- Electrophilic Bromination of Micelle-Associated Alkenes as a Probe of Micelle Structure
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The products and kinetics have been examined for the bromination in aqueous micelles of a series of unsaturated fatty acids, esters, and alcohols.A limited kinetic study of mercuration in SDS micelles is also reported.Bromination products are the following: CTAB micelles, 100percent dibromide; CTAC, principally α-bromochloride, with some bromohydrin and trace dibromide; SDS, a 2:1 mixture of bromohydrin and a bromosulfate ester derived from reaction with the headgroup of the micelle.These products are formed stereospecifically anti,and there is no significant dependence on the original position or geometry of the double bond.The bromination kinetic studies, carried out in SDS, Brij-35, and CTAB micelles, reveal considerably slower rates as compared to those in water and, in contrast to homogeneous media, sensitivities to the double bond position, its geometry and the presence of other unsuturated chains, and an enhanced terminal alkene reactivity.A dependency on micelle charge type and added salts is also observed.Both products and kinetics support a mechanism where the bromonium ion intermediate is formed and trapped in a relatively polar region of the micelle, intimately associated with the headgroup and its counterions.A model, the segment protrusion model, is proposed in which the double bond enters the "reactive" region by protrusion of a chain segment from the relatively nonpolar hydrocarbon region.The rate of reaction is determined by the absolute rate in this region, which is large, offset by the probability of the double bond being found there, which is small.The fraction of double bonds in a reactive state is determined by two factors: the probability that the chain segment containing the double bond will reach an interfacial location and the free energy cost of solubilizing a chain segment in a polar environment.This model is examined in the context of other recent experimentally and theoretically based models of micelles.
- Lennox, R. Bruce,McClelland, Robert A.
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- Merging shuttle reactions and paired electrolysis for reversible vicinal dihalogenations
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Vicinal dibromides and dichlorides are important commodity chemicals and indispensable synthetic intermediates in modern chemistry that are traditionally synthesized using hazardous elemental chlorine and bromine. Meanwhile, the environmental persistence of halogenated pollutants necessitates improved approaches to accelerate their remediation. Here, we introduce an electrochemically assisted shuttle (e-shuttle) paradigm for the facile and scalable interconversion of alkenes and vicinal dihalides, a class of reactions that can be used both to synthesize useful dihalogenated molecules from simple alkenes and to recycle waste material through retro-dihalogenation. The reaction is demonstrated using 1,2-dibromoethane, as well as 1,1,1,2-tetrachloroethane or 1,2-dichloroethane, to dibrominate or dichlorinate, respectively, a wide range of alkenes in a simple setup with inexpensive graphite electrodes. Conversely, the hexachlorinated persistent pollutant lindane could be fully dechlorinated to benzene in soil samples using simple alkene acceptors.
- Dong, Xichang,Roeckl, Johannes L.,Waldvogel, Siegfried R.,Morandi, Bill
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- Preparation of a novel bromine complex and its application in organic synthesis
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Although molecular bromine (Br2) is a useful brominating reagent, it is not easy to handle. Herein, we describe the preparation of a novel air-stable bromine complex prepared from 1,3-dimethyl-2-imidazolidinone (DMI) and Br2, which was identified to be (DMI)2HBr3 by spectral and X-ray techniques. This complex was then used to brominate olefins, carbonyl compounds, and aromatics, as well as in the Hofmann rearrangement. Yields of reaction products using this complex were almost the same or superior to those using other bromine alternatives.
- Nishio, Yuya,Yubata, Kotaro,Wakai, Yutaro,Notsu, Kotaro,Yamamoto, Katsumi,Fujiwara, Hideki,Matsubara, Hiroshi
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p. 1398 - 1405
(2019/02/07)
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- COMPOUNDS USEFUL IN HIV THERAPY
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The invention relates to compounds of Formula (I), vvherein R1 is selected from the group consisting of: Formula (Ia) and (Ib) as well as methods of treating or preventing HIV in subjects.
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Page/Page column 55; 56
(2019/10/01)
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- Configurational Assignment of ‘Cryptochiral’ 10-Hydroxystearic Acid Through an Asymmetric Catalytic Synthesis
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An asymmetric catalytic total synthesis of (S)-10-hydroxystearic acid (1) for comparison of its absolute configuration to that of samples obtained by fermentative hydration of oleic acid is reported. The synthesis involves two catalytic key-steps, namely Ru-catalyzed anti-Markovnikov hydration of 9-decynoic acid (7) to 10-oxodecanoic acid (5), followed by titanium-mediated asymmetric catalytic addition of dioctylzinc (25) to 5 in presence of the chiral ligand N,N’-((1R,2R)-cyclohexane-1,2-diyl)bis(1,1,1-trifluoromethanesulfonamide) (6). The synthesis is short and efficient and avoids use of protecting groups. Ozonolysis of 10-undecynoic acid (9) to 5 provides an alternative entry point into the synthetic route. The double dehydrobromination of (ω,ω-1)-dibromoalkanoic acids to ω-alkynoic acids under a variety of conditions was investigated with 10,11-dibromoundecanoic acid (11) as model substrate and using qNMR to quantify all reaction products. The synthetic approaches presented here have the potential to be generalized to the asymmetric catalytic synthesis of a variety of n-hydroxy-fatty acids.
- Brunner, Andreas,Hintermann, Lukas
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p. 928 - 943
(2016/12/09)
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- Synthesis and functionalization of vinylsulfide and ketone-containing aliphatic copolyesters from fatty acids
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A series of novel aliphatic copolyesters bearing vinylsulfide and ketone functional groups were synthesized via lipase catalyzed polycondensation of vegetable oil derivatives. The vinylsulfide-containing hydroxyacid (VSHA) from 10-undecenoic fatty acid and the ketone-containing hydroxyester (KHE) from methyl oleate were used to obtain random copolymers and further sequential and single-step strategies involving the reactions with thiol and oxyamine were investigated. Good agreement between product and feed stoichiometries was achieved in both reactions for sequential modification, and the order of addition seems not to be a significant parameter. One pot functionalization allows for the single step modification, but not quantitative reactions were achieved.
- Beyazkilic, Zeynep,Lligadas, Gerard,Ronda, Juan Carlos,Galià, Marina,Cádiz, Virginia
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p. 290 - 298
(2015/11/11)
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- Formation of gel and fibrous microstructures by 1-alkyne amphiphiles bearing L-serine headgroup in organic solvents
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The study of amphiphiles that form non-spheroidal, and other assemblies, upon solvation is the key to understanding the relationship between molecular structure and supramolecular morphology. With this aim in mind, we have employed L-serine and L-histidine derivatives that are linked via amide bond to hydrophobic chain. L-Serine amphiphiles form gels in CHCl3, CH2Cl2 and CCl4. Microscopic examinations of these gels reveal the coexistence of tubules, helical ribbons, and spheres. On the other hand, they produce only spherical structures and rods when dispersed in aqueous media (phosphate buffer). In contrast, amphiphiles based on the L-histidine group, neither formed any gel nor produced any microstructures in non-aqueous solvents like CHCl3, but produced spherical structures and helical rods in water. We also examined the effect of introducing 1-yne or 1-ene moieties into the hydrocarbon chain of such amphiphiles. These moieties, when present in the hydrophobic segment, do not perturb the supramolecular assembly features of the respective serine amphiphiles. Actually, 1-yne moiety, when present in the hydrophobic portion of the amphiphiles, gives characteristic UV-fine structures upon aggregation in water and might be used as a non-invasive marker for probing critical aggregate concentration.
- Ragunathan, Kaliappa G.,Bhattacharya, Santanu
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- A new method for the synthesis of (Z)-9-hexadecen-1-al, an importannt pheromone component of Heliothis armigera and many other pests
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A simple and convenient synthesis of (Z)-9-hexadecen-1-al (1), an important sex pheromone component of 1-Heliothis armigera, has been achieved from the cheap and readily available 10-undecenoic acid (2).
- Narasimhan, S.,Mohan, H.
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p. 950 - 953
(2007/10/03)
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- Diacetylenic Liquid Crystalline Diesters
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Diesters of 10,12-docosadiyne-1,22-dionic acid with 4-hydroxy-4'methoxybiphenyl (I), 4-hydroxy-4'-methoxyazoxybenzene (II), and 4-hydroxy-4'-methoxy(2,2'-dimethyl) azoxybenzene have been prepared.The diester I displayed high sensitivity to light and u.v. irradiation while it was not mesomorphic.In contrants, diesters II and III were nematic while displaying considerably less radiation sensitivity.A suggested reason for this difference in behavior is the difference in the molecular packing of the corresponding crystal.The differnce in the mesomorphic behavior between II and III is explained in terms of mesogen broadening and distortion of the mesogen molecule of III by the methyl substituents.Keywords: diacethylenic diesters, synthesis of, liquid crystalline order
- Ozcayir, Y.,Blumstein, A.
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p. 237 - 246
(2007/10/02)
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- Diacetylenic Liquid Crystalline Polymers II: Derivatives of 10,12-Docosadiyne-1,22-Dioic Acid
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Polymers of 10,12-docosadiyne-1,22-dioic acid with different mesogenic groups have been prepared.The mesogenic groups were diphenyl (Polymer I); p-diphenylazoxy (Polymer II); 2,2'-dimethyldiphenylazoxy (Polymer III); 2-methyldiphenylazomethine (Polymer IV) and α-methylstilbene (Polymer V).All polymers crystallized extensively at room temperature, but only polymers I and V displayed an enantiotropic smectic mesophase.The X-ray diffractograms were consistent with a smectic H mesophase for both polymers.Polymers I and V differed also from polymers II-IV by enhanced reactivity of the diacetylenic moiety.A model for chain packing consistent with the X-ray diffraction pattern of the crystalline and the smectic phase is proposed.Keywords: diacetylenic polyesters, synthesis of, liquid crystalline order
- Ozcayir, Y.,Asrar, J.,Clough, S. B.,Blumstein, A.
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p. 167 - 178
(2007/10/02)
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- SIMPLE AND STEREOCONTROLLED SYNTHESIS OF AN OPTIMAL ISOMERIC MIXTURE OF 3,13-OCTADECADIEN-1-YL ACETATES
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A simple route has been developed for the preparation of the optimal isomeric mixture of 3,13-octadecadien-1-yl acetates (ODDA) which is the active sex pheromone of many Synanthedon species.The stereocontrolled formation of double bonds have been achieved via Wittig reaction and subsequent reduction of C-C triple bond.
- Vinczer, Peter,Baan, Gabor,Juvancz, Zoltan,Novak, Lajos,Szantay, Csaba
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p. 1257 - 1270
(2007/10/02)
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