- Synthesis and self-assembly of a heteroarm star amphiphile with 12 alternating arms and a well-defined core
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We report on a stepwise synthesis of a heteroarm starlike amphiphile containing 12 alternating arms (six polystyrene and six poly(acrylic acid)) connected to a hexabiphenyl aromatic core. The synthesis does not involve polymerization, and only commercially available precursors are used. Most importantly, this amphiphile undergoes self-assembly into spherical and wormlike cylindrical micelles in aqueous and methanol solutions, and forms reverse 1D micellar structures in chloroform. This remarkable morphological diversity of the reported amphiphile 1 is believed to be a direct consequence of its well-defined molecular architecture. Copyright
- Teng, Jing,Zubarev, Eugene R.
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- From small building blocks to complex molecular architecture
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We describe a synthesis of a dendrimer-like amphiphile containing a flat rigid core and 12 hydrophobic and hydrophilic arms. We employ a modular approach based on stepwise protection chemistry starting from simple building blocks. The key feature of this approach is the absence of a polymerization step, which makes it applicable for linear monofunctionalized precursors of any kind. This strategy also allows for precise control of the number of arms and ensures their alternating arrangement.
- Zubarev, Eugene R.,Xu, Jun,Gibson, Jacob D.,Sayyad, Arshad
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- Hypovalent titanium and Ti(II)-Ti(III) interconversions
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Treatment of pink titanium(iii) triflate (0.045 M) with HF in triflic acid (CH3SO3H) converts Ti(iii) rapidly to a 1:1 mixture of TiIV and green TiII: (2 TiIII + 4 HF → TiF4 + TiII + 4 H+). This disproportionation is half complete when [HF] added is 0.027 M. Substituted 1,4-benzoquinones are reduced rapidly by Ti(iii) in the absence of fluoride, yielding straightforward logarithmic curves, but reactions of the same quinones with Ti(ii) in fluoride media exhibit more complex profiles, the major portions of which are zero order in oxidant. These reactions are strongly catalyzed by added Ti(iv). Analyses of complex curves are consistent with a reaction sequence initiated by Ti(ii)-Ti(iv) disproportionation, forming Ti(iii), which reacts with the quinone, yielding the quinhydrone, QH. The latter is rapidly reduced by Ti(ii). Values of rate constants obtained from these analyses are in agreement with those for reductions of quinones by Ti(iii), in the absence of fluoride. The Royal Society of Chemistry 2010.
- Dhar, Basab Bijayi,Gould, Edwin S.
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experimental part
p. 1616 - 1619
(2010/06/20)
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- Deuterium and Carbon-13 NMR of the Solid Polymorphism of Benzenehexoyl Hexa-n-hexanoate
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Deuterium and carbon-13 NMR of specifically labeled benzenehexoyl hexa-n-hexanoate in the various solid-state phases are reported.The spectra exhibit dynamic line shapes which change discontinuously at the phase transitions.The results are interpreted in terms of sequential "melting" of the side chains on going from the low-temperature solid phases IV, III, etc., toward the liquid.In phase IV the molecules are very nearly static, except for fast rotation of the methyl groups about their C3 axes.The results in phase III were quantitatively interpreted in terms of a two-site isomerization process ivolving simultaneous rotation by 95 deg about C1-C1 and transition from gtg to g'g't (or equivalently g'tg' to ggt) for the rest of the chain.The specific rate of this reaction at 0 deg C is ca. 1E5 s-1.In phase II additional chain isomerization processes set-in which were, however, not analyzed quantitatively.Further motional modes, involving reorintation of whole chains about their Car-O bonds, appear on going to phase I.In all solid phases the benzene ring remains static.
- Lifshitz, E.,Goldfarb, D.,Vega, S.,Luz, Z.,Zimmermann, H.
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p. 7280 - 7286
(2007/10/02)
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- REDUCTION OF METHYL BENZOYLFORMATE BY REDUCED NICOTINAMIDE ADENINE DINUCLEOTIDE MODEL IN THE PRESENCE OF RHODIZONIC ACID
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The reduction of rhodizonic acid (RA) with 1-benzyl-1,4-dihydronicotinamide (BNAH; NADH model) was carried out at room temperature to obtain tetrahydroxy-p-quinone (THQ) and hexahydroxybenzene (HHB) by two-electron and four-electron reductions, respectively.The reduction of methyl benzoylformate with BNAH proceded smoothly in the presence of RA, although it could not be reduced at all without RA.
- Endo, Takeshi,Takada, Tadayoshi,Okawara, Makoto
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p. 615 - 618
(2007/10/02)
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