Thermal conductivity, thermal effusivity, and specific heat capacity near the lower critical point of the binary liquid mixture n-butoxyethanol-water

Experimental investigations on binary liquid mixtures near the critical mixing point are presently leading to a controversy about the anomaly in the thermal conductivity. A photopyroelectric technique is used to determine the thermal conductivity and the effusivity of the binary liquid mixture n-butoxyethanol-water at its critical concentration near the critical mixing point. It is proven that, contrary to previous reports, there is no critical enhancement in the thermal conductivity. The specific heat capacity is calculated from these results and compared with the results from measurements performed by adiabatic scanning calorimetry.     

Dilute solution properties of a polyurethane. I. Linear polymers

A linear polyurethane of high molecular weight was prepared in solution by the polyaddition of equimolar amounts of ethylene glycol and methylene bis(4-phenyl isocyanate). The polymer was fractionated by using a direct sequential extraction procedure, with a solvent–nonsolvent system consisting of N,N′-dimethylformamide (DMF) and acetone (A). The resulting fractions were characterized by viscosity and lightscattering measurements. The relationship between the intrinsic viscosity and molecular weight was found in DMF at 25°C. to be [η] = 3.64 × 10^?4M^0.71. The unperturbed polymer chain dimensions were determined from intrinsic viscosity measurements carried out under experimentally determined theta conditions.     

On the synthesis and animation of 5-chloro-and 5-bromo-1,7-naphthyridine

A new synthesis of 5-chloro- and 5-bromo-1,7-naphthyridine, using 8-amino-1,7-naphthyridine as starting material is described. On amination with potassium amide in liquid ammonia, the 5-bromo compound undergoes a tele-amination into 8-amino- and 2-amino-1,7-naphthyridine and a Chichibabin reaction yielding 8-amino-5-bromo-1,7-naphthyridine. The reaction with the 5-chloro compound occurs at a much lower rate than the 5-bromo compound and only gives 8-amino-5-chloro-1,7-naphthyridine in a small yield. Convincing ¹H-nmr evidence is presented, showing that the 5-bromo- and 5-chloro-1,7-naphthyridine give addition of the amide ion at position 8 and that the 5-chloro compound also gives addition at position 2.     

Total luminescence of organic molecules of petrochemical interest : Naphthalene,phenanthrene and 1,2,4,5-tetramethylbenzene

Total emission, phosphoroscopically resolved emission, excitation and mean lifetime in the excited triplet state were measured for three organic molecules of petrochemical interest in EPA rigid glass at 77° K. Fluorescence was also measured at room temperature in n-heptane. Methods for the determination of these three molecules in individual solutions are presented and compared with known methods by absorption spectroscopy. An attempt was made to quantify a blend of the three components by luminescence techniques.     

Total synthesis of the marine alkaloid (-)-lepadin B

An enantioselective total synthesis of (-)-lepadin B has been developed starting from (2S,4S)-2,4-O-benzylidene-2, 4-dihydroxybutanal. The key steps in the synthesis include the use of an aqueous intramolecular acylnitroso Diels-Alder reaction to afford the trans-1,2-oxazinolactam and Suzuki cross-coupling reaction to elaborate the (E,E)-octadienyl unit.     

A simple and versatile method for the synthesis of acetals from aldehydes and ketones using bismuth triflate

Acetals are obtained in good yields by treatment of aldehydes and ketones with trialkyl orthoformate and the corresponding alcohol in the presence of 0.1 mol % Bi(OTf)3.4H2O. A simple procedure for the formation of acetals of diaryl ketones has also been developed. The conversion of carbonyl compounds to the corresponding 1,3-dioxolane using ethylene glycol is also catalyzed by Bi(OTf)3.4H2O (1 mol %). Two methods, both of which avoid the use of benzene, have been developed.     

3,6,9,10-tetrahalogenphenanthrene. A new cycliarylation reaction of DDT-derivatives

A simple synthesis of tetrachlorophenanthrene starting from DDT has been realized. 1,1,1,2-tetrachloro-2,2-bis-(4-chlorophenyl)-ethane (I) and its rearranged product 1,1,2,2-tetrachloro-1,2-bis-(4-chlorophenyl)-ethane (V) and other analogs substituted by halogen in the para-position undergo a cycliarylation yielding 3,6,9,10-tetrahalogenophenanthrenes. Partial dechlorination of this tetrachlorophenanthrene yields 3,6-dichlorophenanthrene. Oxidation gives 3,6-dichloro-9,10-phenanthrenequinone, and chlorosulfonation leads to 3,6,9,10-tetrachloro-2,7-bis-(chlorosulfonyl)-phenanthrene. The mechanism of this cyclization reaction in presence of LEWIS acids is discussed and compared with the cyclization of DDT derivatives to yield fluorenones.     

Emission studies of pyrene solutions

Emission spectra of pyrene in hexane have been obtained over a temperature range (from 130 to 260 K) that has not been explored before for concentrations ranging from 10^?4 mole/? to 2 × 10^?2 mole/?. A conventional and new approximation which does not depend on the experimental set-up response functions has been used for evaluating pyrene excimer association energy W_DM and other pyrene parameters. In both methods W_DM agrees quite satisfactorlly, at all concentrations used, with that reported in the literature and obtained by other techniques. However, both approximation fail to yield the right values of the rate parameters at concentrations ? 2 g/?. This set the upper limit of sample solubility to be at C = 2g/? for our range of temperature. Furthermore, the new approximation can probably be used at higher concentration (for higher range of temperature) and even may be used for other organic molecules. There was also no difference in the ratio of the excimer (I_D) to monomer (I_M) quantum yields when an intense laser beam was used as a source of excitation rather than a super-pressure Hg-lamp. This suggested that the concentrations we used might not be large enough. As a result, the laser beam would not create enough density of excited molecules to affect the ratio of I_D/I_M.     

The formation of filamentous structures from iodinated neurotubules.

The porcine neurotubule and its basic subunit were found to be modified in vitro by iodination of amino acids (principally tyrosine) using lactoperoxidase. Iodide ion, H2O2, or lactoperoxidase singly or in any pairwise combination had virtually no effect on neurotubules. However, when all three reagents were present, permitting covalent iodination, it was found that at 0.1 iodotyrosines per tubulin dimer the microtubules unravel to form structures which morphologically resemble strands of protofilaments twisted or wound around each other. These abnormal tubules are stable at room temperature and 4 degrees C. Both monomers of tubulin are labeled to approximately the same extent. Iodinated tubulin (0.1 iodotyrosines/dimer) is unable to assemble in vitro under normal assembly conditions. Heavily iodinated microtubules (8 iodines per tubulin dimer) are similar in morphology to the slightly iodinated structures.     

Darstellung und Kristallstruktur von K3La(NH2)6

Preparation and Crystal Structure of K₃La(NH₂)₆. Single crystals of K₃La(NH₂)₆ were obtained by the reaction of the metals (3 K + 1 La) during five days at 200°C and 4000 atm NH₃ pressure. The compound crystallizes monoclinic with a = 6.74, b = 11.67, c = 7.23 Å and β = 108.1°; the space group is C2/m (No. 12). The lattice contains 2 formula units. The amide ions are arranged in a strongly distorted cubic closepacking. All cations occupy edging anion-octahedra.