Photobromination of Methylnaphthalenes

Taussig, P. R.; Miller, Glenn B. S.; Storms, Phillip W.

doi:10.1021/jo01020a060

Cited by 8 publications

(3 citation statements)

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Section: Halogenation–dehalogenationmentioning

confidence: 99%

“…77 Therefore, it is not possible to homolyze all bromine molecules into radicals at a lower reaction temperature, leading to a lower rate of methyl bromide in direct thermal bromination. [78][79][80][81] The reaction mechanism of bromination-debromination is shown in Figure 3. 82 In the presence of bromine radicals, the hydrogen atom in the aliphatic sidechain of the aromatic ring is a readily radical substitution to form brominated compounds, which then bind to hydrogen on the other aromatic ring at high temperature to form hydrogen bromide.…”

Section: Bromination-debrominationmentioning

confidence: 99%

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Mechanism and application of halogenation–dehalogenation in the development of pitch-based carbon fiber: A review

Liu

et al. 2023

Journal of Engineered Fibers and Fabrics

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Pitch-based carbon fiber, as one of the important engineering materials, has been widely used in aerospace, defense, sports, and other fields. In the long production process of pitch-based carbon fiber, the property of pitch precursor is significant for the mechanical performance of obtained carbon fiber. Thus, it is crucial to improve the property of pitch precursor by efficient means. Halogenation–dehalogenation is a newly developed method for the controllable synthesis of a pitch precursor from the molecular dimension, including fluorination–defluorination, chlorination–dechlorination, and bromination–debromination. This work reviewed the mechanism and application, as well as the advantages and disadvantages of each halogenation–dehalogenation method.

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Section: Halogenation–dehalogenationmentioning

confidence: 99%

Section: Bromination-debrominationmentioning

confidence: 99%

Mechanism and application of halogenation–dehalogenation in the development of pitch-based carbon fiber: A review

Liu

et al. 2023

Journal of Engineered Fibers and Fabrics

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“…The key to this process lies in selective side-chain bromination induced by visible light irradiation. The relatively low bond energy of methyl C–Br is quite beneficial for milder dehydrobromination (200–270 °C). , However, bromination of 1-MNa using equimolar amounts of bromine is a prerequisite, which adds to the cost of materials. Besides, the elaborate vacuum distillation of brominated mixtures to obtain single 1-(bromomethyl) naphthalene is indispensable to control structures and properties of the resultant pitches, but the operation cost is significantly increased.…”

Section: Introductionmentioning

confidence: 99%

Controllable Synthesis of Highly Graphitizable Pitches from 1-Methylnaphthalene via Closed-System Dehydrobromination

Han

Wang

et al. 2018

Energy Fuels

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Novel graphitizable pitches with controllable softening points and methylene-bridged structures were successfully prepared through photobromination of 1-methylnaphthalene (1-MNa) followed by closed-system dehydrobromination (CSD). The structures of bromination products and dehydrobromination pitches were determined using gas chromatography–mass spectroscopy, NMR and laser desorption/ionization-time of flight/mass spectroscopy. It was found that the amount of bromine introduced greatly affected the composition of bromination products. 1-MNa brominated at a bromine/1-MNa molar ratio of 0.75 (BMNa-0.75) demonstrated the highest methyl bromination selectivity (S mb), which was selected as the dehydrobromination precursor. After a CSD/polymerization reaction under 200–250 °C, dehydrobromination pitches with softening points of 148–226 °C were acquired. Compared with open-system dehydrobromination (OSD), CSD endowed bromine radical longer life and boosted intramolecular and intermolecular linking, thereby substantially increasing softening points and coking values. The polymerization degree of CSD-derived pitches is highly regulable depending on dehydrobromination temperature and the amount of tetrahydronaphthalene (tetralin) introduced. Moreover, methyl migration products (naphthalene, 2-methylnaphthalene, dimethyl-naphthalene and trimethyl-naphthalene) together with hydrogenation products (mainly tetralin) were detected by analyzing the hexane-soluble components (HS). The structural features of CSD-derived pitches contributed to some unique properties such as high polymerization degree accompanied by low aromaticity, continuous molecular weight distribution and complex connection types among subunits including α–α′, α–β′, and β–β′. The semicoke with 94% anisotropy of coarse flow texture was synthesized at 420 °C under atmospheric pressure. Well-developed graphitic carbons with graphitization degree of 81.40% and I D/I G of 0.12 was obtained from graphitization of dehydrobromination pitches under 2600 °C.

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Chemistry of thienopyridines. XV. Syntheses of thieno [3,4‐b] ‐ and thieno[3,4‐c] pyridines

Klemm

Johnson

White

1972

Journal of Heterocyclic Chem

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Thieno [3,4-b]pyridine (5) was synthesized by means of the successive steps of (a) photochlorination of 2,3-dimethylpyridine to the bis(chloromethy1) compound, (b) condensation with sodium sulfide, (c) oxidation to the sulfoxide, and (d) catalytic dehydration by means of alumina. Thien0[3,4c]pyridine (6) was obtained in an analogous manner. Spectral properties indicate that 5 and 6 have aromatic character.Of the six possible isomeric thienopyridines (1-6) syntheses on a preparative scale of 1 (4), 2 (5-7), 3 (6,7) and 4 (4,5a) have been reported in recent years. We now present details on the practical syntheses of thieno[3,4-6]pyridine (5) and thieno[3,4c]pyridine (6), originally reported in a brief communication (8). 6a3 Na3 N \ ' ' 3 1 2 3 4 5 6Prior to our studies parent compounds 5 and ti were unknown. Russian workers (9) had reported the condensation of a 3-aminothiophene salt with methyl vinyl ketone to give a mixture of 7-methyl-4 and 7-methyl-5. However, repetition of this reaction and structural studies on the two isolable products (4) indicated that one obtains a mixture of 5and 7-methyl-4, instead. Recently, Spinner and Yeoh (10) reported syntheses of derivatives OH (7) of the 1,3-dihydro-5 system. Treatment of 7a and 7b with acetic acid-hydrogen peroxide gave the corresponding sulfones. Methylation of 7a (with diazomethane) formed 8b, while methylation of 7b (with methyl iodide) gave a product to which an S-methyl structure was assigned. The sulfone of 8b, plus studies on ionization constants and tautomerization of hydroxy compounds, were also described.

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Photobromination of Methylnaphthalenes

Cited by 8 publications

References 0 publications

Mechanism and application of halogenation–dehalogenation in the development of pitch-based carbon fiber: A review

Mechanism and application of halogenation–dehalogenation in the development of pitch-based carbon fiber: A review

Controllable Synthesis of Highly Graphitizable Pitches from 1-Methylnaphthalene via Closed-System Dehydrobromination

Chemistry of thienopyridines. XV. Syntheses of thieno [3,4‐b] ‐ and thieno[3,4‐c] pyridines

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