Cl35 NQR spectra and the transmission effects in the series RSO2Cl

Conclusions It was shown by correlating the Cl³⁵ NQR frequencies with the Taft _I and _c parameters that the effect of substituents, which are either capable of conjugation (Hal, OR, NR₂) or are alkyl groups, is transmitted to the chlorine atom through the SO₂Cl group by a practically purely inductive means.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 486–488, February, 1970.     

Sizes and interfacial free energies of crystallites formed from fractionated linear polyethylene

Replicas of fracture surfaces of fractions of linear polyethylene, which were crystallized at elevated temperatures for extended time periods, were examined by electron microscopy. Striated. lamella-type crystallites were observed for all molecular weights over the range 3.2 × 10³?5.7 × 10⁵. In agreement with Anderson's previous report, for molecular weights of 12,000 or less, the crystallite thicknesses were comparable to the extended chain length. As the molecular weight increased above this level, however, the crystallite sizes increased only slightly and hence at high molecular weights were very much smaller than the extended chain length. From the measured melting temperatures, crystallite interfacial free energies were calculated from the theory for the melting of finite size crystals comprised of chains of finite length. The crystallite interfacial free energy was found to increase with molecular weight. Based on these results, a crystallization process is outlined which allows for the formation of either extended chain crystallites, or crystallites whose size is much smaller than the extended chain length without any change in nucleation mechanism or arbitrary adjustment in growth mechanism with molecular weight.     

Influence of HCl on the stability of liquid lamellae between two colliding bubbles in aqueous solutions ofn-fatty acids

The effect of HCl on life time of liquid lamellae created between two colliding bubbles in aqueous solutions ofn-fatty acids were studied. The results show, that the addition of HCl has a pronounced influence on life time of the lamellae. At low fatty acid concentration the lifetime of the lamellae in the acidified solution is higher than in the nonacidified solution, but at higher fatty acid concentration the effect reverses. The analysis of these experimental results show that the characteristic influence of HCl on lamellae lifetime can be explained by the formation of distinct association states of the fatty acids in the liquid phase at different concentration ranges. The results are discussed with respect to bubble coalescence in gas-liquid contactors.     

PHYCOBILIPROTEINS: COMPARISON OF SOLUTION AND SINGLE CRYSTAL FLUORESCENCE FOR C-PHYCOCYANIN AND B-PHYCOERYTHRIN*

Abstract— Trimeric and hexameric solution forms of C-phycocyanin (CPC) from the cyanophyte Agme-nellum quadruplicatum have been isolated and their spectral properties compared to those obtained from single crystals. Although the absorbance peak of a suspension of small C-phycocyanin crystals is red-shifted only 7 nm relative to the solution forms, the single crystal fluorescence is red-shifted 60 nm relative to the solution forms. The crystal fluorescence spectrum exhibits a single peak at LD_max= 708 nm when excited at 514.5 or 530.9 nm and two peaks (LD_max= 661 and 708 nm) when excitation occurs at 568.2 nm. Fluorescence depolarization measurements indicate that extensive energy transfer could occur for both solution and crystal forms with the latter being dependent upon the relative orientation of the crystal with respect to the excitation dipole. Similar results were obtained with B-phycoerythrin (BPE) from the red alga Porphyridium cruentum where the single crystal fluorescence is red-shifted =50nm relative to the solution spectra with two peaks (LD_max= 583 and 617 nm) observed whose relative intensities are dependent on the excitation wavelength (LD_max– 514.5 and 530.9 nm). Single crystal fluorescent lifetimes exhibited considerable shortening relative to that observed for the solution forms. The implications of these results are discussed with respect to the possible relationships of the crystalline structures to the assembly forms present within phycobilisomes.     

Constitution moleculaire d'α,ω-difluoropolydimethylsiloxanes equilibres obtenus par une reaction de redistribution

α,ω-Difluoropolydimethylsiloxanes F[(CH₃)₂SiO]_n(CH₃)₂SiF have been prepared by reaction of (CH₃)₂SiF₂ with cyclic dimethylsiloxanes [(CH₃)₂SiO]_n (n = 3 or 4). An equilibrium is reached in the redistribution of fluorine vs. oxygen atoms after ca. 24 h at 200°C or 15 days at 150°C when catalysed by AlCl₃. 16 equilibrated samples of varied (R = F/Si) overall compositions have been analysed by ¹H and ¹⁹F NMR and by VPC. The presence of rings has been established for the lower values of R. The molecular constitution of the equilibrated samples is described by a set of constants. The abundance of the end units

is slightly larger than expected from random distribution. The good resolution of the spectra permits the distinguishing of the 9th order of environment of the end units and the 5th order for the middle units and the verification that there is no preferential association among the building units, and thus the proportion of chains of various lengths obeys Flory's random distribution mode. The equilibrium molecular constitution of these α,ω-difluorosiloxanes is close to that of their dichloro analogs; the substitution of chlorine by fluorine atoms at the end of the chains thus appears to cause little perturbation. On the other hand, the kinetic evolution of the reaction appears to be different, since the first species which forms is always the pyro molecule

instead of long chains and large rings as in the case of the chloro analogs.     

Synthesis and reactions of β-(5-halo-3-uracyl) propionic acids

The reaction of elementary bromine and iodine with -(3-uracyl)-propionic acid has given the corresponding -(5-bromo-3-uracyl) and -(5-iodo-3-uracyl)propionic acids. The methyl esters and amides of the acids have also been synthesized for the first time.     

Reaction of styrene with sulfur and triiron dodecacarbonyl and the molecular structure of the complex Fe2(CO)6(SCH2S)

Reaction of excess styrene with Fe₃(CO)₁₂ and sulfur (60°C, 15 h, Ar, S/Fe₃(CO)₁₂ 0.6 g-atom/mole) gave Fe₂(CO)₆S₂, Fe₃(CO)₉S₂, Fe₂(CO)₆(S₂CO), Fe₂(CO)₆S₂(PhCHCH₂), PhCHCH₂S₄, and a novel binuclear complex Fe₂(CO)₆(S₂CH₂S), whose structure was analyzed by x-ray crystallography. The crystals are monoclinic, a=7.764(3), b=13.205(4), c=6.628(6) Å, =98.97(3)°. V=671.2(7) ų, Z=2, space group P2₁/m. The bond lengths are Fe-Fe 2.520(2), Fe-S 2.236(2), S-S 2.078(4), C-S 1.825(12), Fe-CO 1.784(8), and CO 1.148(9) Å.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 930–934, April, 1991.     

Ligand exchange reactions of ferrocene with phenanthrene or 9,10-dimethylphenanthrene in the presence of aluminum chloride and aluminum

Ligand exchange reactions between phenanthrene or 9,10-dimethylphenanthrene with ferrocene effected in the presence of AlCl₃-Al were carried out under a variety of conditions. With phenanthrene (I), hydrogenation at the C-9 and C-10 positions could take place during the reaction and the cationic products obtained were the η⁶-phenanthrene-η⁵-cyclopentadienyliron and η⁶-9,10-dihydro-phenanthrene-η⁵-cyclopentadienyliron moncations (II and III), and the η⁶-phenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron and η⁶-9,10-dihydrophenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron dications (IV and V). With 9,10-dimethylphenanthrene (VI), reactions carried out in refluxing cyclohexane gave the non-hydrogenated η⁶-9,10-dimethylphenanthrene-η⁵-cyclopentadienyliron monocation (VII) and η⁶-9,10-dimethylphenanthrene-$\text{trans}$-$\text{bis}$-η⁵-cyclopentadienyliron dication (VIII). When higher temperatures were used in an attempt to promote hydrogenation, decomposition predominated and no cationic product could be obtained. These finding are discussed and contrasted with previous results obtained from similar reactions using anthracene or 9,10-dimethylanthracene.