High Optical Rotation Research Articles

Ferrimagnetic Cobalt Ferrite Films Prepared by the Sol-Gel Process

ABSTRACTFerrimagnetic oxide films have been shown to have potential for use as Magneto-optical information storage Materials. Cobalt ferrite films are particularly interesting for magneto optical information storage due to their high magneto optical rotation [1]. In this work, synthesized soluble cobalt (II) and iron (III) Methoxyethoxides were mixed in stoichiometric ratios for use as Co and Fe precursors in the preparation of CoFe2O4ferrimagnetic films. The decomposition of the precursors was characterized by thermogravimetric analysis.CoFe2O4 films were prepared by the dip coating technique using fused silica substrates. These films were then heat treated at temperatures ranging from 200°C to 600°C to study the transformation from an amorphous film to a crystalline film as determined by x-ray diffraction. The Magnetic hysteresis behavior of the films as a function of heat treating temperature and hence crystallinity was also studied. As a general trend, films having a greater degree of crystallinity exhibited larger values of saturation magnetization and remanent Magnetization. The amorphous film was found to exhibit the highest coercive field, but low values of saturation and remanent Magnetization. The effect of heat treating under the influence of a magnetic field of 1.88 kÖe was found to enhance crystallization only slightly and had very little effect on the magnetic properties of the film.

Synthesis and propeller-propeller transition of optically active poly(diphenyl- o-methoxyphenylmethyl methacrylate)

Diphenyl- o-methoxyphenylmethyl methacrylate was polymerized with several organolithium complexes of chiral ligand such as (−)-sparteine (Sp) and (S,S)-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane (DDB). (+)-DDB was effective in preparing a polymer of high optical rotation, whereas (−)-Sp only gave oligomers with low optical rotation for the repulsive hindrance between the bulky ester group and the rigid ligand. The optical rotation of the polymer decreased rapidly to a constant value due to the propeller-propeller transition, which has been demonstrated by 1H n.m.r. and circular dichroic spectra.

Synthesis and ring-opening polymerization of optically pure mesogenic malolactonates

Abstract Optically pure malolactonate monomers containing biphenyl mesogenic groups with either an ethylene or a hexamethylene spacer were prepared from optically pure malic acid and polymerized with alkylaluminoxane catalysts to form a series of new chiral side chain liquid-crystalline polymers, which contained the chiral centres in the backbone. The mesogenic malolactonate monomers were determined to be optically pure by 1H NMR spectroscopy of the β-lactone complexed with a chiral europium shift reagent. Both the methylaluminoxane and isobutylaluminoxane catalysts gave polymers having bimodal molecular weight distributions, the latter catalyst yielded a larger amount of the higher molecular weight fraction than the former. The polymers showed high optical rotations, high degrees of isotactic stereoregularity, and enantiotropic liquid-crystalline properties, all of which were influenced by the molecular weight distribution. Copolymers of malolactonate monomers with different spacers were also prepared an...

Helix Sense-Selective Polymerization of Chloral with Chiral Alkoxide Initiators: Tuning the Chiroptical Properties of the Polymer

The helix sense-selective polymerization of chloral with chiral lithium alkoxides derived from R(−), S(+)-2-octanol and four mono-hydroxy sterols afforded optically active polymer samples with high solid state optical rotations at the sodium D-line (589 nm). This chiroptical behavior stemmed from a predominance of a single screw direction along the polymer’s rigid helical backbone. The sign and magnitude of the optical rotation enhancements were found to depend upon both initiator structure and the conditions under which the polymerizations were carried out. By carefully manipulating experimental conditions, polychloral samples with specific rotations ranging from (+) 4000° to (−) 4000° were readily prepared. Model end-group studies confirmed that the presence of asymmetric initiator fragments in the polymer contributed little to the observed optical rotations reported here. Polychloral prepared with achiral or racemic initiators was optically inactive.

Asymmetric deprotonation of prochiral ketones using chiral lithium amide bases

A number of chiral secondary amines have been prepared and used as precursors to the corresponding chiral lithium amide bases. Treatment of either cis -2,6-dimethylcyclohexanone or 4- tert -butylcyclohexanone with a chiral lithium amide, followed by electrophilic quench, gives chiral products in up to 88% enantiomeric excess. The results with 4- tert -butylcyclohexanone are in disagreement with an earlier literature report, giving products of lower enantiomeric excess but higher optical rotation.

ChemInform Abstract: Synthesis of Novel Chiral 2,3‐Dihydro‐1,3,4‐thiadiazoles with Extremely High Optical Rotations: X‐Ray Crystal Structure of (2R)‐D‐Mandeloyl‐5‐methylthio‐2‐phenyl‐2,3‐dihydro‐1,3,4‐thiadiazole.

AbstractThe methylthiothiocarbonylhydrazone (I) reacts with the enantiomeric phenyldioxolanedione (II) in the presence of trifluoroacetic acid to give the diastereomeric dihydrothiadiazoles (+)‐(III) and (‐)‐(IV) or (‐)‐(III) and (+)‐(IV).

Synthesis of Novel Chiral2,3-Dihydro-1,3,4-thiadiazoles with Extremely High Optical Rotations: X-Ray Crystal Structure of (2R)-D-Mandelyl-5-methylthio-2-phenyl-2,3-dihydro-1,3,4-thiadiazole

L'acylation de methylthiothiocarbonylhydrazone de bromo-4 benzaldehyde par une phenyl-5 dioxolanne-1,3 dione-2,4 chirale conduit aux composes du titre

Partial synthesis and properties of a series of N-acyl sphingomyelins.

A series of sphingomyelins (SM) with different chain length fatty acids (C14:0, C16:0, C18:0, C20:0, C22:0, and C24:0) N-linked to the primary amino group of sphingosine have been synthesized starting with bovine brain SM. Two different acid hydrolysis procedures, butanolic HCl (H. Kaller, 1961. Biochem. Z. 334: 451-456) and methanolic HCl (R.C. Gaver and C.C. Sweeley. 1965. J. Am. Oil Chem. Soc. 42: 294-298), were used and the resultant sphingosylphosphocholine (SPC) was converted to SM using two acylation methods: using fatty acid imidazolide to yield the O-acyl, N-acyl SPC, followed by mild alkaline hydrolysis for selective deacylation at the O-acyl linkage, and selective acylation at the amino group of SPC using the free fatty acid in the presence of dicyclohexylcarbodimide. Following chromatographic purification, N-acyl SM were obtained in high yield (80-90%), and were characterized by a combination of thin-layer chromatography, high performance liquid chromatography, chemical analysis, optical rotation, circular dichroism, infrared spectroscopy, 13C NMR, and sphingosine base analysis. The N-acyl SM were chemically homogeneous with respect to fatty acid composition and the sphingosine base composition resembled that of the starting bovine brain SM. However, as a consequence of the epimerization at C-3 of SPC in both acid hydrolysis procedures, the resulting N-acyl SM consisted of mixtures of D-erythro and L-threo sphingomyelins. By differential scanning calorimetry hydrated C14:0 to C24:0 SM exhibited gel-liquid crystal transitions in the range 30-50 degrees C but the chain length dependence was complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Lyotropic mesophase of cellulose in ammonia/ammonium thiocyanate solution

AbstractSolutions of cellulose in a mixture of 27:73 (w/w) of liquid ammonia and ammonium thiocyanate become liquid crystalline at room temperature above a certain critical concentration which depends on the degree of polymerization of the dissolved cellulose. The high optical rotations of the solution suggest that the cellulose mesophase is cholesteric in nature. In the two‐phase region, the cellulose solutions exhibit negatively birefringent spherulites that possess both ringed and nonringed internal structures. The anisotropic solutions can be oriented by shear, indicating high potential for spinning them into useful fibers.

ChemInform Abstract: Chiral Complexes Polymerize Methacrylate Esters to Give Helical Polymers That Mutarotate by Uncoiling.

AbstractThe reaction of the catalysts (S)‐(Ia)‐ KOtBu, (S,S)‐(Ib) ‐ KOtBu, and (S,S)‐(II)‐ LiBu with (IIIa), the reaction of (S)‐ or (R)‐(Ia)‐ KOtBu with (IIIb), and the reaction of (S)‐(Ia)‐ KOtBu with (IIIc) gave highly isotactic polymers (isotacticity 80‐90%) with high optical rotations whose sign depended on the configuration of the catalyst and was independent of the nature of R2 in the ester monomer (III).

High frequency non-mechanical optical linear polarisation state rotator

A high frequency non-mechanical optical linear polarisation state rotation generator is described which may be directly applied to measurement systems requiring switched or continuously modulated linear polarisation states. Rotation rates in excess of 100 kHz have been demonstrated.

Optically active poly(diphenyl‐2‐pyridylmethyl methacrylate): Asymmetric synthesis, stability of helix, and chiral recognition ability

AbstractDipheny‐2‐pyridylmethyl methacrylate (D2PyMA) was anionically polymerized with several organolithium complexes of chiral ligands such as (‐)‐sparteine (Sp), (S,S)‐( + )‐ and (R,R)‐(‐)‐2,3‐dimethoxy‐1,4‐bis(dimethylamino)butane [(+)‐ and (‐ )‐DDB], (S)‐(‐)‐1 ‐ methyl‐2‐(piperi‐dinomethyl)pyrrolidine (MPP), (S,S)‐( + )‐3,4‐dimethoxy‐N‐(2‐(dimethylamino)ethyl)pyrrolidine (DDEP), and (S,S)‐(+ )‐N‐benzyl‐3,4‐dimethoxypyrrolidine (BDP) in toluene at low temperature. Sp complexes gave a polymer of low optical activity. DDB was a better chiral ligand, and its complex, particularly the complex with N,N'‐diphenylethylenediamine monolithium amide (DPEDA‐Li), was effective in preparing a polymer of high optical rotation. A THF‐soluble portion of the polymer obtained with (‐)‐DDB‐DPEDA‐Li showed [α]25/365 about ‐ 1400°, which was comparable to that of poly(triphenylmethyl methacrylate) (PTrMA) with pure one‐handed helical structure. However, in the polymerization with DDB‐DPEDA‐Li, optical rotation of the polymer depended greatly on polymerization conditions, such as monomer and initiator concentrations, reaction temperature, and polar additives. Fractionation by THF and/or gel permeation chromatography of the obtained polymers revealed that poly(diphenyl‐2‐pyridylmethyl methacrylate) (PD2PyMA) consisted of a mixture of (+)‐ and (‐)‐ polymers which probably were not enantiomeric to each other. DDEP‐DPEDA‐Li and DDEP‐fluorenyllithium complexes were also efficient chiral initiators that gave polymer of the same or higher optical rotation in comparison with DDB complexes. The optical rotation of PD2PyMA in CHCl3‐2,2,2‐trifluoroethanol (90:10) slowly changed with time. Optically active PD2PyMA coated on macroporous silica gel resolved racemic compounds as a chiral stationary phase for high‐performance liquid chromatography (HPLC).

A Three‐Blade Propeller Compound with Seven Bracketed Benzene Rings

High optical rotation and unusually high optical stability are exhibited by the helically chiral hydrocarbon 1. Its synthesis was achieved starting from stilbene by heating the syn-syn-anti and syn-anti-anti conformers formed upon cyclization of a hexaphenylbenzene derivative, followed by racemic resolution.

Characterization of the highest optically active fraction of shale oil

A shale oil sample from an above-ground 150 ton retort, designed to simulate the in-situ retort process, was vacuum distilled to obtain narrow distillate fractions. The optical rotation was measured for each distillate cut. The fraction with the highest optical rotation (470 °–485 °C) was subjected to elution chromatography using hexane, benzene and methanol, respectively. The resulting saturated fraction (hexane cut) was investigated by computerized gas chromatography-mass spectrometry. Three steranes, four pentacyclic triterpanes and five normal alkanes were identified, and the partial structures of two other compounds have been suggested.

Mesomorphic solutions of cellulose triacetate in halogenated organic acids and mixtures of trifluoroacetic acid and dichloromethane

AbstractCellulose triacetate (CTA) forms liquid‐crystalline solutions in trifluoroacetic acid, dichloroacetic acid, and mixtures of trifluoroacetic acid and dichloromethane. Brilliant iridescent coloration, high optical rotations, and birefringent regions with swirl‐like fingerprint patterns suggested the formation of cholesteric liquid crystals. Trifluoroacetic acid–dichloromethane is a particularly excellent solvent mixture to form liquid‐crystal solutions of cellulose acetate. Crude bulk viscosity measurements confirm the formation of an anisotropic phase, and the temperature dependence of the critical concentration for formation of the anisotropic phase, obtained by bulk viscosity measurements at various temperatures, provides confirming evidence. Viscosity decreases with aging, suggesting that CTA is slowly degraded in the solvents studied. This is also confirmed by optical rotatory measurements and by polarizing microscope observations. The miscibility gap is observed as a function of molecular weight, and the differences between the experimental data and Flory's prediction are discussed.

Functional Monomers and Polymers. LXXXIII. Synthesis of Optically Active Polymers from trans- and cis-2-Methyl-1,3-pentadienes by Asymmetric Inclusion Polymerization in Deoxycholic Acid Canals

Optically active polymers of trans- and cis-2-methyl-1,3-pentadienes were prepared by asymmetric inclusion polymerization in deoxycholic acid canals. All of the polymers prepared were found to be of 1,4-trans, head-to-tail structures and showed high optical rotations of (+) sign. It was also found that the optical activity changes reversibly with temperature.

Sphingolipid base metabolism. Chemical syntheses and properties of N-acetyl derivatives of 4R-, 4S-S, 5R-, and 5S-hydroxysphinganine

The following compounds were prepared by chemical synthesis from tribenzoylsphingosine: (2S,3S,4S)-2-acetamido-1,3,4-trihydroxyoctadecane, (2S,3S,4R)-2-acetamido-1,3,4-triydroxyoctadecane, (2S,3S,5S)-2-acetamido-1,3,5-trihydroxyoctadecane, and (2S,3S,5R)-2-acetamido-1,3,5-trihydroxyoctadecane. These compounds were characterized by melting point determination, low and high resolution mass spectra, infrared, optical rotation, chromatographic, and chemical degradation studies. In addition, each of the compounds was converted to the corresponding free base and N-benzoyl derivative. (2S,3S,4R)-2-Benzylamino-1,3,4-trihydroxyoctadecane was prepared from the N-benzoyl derivative of authentic phytosphingosine.

Galactosamine polymer isolated from the cell wall of Neisseria sicca.

A D-galactosamine polymer having a molar ratio of galactosamine–acetyl–phosphorus (1.0:1.0:0.35) has been isolated from the cell wall of Neisseria sicca. Its homogeneity was established by free-boundary electrophoresis, ultracentrifugal sedimentation, and gel permeation chromatography. Molecular weight estimation by reducing end group assay gave a value of [Formula: see text] 18 500. Methylation analysis indicated that the main glycosidic linkages were (1 → 4) and (1 → 6) with a minimum of 10% branch points. The glycosidic bonds were indicated as being in the α configuration by the high positive optical rotation of the polysaccharide and also from infrared spectrum evidence. Both the acetyl and phosphate contents were relatively unchanged by the Hakamori methylation procedure. Although galactosamine polymers have been found in a number of fungi, the present instance appears to be the first report of their presence in bacteria.

Binding of Bilirubin to Low-Affinity Sites of Human Serum Albumin in Vitro Followed by Co-Crystallization

Human serum albumin has three hydrophobic binding sites for bilirubin, one high affinity and two subordinate sites. At pH 7.4 the two molecules of bilirubin bound at the latter sites are unstable, since the equilibrium concentration of free bilirubin is higher than the solubility. Co-crystallization takes place, resulting in a suspension of micro-crystals containing about 200 molecules of bilirubin for each albumin. The fresh suspension shows a high optical rotation with a negative Cotton effect, indicating that the bilirubin molecules are arranged in an optically active pattern, the asymmetry originating from the albumin.

HOT-PRESSED CdCr2S4: AN EFFICIENT MAGNETO-OPTIC MATERIAL

The ferromagnetic semiconductor CdCr2S4 has been prepared in the form of hot-pressed polycrystalline samples having high optical transmission and Faraday rotation in the near-ir spectral region. In the region 900–1400 nm, the figure of merit exceeds 60° dB−1 at 4.2 °K and 30° dB−1 at 80 °K. It is thus an efficient and potentially useful magneto-optic material at liquid-nitrogen temperature.