0.5 (when [PILi] <5 X 10 mol/l) with decreasing concentration of poly(isoprenyl)lithium in benzene can be explained in terms of the intermediacy of a dimeric association state as shown in Equation 7.16 [87]. 

Using high vacuum techniques and high-purity, gaseous carbon dioxide it has been reported recently that carbonation of poly(styryl)lithium, poly(isoprenyl) lithium, and poly(styrene-b-isoprenyl)lithium in benzene produces the... 

Boron, Thallium, and Indium.—Further reactions of lithium salts of carbabo-ranes with hexafluorobenzene (Vol. 1, p. 233) to give 1,4-dicarbaboranyl derivatives, have been described. The lithium salt o-MeCBioHioCLi reacts with chloropentafluorobenzene to give the derivative 4-ClCeF4-CBioHioCMe-o which undergoes chlorine exchange with butyl-lithium in benzene, the... 

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