Purification and Freezing Point of Phenanthrene<sup>1</sup>

Feldman, Julian; Pantages, Peter; Orchin, Milton

doi:10.1021/ja01153a091

Cited by 23 publications

(7 citation statements)

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“…Sodium-dispersion techniques (6) may allow shorter reaction times. Recrystallization from absolute ethanol raises the anthracene content in phenanthrene (7), and should be avoided wherever possible. Reaction of sodium with carbazole, fluorene, and dibenzothiophene in a simulated crude phenanthrene results in their simultaneous removal also (runs 4, 5).…”

Section: Resultsmentioning

confidence: 99%

Use of Sodium to Remove Anthracene and Other Impurities from Phenanthrene.

Blaustein¹,

Metlin²

1965

Anal. Chem.

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Section: Resultsmentioning

confidence: 99%

Use of Sodium to Remove Anthracene and Other Impurities from Phenanthrene.

Blaustein¹,

Metlin²

1965

Anal. Chem.

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“…(c) Fractional distillation using a carrier vapour such as ethylene glycol (cf. Feldman, Pantages & Orchin 1951).…”

Section: Methodsmentioning

confidence: 99%

Melting and crystal structure. The onset of ‘rotation’ on melting

Al-Mahdi¹,

Ubbelohde²

1953

Proc. R. Soc. Lond. A

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Extensive randomization of molecular orientations or ‘rotation’ is generally thought to occur on melting of certain fairly simple substances. The onset of ‘rotation’ on melting of more complex molecules is reviewed. Special attention has been directed to the behaviour of ‘stiff’ molecules such as benzene derivatives and fused aromatic rings, for which intramolecular crumpling in the melt is likely to be unimportant. The fractional increase in volume ∆ V f /V s on melting has been evaluated for a range of compounds from existing density measurements. ∆ V f /V s has also been determined experimentally for the molecules 2, 6-dimethyl naphthalene, 2, 3-dimethyl naphthalene, acenaphthene, anthracene, phenanthrene and chrysene. Using bond-distances and Van der Waals repulsion envelopes established by X-ray studies, the increase in volume required to permit ‘rotation’ about different molecular axes in the melt has been calculated. Comparison with the volume increase on melting observed experimentally shows that in many melts containing ‘stiff molecules’ there can be no ‘rotation’ of the molecules. In the present experiments no anomalies occur in such melts even 50° above the melting-point, but it is not yet possible to say whether ‘rotational’ transitions would be observed at higher temperatures in the liquids, similar to the well- known transitions in crystals. On the other hand, ‘rotation’ about at least one of the molecular-axes probably does accompany melting for some of the molecules studied, including benzene, bromobenzene, p -xylene, acenaphthene, naphthalene and 2, 6- but not 2, 3-dimethyl naphthalene.

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“…Phenanthrene C 14 D 10 was freed from anthracene impurities by refluxing with maleic anhydride. 6 Single crystals were grown from the melt doped with 1.6% phenanthrene C 14 D 10 .…”

Section: Production Of High Long-lasting Dynamic Proton Polarizatiomentioning

confidence: 99%

Production of High, Long-Lasting, Dynamic Proton Polarization by Way of Photoexcited Triplet States

1985

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In a crystal of fluorene C13H10 doped with phenanthrene Q4D10 a proton spin polarization of 42% has been obtained by means of microwave-induced optical nuclear polarization involving the photoexcited triplet state of the guest. This result makes the system a promising candidate for frozen targets and for the study of magnetic ordering of nuclear spins, where the paramagnetic centers used in conventional dynamic nuclear polarization cause great complications.PACS numbers: 76.70.Ey, 29.25.Kf, 76.70.Hb Dynamic nuclear polarization (DNP) is a technique used to obtain highly polarized nuclear spins for polarized targets in high-energy physics, for the study of magnetically ordered nuclear spins in solid-state physics, and for the enhancement of NMR sensitivity in a variety of other fields. 1 In a conventional DNP experiment the sample, doped with a small amount of centers that are paramagnetic in the ground state, is cooled to liquid-helium temperature and placed in a strong external magnetic field. Then the electron-spin polarization is transferred to the nuclear spins by means of microwave irradiation. Unfortunately, the paramagnetic centers, which are needed for the DNP process, perturb the subsequent experiments on the polarized-nuclear-spin system. In particular, they cause the decay of the nuclear-spin polarization in socalled frozen targets.Recently it was shown that DNP can also be achieved by use of molecules that are diamagnetic in the ground state and paramagnetic in a photoexcited triplet state. 2,3 This technique is called microwaveinduced optical nuclear polarization (MIONP). The energy-level schemes involved are shown in Fig. 1. For a MIONP experiment, a molecular host crystal is I / * l-Vfe) excitation / |-!+ 1 /2> decay FIG. 1. (a) The photoexcitation cycle creating the paramagnetic triplet state, (b) The Zeeman energy levels to be considered for the dynamic nuclear polarization.doped with a small concentration of guest molecules. uv light excites the guest molecules from the diamagnetic singlet ground state S 0 via the excited singlet state Si to the paramagnetic triplet state T Q . A strong magnetic field is applied, resulting in the Zeeman splitting shown in Fig. 1 (b) for the simplified case of one triplet spin and one proton spin. Dynamic nuclear polarization by the solid effect 1 takes place by the transference of the triplet-spin polarization to the nuclear spins by means of a microwave field with a frequency tuned to, e.g., the | -1, -y) *•* |0, + y) transition. The attraction of this technique is that the perturbing paramagnetic centers can be removed once the proton spins are polarized by the shutting off of the excitation light so that the guest molecules decay from the triplet state to the diamagnetic ground state.So far, MIONP experiments have been performed by modest means (microwave frequencies of 9 GHz and temperatures of 1.2 K) and the resulting nuclearspin polarizations were relatively small. 2,3 In this Letter, a MIONP experiment is described that was designed especially for obta...

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Purification and Freezing Point of Phenanthrene¹

Cited by 23 publications

References 0 publications

Use of Sodium to Remove Anthracene and Other Impurities from Phenanthrene.

Use of Sodium to Remove Anthracene and Other Impurities from Phenanthrene.

Melting and crystal structure. The onset of ‘rotation’ on melting

Production of High, Long-Lasting, Dynamic Proton Polarization by Way of Photoexcited Triplet States

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Purification and Freezing Point of Phenanthrene1

Cited by 23 publications

References 0 publications

Use of Sodium to Remove Anthracene and Other Impurities from Phenanthrene.

Use of Sodium to Remove Anthracene and Other Impurities from Phenanthrene.

Melting and crystal structure. The onset of ‘rotation’ on melting

Production of High, Long-Lasting, Dynamic Proton Polarization by Way of Photoexcited Triplet States

Contact Info

Product

Resources

About

Purification and Freezing Point of Phenanthrene¹