The analysis of organolithium compounds

Gilman, Henry; Cartledge, Frank K.

doi:10.1016/s0022-328x(00)83259-3

Cited by 434 publications

(235 citation statements)

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“…The cyclohexane and tetrahydrofuran was dried over sodium/benzephenone in an argon environment for at least three days prior to use. Secbutyllithium (Aldrich, Milwaukee, WI, 1.3 M in cyclohexane) and n-butyllithium (Aldrich, 1.6 M in cyclohexane) were used as received and titrated at least three times before each experiment using the method described by Gilman [21]. The diethylether (Mallinkrodt, Paris, KY) was dried over sodium/benzephenone in argon for at least three days and the dibromoethane (Aldrich) was dried over phoshorous pentoxide (Fisher, Pittsburgh, PA) for 12 h prior to use.…”

Section: Methodsmentioning

confidence: 99%

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D₃)

Hawkridge

Gardella

2003

J. Am. Soc. Mass Spectrom.

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Matrix assisted laser desorption ionization (MALDI) was used to study the organolithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D 3 ) in a mixed solvent system. The mass spectral peak intensities were monitored to determine the effects of polymerization time, initiator concentration, and reaction temperature on the formation of the mono, di, and trisiloxanolate initiator species and the extent of chain redistribution. The three initiator species were formed by reacting n-butyllithium and sec-butyllithium with D 3 in nonpolar solvent. The mass spectral results showed that sec-butyllithium and n-butyllithium form different populations of initiator species under the same conditions and that the measured mass spectral peak intensities do not accurately represent the population of siloxanolate initiator species prior to propagation. The changes in peak intensities were attributed to chain redistribution. . The molecular weight and product purity in these systems are difficult to control because both methods are susceptible to side reactions that broaden the polydispersity (M w /M n ). The most common side reactions are chain redistribution and cyclization shown in Scheme 1. Chain redistribution occurs when a propagating chain reacts with another chain to remove a segment of polymer without terminating the reaction. Cyclization occurs when a propagating chain reacts with itself to form cyclic species (D 3 , D 4 , D 5 , etc.). This type of side reaction is commonly referred to as chain backbiting. Lee et al. [3] first reported a new method for producing narrow molecular weight PDMS that was free of cyclic impurities. It was shown that n-butyllithium opened the D 3 ring in nonpolar solvents to form lithium siloxanolate initiators but did not propagate without the addition of a small amount (1-3%) of base promoting solvent (in this case these include polar aprotic solvents such as DMSO and THF). The control of the initiator basicity coupled with the high reactivity of the D 3 monomer significantly reduced chain redistribution and eliminated the formation of cyclic impurities.The reaction between organolithium initiators and D 3 is not well understood due in large part to the unique behavior of the initiators and the lithium counterions in solution. Organolithium compounds associate in nonpolar solvents to form aggregated species of various degrees due to the electron deficient nature of the lithium atom [4]. N-butyllithium, for example, forms a hexameric aggregate [5] whereas sec-butyllithium forms a tetrameric aggregate [6] in hydrocarbon solvents. Studies involving the reaction of organolithium species with styrene [7,8] and dienes [8,9] have shown that the degree of association directly affects the reactivity. The less associated organolithium species are found to be generally more reactive. Upon reacting with D 3 , it has been proposed that the lithium counter ions associate to form lithium siloxanolate aggregates. The degree to which these proposed structures are associated and the mech...

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Section: Methodsmentioning

confidence: 99%

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D₃)

Hawkridge

Gardella

2003

J. Am. Soc. Mass Spectrom.

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“…All the solvents were further distilled from polystyryllithium under reduced pressure immediately before use. tert-Butyl-lithium (t-BuLi) (Aldrich, 1.3 M solution in cyclohexane) was diluted with cyclohexane and the final concentration (0.2N) was determined by double titration [20], metaDiisopropenylbenzene (m-DIB, Aldrich) was dried over CaH 2 for 24 h, and finally distilled from fluorenyllithium before use. 1,1-Diphenylethylene (DPE, Aldrich) was dried over sec-BuLi and distilled from diphenylmethyl-lithium before use.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and characterization of hydrogenated poly[alkylmethacrylate(-b-styrene)-b-butadiene-b-(styrene-b-) alkylmethacrylate] triblock and pentablock copolymers

Yu¹,

Yu²,

Dubois³

et al. 1997

Polymer

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Triblock and pentablock copolymers of the X(Y)B(Y)X type have been synthesized by the sequential living anionic polymerization of butadiene (B), styrene (Y) and alkylmethacrylate (X), respectively. The diadduct of tBuLi onto m-diisopropenylbenzene (m-DIB) has been used as a difunctional initiator. Methylmethacrylate (MMA), t-butylmethacrylate (tBMA) and isobornylmethacrylate (IBMA) have been used as precursors of the outerblocks X. The polybutadiene (PBD) midblock that contains ca 42-45% 1,2-units has been selectively hydrogenated into a saturated poly(ethylene-co-1-butene) (PEB) block. The homogeneous hydrogenation catalysis has no deleterious effect on the copolymer integrity. These completely soluble thermoplastic elastomers have been characterized by FT i.r., n.m.r., d.s.c. and d.m.a. The PEB midblock has a low T g (-50°C) and a small propensity to crystallize. The effect of hydrogenation on the morphology and mechanical properties depends on the outer block. Upon hydrogenation of the PBD midblock in polymethylmethacrylate (PMMA) and polyisobornylmethacrylate (PIBMA) containing triblock copolymers, the ultimate tensile strength is increased (except for a hard block content > 50%) due to a sharper phase separation, whereas the elongation at break is decreased. The extent of phase separation is reduced in polyt-butylmethacrylate(PtBMA) containing triblock copolymers upon hydrogenation and the ultimate tensile strength is slightly decreased. Stereocomplexation of the syndiotactic PMMA outerblocks is observed to occur upon blending with isotactic PMMA

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“…20 In this case, two sacrificial ampules are needed; the first is treated as mentioned previously, and the second is treated as follows: the ampule is quenched into a solu- tion that contains a reactive electrophile such as benzyl bromide; the product of this reaction is then titrated with HCl to a phenolphthalein end point. The concentration of organolithium is manifested in the difference between the two titration results.…”

Section: The Following Sequence Is Best Accomplished Somewhat Quimentioning

confidence: 99%

Experimental techniques in high‐vacuum anionic polymerization

Uhrig

Mays

2005

J. Polym. Sci. A Polym. Chem.

278

263

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Experimental methods used in high‐vacuum anionic polymerization are described in detail, with extensive illustrations to demonstrate proper procedures and techniques. These descriptions include construction and operation of the vacuum line, handling purification chemicals, ampulization techniques, short‐path distillations, initiator synthesis, polymerization procedures, and linking reactions using chlorosilanes. A primary emphasis is placed on safety. We believe that this review of these methods will be useful to scientists working in the field of anionic polymerization and may also benefit other researchers in performing tasks requiring ultra‐high‐purity reaction conditions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6179–6222, 2005

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The analysis of organolithium compounds

Cited by 434 publications

References 16 publications

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D₃)

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D₃)

Synthesis and characterization of hydrogenated poly[alkylmethacrylate(-b-styrene)-b-butadiene-b-(styrene-b-) alkylmethacrylate] triblock and pentablock copolymers

Experimental techniques in high‐vacuum anionic polymerization

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The analysis of organolithium compounds

Cited by 434 publications

References 16 publications

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D3)

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D3)

Synthesis and characterization of hydrogenated poly[alkylmethacrylate(-b-styrene)-b-butadiene-b-(styrene-b-) alkylmethacrylate] triblock and pentablock copolymers

Experimental techniques in high‐vacuum anionic polymerization

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Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D₃)

Evaluation of matrix-assisted laser desorption ionization mass spectrometry for studying the sec-butyllithium and n-butyllithium initiated ring-opening polymerization of hexamethylcyclotrisiloxane (D₃)