Synthesis of phenylpyrrolylpyrroles. Part II

A series of methyl or ethyl 3-(N-arylpyrrol-3-yl)-1H-pyrrole-2-carboxylates and 2,4-dicarboxylates have been synthesized using an alkyl isocyanides addition-cyclization with N-arylpyrrole derivatives such as the carboxaldehydes and nitropropenes.     

Synthesis of condensed quinoxalines. Part II

A novel efficient synthesis of fluorescent, fused quinoxalines was achieved. 7-Triazolyl-1,4-dioxino[2,3-b]-quinoxalines were synthesized by the diazotisation of 7-amino-1,4-dioxino[2,3-b]quinoxaline and coupling with selected aromatic amines followed by air oxidation. Diazotised aryl amines were coupled with 7-amino-1,4-dioxino[2,3-b]quinoxalines followed by subsequent air oxidation afforded 1,4-dioxino[2,3-b]quinoxalino-[6,5-d]1,2,3-triazoles. 7-Amino-1,4-dioxino[2,3-b]quinoxaline was condensed with conjugated enol ethers followed by cyclization in dowtherm resulted in 1,4-dioxino[2,3-b]quinoxalino[6,5-b]pyridines.     

Metal-Ammonia Reduction. Part II. Space-Conjugated Olefins

Whilst metal-alcohol-liquid ammonia conditions do not reduce isolated double bonds², the “space-conjugated”³ norbornadiene has been shown to reduce to norbonene⁴. This result has been interpreted as the consequence of the availability of a low energy antibonding orbital arising from the proximity interaction of the two double bonds. The “nonclassical radical anion” 1 has been proposed⁴ as the intermediate though no nortricyclene could be detected to support this suggestion. However nortricyclene was produced when lithium in ethylamine was used as the reducing agent.⁵     

Hydrofluorination and bromofluorination of halogeno-substituted ethyl cinnamates and related compounds

We have effected bromofluorination of six olefins (unsubstituted and α or β halogeno-substituted ethyl cinnamates) and ethyl propiolate with N-bromosuccinimide: hydrofluoric acid: pyridine and the hydrofluorination of two β halogeno-ethyl cinnamates and ethyl propiolate with hydrofluoric acid: pyridine. The bromofluorination proceeds with Markovnikov-type and α-halogeno-substituted ethyl cinnamates but faster and not stereospecific for the β-substituted ones and ethyl propiolate. This difference is interpreted for cinnamates as a change in transition state from a bridged bromonium ion to an open-chain ion.     

Kinetics of polymerization of N-tert-butylacrylamide. Part II

The effect of ferric chloride on the kinetics of the radical polymerization of N-tert-butylacrylamide has been investigated in methanol solution at 25°C, with the use of 4,4′-dicyano-4,4′-azodipentanoic acid as initiator. A shrinkage factor of 0.193 mmole polymerized for 1 mm contraction in a capillary of 1 mm diameter has been obtained from density measurements. In the absence of ferric chloride, rates of polymerization were found to be proportional to the concentration of monomer and to the square root of the initiator concentration. With ferric chloride present, the rate of polymerization becomes directly proportional to the initiator concentration and inversely proportional to the concentration of ferric salt. From measurements of the rates of production of ferrous iron, the specific rate constant of the initiation reaction has been found to be (1.8 ± 0.4) × 10^?6sec^?1 at 25°C, compared with a value of 7.63 × 10^?8 sec^?1 calculated from the kinetic data obtained with no ferric salt present. The value of the ratio k_p/k₄. where k_p is the propagation coefficient and k₄ is the velocity coefficient for termination by ferric chloride, has been calculated to be 6.0 × 10^?4 at 25°C, which is considerably smaller than the value found for the ferric chloride-terminated polymerization of acrylamide in water. This markedly lower value of k_p/k₄ has been attributed principally to the steric effect of the tert-butyl group on the magnitude of k_p.     

Analytical techniques in neurochemistry. Part II

Part I of this article covered chromatographic and mass spectrometric techniques currently in use in the neurosciences. In Part II, the applications of spectrophotometric techniques, radiological and immunological techniques, in vivo electrochemical and perfusate analysis techniques are reviewed. Some comparative studies conclude the review.     

Theory of direct atom-molecule reactions. Part II

Processes that may be considered as sequences of pair collisions giving rise to the stable molecule AB are discussed on the basis of a general method of representing the cross-section of A+BC AB+ + in the impulse approximation via a mean over the initial state of BC. It is shown that such processes resemble the one-step processes considered in part I in not being purely classical in character (contrary to the assumptions of [2]) and in being substantially dependent on the mode of overlap of the wave functions_BC and _AB even at high collision energies. The reactions T+H₂HT+H, T+D₂ DT+D are considered on the basis of the general method.     

Theory of chemical reactions in solids. Part II

The probability W is deduced for an elementary chemical reaction due to fluctuations in a solid. W is found as a function of the phonon coupling constant. It is shown that anomalous diffusion kinetics can occur.     

Photochemistry of ommochromes and related compounds. Part II

The visible light irradiated solutions of the 1-methyl-1-(1′-[11-(β-aspartoyl-methyl ester-imino)]ethenyl]-ketal-1H,5H-pyrido[3,2-a]phenoxazin-5-one ( 1 ) and the 1,5-dimethoxy-11-(β-aspartoyl-N-acetyl-methyl ester)-pyrido[3,2-a]phenoxazine ( 2 ) [1], in methanol and acidic methanol, are examined. Both methanolic solutions undergo light induced transformation according to an opening of the phenoxazinone and phenoxazine systems, not reversible in darkness. On the contrary, 1 and 2 in methanol-acid solutions, under visible light irradiation, yield a solvent photoaddition, reversible in darkness. Some phototransformation products are examined and a plausible mechanism, for the reactions explanation, is suggested.     

Polarographic Investigations of Functionalized Alkanephosphonic Acids. Part II

Abstract

In this presentation we attempted to verify the enigmatical problem of the polaro-graphical activity of the phosphonic function, especially its electrochemical reduction. Thus, the first report on the polarographic activity of the nitro substituted phenylphos-phonic acid was presented by Kosolapov and Jenkins in 1957 [2].     

Aromatic Amines in Organic Synthesis. Part II. p-Aminocinnamaldehydes

Ten derivatives of p-aminocinnamic aldehydes were prepared from the reaction of either aromatic amines with dimethylaminoacrolein or benzaldehydes with acetaldehyde. Their chemical structure and purity were verified by ¹H NMR, ¹³C NMR and IR spectroscopic methods. We found that the synthesis applying dimethylaminoacrolein as the reagent gets better yields than the one based on the reaction with acetaldehyde. The yields of the cinnamic aldehydes varied according to the type of the amino group and the number and position of the substituents. The basic spectroscopic properties of the p-aminocinnamic aldehydes are also described since the compounds may be a precursor for the synthesis of dyes for diverse applications, e.g., in medicine and optoelectronics.     

Metal benzoylpivaloylmethanates. Part II. 1,4-dioxane adducts of copper(II) chelates

Summary 1 : 1 Dioxane adducts of Copper(II) chelates withpara-subtituted benzoylpivaloylmethanes have been synthesized and their u.v., vis., i.r., mass, e.p.r. spectra as well as their magnetic moments and thermal stabilities investigated. Powdered samples of undiluted magnetically adducts were found to give well resolved e.p.r. spectra; the (S = 1) g_| signal being split into nine lines. Magnetic susceptibilities measured down to 4 K did not reveal exchange interactions. The uncommon structure of the e.p.r. spectra is believed to be due to the dimeric structure of the adduct in which an interion dipolar zero-field splitting of the triplet state occurs. The Cu-Cu distance estimated from the e.p.r. D_dd parameter is found to be 7.4 Å.     

Dehydrochlorination reactions in polymers. Part II. Chlorinated polystyrene

The dehydrochlorination of chlorinated polystyrene was studied in the temperature range 120–220°C., when HCl was the sole volatile product. The dehydrochlorination was accompanied by the slow development of color and chain scission. The elimination rate fell too rapidly with reaction extent to be accounted for by reduction of reagent. Solution studies in o-dichlorobenzene indicated that the reaction was initially first-order in polymer concentration but was retarded by the polyene reaction products. The overall elimination was interpreted as a radical process in which the product was an active retarder. These observations are also valid for the elimination of HBr from brominated polystyrene.     

Electrochemical cyclization of unsaturated hydroxy compounds. Part II. Phenylselenolactonization

Phenylselenolactonization was performed, in one step, by electrolysis of Δ4- and Δ5 -unsaturated carboxylic acids and diphenyl diselenide in methanol containing ammonium bromide.     

Thermal analysis of hectorite. Part II. Differential thermal analysis

The thermal behavior of the SHCa-1 hectorite source clay specimen was studied by the technique of computerized differential thermal analysis (DTA) using dynamic nitrogen, dynamic air, dynamic carbon dioxide, and static air atmospheres. The atmospheric dependence of the DTA thermal curves was established. A series of samples heated in dynamic nitrogen purge was analyzed by X-ray diffraction spectrographic techniques to establish the high temperature phases of the SHCa-1 (carbonate-contaminated) hectorite specimen. Differential thermal analysis was also performed on a processed (carbonate-cleaned) hectorite specimen using dynamic nitrogen atmosphere. Additional TG-DTG thermal curves were included in this portion of the study.     

The isothermal flash problem. Part II. Phase-split calculation

Algorithms for calculation of multiphase equilibrium at given temperature and pressure using a single Equation of State as the thermodynamic model are described. The use of stability analysis to generate initial estimates and of second order convergence methods lead to rapid solution even in the immediate vicinity of critical points.     

Methylpyridylbenzimidazoles. Part II. Bridged mono and bis-quaternary salts

The reaction of 2-(4-methyl-2-pyridyl)benzimidazole and of its N long alkyl chain derivatives with 1,3-dibromopropane led to cyclic bis-charged salts. Their spectroscopic (nmr and uv) and surface properties are briefly discussed. It turned out to be interesting to compare the similar behaviour of these salts and the corresponding well known derivatives of 2,2′-bipyridyl.