Activity, optical s. under

Of course, whether the symmetry groups for armchair and zigzag tubules are taken to be (or or T>2 /, the calculated vibrational frequencies will be the same the symmetry assignments for these modes, however, will be different. It is, thus, expected that modes that are Raman or IR-active under or T) i, but are optically silent under S>2 h will only show a weak activity resulting from the fact that the existence of caps lowers the symmetry that would exist for a nanotube of infinite length. 

M. le Blanc gave the refractive indices of solii. of potassium and rubidium bromides as 1 5593 and 1 5533 respectively, when the densities are 2"738 and 3 314 respectively. Hence the refraction eq. of potassium bromide by Gladstone and Dale s formula is therefore 24 32 and by Lorentz and Lorenz s formula 14-05 the corresponding values for rubidium bromide are27"62 and 15"98. The mol. refractions of potassium bromide in soln. by the two formulae are respectively 25"11 and 14 70 and of rubidium bromide in soln., 27 85 and 16 33. The mol. refractions of these salts are therefore greater in soln. than in the solid form. Crystals of potassium bromide, says H. Marbuch, exhibit optical activity. A. S. Newcomer found that sodium chloride was the only salt relatively soluble and yet capable of emitting fluorescent rays in the mid-ultra-violet region of the spectrum under the influence of X-rays. 

Until quite recently the isolation of optically active seienoxides has been limited to those contained in steroids (isolated as diastereoisomeis). < The difficulty in obtaining these compounds was attributed to the racemization through the achiral hydrated intermediates. Simple optically active sel enoxides (S-11% ee) were first prepared by kinetic resolution. Direct oxidation of selenides to seienoxides was first reported using optically active oxaziridine derivatives under anhydrous conditions, but the extent of the asymmetric induction was somewhat unsatisfactory with methyl phenyl selenide as substrate (8-9% Recently much improved enantiomeric excesses (45-73%) were achieved with new oxaziridine reagents such as (70). An attempt at the asymmetric oxidation of more bulky selenides was independently carried out using Bu OCl in the presence of (-)-2-octanol (equation 55), but resulted in unsatisfactory enantioselectivities (ee 1%). Much better results were obtained by the oxidation of p-oxyalkyl aryl selenides (ee 18-40% equation 56) 27 gjyj selenides (ee 1-28%) using... 

T.F. Walsh and co-workers synthesized two (S)- 3-methyl-2-aryltryptamine based gonadotropin hormone antagonists via a consecutive Larock indole synthesis and Suzuki cross-coupling. The required (S)-P-methyltryptophol derivatives were prepared by coupling 4-substituted o-iodoanilines with optically active internal alkynes under standard conditions. The resulting 2-trialkylsilyl substituted indoles were then subjected to a silver-assisted iododesilylation reaction to afford the 2-iodo-substituted indoles that served as coupling partners for the Suzuki cross-coupling step. 

Di(isopinocampheyl)borane Resolution of racemic ethylene derivatives with optically active boranes s. 19, 720 Lithium tetrahydridoborate s. under (C2H )gN,HCl Sodium tetrahydridoborate/boron fluoride Boranes from ethylene derivatives s. 16, 753... 

Aluminum chloride s. under Li[AlHJ Microorganisms Optically active lactones from ketocarboxylic acids... 

A soln. of 0.5 mole of ethyl a-hydroxyisobutyrate in ether added dropwise to a soln. of p-dimethylaminophenyllithium prepared from 2 moles of p-bromo-dimethylaniline and 4 moles of small pieces of Li-ribbon (preferably containing ca. 0.6% Na) in anhydrous ether under Ng, and refluxed 5 hrs. l,l is-(p-di-methylaminophenyl)-2-methyl-1,2-propanediol. Y 86% based on ethyl a-hydroxyisobutyrate. F. e., also with a-alkoxyesters and a-alkoxylactones, s. J. B. Wright and E. S. Outsell, Am. Soc. 81, 5193 (1959) optically active compounds s. D. J. Gram et al.. Am. Soc. 81, 5740 (1959) effect of sodium content of lithium on the prepn. of organolithium compounds s. a. G. W. Kamienski and D.L. Esmay, J. Org. Ghem. 25, 1807 (1960). 

Optical coating(s), active Film structures that change their optical properties under an external stimulus. 

Carbonylative Ring Expansion. When either a- or p-pinene (30) or (31) is heated neat with an equimolar amount of Fe(CO)s under an initial pressure of 30 psi CO at 160°C, two ketones (32) and (33) are obtained, formed by insertion of CO into the cyclobutane ring (eq 12). Both ketones are optically active. 

Studies of reaction mechanisms ia O-enriched water show the foUowiag cleavage of dialkyl sulfates is primarily at the C—O bond under alkaline and acid conditions, and monoalkyl sulfates cleave at the C—O bond under alkaline conditions and at the S—O bond under acid conditions (45,54). An optically active half ester (j -butyl sulfate [3004-76-0]) hydroly2es at 100°C with iaversion under alkaline conditions and with retention plus some racemization under acid conditions (55). Effects of solvent and substituted stmcture have been studied, with moist dioxane giving marked rate enhancement (44,56,57). Hydrolysis of monophenyl sulfate [4074-56-0] has been similarly examined (58). 

The configuration of the amine was retained, except in the case of amino acid derivatives, which racemized at the stage of the pyridinium salt product. Control experiments showed that, while the starting amino acid was configurationally stable under the reaction conditions, the pyridinium salt readily underwent deuterium exchange at the rz-position in D2O. In another early example, optically active amino alcohol 73 and amino acetate 74 provided chiral 1,4-dihydronicotinamide precursors 75 and 76, respectively, upon reaction with Zincke salt 8 (Scheme 8.4.24). The 1,4-dihydro forms of 75 and 76 were used in studies on the asymmetric reduction of rz,>S-unsaturated iminium salts. 

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