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The chemical stability of methotrexate (I) in aqueous solution protected from light was studied utilizing an HPLC procedure. The investigation of the kinetics of degradation took place in aqueous buffer solutions at 85°C over the pH-range of 0–12. The pH-rate profile obtained from first-order kinetic plots showed maximum stability at about pH 7. An Arrhenius-type plot indicated a shelf-life at pK ~ 8.5 of about 4.5 years at 25 °C. At pH above 6.5 N 10 -methyl-folic acid (II) was the only degradation product while in acidic solution several compounds are formed.

Three amphiphilic heptakis (6-alkylamino-6-deoxy) -β-cyclodextrins, (2a) (alkyl=C4H9), (2b) (alkyl=C8H17) and (2c) (alkyl=C12H25) were synthesized. (2b) and (2c) due to their long alkyl chains were readily soluble in chloroform. (2c) was soluble even in benzene. These amines became soluble in water when protonated, and (2b), (2c) showed surface activities with definite cmc values.These amines were also observed to form strong complexes with methyl orange in aqueous buffer solution (pH5.60).

The oxyferro intermediate of highly purified microsomal P-450 from rabbit liver was formed and stabilized at −30°C in a mixture of aqueous buffer and glycerol ( 1 1 ). Absolute and difference (Fe2·+O2-Fe3+) spectra of this intermediate appear to be very similar to those obtained under either steady state kinetics or stopped flow conditions on the same cytochrome as well as on bacterial P-450cam. (Absolute and difference spectra present maxima at 420 and 557–558 nm and a broad maximum at 442 nm respectively). As temperature increases the oxyferro intermediate autoxidizes and ferric cytochrome P-450 is restored. This reaction appears to follow biphasic first order kinetics. The rate constant of both phases decreases with temperature and increases with protons concentrations.

The diffusion kinetics of the cationic dye thionine from an aqueous buffer solution into the two acrylic fibers Dralon X-100 and Dunova was studied at various temper atures between 59.0°C and 98.5 °C. The two fibers are practically identical with respect to chemical composition. The glass transition temperatures in the dry state (Tg) and in water (TD) are the same within experimental error. They differ physically, however, with respect to overall porosity and pore size distribution. The evaluation of diffusion kinetics as a function of temperature and their comparison with the temperature dependence of free diffusion in water, as well as desorption experiments, demonstrate that the pore model mechanism and the free volume (segment mobility) mechanism operate simultaneously. The first is dominant for the porous fiber Dunova and the second for the less porous fiber Dralon.

Summary Picolinic acid and dipicolinic acid have been successfully reduced to the corresponding alcohols by controlled potential electrolysis at mercury cathodes in slightly acidic aqueous buffer solutions.

The oxidation of 2-(α-hydroxybenzyl)- and 2-(1-hydroxyethyl)thiazolium ions with 3-methyllumiflavin was studied kinetically in an aqueous buffer solution. The results indicate that the rate-determining step is carbanion formation followed by rapid oxidation. The carbanion formation was subjected to general base catalysis.

4,2-Chloronitrobenzenediazonium ions in aqueous buffer solutions between pH 2.9 and 7.9 do not hydrolyze by dediazoniation as previous authors have assumed, but by denitration. The isomeric 2,4-compound reacts by denitration (ca. 70%) and dechlorination (ca. 30%). The reactions are general base catalyzed. The products and kinetics are consistent with an SNAr-mechanism in which the general base-catalyzed addition of a hydroxyl group at the reacting C-atom is rate-limiting. The rate maxima at or near the pH-values corresponding to (pK1 + pK2)/2 of the diazonium ⇄ cis-diazotate equilibria can be rationalized on the assumption that the diazonium ion is the only equilibrium form of the diazo compound which enters the substitution proper, and the superposition of the rate term kB[B] of all nucleophiles involved (H2O, OH− and buffer bases).

The 14C-labelled antibiotics [2-14C]mupirocin, and [thienyl-3-14C]temocellin cannot be satisfactorily purified on a small scale by conventional methods of chromatography or recrystallisation. Their purification was successfully achieved by high-efficiency preparative-scale reversed-phase high-performance liquid chromatography. The purifications employed 250 mm × 10 mm I.D. or 22 mm I.D. stainless-steel columns packed with Merck LiChrosorb RP-18 (10μm) stationary phase which were eluted with aqueous buffer solutions at flow-rates of 10–25 ml min-1 using conventional analytical instrumentation.

Spectral studies of morin in aqueous ethanol and other alcohols have been carried out as a function of its concentration and that of ethanol, and the pH of aqueous buffer. The effect of gamma radiations on morin solution in ethanol was also studied as a function of dose in the range of 0.15–2.28 kGy and of morin concentration (10−5–10−4 mole·dm−3). Morin concentration in ethanol solution showed a linear response for G values to a dose of 1.83 kGy. Molar absorption coefficients (e) for morin in ethanol have been estimated to be∈260nm=2.28·104 dm3·mol−1·cm−1 and∈291nm=8.22·103 dm3·mol−1·cm−1 for unirradiated and∈291 nm=1.75·104 dm3·mol−1·cm−1 for irradiated solutions to a dose of 1.83 kGy.

Potassium diisopropylamide (KDA) has been used to efficiently generate the anions of oxime ethers and dimethylhydrazones. As a deprotonating agent, KDA is superior to BuLi and LDA. The corresponding cuprates are extremely oxygen sensitive, but undergo 1,4-addition with cyclohexenone, and the resulting potassium enolates can be trapped with aqueous buffer or ClSiMe 3 . Attempted trapping with either Ac 2 O or AcCl in the presence of diisopropylamine fails.

Ap(NH2)dT was synthesized as a model compound for a study of the stability of the phosphodiester-amide interribonucleotide linkage in neutral aqueous solution, by photolyzing AnBnp(NH2)dT in anhydrous p-dioxane. Ap(NH2)dT proved to be unstable even under anhydrous conditions and could not be isolated. It was rapidly decomposed in neutral aqueous buffer solution, at 25°C, to give A>p, dT and ApdT. Three unstable intermediates of this decomposition, A>pNH2, ApNH2 and A>pdT were detected by 31P NMR. On the basis of the structure of the products, a mechanism is proposed for the decomposition.

1. The reduction of 2-oxy-4,6-dimethylpyrimidine in aqueous buffer solutions and on electrodes with low hydrogen-overvoltage (Pt and Rh) proceeds through an electrocatalytic mechanism leading to the formation of 2-oxo-4,6-dimethyl-1,3-diazacyclohexane. 2. The fact that neither the solution pH nor the nature of the metal had any effect on the reduction rate could be due to peculiarities in the adsorptional behavior of the 2-oxy-4,6-dimethylpyrimidine.

The nonenzymatic reduction of nitrosobenzene by NADPH and NADH in aqueous buffer solution at 25°C is described. Both reactants quantitatively convert nitrosobenzene to phenylhydroxylamine. Rate constants for reduction ( k r ) were determined spectrophotometrically and found to be identical at pH 5.7 and 7.4 and independent of buffer concentration. The values of k NADH (124–149 M −1 sec −1 ) and k NADPH (131–170 M −1 sec −1 ) are essentially identical. The reaction is not subject to general catalysis or specific salt effects. The oxidation of phenylhydroxylamine by NAD(P) to nitrosobenzene is only stimulated by a factor of 1.2 over oxidation in its absence (when the ratio of NADP: phenylhydroxylamine was 8:1).

Reaction of alicyclic-1,2-diones (2a–d) with dimethyl 3-ketoglutarate 1 at room temperature in aqueous buffer (pH = 5.6) provided good yields of the tetramethylpropellanedione tetracarboxylates (3a–d), respectively. Hydrolysis and decarboxylation of the β-ketoester functions, followed by Wolff–Kishner reduction of the corresponding propellanediones (4a–d) has resulted in synthesis of [10.3.3]-, [6.3.3]-, [4.3.3]-, and [3.3.3]propellanes (5a–d). The 13C nmr of propellanes 5a–c are also reported.[Formula: see text]

The influence of the pH and temperature on hydrolytic decomposition of gibberellic acid in aqueous buffer solutions was studied. The individual split-products of hydrolysis were determined by paper chromatography, with simultaneous spectrophotometric evaluation of the gibberellenic acid concentration.

The quantitative determination of phenols in water and waste water is attempted by condensation with 4-aminoantipyrine and oxidation under alkaline conditions to a colored product. The major chemical factors that influence this reaction are pH value between 8.0 and 11.0, the type of aqueous buffer, and the type of substituted phenol. These three factors influence the analytical and molecular sensitivities as well as the wave length of maximum absorbance. A “total phenol” determination is not possible with the 4-aminoantipyrine technique as currently practiced.

Autoxidation of linoleic acid and methyl linoleate emulsions in aqueous buffer solutions was studied by the rate of oxygen uptake. The oxidation rates of methyl linoleate emulsions increased with an inerease in the pH of the buffer solution. With linoleic acid, oxidation rates rose until the increase reached its peak at pH 5.50 and then decreased gradually to a minimum at pH 8.00.

The distribution behaviour of the complexes formed between the terdentate ligand, pyridine-2-aldehyde-2'-pyridylhydrazone, and Zn(II), Cd(II), Fe(II), Cu(II), Ni(II), Mn(II) and Pd(II) has been studied between aqueous buffer and chloroform. Results are interpreted in terms of the complexes in the aqueous solution and the loss of a proton from each coordinated ligand to form an uncharged, extractable species. The suitability of PAPHY as a spectrophotometric reagent used in conjunction with a solvent extraction procedure is discussed.

SUMMARY A radioimmunoassay for oxytocin in aqueous solution is described, with a sensitivity comparable with the best current bioassays. It is highly specific; arginine-vasopressin and lysine-vasopressin interfere only at 1000-fold greater concentration, while bradykinin, histamine, acetycholine and many other substances, which interfere with some bioassays, have no effect. In certain circumstances, there is a dissociation between loss of biological and immunological activity. Thus reducing agents had no effect on immunological activity, in contrast to their effect on biological activity. In late pregnancy plasma, the biological activity of oxytocin is destroyed more rapidly than the immunological activity. Radioimmunoassays have considerable advantages over bioassays both in convenience and specificity. However, bioassays should be employed for reference purposes because of the dissociation between biological and immunological activity that may occur.

— Mice were injected intracerebrally with radioactive leucine 30 min before decapitation. A double-label technique was used; e.g. [3H]leucine in control, untreated mice and [14C]leucine in morphine-tolerant (dependent) mice. Proteins were extracted sequentially from mouse brain with aqueous buffer, Triton X-100, and sodium lauryl sulphate. Each extract was subjected to electrophoresis on discontinuous, porosity-gradient acrylamide gels. When the protein patterns from untreated, acutely morphinized mice were compared with those from morphine-tolerant (dependent) mice, we observed no differences in the amounts of protein or of radioactivity in any of the 55 discrete bands.

1. It was shown that when polyethylene glycol (PEG) was added to suspensions of food particles in aqueous buffer solutions, its distribution in the total water of the food mass was not uniform. The marker was excluded from a large proportion of the water contained in the swollen food particles. This effect was independent of temperature, pH, and, within limits, the time of contact.2. It was shown that the theoretical concentration (C0), assuming a uniform distribution of marker, could be calculated from the observed concentration (C), weight of food in suspension (W) and the total volume of water (V), using the equation C = C0(I + b[W/V]) where b is constant for any given food. The addition of PEG solution to dry food particles gave a smaller effect.3. The distribution of PEG was usually, but not invariably, more uniform in a suspension of roughages than in a suspension of concentrates.4. Possible implications of these findings with respect to marker experiments with PEG are discussed.

Detailed studies have been made on the hydrolysis of Na[BPhnPyl4-n] type (where PhC6H5, PylC4H4N, n = 0, 1, 2. 3) pyrryl-1-borates in aqueous buffer solution. The hydrolysis of pyrryl-1-borates is a kinetically second-order reaction and is catalysed by hydrogen ions. The rate constant- and ΔH≠values of pyrryl-1-borates considerably depend on the electronegativities of the substituents. The hydrolytic stability of the B--Pyl bond was compared with that of other BX bonds (XH, C6H5, CH3COO). In the hydrolysis of pyrryl-1-borates the corresponding borane and pyrrole are formed directly. Uber die Hydrolyse der Pyrrolyl-1-borate Es wurde die Hydrolyse der Pyrrolyl-Borate vom Typ Na[BPhnPyl4-n] (Ph–C6H5, PylC4H5N, n = 0, 1, 2, 3) in Puffer-Losungen eingehend untersucht. Kinetisch ist die Hydrolyse der Pyrrolyl-Borate eine Reaktion von zweiter Ordnung, sie wird von Wasserstoff-Ionen katalysiert. Die Grose der Geschwindigkeitskonstanten und ΔH=-Werten hangt wesentlich von der Elektronegativitat der Substituenten ab. Es wurde die hydrolytische Stabilitat der B–-Pyl Bindung mit anderen B–-X Bindungen (XH, C6H5, CH3COO) verglichen. Die entsprechenden Boran- und Pyrrol-Verbindungen entstehen unmittelbar bei der Hydrolyse der Pyrrolyl-Borate.

The absorption of chloroform by α- and β-lipovitellin from chloroform-saturated aqueous buffer solutions has been measured quantitatively. Absorption is rapid and reaches equilibrium values of 13 and 22% of the dry weights of α- and β-lipovitellin respectively. Ultracentrifugal examination of these lipovitellin solutions shows that chloroform absorption produces a heavier fraction that is not homogeneous and probably consists of aggregates. There appears to be a threshold concentration of chloroform in the aqueous solutions below which none is absorbed by the lipovitellins. Similar, but less extensive, experiments with the low-density lipoprotein of yolk and yolk lecithin have shown that they also absorb chloroform under the same conditions.

SUMMARY This work was done to determine if 60 mc/sec R-F energy has a selective killing effect on microorganisms other than that attributable to heat. The organisms studied were Saccharomyces cerevisiae, Escherichia coli, and Bacillus subtilis, An aqueous buffer medium was used to suspend the microorganisms for the irradiation treatments. No killing effect of the R-F energy per se on the organisms was observed at any of the various buffer pH values, nor was there an obsevable synergistic killing effect of R-F energy and heat on the microorganisms in any of the buffer. However, a synergistic killing effect of ethanol and heat at 48.8°C was demonstrated on S. cerevisiae. Irradiating S. cerevisiae and E. coli in several liquid foods also failed to show a selective killing effect of R-F energy.

By amino acid analyses and radioactive titration of cleaved S–S bonds on reduction, it was shown that the hinge region of IgG3 and its F(ab′)2 fragment seem to contain 15 S–S bridges. About three of the bridges are not reduced by 0.01 M dithiothreitol in aqueous buffer, and, in addition, this treatment cleaved the F(ab′)2 fragment into two Fab′ subunits. The observation, therefore, may support the idea that the γ3-chain contains an extra intrachain disulphide loop.

Electrocapillary curves, concentration effects, and instantaneous current measurements indicate the importance of adsorption of the electroactive substance in determining the shape of the polarograms of ω-diazoacetophenones in aqueous buffer solutions. Potential-step transients show that the electrolytic reduction of adsorbed diazoketone is autocatalytic. Rate constants are reported for the autocatalytic reduction of some adsorbed diazoketones.

By applying the technique of real partition chromatography1 to systems in which aqueous buffer solutions are used as the stationary phase, natural or semi-synthetic penicillins of closely related structure can be satisfactorily separated. Water-saturated alkanols of proper polarity and buffers of proper pH are chosen as the mobile and stationary phases, respectively, according to the polarity of the penicillin to be chromatographed. Examples of penicillins separated are ampicillin vs. epicillin, their N-acetyl derivatives, penicillins G. vs. penicillin V, m- vs. p-hydroxybenzylpenicillins and m- vs. p-hydroxyampicillins.

(1) The bromination of the disodium salt of 2-naphthol-6,8-disulphonic acid (G-salt) with hypobromous acid in aqueous buffer solutions has a hydrogen isotope effect (kH/kD = 2.08 ± 0.10) which is independent of the reactant concentrations.

The presence of small amounts of chlorine or bromine greatly accelerates the rate of absorption of CO 2 in aqueous buffer solutions. This is because the halogens are hydrolysed to OCl − or OBr − , which are powerful catalysts for the reaction between CO 2 and water. An approximate mathematical analysis is given, and agrees reasonably with the observations.

The polarographic behaviour of ω-diazoacetophenone and 12 meta- and para-substituted ω-diazoacetophenones has been studied in aqueous buffer solutions. The polarograms generally show three waves corresponding to successive reduction of the diazo-ketone to the corresponding ω-aminoacetophenone, acetophenone, and either 2-phenylethanol or 2,3-diphenylbutane-2,3-diol. The reduction scheme may be represented: first wave, XC6H4·CO·CHN2+ 7H++ 6e → XC6H4·CO·CH2·NH2+ NH4+, second wave, XC6H4·CO·CH2·NH2+ 3H++ 2e → XC6H4·CO·CH3+ NH4+, third wave, XC6H4·CO·CH3+ 2H++ 2e → XC6H4·CH(OH)·CH3, or 2XC6H4·CO·CH3+ 2H++ 2e →[graphic omitted] where X is the meta- or para-substituent (including H). For the p-nitro-substituted compound an additional wave is observed, preceding that for the diazo-ketone reduction, and corresponding to reduction of the nitro-group.The polarographic behaviour of p-bromo-ω-diazoacetophenone and preparative controlled potential electrolysis experiments indicate that the six-electron reduction follows the scheme: XC6H4CO·CHN2+ 2H++ 2e → XC6H4CO·CH:N·NH2, XC6H4CO·CH:N·NH2+ 2H++ 2e → XC6H4CO·CH2·NH·NH2, XC6H4CO·CH2·NH·NH2+ 3H++ 2e → XC6H4CO·CH2·NH2+ NH4+

Electroosmosis is measured of wool yarn and fabric in equilibrium with aqueous buffer solutions. The electroosmotic flow vs. pH curve shows a minimum ascribed to fiber conductance. Approximate equations are developed to account for this effect. Transport of water through the fibers is estimated to be negligible. The surface of natural wool is isoelectric near pH 3. This is considerably lower than the IEP of any known wool protein fraction. The variability of surface IEP may result from mechanical damage to wool in processing. It is shown that in a recently developed practical process for shrinkproofing wool fabrics, a polyamide film is grafted onto the fiber surface.

SUMMARY The proteins extracted by aqueous buffer from the females of six Heterodera spp. were separated into bands by polyacrylamide gel electrophoresis and the patterns compared. Heterodera schachtii and H. trifolii, with lemonshaped cysts, had a similar pattern of bands, differing greatly from that of the round-cyst nematodes H. virginiae and H. rostochiensis. Ten pathotype A populations of H. rostochiensis had similar patterns, distinguishable from those of twelve pathotype E populations by the absence of two bands and by the presence of another rarely found in pathotype E. Bands from pathotype B populations were indistinguishable from those of pathotype E. No consistent difference was detected between populations of the same pathotype. These results support the suggestion by Jones, Carpenter, Parrott, Stone & Trudgill (1970) that H. rostochiensis Woll. comprises two species.

The results of study of the corrosive-mechanical wear of normalized steel 45 treated with a laser beam (Hl00 = 7800 MN/m 2) [2] when rubbed against nitrided steel 40KhNMA (HB = 7000 MN/m2), which was hardened and then subjected to low-temperature tempering, against chromium-modified cast iron KhI5M (HB = 5600 MN/m 2) [3], pearlitic cast iron SCh24-44 (HB = 2400 MN/m2), and bronze BrKMts3-1 (HB = 1700 MN/m 2) are set forth in the present study. The initial roughness of the effective surface corresponded to an eighth c l a s s s u r f a c e . Aqueous buffer so lu t ions with pH = 6 and oH = ! ! we re employed as c o r r o s i o n a c t i v e media . The t e s t s were conducted in a c c o r d a n c e with a s u r f a c e f r i c t i o n s cheme at a s l id ing r a t e of 1 m / s e c within the n o r m a l p r e s s u r e r ange (P) of 2-12 ~ N / m 2 [4].

Die Titelverbindungen 1a-d setzen sich in wasriger Losung bei pH 7.4 mit Singulett-Sauerstoff praktisch quantitativ zu den Hydraziden 3a-d um. Die 1H- und 13C-Spektren von 3 zeigen das Vorliegen rotationsisomerer Formen bei Raumtemp. Die Produkte 3 werden unter Elektronenstosionisation massenspektrometrisch untersucht. Reaction of 1O2 with 4-Amino-3-pyrazolin-5-ones The title compounds 1a-d react with 1O2 in aqueous buffer (pH = 7.4) to form the hydrazides 3a-d in nearly quantitative yields. The 1H- and 13C-nmr spectra of 3 indicate the presence of rotameric isomers at room temperature. Products 3 are investigated by means of mass spectrometry.

Oligomeric polypeptides predominate among the nonhistone nuclear proteins of the avian erythrocyte. Two of these are converted to smaller species by several minutes in boiling aqueous buffer at pH values of 4.0–4.5 and below. Polypeptides corresponding to the species generated by this treatment are also isolated from the cell in the absence of acid treatment. This result indicates that several nuclear structural proteins could derive from a common polypeptide chain.

SUMMARY In prokaryotic organisms, there is strong evidence that the DNA is underwound or negatively supercoiled. The degree of supercoiling of intracellular DNA is less certain, and various estimates that can be made from existing data place the specific linking difference (superhelical density) of intracellular DNA in prokaryotes around −0·04. The effects of negative supercoiling on DNA structure are illustrated by the flipping of alternating C-G or T-G sequences from right-handed B-helical form to the left-handed Z-helical form. For a plasmid containing a 42 base-pair alternating C-G insert, the B-to-Z transition occurs at a specific linking difference of −0·031 in a dilute aqueous buffer; the same transition occurs at a specific linking difference of −0·041 for a plasmid containing a 42 base-pair alternating T-G insert. The probing of the structure of a particular sequence of intracellular DNA is discussed.

The detection of general-base catalysis in the presence of predominating specific-base catalysis in aqueous buffer solutions is examined for various relationships between k 0 cat and k 0 OH , the bimolecular rate constants for general-base and hydroxide-ion attack. The three experimental variables that affect the detection of buffer-base catalysis are the type of buffer, conjugate-acid concentration, and ionic strength. Various buffers used in pharmaceutical kinetic studies are considered, and it is concluded that buffers with high K a values favor detection. Additionally, high conjugate-acid concentrations and ionic strengths appear to optimize the detection of general-base catalysis.

The preferential interaction of calf brain tubulin with glycerol in an aqueous buffer (0.01 m -NaPi, 0.02 m -NaCl, 10−4 m -GTP, pH 7.0) has been investigated by densimetry. The apparent specific volumes of tubulin at constant chemical potential of the diffusible components were determined at 0, 10, 20 and 30% ( v v ) glycerol. Application of multicomponent solution thermodynamics shows that tubulin is preferentially hydrated in aqueous glycerol solvent and that such interaction results in thermodynamic destabilization of the system by raising the chemical potentials of both glycerol and tubulin. Interpreted in terms of the Wyman linkage function, the unfavorable free energy change brought about by the preferential protein-glycerol interaction can account for the glycerol enhancement of tubulin self-assembly in vitro into microtubules as well as offer a rationale for glycerol stabilization of the native tubulin conformation.

A versatile method for the determination of the ionization of guanosine is described. Suitably derivatized alkyl-guanosines are partitioned between organic solvents and aqueous buffer solutions at various pH values. Ionization is revealed by a change in partition coefficient with pH. The method is ideally suited for application to micro samples since any quantitative method can be used to determine the partition coefficient. A procedure for distinguishing N 1 or O 6 , N 2 , and C 8 alkylation of guanosine is described.

In neutral aqueous buffer adrenochrome ( 1 ), the first isolable intermediate in the oxidation of adrenalin, undergoes rearrangement to give, besides adrenolutin ( 2 ), a yellow compound which was assigned the dimeric structure 6 . Under anaerobic conditions, compound 6 is the major reaction product (about 60 % yield). In the presence of air a more complex pattern of products is formed including, besides 6 , the hitherto unknown 5,6-dihydroxy-l-methyl-2, 3-indoledione ( 10 ) and a related compound identified as the 4,4'-dimer 11 .

In neutral aqueous buffer adrenochrome ( 1 ), the first isolable intermediate in the oxidation of adrenalin, undergoes rearrangement to give, besides adrenolutin ( 2 ), a yellow compound which was assigned the dimeric structure 6 . Under anaerobic conditions, compound 6 is the major reaction product (about 60 % yield). In the presence of air a more complex pattern of products is formed including, besides 6 , the hitherto unknown 5,6-dihydroxy-l-methyl-2, 3-indoledione ( 10 ) and a related compound identified as the 4,4'-dimer 11 .

Reaction of alicyclic-1,2-diones (2a–d) with dimethyl 3-ketoglutarate 1 at room temperature in aqueous buffer (pH = 5.6) provided good yields of the tetramethylpropellanedione tetracarboxylates (3a–d), respectively. Hydrolysis and decarboxylation of the β-ketoester functions, followed by Wolff–Kishner reduction of the corresponding propellanediones (4a–d) has resulted in synthesis of [10.3.3]-, [6.3.3]-, [4.3.3]-, and [3.3.3]propellanes (5a–d). The 13C nmr of propellanes 5a–c are also reported.

The anodic oxidation of ephedrine was reexamined in aqueous buffer solution at pH 10. Cleavage of the (α) C-(β) C bond occurs predominantly in the initial chemical process to give benzaldehyde, rather than the usual C-N bond fission such as that observed in the simple aliphatic amines. A revised scheme for the anodic oxidation is proposed.

The electrochemical characteristics of nitrosochloramphenicol have been studied in aqueous buffer systems (pH 7.1) using direct current (d.c.) and differential pulse polarography, cyclic voltammetry and coulometric techniques. Up to 4 charge-transfer steps can be identified. The first reduction step is reversible both chemically and electrochemically, the charge-transfer product showing no tendency to undergo further reaction on the electrochemical time-scale. In contrast, the second reduction step is irreversible, with the product undergoing a fast following reaction to yield a redox-active species which was detected by cyclic voltammetry. From the data and by comparison with related systems, two reduction mechanisms are possible and are discussed.

The development of a method for separating and determining phenoxyacetic herbicide residues in biological materials is described. The sample is extracted with solvent at low pH and the phenoxy acids are separated from coextracted matter by partitioning between solvent and aqueous buffer at pH 6.2 and subsequent thin-layer chromatography. Quantitative results are obtained by eluting the phenoxy acids from the adsorbent and photometric determination by means of the chromotropic acid reaction. Phenoxyacetic derivatives added to a variety of biological materials at the levels 4–100 p.p.m. were recovered to about 70–90 %, with a standard deviation of 3–5 %. The detection limit of the thin-layer chromatographic step is about 0.1—0.2 µg of phenoxy derivative, or less than 0.1 p.p.m., with a 3-g aliquot of sample, and the photometric step allows the determination of about 0.3 p.p.m. of phenoxy derivative (in a 3-g aliquot). The method can be modified to include also homologous phenoxyaliphatic acids and dinitrophenols. The method has been used during several years for toxicological and residue analysis in a variety of biological materials. Eine Methode zur Isolierung und Bestimmung von Phenoxyessigsaureruckstanden in biologischem Material wird beschrieben. Die Probe wird mit Losungsmittel bei niedrigem pH extrahiert, die Phenoxyessigsauren werden von Extraktivstoffen durch Verteilung zwischen Losungsmittel und Pufferlosung vom pH 6,2 und Dunnschichtchromatographie getrennt. Quantitative Resultate werden durch Eluierung der Phenoxyessigsauren vom Adsorbens und photometrische Bestimmung nach fruher beschriebenem Chromotropsaureverfahren erhalten. In Zusatzversuchen mit biologischem Material verschiedener Typen wurden die zugesetzten Phenoxyessigsaurederivaten zu rund 70–90 % wiedergewonnen, mit einer Standardabweichung von 3–5 %. Die Nachweisgrenze der dunnschichtchromatographische Methode liegt bei zirka 0,1–0,2 µg Phenoxyderivat, was weniger als 0,1 p.p.m. entspricht, auf 3 g Probe berechnet. Die photometrische Bestimmung erlaubt Bestimmung von zirka 0,3 p.p.m. (auf 3 g Probe berechnet). Diese Methode lasst sich auch fur die Bestimmung homologer phenoxyaliphatischer Sauren und Dinitrophenole modifizieren. Das beschriebene Verfahren hat sich fur Analyse von biologischem Material verschiedener Art bewahrt und ist seit mehreren Jahren fur die toxikologische Analyse und Ruckstandsanalyse angewandt worden. En metod for isolering och bestamning av fenoxiattiksyrederivat i biologiskt material beskrives. Provet extraheras med losningsmedel vid lagt pH och fenoxiattiksyrorna separeras fran extraktivamnen genom fordelning mellan losningsmedel och vattenfas av pH 6,2 samt tunnskiktskromatografi. Efter eluering fran adsorbens bestammas fenoxiattiksyrorna kvantitativt enligt en tidigare beskriven kromotropsyremetod. Vid analys av olika typer av biologiskt material, forsatta med fenoxiattiksyrederivat i koncentrationsomradet 4–100 p.p.m., erholls utbyten fran 70 till c:a 90 %, med en standardavvikelse av 3–5 %. Pavisbarhetsgransen i det tunnskiktskromatografiska steget ar c : a 0,1–0,2 µg fenoxiderivat, motsvarande mindre an 0,1 p.p.m. beraknat pa 3 g prov. Den fotometriska bestamningen tillater bestamning av c:a 0,3 p.p.m. (beraknat pa 3 g prov). Metoden kan modifieras for bestamning aven av homologa fenoxialifatiska syror och dinitrofenoler. Den beskrivna metoden har visat sig tillamplig pa biologiska material av vitt skiftande typer och har an vants under fiera ar for toxikologisk analys och restanalys.