Double Bond System Research Articles

Regioselective reaction of functionally substituted mono-, di-, and triolefins with alkylmagnesium compounds, catalyzed by Cp2ZrCl2

1. In the presence of catalytic quantities of Cp2ZrCl2 Et2Mg and EtMgBr react regio-selectively with α-olefins with different structures to form higher asymmetrical organomagnesium compounds. 2. Electron acceptor substituents at the allyl atom reduce noticeably the activity of the double bond in the reaction with the alkyl magnesium compounds; the nature of the allyl substituent has practically no influence on the regioselectivity of the process. Functional substituents removed from the vinyl group have little influence on the reactivity of the latter in the reaction with the alkyl magnesium compounds. 3. The presence of an acetylenic bond in the α-olefin molecule or of a conjugated double bond system inhibit this reaction.

Photochemical reaction of 7,8-dihydrorhodopsin at low temperatures

The photoreaction of 9- cis-7,8-dihydrorhodopsin was examined at liquid nitrogen temperatures (−180°C) in order to elucidate the photochemical events in visual pigments. This rhodopsin analog was prepared by incubating 9- cis-7,8-dihydroretinal with bovine opsin in the dark. 9- cis-7,8-Dihydrorhodopsin ( λ max = 427 nm) was cooled to −180°C, and then irradiated at −180°C with a 390 nm light, resulting in formation of its bathochromic product ( λ max = roughly 465 nm). This result indicates that the presence of four double-bonds adjacent to the Schiff base nitrogen is sufficient to allow formation of a bathochromic product. Thus, the mechanism of formation of bathorhodopsin (in bovine rhodopsin system) may be considered as some change of the interaction between the conjugated double-bond system from C-9 to the Schiff base nitrogen and its surrounding charges in opsin, caused by rotation of 11–12 double-bond.

Activation of phosphodiesterase in frog rod outer segment by rhodopsin analogues

Activation of guanosine 3′,5′-cyclic monophosphate (cGMP) phosphodiesterase (EC 3.1.4.35) in frog rod outer segment membrane by rhodopsin analogues has been investigated. A rhodopsin analogue modified at the Schiff-base linkage ( N-retinyl-opsin) or the β-ionone ring (3-dehydro-rhodopsin) in the retinylidene chromophore of rhodopsin has some ability in activation of the enzyme. In consideration of our previous observation that opsin including a retinal-oxime can activate the enzyme, it seems likely that the Schiff-base linkage is not always necessary for the phosphodiesterase activation. On the other hand, a change in the length of the side chain of retinal (complex of opsin and β-ionone, β-ionylideneacetaldehyde or retinylideneacetaldehyde) or dissection of the conjugate double-bond system of the side chain (retro-γ-rhodopsin) remarkably reduces the activation ability. However, 5,8-epoxy-rhodopsin having a similar dissected conjugate double-bond system induces some enzyme activation because of its rigid conformation around C 7-C 8-C 9 single bonds. Consequently, it is suggested that the necessary portion of rhodopsin chromophore for the activation of the enzyme is the rigid conjugate double-bond system between the β-ionone ring and the Schiff-base linkage in its all- trans form.

Selenium-nitrogen and tellurium-nitrogen compounds

Te-N and Se-N compounds are notoriously unstable. However, starting with H 2NTeF 5 or (CH 3) 3SiNHTeF 5 a variety of tellurium nitrogen compounds have been prepared, such as F 5TeNSF 2, F 5TeNPF 3, F 5TeNCl 2 a.o. A crystal structure is given of F 5TeNWCl 4, and an electron diffraction structure of F 5TeNCO. Whereas F 5SNCO has a similar structure, F 5SeOCN appears as cyanate! The first selenium-nitrogen double bond systems have been prepared with F 5TeNSeCl 2 and F 5TeNSeF 2.

Kohlensäureesterphosphide – Synthese und Cyclisierungsreaktionen/Carbonic Ester Phosphides – Synthesis and Cyclization Reactions

Abstract Carbonic ester phosphides, RPHCOORʹ and RP(COORʹ)2, have been prepared by the reaction of ClCOORʹ with primary phosphines RPH2 in the presence of K2CO3. Some compounds of RPHCOORʹ series are transformed into P-heterocycles through addition of the P-H group to the C = C doublebond systems. The 31P NMR data, IR and mass spectra of the novel compounds are presented and discussed.

13C nuclear magnetic resonance spectroscopic analysis of seed oils containing conjugated unsaturated acids

Abstract13C Nuclear magnetic resonance spectroscopy has been used in a nondestructive investigation of conjugated unsaturated acids in seed oil triacylglycerols. Spectra of seven seed oils, fromPunica granatum, Cucurbita palmata, Jacaranda mimosifolia, Centranthus ruber, Catalpa bignonioides, Chilopsis linearis andCalendula officinalis, containing among them six isomeric trienoic acids,cis,trans,cis‐ andtrans,trans,cis‐8,10,12‐,cis,trans,cis‐, cis,trans,trans‐, trans,trans,cis‐ andtrans,trans,trans‐9,11,13‐octadecatrienoic acids, and of the oil ofImpatiens balsamina containingcis,trans,trans,cis‐9,11,13,15‐octadecatetraenoic acid, have been examined. Structures of component acids were derived from shifts of double bond carbons and of carbons close to the double bond systems. Compositions of the oils were obtained from signal intensities. Results were similar to those obtained by older methods. Only oil ofCentranthus ruber contained more than one major conjugated acid; bothcis,trans,trans‐ andtrans,trans,trans‐9,11,13‐octadecatrienoic acids were found. The latter acid is now thought to occur naturally.

The principle of vinylogy

The principle of vinylogy recognizes the possibility that the inductive effect of a functional group is transmitted through a double bond or a conjugated system of double bonds.

Preparation and structure of 2-acetyl-2,3-epoxycarane

1. 2-Acetyl-α-2,3-epoxycarane which exists in solution as a single gauche conformer with minimal polarity was synthesized by the epoxidation of 2-acetyl-2-carene by perphthalic acid. 2. The conjugation in the system of double bonds in 2-acetyl-2-carene is disturbed due to acoplanarity of the C=C-C=O fragment.

Effect of adjacent units during thermal degradation of copolymers of vinyl chloride with vinyl acetate

It is shown that the introduction of vinyl acetate units into the PVC chain raises the random elimination of HCl since the groups—OCOCH 3 exert a destabilizing influence on the adjacent vinyl chloride units. At the initial stages of degradation, the rate of formation of HCl and CH 3COOH is a function of three individual rate constants which characterize the reactivity of the vinyl chloride units having zero, one or two adjacent vinyl acetate units respectively and the rate constants for the formation of polyconjugated systems of double bonds ▪

7] Arachidonic acid-12-lipoxygenase from bovine platelets

Publisher Summary This chapter describes the assay, partial purification, and properties of arachidonic acid-12-lipoxygenase that is available in large quantities from blood platelets of slaughterhouse animals. In partial purification of arachidonate lipoxygenase described in the chapter, the enzyme was found for the greater part in the 100,000g supernatant after freezing and thawing the platelets three times. Further fractionation was possible with (NH 4 ) 2 SO 4 . The lipoxygenase in intact platelets was rather stable and can be kept for at least 1 week at 0°. Lipoxygenase activity can be determined in intact platelets or crude, turbid enzyme preparations by incubations with radioactive arachidonic acid. The products were separated by thin-layer chromatography, and their radioactivity was measured. A simpler and quicker method can be used in more purified, clear enzyme solutions: the increase in UV absorption at 234 nm due to the formation of a conjugated system of double bonds was followed continuously.

Mechanism of urocanase as studied by deuterium isotope effects and labeling patterns.

Nicotinamide adenine dinucleotide (NAD) dependent urocanase (4'-imidazolone-5'-propionate hydro-lyase, EC 4.2.1.49) from Pseudomonas putida was found to catalyze an exchange reaction between solvent and the 4'-hydrogen of urocanate or imidazolepropionate at a rate faster than that of overall deuterium was compared to unlabeled urocanate as a substrate, no isotope rate effect was noted. For examination of the possibility of an NAD+-mediated intramolecular hydride transfer of the 4'-hydrogen to a position on the side chain of oxoimidazolepropionate, the origins of hydrogen at positions 2 and 3 in the propionate chain were studied as a function of reaction time and extent of exchange of the 4'-hydrogen. No transfer of hydrogen from the 4' position to the side chain was observed, thereby eliminating mechanisms requiring hydride transfer via NADH between these positions. Catalytic rates in 1H2O vs. 2H2O revealed a 3-fold difference which was ascribed to a rate-limiting proton addition step. Similarly, a 5-fold decrease in Vmax was found for the reverse reaction when oxoimidazole[2,3-2H2]propionate was compared to unlabeled oxoimidazolepropionate. These data support a mechanism involving water addition across the conjugated double bond system of urocanate, rather than an internal oxidation--reduction process, yet NAD+ is required. A mechanism is proposed which uses electron delocalization in the imidazole nucleus, via an imidazole--NAD adduct, to facilitate water attack and subsequent formation of oxoimidazolepropionate.

Transition-metal Complexes of Pyrrole Pigments. XVII. Preparation and Spectroscopic Properties of Corrole Complexes

Abstract Nickel(II), copper(II), and cobalt(III) complexes were prepared with corroles; 2,3,7,8,12,13,17,18-octaethylcorrole (OEC), 2,3,17,18-tetramethyl-7,8,12,13-tetraethylcorrole (MEC), and 8,12-bis[2-(ethoxycarbonyl)ethyl]2,3,7,13,17,18-hexamethylcorrole (PMC). For the coordination with nickel and copper ions, the corroles acted as dianionic ligands to yield electrically neutral complexes. These complexes exhibited metalloporphyrin-like electronic spectra, while they showed spectra which bear a much closer resemblance to those for metalloporphyrins as the anionic complexes were formed upon addition of alkali. The corroles coordinate to tervalent cobalt as trianionic ligands to form neutral complexes, which were reduced to the corresponding cobalt(II) complexes with sodium hydroborate. These reduced species gave a unique set of g-values (g1>>g2>g3) for the complexes of macrocyclic ligands with conjugated double bond system. The plausible coordination geometry as well as the structural properties of the corrole ligands has been discussed.

Thermal degradation of copolymers of vinyl chloride with vinyl acetate

The method of solid- and liquid-phase ozonization has been used to determine the content, distribution and chemical structure of unsaturated CC bonds in the macromolecules of copolymers of vinyl chloride and vinyl acetate (VCVA) containing 11·4±1·2 mole% VA. It was found that chain termination in the copolymerization process occurs mainly on VA with the formation of terminal CC bonds with structure of types: CH 2CH(OCOCH 3)∼, CH(OCOCH 3)CH∼ and (CH 2CH)OCOCH 2, whose content amounts to 4 × 10 −3 mole/mole copolymer. It was found that the presence of isolated VA units in the polymer chains accelerates the reaction of statistical HCl elimination from ∼CH 2CHCl units, and has a significant inhibiting influence on the formation of CC polyconjugated double bond systems.

Biochemical studies on carotenoids. part X. Further studies on the acquisition of novel optical activity on interaction of lutein and other carotenoids with proteins.

Lutein had novel spectroscopic properties in the visible region on the formation of complexes with several proteins [S. Takagi, M. Shiroishi and T. Takagi, Agric. Biol. Chem., 44, 2111 (1980)]. The effects of pH, molar ratio of lutein to protein, and the variety of protein on the phenomenon was studied. The phenomenon was insensitive to these parameters. Solubilization into micelles of deoxycholate was found to induce no optical activity in contrast to bilirubin by Perrin et al. [J. H. Perrin and M. Wilsey, Chem. Commun., 769 (1971)]. It is strongly suggested in this paper that the observed changes in spectroscopic properties including the novel one in circular dichroism come chiefly from mutual interactions between lutein molecules in the complexes. Changes in spectroscopic properties comparable to those for lutein were observed with β-cryptoxanthin but not with canthaxanthin or ethyl β-apo-8'-carotenoate, although the latter two formed complexes with ovalbumin. The presence of at least one asymmetric carbon atom in the ionone rings seems to be essential for the novel spectro-scopic changes to be observed. The possible correlation of the trans-cis conformational change in the conjugated double bond system was discussed. The optical activity was presumed to come from the intermolecular dipole-dipole coupling with the chiral spatial orientation.

Three Variants of the [2 + 2]‐Cycloaddition of Bicyclopropylidene

Bicyclopropylidene (1) has recently become readily accessible, and is a suitable synthon for construction of dispiro compounds. Compound (1) reacts very smoothly with a number of electron-poor double-bond systems. Thus with tetracyanoethylene it forms the products (3), (4), and (5)—presumably via the zwitterion (2). Only two kinds of cycloaddition are accomplished with chlorosulfonyl isocyanate and phenyltriazolinedione.

Nickel-catalysed reactions of olefins with =C=N- double bond systems

The reactions of Schiffs' bases, hydrazones, 2,3diazabutadienes and 2-azabutadienes with butadiene or activated monoenes in the presence of nickel catalysts lead to new classes of compounds, which are isolated as mixtures of isomers. The ratio of the isomer distribution can be controlled inside wide limits by variation of the nickel ligands and the reaction parameters. A comparison with the nickel-catalysed oligomerisation of butadiene or the cooligomerisation of butadiene with mono-olef ins shows that the reaction products in the two cases are not analogous. INTRODUCTION In the last twenty years the chemistry of nickel-catalysed reactions of olefins and alkynes has undergone a vigorous upsurge. This interest is connected above all with the discovery of bis(cycloocta-l,5-diene) nickel(O) in the year 1960 (1). In the following years the Mulheirn group particularly occupied itself with possible new syntheses of cyclic and linear compounds from simple olefins and acetylenes. 2 ' L) + L) + LJ — _ ___ , — Ii + Fig. 1 Characteristic nickel-catalysed reactions In spite of the multiplicity of reactions catalysed homogeneously by nickel and their simplicity and selectivity only very few have awakened the interest of the chemical industry. In addition to the trimerisation of butadiene to 1,5,9-cyclododecatriene (2), the starting material for 'Nylon 12 and dodecandicarboxylic acid, they are: a) The addition of HCN to butadiene giving adiponitrile, the starting material for hexamethylenediamine (3). b) The cooligomerisation of ethylene and butadiene to 1,4hexadiene, an important comonomer for the polymerisation of ethylene arxpropylene with an unsymmetrical diene (4).

Thermal oxidative breakdown of plasticized polyvinylchloride

The addition to PVC of ester plasticizers considerably changes the rate of breakdown processes—elimination of HCl, formation of statistical isolated >C=C< bonds and the formation of poly-conjugated systems of double bonds in the macro-molecules. The ratio of rates of these processes depends on the oxidative stability of the plasticizer its concentration and partial oxygen pressure in the reaction zone. Products of oxidation of esters intensify the formation of polyene systems, whereas actinometer coupled with an F-116/1 microvoltmeter. Within the wavelength interval specified the intensity was varied from 6 × 10 14 to 1·5 × 10 15 quantum cm −2sec −1. The exposure time was 10–300 sec. The electronic spectra were measured with an SP-700 spectrophotometer; an IKS-29 spectrophotometer was used for the IR spectra. The differential quantum yield of the PVCA oxidation product was measured by a standard method [5], using monochromatic light. The wavelength selected was in the interval 400–440 nm, such that the intensity of the light absorbed did not exceed 20% on that of the incident light. The amount of light absorbed was calculated in line with the Lambert-Beer law.

Isomerization of the double bonds of a conjugated fatty acid during beta-oxidation.

The beta-oxidation of an unsaturated fatty acid containing conjugated double bonds at odd-numbered carbon atoms has not previously been studied. It is, therefore, not clear whether, during the beta-oxidation of such an acid, the double bonds will be isomerized by enoyl-CoA isomerase (delta 3 - delta 2-enoyl-CoA isomerase) with the loss or retention of its conjugated nature. To investigate the problem, (E,E)-3,5-octadienoyl-CoA was synthesized for use as a model substrate, and enoyl-CoA isomerase was partially purified from bovine liver. The isomerization was followed by spectrophotometric and gas liquid chromatographic methods, and the results suggested that the isomerization of the model substrate proceeded with retention of a conjugated double bond system. It is, therefore, proposed that the beta-oxidation intermediate of alpha-eleostearic acid (delta 9,11,13 fatty acid) will also isomerize with retention of the conjugated double bond system.

Photochemical reaction of 9- cis-retro-γ-rhodopsin at low temperatures

9- cis-Retro-γ;rhodopsin ( λ max = 420 nm) was prepared from 9- cis-retro-γ-retinal and cattle opsin. After cooling to liquid nitrogen temperature (77 K), the pigment was irradiated with light at 380 nm. The spectrum shifted to the longer wavelengths, owing to formation of a batho product. This fact indicates that the conjugated double bond system from C-5 to C-8 of the chromophoric retinal in rhodopsin was not necessary for formation of bathorhodopsin. Reirradiation of the batho product with light at wavelengths longer than 520 nm yielded a mixture composed of presumably 9- or 11- cis forms of retro-γ-rhodopsin. These three isomers are interconvertible by light at liquid nitrogen temperature. Thus the retro-γ-rhodopsin system is similar in photochemical reaction at 77 K to cattle rhodopsin system. Each system has its own batho product. Based on these results, it was infered that the formation of bathorhodopsin is due to photoisomerization of the chromophoric retinal of rhodopsin and is not due to translocation of a proton on the ring or on the side chain from C-6 to C-8 of the chromophoric retinal to the Schiff-base nitrogen.

Reactions of carbonyl compounds in the presence of phase transfer catalysts

1. Quantum chemical CNDO/BW calculations with optimization of geometries have been carried out on the keto and enol forms of acetone, mesityl oxide, and methyl ethyl ketone, and on the carbanions resulting from various types of deprotonation in these compounds. 2. The keto forms of acetone and mesityl oxide are considerably more stable than the enol forms, while the enolate anions resulting through from heterolytic rupture of the OH bond in the enol forms pass over into the keto form anions with zero activation energy. 3. The calculated gas-phase acidities of the compounds in question here increase in the order: acetone, methyl ethyl ketone, mesityl oxide. 4. Proton detachment from the γ-CH3 group of theβ-form of mesityl oxide, from the secondary C atom of theα-form, or from the hydroxyl group of the enol form leads, in every case, to the same anion structure, namely anα-form carbanion with an unconjugated system of single and double bonds. This, and the anion resulting from proton detachment from theα-methine C atom of theβ-form, are the most stable of the mesityl oxide carbanions. 5. The H atoms bound to the secondary C atom are the most acidic hydrogens in methyl ethyl ketone. Theα-CH3 group acidity is the same in each of the compounds covered by this work.