The Influence of Tetrahydrofuran on the Reaction of <i>n</i>-Butyllithium with Benzyl Chloride: Halogen-Metal Interconversion <i>vs</i>. α-Hydrogen-Metal Interconversion

Hoeg, Donald F.; Lusk, Donald I.

doi:10.1021/ja01059a041

Cited by 37 publications

(9 citation statements)

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“…The difference between these observations and those quoted above may well be due to differences in solvent medium. The insensitivity to temperature is consistent with the findings of Hoeg and Lusk (23) in their study of stilbene production during the reaction of nbutyllithium with benzyl chloride, as a function of temperature and solvent. They have shown that in THF the yield of stilbene produced by a-hydrogen-metal interconversion is relatively insensitive to temperature changes above 2OOC.…”

Section: Discussionsupporting

confidence: 89%

The preparation of graft copolymers of polystyrene with poly‐2‐vinylpyridine

Gervasi

Gosnell

Stannett

1968

J. polym. sci., C Polym. symp.

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SynopsisGraft copolymers have been prepared with polystyrene backbones and poly-2-vinylpyridine side chains. The approach used was to couple together two preformed polymers which were themselves separately characterized. Thus, a knowledge of the overall composition and separate descriptions of the two homopolymers gave reasonably well defined grafts. The living-polymer technique of Szwarc was found to be well suited to this approach. Polystyrene backbones were prepared by anionicpolymerization, with M,/Mn values of less than 1.1 and then chloromethylated to provide reactive grafting sites. The poly-Bvinylpyridine side chains were also prepared by anionic polymerization and, while still active, were allowed to react with the chloromethylated polystyrene. The homopolymers were removed by solvent extractions, leaving the graft copolymer as a residue. The molecular weight of the graft was then determined by osmotic-pressure measurements. Several features of the synthesis and characterization of the grafts and of the homopolymers are discussed. Within very broad limits this method permitted an unrestricted choice of backbone and of side-chain length and of the average number of side chains per backbone. 207

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Section: Discussionsupporting

confidence: 89%

The preparation of graft copolymers of polystyrene with poly‐2‐vinylpyridine

Gervasi

Gosnell

Stannett

1968

J. polym. sci., C Polym. symp.

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“…The number of chloromethyl functions per backbone polymer molecule was about 85. The number-average molecular weight of the chloromethylated polystyrene was determined by osmotic pressure measurement in benzene at 37°C to be 3.92xl0 4 • These results show that Volhard's method is one useful measurement for determining the chlorine content. Polystyryl anion was prepared by polymerization of styrene monomer with cumyl potassium in THF.…”

Section: Methodsmentioning

confidence: 82%

Formation of Multi-Branched Graft Copolymer by Coupling Reaction

Ishizu

Fukutomi

Kakurai

1975

Polym J

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ABSTRACT:Chloromethylated polystyrene was reacted with polystyryl anion at -78°C and at 20°C in mixed solvents (good solvent (tetrahydrofuran (THF)-poor solvent (methylcyclohexane)) and in THF. The decrease in the concentration of the living end was measured photometrically by using a reaction apparatus equipped with an optical cell able to work at low temperatures. The coupling reactions at -78°C ceased within about 15 min. However, the number of branches per backbone polymer molecule increased slightly for all times longer than about 20 min at 20°C. One explanation of our results is that the pendant groups were hindered by the grafted polymer chain and the subsequent grafting of the living polymer onto the coupling agent occurred less readily or not at all in some cases, especially when the molecular weight of the polystyryl anion was large and the content of the poor solvent in the reaction mixture was high.KEY WORDS:In a previous paper/ we dealt with the formation of a backbone and a single branched chain (1 : 1-graft copolymer) by the coupling reaction between PMMA and poly(a-methylstyryl) anion. We concluded that the structure of 1 : 1-graft copolymer was suffered changes by the reaction conditions: i.e., the ratio of good solvent (THF) to poor solvent (methylcyclohexane), even when the same degree of polymerization (DP) of PMMA and poly(a-methylstyryl) anion were used. Our results have shown that all pendant groups of the backbone polymer were not reacted with equal probability under various reaction conditions even at the initial stage of this reaction.In the present paper, we describe an investigation of the formation of a multi-branched graft copolymer by the coupling reaction of polystyryl anion with chloromethylated polystyrene. Several factors are considered to be important in determining the extent of reaction between the pendant groups on a polymer chain and a reactive group on the end of a polymer chain and these factors are of no significance for a similar reaction between the pendant groups and a low-molecular-weight reagent. One of these factors is the hindering effect of the polymer chain. EXPERIMENTALAltares, et al., 2 and Pannel1 3 have reported the reaction of living polymer with chloromethylated polystyrene. According to their results, the comb-shaped polystyrene was obtained in this reaction. It was often suggested that if the lithium salt of styryl anion was used as the initiator, various side reactions would occur in the coupling reaction between the chloromethyl group and styryl anion, resulting in the crosslinking between parent polymers. 2 ' 4 However, it was also claimed 5 that such side reactions were negligible if potassium salt was used instead of lithium salt. The polystyrene was chloromethylated6 with chloromethyl methyl ether using stannic chloride as a catalyst. The parent polymer was prepared by polymerization of styrene monomer with cumyl potassium in THF. The molecular weight of the parent polymer determined by viscometric measurement was 3.52x 10 4 • The chlorine content...

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“…The spectrum was identical with the infrared spectrum of authentic ¿rans-pinocarveol. 14 The gas chromatographic retention times of the two samples on hyprose and on didecyl phthalate were also identical.…”

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confidence: 77%