Comments on the paper by Dr. C.A. McAuliffe

The first cyclopentadienylplutonium(IV) compounds, (η⁵-C₅H₅)₃PuCl and (η⁵-C₅H₅)₃Pu(NCS) have been prepared, the former by reaction of Cs₂PuCl₆ with TlC₅H₅ in CH₃CN and the latter by treating the chloride with KNCS in tetrahydrofuran. Both compounds are isostructural with ther U^IV and Np^IV analogues. The IR and UV/visible spectra of the new compounds are reported.     

Research on the aromas. On the aroma of coffee. I

The analysis of a coffee concentrate is described: 202 constituents have been identified, 154 of which for the first time. Some of these compounds are new chemicals; their synthesis is described. Most identifications are based upon mass spectrometry combined in many cases with IR. spectrometry and comparison with reference compounds. MS. and IR. data are given in detail. The analysis shows that a large number of minor constituents is present, many of which could not be identified.     

Research on the aromas. On the aroma of coffee. II. Pyrazines and pyridines

Pyrazines and pyridines occurring in a coffee concentrate are analyzed by two procedures. 24 compounds have been identified and the presence of some 10 more is revealed. The syntheses, mass and infrared spectral data of reference compounds are given.     

On the Use of the Knox Equation. I. the Fit Problem

Abstract

To obtain significant A, B, and C parameters of the Knox equation, which corresponds to the plot of the reduced plate height, h, versus the reduced linear velocity, v, actual results must be fitted correctly. The Knox equation is analyzed, the rôle of each individual parameter is shown. The equation producing the coordinates of the minimum plate height (maximum efficiency) is fully derived from the derivative of the Knox equation. Two tables giving the minimum coordinates for usual A, B, and C ranges are listed. The classical fit method is derived and analyzed. A graphical fit method which uses the remarkable graphical capabilities of modern spreadsheet packages is described. A synthetical set of data was fitted. It is demonstrated that each Knox parameter, obtained through fit procedures, must be given with the fitting confidence interval which is often in the 20% range.     

Chemistry of the diazeniumdiolates. 3. Photoreactivity

We have found O(2)-substituted diazeniumdiolates, compounds of structure R(2)N-N(O)=NOR' that are under development for various possible pharmaceutical uses, to be rather photosensitive. With R = ethyl and R' = methyl, benzyl, or 2-nitrobenzyl, the observed product distributions suggest that two primary pathways are operative. A minor pathway involves the extrusion of nitrous oxide (N(2)O) with simultaneous generation of R(2)N(*) and R'O(*), which may then form amines, aldehydes, and alcohols. The major reaction pathway is an interesting photochemical cleavage of the N=N bond to form a nitrosamine (R(2)NN=O) and an oxygen-substituted nitrene (R'ON). The intermediacy of the O-nitrene was inferred from the production of abundant oxime, via rearrangement of the O-nitrene to a C-nitroso compound (R'ON --> O=NR'), and subsequent tautomerization to the more stable oxime. Involvement of the O-nitrene was confirmed by trapping with 2,3-dimethyl-2-butene to form the aziridine and with oxygen to generate the nitrate ester. 2-Nitro substitution on the benzyl derivative had surprisingly little effect on the reaction course. For each compound examined, minor amounts of nitric oxide (NO), presumably produced by secondary photolysis of the nitrosamine, were observed. Time-resolved infrared experiments provided additional support for the above reaction pathways and confirmed that the nitrosamine is a primary photoproduct. We have also found that the relative contributions of the reaction pathways can be altered in certain derivatives. For example, when R' = 2,4-dinitrophenyl, the contribution of the nitrosamine/O-nitrene-forming pathway was diminished. Pharmacological implications of these results are discussed.     

Pseudomonas cytochrome c peroxidase. XIII. pH-denaturation of the enzyme.

The effect of pH on the oxidized Pseudomonas cytochrome c peroxidase molecule was studied by measuring the peroxidatic activity, the sedimentation velocity, the circular dichroic spectra in the far UV and Soret regions, and the optical absorption spectra of the enzyme in the pH range 2.5-13.0 at a constant ionic strength (micron = 0.1). The enzyme was stable in a narrow pH region, pH 6.0 - 7.4. In the low pH range the gross tertiary structure was observed to change quite simultaneously with the enzymatic activity and secondary structure. The optical absorption spectra indicated that there were no coordinated internal protein liqands in the 6th coordination positions of the heme prosthetic groups at the lowest pH studied. In the high pH range the secondary structure and the protein environment of hemes were observed to remain stable after the tertiary structure had changed and the activity had decreased. According to the optical absorption spectra the 6th internal protein ligands of hemes were retained at the highest pH studied.     

Improvements in the thin-layer chromatography of natural products. I. Thin-layer chromatography of the aflatoxins.

During the period which has elapsed since the aflatoxins were first isolated, one of the main problems has been the separation of the individual aflatoxins in pure form from aflatoxin-containing extracts. This separation has been best effected by thin-layer chromatography, and in this paper we describe how some of the difficulties may be overcome by using an appropriate combination of solvent system and silica gel preparation. For the examination of aflatoxin-containing extracts from the mycelia of Aspergillus flavus moulds, an initial freeze-drying step has been found to improve appreciably the quality of the chromatograms obtained.     

Polymer battery R&D in the U.S.

Polymer electrolytes that have been developed for battery applications fall into two general classes, neat or “pure” polymer and plasticized or gel in which the polymer is combined with a conducting organic electrolyte. The polyethylene oxide (PEO) and its modifications are typical of the “pure” polymer electrolytes. They have poor conductivity at room temperatures, but at elevated temperatures, their conductivity is of the order of 10⁻³ to 10⁻⁴ S/cm. The PEO electrolytes have found application in the high temperature (>60°C) lithium metal anode battery systems. The high temperature necessary for good operation makes them unsuitable for use in small consumer appliances. The polymer electrolyte battery development activities have resulted in several high performance battery systems now just entering the market. Not all of the developments have resulted in commercial cell production. The commercialization activities of high performance lithium‐ion (Li‐Ion) batteries have been based on two general plastic polymer systems: poly‐vinylidene difluoride‐hexafluoropropylene copolymer (PVdF‐HFP) and polyacrylates. The polymer cells are expected to have advantages in manufacturing, flexibility, thin cell formats and lightweight packaging. Important parameters in PVdF gel electrolyte performance include the electrolyte type (combination of organic carbonates), temperature, and HFP copolymer content. Li‐Ion coin cells fabricated with a polyolefin separator with either liquid electrolyte or with the PVdF gel polymer electrolyte have equivalent performance.     

On the birthday of R. M.-F. Salikhdzhanova

Chronicle

On the birthday of R. M.-F. Salikhdzhanova     

Catalysis in aprotic solvents. Effect of the polarity of the catalyst.

The catalytic constants for the $\text{n}$-butylaminolysis of sultones in aprotic-apolar solvents are linearly correlated with a combination of the hydrogen-bonding parameter and the polarity parameter of the catalyst.     

Radical Ions in the Pentalene Series. Part. I. 1,3,5-tri-t-butylpentalene

The ESR. spectra of the radical anion and cation of 1, 3, 5-tri-t-butylpentalene (II) have been reexamined under higher resolution. With the assistance of the ENDOR. technique, the coupling constants of all protons in II?. and II?. could be determined. The experimental data agree satisfactorily with the values predicted by the simple MO model which suggests that the π-spin distributions in II?. and II?. should not strongly differ from those in the corresponding radical ions of parent pentalene (I). As in the case of other non-alternant hydrocarbons, the proton coupling constants for II?. are very sensitive to experimental conditions, due to the association of the radical anion with its counterion. Spectra of II?. taken at low temperatures (down to 133 and 163 K for ESR. and ENDOR., respectively) have not revealed specific line-broadening which could arise from the bond shift between the two Kekulé-structures of pentalene.     

1H n.m.r. investigation on the site of hydration in the asymmetric diazanaphthalenes

The site of hydration for 1,6- and 1,7-naphthyridine has been determined by specific line broadening in the ¹H n.m.r. spectra on the addition of water. The site of hydration appears to be the same as the site of protonation (β-nitrogen atom). The site of hydration in quinazoline has been shown to be the α-nitrogen atom. This strongly indicates that the site of protonation in this compound will also be at that nitrogen.     

四块瓦化学成份的研究(Ⅱ)

四块瓦(Chloranthus Holostegius)为金粟兰科多年生草本植物,分布于云南、广西和贵州等地。全草有毒,具有抗菌、消炎、散瘀活血的功效。对四块瓦化学成份的研究尚未见报道,作者从其根的石油醚、乙醚和乙醇的提取液中,分离得到五个结晶单体。     

Theoretical analysis of the influence of the adsorption process on the voltammetric curves in the case of a second order adsorption step followed by a first order charge transfer reaction: Part III. Variation of the transfer coefficient and application to semiconductor electrodes in l.p.s.v. and s.s.c.v.

The kinetic behaviour of a two-step sequential reaction including a 2nd order adsorption process is treated theoretically in the case of semiconductor electrodes. It is shown that the electronic structure of the semiconductor can be taken into account in some simplified cases by introducing a formal transfer coefficient comprised between 0 and 1 and potential independent. In both linear potential sweep voltammetry and steady state cyclic voltammetry, the usual characteristic features (E_M, _M, i_M) of the voltammetric curves are calculated as a function of the sweep rate for different values of the transfer coefficient.     

On the Use of the Knox Equation. II. the Efficiency Measurement Problem

Abstract

The Knox equation, which relates the reduced plate height, h, to the reduced linear velocity, v, has a great importance in column and stationary phase testing. Significant A, B, and C terms of the Knox equation cannot be obtain with erroneous plate heights, h. Four methods for efficiency determination, the inflection (0.6H) method, the height/area method, an asymmetry based (0.1H) method and the moment method, were critically compared using 200 real chromatograms. Efficiency obtained using Gaussian assuming methods were highly overestimated, while the asymmetry based method gave quite acceptable results. Using the exponentially modified Gaussian model, it is demonstrated that the b/a ratio (the sum b + a is the peak-width at 10% of the peak height) is not an empirical figure of merit but can be related to a “peak skew” expression.     

A model describing the kinetics of micellization at concentrations exceeding the second c.m.c.

We have extended an earlier kinetic model describing micelle formation from chemical relaxation studies to examine the observation of an additional relaxation which is accompanied by the occurrence of the second c.m.c. It is concluded that this second relaxation is associated with conformational changes in the micelles.