Mobility of some ions produced by tritium betas

The aqueous solution of coumarin has been studied spectrophotometrically as a -ray dosimeter and effects of temperature and light conditions on the stability of response during post-irradiation storage have been studied. Post-irradiation storage at room temperature in dark showed that after a very small increase in absorbance within the first 6 d, the response of the dosimeter was stable up to 42 d. At lower temperature (–15 °C), there was some decrease in absorbance within the first 24 h followed by a stable response up to 35 d. For post-irradiation storage at higher temperatures (40, 60 °C) the dosimeter, apart from some initial increase in absorbance, showed a nearly stable response up to 25 d. The effect of different light conditions during post-irradiation storage has also been studied. When stored in fluorescent light the response was almost stable from 6 d till about 40 d. In diffuse sunlight, the response was stable up to about 35 d at 360 nm and 370 nm but showed a somewhat unstable behavior at 347 nm. The dosimetric solutions were unstable when exposed to direct sunlight.     

Benzolactams. 4. Reaction of 3',4'- or 4',5'-dialkoxy-substituted 1-(2'-Bromobenzyl)-2-ethoxycarbonyl-1,2,3,4-tetrahydroisoquinolines with alkyllithium. 1,2 and 1,4 additions of alkyllithium to benzolactams

Treatment of 1-(2'-bromo-3',4'-dialkoxybenzyl)-1,2,3, 4-tetrahydroisoquinoline carbamates, 1a,c, with excess alkyllithium gave 8-oxoberbines, 2a,c, which were successively attacked in situ with another molecule of alkyllithium to give 1,2 and/or 1,4 addition products. A primary alkyllithium, such as MeLi or BuLi, gave a 1,2 addition product, 8-methyleneberbine 9a or 8-butylideneberbine 3a. t-BuLi preferred 1,4 addition, followed by elimination of the alkoxy group, to give 9-tert-butyl-8-oxoberbine 6a or 7c. s-BuLi gave a mixture of 1,2 and 1,4 addition products, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3,4-tetrahydroisoquinoline 4a and 9-s-butyl-8-oxoberbine 5a. Similar treatments of carbamate 1b having no alkoxy group at its 3' position gave 1,2 addition products, 8-butylideneberbine 3b, 1-[2'-(2' '-methylbutyryl)benzyl]-1,2,3, 4-tetrahydroisoquinoline 4b, and 1-(2'-pivaloylbenzyl)-1,2,3, 4-tetrahydroisoquinoline 6b, in all cases. Reactions of 1a with s-BuMgCl and isoPrMgCl also gave the 1,4 adduct, 5a, and its 9-isoPr analogue, 12a. Treatment of 9a with excess NaBH(4) in AcOH gave (+/-)-coralydine (10b).     

Coordination Complexes of Some Group(IV) Halides with Monodentate Schiff Bases

Coordination compounds resulting from the interaction of N-(phenyl)benzalaldimine and its derivatives containing a methyl group in different positions of the aniline ring and group(IV) halides, MX₄ (where M = Si or Sn and X = Cl or Br), have been prepared and characterized by elemental analyses and electronic, infrared and Raman spectra.     

PHOTOREACTIVATION OF THYMINE-STARVED ESCHERICHIA COLIBs-1

Abstract —Thymine starvation prior to 254 nm ultraviolet light (UV) exposures has been found to decrease the level of maximum photoreactivation in Escherichia coli B _s-1. The dark equilibrium level of photoreactivating enzyme-substrate complexes was determined from the levels of photoreactivation obtained with exposures to single flashes of high-intensity light. The kinetics indicate that photoreactivating enzyme concentration does not decrease as a result of thymine starvation. The UV sensitivities of normal and thymine-starved cells are found to be the same. Photoreactivation by sequential flashes shows a lesser number of total photorepairable lesions in starved cells. It is concluded that thymine starvation renders a portion of the dimers inaccessible to the photoreactivating enzyme, thus lowering the level of maximum photoreactivation.     

Singlet–triplet splittings as obtained from the Xα-scattered wave method: A theoretical analysis

The theoretical determination of singlet–triplet splittings of the excited states of closed-shell molecules is discussed with emphasis on the use of the Xα–scattered wave method. With this method, splittings can be computed in two independent ways. Both will have corrections due to orbital relaxation effects. The singlet–triplet splittings obtained with the Xα–scattered wave method for several large organic molecules are reviewed. It is seen that the results using the two splitting formulas differ by a large amount; in fact, they differ by the magnitude of the computed splitting. We provide a criterion for choosing the results obtained with one method over the other by showing that they both give upper bounds to the best result obtainable within the framework of the model. However, because of the large differences between the two methods, the quantitative value of the splitting should be viewed with caution.     

The stability of silver iodide sols in the presence of polyacrylic acids of various molecular weights

Summary The effect of a series of polyacrylic acids, ranging in molecular weight from 1.67×10⁴ to 2.36×10⁶, on the stability of positively charged silver iodide particles has been examined. Flocculation of the sol occurred at a well defined concentration of polyacrylic acid,c _f , and a further increase in concentration of the polyelectrolyte caused restabilization of the sol. Over the range examinedc _f appeared to be related to the viscosity average molecular weight of the acid,M _v , by an equation of the form,c _f =a ·M _v ^{– b} wherea andb are constants.     

Effects of temperature on styrene–methacrylonitrile copolymerization

The free-radical copolymerization of styrene and methacrylonitrile was studied in toluene solution at 60, 90, and 120°C. Copolymer composition was estimated from gas-chromatographic measurement of unreacted monomer concentrations. Reactions were carried to about 20% conversion to minimize analytical errors. Reactivity ratios were calculated by using an integrated form of the Mayo-Lewis simple copolymerization equation. Reactivity ratios were not sensitive to reaction temperature. The values at 90°C are r₁ = 0.41 (methacrylonitrile) and r₂ = 0.37 (styrene). The r₁ values are higher than those reported by other workers, presumably because of advantages in the present analytical technique and calculation method. The negligible temperature dependence of reactivity ratios is in accord with theory. If monomer pairs exhibit pronounced dependence of reactivity ratios on polymerization temperature, this may indicate a change in mode of placement of units in the polymer chain.     

Dimethylzinc-mediated addition of alkenylzirconocenes to alpha-keto and alpha-imino esters

[reaction: see text] Hydrozirconation of alkynes followed by in situ transmetalation to dimethylzinc and 1,2-addition to activated ketones and N-diphenylphosphinoylimines leads to tertiary allylic alcohols and amines in high overall yield. With 8-phenylmenthol as the chiral auxiliary, si-face attack proceeds in good to excellent diastereoselectivities.     

Spectral-luminescent analysis of sugar cane juice

A spectral-luminescent analysis has been made of the low-, medium-, and high-molecular mass fractions of sugar cane juice. The presence of pigments was detected in all the fractions. The medium-molecular-mass fraction was distinguished by the most considerable and most diverse composition of the pigments, a substantial contribution to which was made by the products of the alkaline decomposition of sugars. The amounts of pigments in all the fractions of the juice depended on the age of the plant. A pronounced dependence on the age of the plant was characteristic for the medium-molecular-mass fraction.B. I. Stepanov Institute of Physics, Belorussian Academy of Sciences, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 456–459, May–June, 1993.     

Influence of electronegative substituents on the electronic spectra of the porphyrins in the form of dications

The positions of the electronic absorption bands and also the intensities of the Soret bands of the porphyrins with ethoxycarbonyl substituents in the form of dications have been calculated by the LCAO MO method in Huckel's approximation. Comparison with the experimental results shows good agreement.