Direct synthesis of palladium porphyrins from acyldipyrromethanes

[reaction: see text] Palladium porphyrins are valuable photosensitizers and luminescent agents in biology and materials chemistry. New methodology is described wherein a 1-acyldipyrromethane is converted into the palladium chelate of a trans-A(2)B(2) porphyrin via a one-flask reaction. The reaction entails self-condensation of the 1-acyldipyrromethane in refluxing ethanol containing KOH (5-10 mol equiv) and Pd(CH(3)CN)(2)Cl(2) (0.6 mol equiv) exposed to air. This direct route to palladium porphyrins is more expedient than the four steps of the traditional synthesis: (1) reduction of the 1-acyldipyrromethane; (2) acid-catalyzed condensation; (3) oxidation of the porphyrinogen intermediate; and (4) metal insertion. The new synthesis requires neither acid nor DDQ and formally entails only a 2e(-) + 2H(+) oxidation overall versus the traditional multistep synthesis which requires a 2e(-) + 2H(+) reduction per each 1-acyldipyrromethane (4e(-) + 4H(+) overall) followed by a 6e(-) + 6H(+) oxidation. The analogous reaction of a 1,9-diacyldipyrromethane and a dipyrromethane also gives the palladium porphyrin. Seven palladium porphyrins have been prepared in yields of 25-57%. The direct route also can be used with Cu(OAc)(2).H(2)O to give the copper porphyrin albeit in low yield. In summary, this methodology readily affords palladium porphyrins directly from acyldipyrromethanes.     

An electromagnetic vibrator for electrodes used in polarography and amperometric titrations

Details of the construction of au electromagnetic vibrator for micro-clcctrodes are given, The design embodies a centring guide which constrains the vibration in one direction only. The instrument is suitable for polarography and amperometric titrations.     

A survey of acid catalysts for use in two-step, one-flask syntheses of meso-substituted porphyrinic macrocycles

[reaction: see text] Diverse Lewis acids and Bronsted acids were examined in the two-step, one-flask synthesis of meso-tetraphenylporphyrin, N-confused tetraphenylporphyrin, and tetraphenylsapphyrin. The scope of acid catalysis was found to be very broad, with 35 of 45 acids providing TPP in yields ranging from 5% to 58%. NC-TPP was also widely observed in yields of 1-40%, and TPS was infrequently observed in yields of <1%. Additionally, conditions were found for direct preparation of magnesium TPP and copper TPP.     

Toward the quantification of vocal efficiency

Quantifiable aspects of vocal fold vibration may be inferred by means of the electrolaryngograph. Changes in inferred vocal fold closed quotient are considered as a possible correlate of acoustic efficiency variation; automatic measures of closed quotient compare favorably with results obtained from inverse filtering of the speech pressure waveform. This article describes closed quotient measures based on electrolaryngographic analysis of 18 trained and untrained men singers, and results show a significant difference in mean vocal fold closed quotient between trained and untrained singers.     

The centrifugal distortion constants of disulfur monoxide

The microwave spectrum of the molecular transient disulfur monoxide, S₂O, has been reexamined and the microwave measurements have been extended into the millimeterwave region. From the present data, the following ground-state rotational constants and quartic distortion constants have been obtained (MHz):

$\text{A = 41915.44,}\text{B = 5059.07,}\text{C = 4507.19}$

$\text{δ}{}_{\mathrm{J}}\text{= 1.895 X 10}{}^{\mathrm{?}}\text{, δ}{}_{\mathrm{JK}}\text{= ?3.192 X 10}{}^{\mathrm{?2}}\text{,}\text{δ}{}_{\mathrm{K}}\text{= 1.197 X 10}{}^0$

$\text{δ}{}_{\mathrm{J}}\text{= 3.453 X 10}{}^{\mathrm{?4}}\text{and δ}{}_{\mathrm{K}}\text{= 1.223 X 10}{}^{\mathrm{?2}}$

The centrifugal distortion constants obtained from the rotational spectrum are used to discuss the vibrational spectrum of disulfur monoxide.     

The microchemical electrolytic analysis of alloys in hydrochloric acid solutions : Brasses and bronzes

The microchemical electrolytic analysis of alloys employing the methods of Sand and Lindsey for potential control have been extended to include complete analyses of brasses and bronzes in chloride solutions. The methods, employing from 5 to 20 milligrams of material, may be completed in about 2 hours (excluding the time necessary to bring the sample into solution) and are especially useful in circumstances where only a few milligrams of sample are available.     

The electrolytic separation from thorium nitrate of thorium c (212Bi) and thorium b (212Pb) in chloride solution

An electrodeposition process is described for separating thorium C and thorium B from radio-chemically “old” samples of thorium nitrate in hot 0.5N hydrochloric acid solution. The thorium C is first deposited on either platinum or nickel cathodes of special design using a controlled potential at the cathode, followed by the deposition of thorium B. Weights of the order of 10^-15 g ThC are involved.     

Cyclodextrin-promoted energy transfer for broadly applicable small-molecule detection

Reported herein is the development of non-covalent, proximity-induced energy transfer from small-molecule toxicants to organic fluorophores bound in the cavity of γ-cyclodextrin. This energy transfer occurs with exceptional efficiency for a broad range of toxicants in complex biological media, and is largely independent of the spectral overlap between the donor and acceptor. This generally applicable phenomenon has significant potential in the development of new turn-on detection schemes.     

Four good decades of OR in the Canadian Department of National Defence

The first half of the period between 1950 and 1990 offered ideal circumstances for the development of operational research in the Canadian Defence Department. Rapid change and the continuous progress in technology provided great opportunities for military OR. Experience demonstrated the value of a dispersed organisation, with its personnel managed centrally but its projects selected by the unit to which it was attached. Frequent movement of scientists enhanced their versatility. Much of the OR dealt with the technical performance of equipment and the determination of the procedures and tactics to best exploit its capabilities. Examples are given of OR projects conducted on operational problems of the air force, the navy, and the army, and of problems in logistics, in personnel, and in strategic, social and economic questions. When downsizing struck, it was the original types of OR which survived.     

Construction of previously inaccessible 2-amino-4-benzyl substituted oxazoles

A process for the synthesis of 2-amino-4-benzyl-oxazoles is reported.