نتایج جستجو برای: chiral center

تعداد نتایج: 319485  

In the present paper, the expressions for scalar and vector potentials in lossless isotropic chiral media are analyzed. Propagating eigenvalues of these potentials are then obtained. Furthermore by decomposition of sources and fields in a chiral medium, we introduce the auxiliary right-and left-handed potentials and find the associated fields. These potentials are used to solve the problem of a...

Journal: :Dalton transactions 2010
Julia V Dickschat Slawomir Urban Tania Pape Frank Glorius F Ekkehardt Hahn

The N,N'-dimesitylene substituted o-phenylenediamine 1 reacts with Sn[N(SiMe(3))(2)](2) under formation of the monomeric N-heterocyclic stannylene 2, while the chiral N,N'-substituted o-phenylenediamine 3 reacts with E[N(SiMe(3))(2)](2) (E = Ge, Sn) under formation of the chiral germylene 4 and the chiral stannylene 5, respectively. X-Ray diffraction studies with both stannylenes demonstrated t...

1998
G. P. CRAWFORD

The correlation between molecular structure and electrooptic performance is studied for novel room temperature chiral smectic A liquid crystals. It is observed that slight modifications of the hydrocarbon chain connected to the chiral center result in dramatic differences in their electrooptic performance. If the hydrocarbon chain is shortened or if a double bond is localized at the end of the ...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه شهید بهشتی - دانشکده علوم 1377

در این پایان نامه با هدف نهایی تعیین بار فرمیونی سالیتونها، جفت شدگی میدانهای فرمیونی و سالیتونی در نظر گرفته شده است . در فصل اول مفاهیم سالیتون و امواج سالیتاری مورد بررسی قرار گرفته، و در این راستا چنین امواجی با مثالهایی در 1+1 و 1+2 بعد توصیف گردیده اند. در فصل دوم قطبیده شدن خلاء فرمیون (vacuum polarization: vp) در حضور میدان سالیتونی مورد بررسی قرار گرفته. در این زمینه در سال 1994 گوشه و...

Journal: :Science 2016
Brett A McGuire P Brandon Carroll Ryan A Loomis Ian A Finneran Philip R Jewell Anthony J Remijan Geoffrey A Blake

Life on Earth relies on chiral molecules-that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere. We present the astronomical detection of a chiral molecule, propylene oxide (CH3CHCH2O), in absorption toward the Galactic center. Propylene oxide is detected in the gas phase in a co...

Journal: :Journal of the American Chemical Society 2005
Yun Jeong Hwang Ansoon Kim Eunkyung Hwang Sehun Kim

We have investigated the chiral adsorption configurations of styrene on Ge(100) using scanning tunneling microscopy at 300 K. The chemisorbed styrene on a single Ge dimer reduces the symmetry of the molecule, which produces a chiral center, and leads to the (S) or (R) chiral on-top configuration. We have found that the dimeric adsorption of styrene induced by the Ge surface dimer structure form...

Journal: :ACS Catalysis 2021

The enantioselective intramolecular oxyamination of unsaturated alkoxyamines using a hybrid catalytic system consisting Cp*RhIII/chiral disulfonate/CuOAc is described. Tetrahydrofuran derivatives with tetrasubstituted chiral center were obtained under the optimized conditions in 91:9–97:3 er. use sterically hindered disulfonate and Cu additive was essential for high enantioselectivity.

2012
San N. Khong Ohyun Kwon

The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines c...

A common approach in resolving enantiomers of chiral basic drugs by capillary electrophoresis (CE) is to use cyclodextrins (especially their anionic derivatives) as chiral selector in the acidic buffer (pH ≤ 3) in normal or reversed (carrier) mode. Then, some organic modifiers are added to the buffer solution if the resolution is not satisfactory. In case of cetirizine (CTN), applying the same ...

Journal: :Chemical & pharmaceutical bulletin 2002
Masashige Yamauchi Kazuhiro Itai Yuko Honda

The enantioselective Lewis acid-catalyzed Diels-Alder reaction of 3-(2-propenoyl)-1,3-oxazolidin-2-one 8 with cyclopentadiene was examined using a series of chiral mox ligands 2-6, deferring in the side chain at 2-position of the chiral oxazoline and in the nature of the substituent at the chiral center (4-position) of the oxazoline ring, and a combination of N-[(1R)-2-chloro-1-phenylethyl]-2-[...

نمودار تعداد نتایج جستجو در هر سال

با کلیک روی نمودار نتایج را به سال انتشار فیلتر کنید