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(±)-2,5,12-Trihydroxy-1,2,3,4-tetrahydronaphthacene-6,11-dione-2-carboxylic acid was found to readily afford the racemic title compound by successive treatments with N,N′-carbonyldiimidazole and methylmagnesium bromide in the presence of trimethylsilyl triflate. The same reaction scheme could also furnish the optically pure title compound from the (R)-carboxylic acid produced by the optical resolution.

The detection of surface species by chemical trapping is described and discussed. The results obtained by scavenging intermediates in CO-H 2 and CO 2 -H 2 reactions show the relevance of this method to the study of reaction mechanisms in heterogeneous catalysis. Quantitative detection of some species (carboxylate, formyi, methoxy) is achieved and a correlation has been found between activity and surface species on a Pd/MgO-SiO 2 catalyst. A reaction scheme is proposed for the CO-H 2 and CO 2 -H 2 reactions.

Catalytic reactions of 1,3-butadiene with ketones were carried out with a nickel-ligand system to give stereoselectively tertiary alcohols having a (2Z, 5E)-2,5,7-octatrienyl- or a (2Z, 6E, 9E)-2,6,9,11-dodecatetraenyl chain. Similar reactions of isoprene gave a mixture of terpenic and apoterpenic alcohols. A possible reaction scheme was discussed in terms of an insertion of the carbonyl group to a σ-allyl end of octadienyl or dodecatrienyl nickel complexes.

A number of ketones and carboxylic acids have been examined for direct and indirect chemiluminescence with 9,10-diphenylanthracene and 9,10-dibromoanthracene by air oxidation. From the finding that the efficiency of the chemiluminescence was dramatically influenced by the class of the C–H bond adjacent to the carbonyl group, it was concluded that the molecules with a –COCH– group surely give an excited product during air oxidation in alkaline aprotic solvents. The reaction scheme was consistent with the evidence that most simple carboxylic acids exhibited no chemiluminescence, probably because the C–H bond adjacent to the carboxyl group is no more acidic, but keto acids exhibited emission. In several compounds, however, the chemiluminescent reaction was retarded by other functional groups.

The cycloaddition of aromatic nitrile oxides(2a=benzo-; 2b=p-tolu-; 2c=mesitylenecarbo-) with 1,3,5-triazine(1) is reported. The corresponding 3-substituted 1,2,4-oxadiazoles(3a,b,c) are obtained in fair yields only when BF3 is added. It was stoichiometrically confirmed that one mol of 1 behaves so as to supply three mols of azomethine radicals. A reaction scheme initiated from a two-step cycloaddition of 2 to 1 activated by BF3 is suggested. The mixture, 1 : 2c : BF3=1 : 3 : 1, afforded a better yield of 3c(69%) than an equimolar mixture of 2c with ethyl formimidate or formamidine.

Two sex pheromones, periplanone A and periplanone B were isolated from the American cockroach Periplaneta americana. The technique is described for collecting periplanone B from the alimentary tracts of virgin females. Periplanone A was extracted from the excreta of the insects. Mass spectral analysis of the pheromones and related compounds were performed and the results are reported here. Evidence is presented suggesting that periplanone A is in fact a degradation product of periplanone B. A reaction scheme is considered for the pathway: periplanone B periplanone A (stable, but inactive) PA 22–VII.

The 11-mono and 12-mono- and 11,12-dideuteroretina1 (in the all-trans, 9-cis, 11-cis and 13-cis form) with > 98% chemical purity and > 95% mono- and dideuterium incorporation were prepared using the same scheme for all three compounds. The all-trans, 9-cis and 13-cis-10-monodeuteroretinal isomers were prepared with good chemical purity (> 99%) and 82% monodeuterium incorporation via a different reaction scheme.

A detailed investigation of the mechanism of cyanogen oxidation is presented. Recent induction time measurements of ignition in cyanogen–oxygen–argon mixtures behind reflected shocks are computer modeled to obtain an agreement between the experimental and calculated values. A 15-step reaction scheme is suggested to reproduce the parameters E and βi in the experimental parametric relation: τ = 10αexp(E/RT)IICiβi. An explanation is offered to the very strong dependence of the induction time on the cyanogen concentration and the very weak dependence on the oxygen concentration. The sensitivity spectrum shows that the induction time is highly dependent on the O + C2N2 NCO + CN and NCO + M N + CO + M reactions (shortened) and the O + NCO CO + NO and N + NCO N2 + CO reactions (increased).

Als unverzweigte offene Kette bezeichnet man ein Reaktionsschema, in welchem die entstehenden Zwischenprodukte im jeweiligen Folgeschritt wieder umgesetzt werden und bei dem fur jede Teilreaktion nur ein Reaktionsweg moglich ist. Christiansen hat fur ein solches Reaktionsschema die Reaktionsgeschwindigkeit in Abhangigkeit von der Ausgangskonzentration und von den Reaktionswahrscheinlichkeiten der Einzelschritte berechnet, und zwar auch bei Einschlus irreversibler Teilschritte. Bei Ubertragung dieser Rechnung auf elektrochemische Reaktionen ist zusatzlich der Einflus der Belegung der Elektrode mit Zwischenprodukten zu beachten. Wir haben das Schema der unverzweigten Kette auf die irreversible anodische Oxidation von Ameisensaure an Platin in schwefelsaurer Losung angewendet. Als Ergebnis erhalten wir, das der Ubergang des ersten Elektrons geschwindigkeitsbestimmend ist. Zur Identifizierung von Zwischenprodukten wird eine massenspektrometrische Methode vorgeschlagen. A reaction scheme is called an unbranched open chain, if the developed intermediates react in the following step and if only one reaction path exists. For such reaction schemes Christiansen has calculated the reaction rates as functions of the concentrations and the reaction probabilities of the individual steps, including irreversible steps. If these calculations are applied to electrochemical reactions one has to consider in addition the influence of the adsorbed intermediates. We have applied the scheme of the unbranched open chain to the irreversible anodic oxidation of formic acid on platinum in acid solutions. The results show, that the first electron transfer is rate determining. To identify adsorbed intermediates a mass-spectrometric method is suggested.

The reduction of Zn 2+ ions in KCl (pH 3.0) has been investigated at Hg, Zn(Hg) and solid Zn. A reaction scheme is suggested by analogy with Cu(su2+) reduction

In the reaction of tricyanoethylene (TCE) with phenoxazine in DMF at 100 ° C, in addition to the principal reaction product —viz., 3-(tricyanovinyl) phenoxazine — 3-dicyanomethylene-3H-phenoxazine and 3-phenoxazinyl-3-(3H-phenoxazinylene)-cyanomethane are formed in small amounts. The latter two compounds were also obtained from phenoxazine and dibromomalononitrile. Phenothiazine reacts similarly with tetracyanoethylene. A reaction scheme is proposed, and in this scheme the formation of side products is explained by significant electron transfer in the tetracyanoethylene-heterocycle system. For the first time, 1,6 cleavage of HCN was detected, in which (in contrast to the known 1,6 cleavage of HCN from carbon atoms) the hydrogen is split out from the nitrogen atom.

The thermal decomposition of trifluoroacetaldehyde at temperatures f 471 to 519°C has been studied by measuring the rates of formation of CF3H and C2F6. It is concluded that the high-pressure reaction mechanism involves a Rice-Herzfeld reaction scheme with first-order initiation and second-order termination via CF3 combination. However, a falloff in reaction rates is observed at pressures below 100 mmHg. The Arrhenius parameters of the three rate constants corresponding to the overall reaction, the initiation reaction, and an abstraction reaction have been evaluated.

Autoxidation and inhibited oxidation of pentaerythrityl tetraalkanoates, PETA, at elevated temperatures of 180 to 220°C have been investigated using a representative ester, pentaerytbrityl tetra heptanoate, PETH.1 In order to better understand reactions occurring in alkyl chains of PETA, similar studies were carried out with n-bexadecane (HD), at 120 to 190°C.2,3 Based on the results of these studies, a general reaction scheme describing liquid phase autoxidation of organic compounds at temperatures of 120 to 220°C has been proposed.4 In this paper, kinetic and mechanistic information applicable to autoxidation of PETA is summarised and our recent contributions in the area of inhibition at elevated temperatures are reviewed.

The reaction between [Fe(S2CNR2)3](R = CH2Ph or Et, NR2= morpholino) and iodine in methylene chloride has been studied by means of spectrophotometric methods. Intermediate and product spectroscopic analyses have led to the following reaction scheme: [Fe(S2CNR2)3]+ I2 [graphic omitted] [Fe(S2CNR2)3]·I2 [graphic omitted] [Fe(S2CNR2)3]++ I3– [graphic omitted] [Fe(S2CNR2)2I]+½(S2CNR2)2+ I2 A fast equilibrium reaction to give a 1 : 1 adduct [Fe(S2CNR2)3]·l2 precedes oxidation of iron(III) to iron(IV) to give [Fe(S2CNR2)3]l3′ which is in equilibrium with the five-co-ordinated [Fe(S2CNR2)2l], tetra-alkylthiuram disulphide, and iodine.

It is shown that mixtures of two isomeric benzolactams, viz., compounds of the benzamide and anilide type, are formed in the intramolecular amidation of arylalkylhydroxamic acids under the influence of polyphosphoric acid (PPA). A general reaction scheme that includes three pathways, viz., direct amidation, Lossen rearrangement of the hydroxamic acids with subsequent cyclization of the isocyanates, and Beckmann rearrangement of the oximes of the cyclic ketones formed in the thermal cleavage of the starting hydroxamic acids in PPA, is proposed on the basis of a study of racemic and optically active arylalkylhydroxamic acids.

The reaction of primary and secondary alkyl iodides and bromides with Hg(OAc)2 and HgCl2 in tetrahydrofuran (THF) affords the THF-incorporated compounds (1), RO(CH2)4X [X=OAc and Cl, respectively], in good yields. When HgBr2 and aqueous or alcoholic Hg(ClO4)2 were used as mercury(II) salts, the yields of 1(X=Br, OH, and OR′) were low. Similar treatment with HgI2 gave scarcely any 1. A reaction scheme which involves O-alkyltetrahydrofuranium ion as the intermediate is proposed for the formation of 1.

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 pressure dependences of the emission intensities at 326.1 and 432 nm in the cadmium-photosensitized reaction of ammonia have been measured. In order to interpret the nonlinear Stern-Volmer plots for the quenching of the 326.1 nm resonance line, the following reactions have to be taken into account in the reaction scheme: Cd*+NH3\ightleftharpoonsCdNH3*V, CdNH3*V+M→CdNH3*+M. The pressure dependence of the emission from the CdNH3* complex (at 432 nm) was also well explained in terms of a reaction scheme involving the above reactions.

Influence of halide ions (Cl−, Br−, I−) on the electrochemiluminescence (ecl) of 9,10-diphenplanthracene (DPA) is studied by using controlled-potential double-step method. It is confirmed that the ecl begins to appear at the anodic potential corresponding to the potential of the first anodic half-wave potential of each halide ion and that, passing through an intensity maximum, it disappears at more positive potential. Similarly, when the cathodic potential is changed, the ecl appears at the first cathodic half-wave potential of DPA and disappears at more negative potential than the second half-wave potential of DPA. These facts indicate that the ecl must be due to the reaction between oxidised species of halide ions (presumably trihalide ions) and monovalent DPA anion radicals. The mechanism for the formation of the excited singlet state of DPA is reasonably explained by assuming a reaction scheme containing a mono-halogenated DPA radical as an intermediate.