Showing papers on "Substituent published in 1968"

Esters of cyanic acid

Abstract: IN WHICH R IS AN ALKYL OR CYCLOALKYL RADICAL CONTAINING AN ELECTRON-ATTRACTING SUBSTITUENT, AN ARYL RADICAL, A SUBSTITUTED ARYL RADICAL FREE FROM THE SIMULTANEOUS PRESENCE OF STERICALLY HINDERED SUBSTITUENTS IN BOTH ORTHO POSITIONS TO THE CORRESPONDING -O-C$N GROUP OR HETEROCYCLIC RADICAL, AND X IS A WHOLE NUMBER FROM 1 TO 6. R$O-C$N)X CYANIC ACID ESTERS HAVING THE FORMULA

Polyelectrolytes prepared from perfluoroalkylaryl macromolecules

Abstract: The synthesis of a new generation of high-capacity oxidation-resistant ion-exchange resins and membranes is described which are sulfonic acid polyelectrolytes prepared from high molecular weight poly-α,β,β-trifluorostyrene. The difficult sulfonation of poly-α,β,β-trifluorostyrene is discussed in terms of the finding that this sulfonation must be effected upon an aromatic ring possessing a meta-directing substituent group. The oxidative stability of these new types of perfluoroalkyl aromatic sulfonic acid polyelectrolytes is both demonstrated and described with comparisons to their polystyrenesulfonic acid homologs. The difference in their oxidation–depolymerization stabilities is described in terms of benzylic carbon substituents.

High resolution mass spectrometry.—II Some substituted benzothiazoles

Abstract: The mass spectra of nineteen substituted benzothiazoles have been recorded and the identity of the various ions in the mass spectra has been established by high resulution (accurate) mass measurement. Deuterium labelling has been used to elucidate the fragmentation processes of these compounds. The parent compound of the series, benzothiazole, exhibits the loss of hydrogen cyanide and carbon monosulphide from the parent ion as the most important decomposition pathways. The hydrogen atom concerned in the loss of hydrogen cyanide is shown to originate from the 2-position of benzothiazole, while in 2-substituted benzothiazoles, different mechanisms are apparent for the loss of hydrogen cyanide, and these are clarified by deuterium labelling. Some substituted benzothiazoles can lose sulphur from their molecular ions, a process which does not occur in benzothiazole itself. The substituted benzothiazoles undergo many other types of fragmentations, in some cases retaining the substituent, and in other cases losing it prior to collapse of the thiazole ring.

Fluorine-19 nuclear magnetic resonance studies on some polyfluroaromatic compounds and their metal complexes

Abstract: The high-resolution fluorine-19 n.m.r. spectra of several polyfluoroaromatic compounds and of derived transition-metal complexes are presented and discussed. Substituent shielding parameters are tabulated for many commonly encountered functional groups, and details of the identification of complex products from the reaction of the anion [(π-C5H5)Fe(CO)2]– with C6F5CN, 1,2-C6F4I2 and C6F5Br are given. The nature of the complexes formed has been confirmed by use of high-resolution mass-spectrometric techniques in the latter two cases.

2-amino-adenosine derivatives

Abstract: NOVEL 2-AMINO-ADENOSINE DRIVATIVES CHARACTERIZED BY CARDIAC AND CIRCULATORY ACTIVITY AND BY THEIR HIGH CORONARY SPECIFICITY HAVING THE FOLLOWING STRUCTURAL FORMULA: 2-NH2,6-(R1-N(-R2)-),9-(3,4,5-TRI(HO-)-2-TETRAHYDRO- PYRANYL)-9H-PURINE WHEREIN R1 IS HYDROGEN, A SUBSTITUTED OR UNSUBSTITUDED, SATURATED OR UNSATURATED, STRAIGHT OR BRANCHED CHAIN ALIPHATIC HYDROCARBON RADICAL, WHEREIN SAID SUBSTITUENT IS AT LEAST ONE OF AMINO, ALKYLAMINO, DIALKYLAMINO, ACYLAMINO, ALKOXY, ACYLOXY, HYDROXY, MERCAPTO, ALKYLMERCAPTO, CARBOXY, CARBOXY ALKYL OR CARBOXAMIDO AND R2 IS A SATURATED OR UNSATURATED CYCLOALKYL RADICAL WHICH CAN CARRY ENDOALKYLENE RADICALS OR ANNELLATED, SATURATED OR UNSATURATED CYCLIC ALIPHATIC HYDROCARBON RADICALS, WHEREIN SAID SUBA-X-3, WHEREIN A IS A SUBSTITUTED OR UNSUBSTITUTED, SATURATED OR UNSATURATED, STRAIGHT OR BRANCHED CHAIN, OR CYCLIC ALIPHATIC HYDROCARBON RADICAL, WHEREIN SAID SUBSTITUENT IS AT LEAST ONE OF HYDROXY, ACYLOXY, CARBOXY AND ARYL RADICALS, X IS A VALENCY BOND, AN OXYGEN OR SULFUR ATOM, ALKYLATED IMINO OR ACYLATED IMINO, AND B IS A SUBSTITUTED OR UNSUBSTITUTED ALKYL, ALKENYL, ARYL, FURYL, PYRIDYL, INDOLYL OR IMIDAZOLYL RADICAL, WHEREIN SAID SUBSTITUENT IS AT LEAST ONE OF HALOGEN, ALKYL, HALOALKYL, ALKOXY, ARYLOXY, ACYLOXY, HYDROXY, MERCAPTO, ALKYLMERCAPTO, NITRO, CARBOXY, CARBOXYLALKYL AND METHYLSULFONYLAMINO RADICALS.

Nature of the coordination bond in metal complexes of substituted pyridine derivatives. I. The substituent effect on the coordination bond

Abstract: The nature of the coordination bond in some metal complexes of 4-substituted pyridines has been investigated by thermodynamic and infrared spectroscopic methods. The effects of the substituents upo...

Magnetic Moments and d–d Bands of N-n-Propanolsalicylaldiminato-copper(II)

Abstract: The reaction of cupric acetate with the reaction mixture of γ-aminopropyl alcohol and substituted salicylaldehydes in ethanol gave dimeric copper(II) complexes. The postulated structure of these complexes makes it possible to test the substituent effect transmitted to the coordinating atoms which are not in the superexchange pathway between copper-(II) ions in a pair. The magnetic moments observed at room temperature were corrected for the temperature variations to those at 25°C by graphic method based on Bleaney and Bowers’ equation. The observed substituent effect on the relation between μeff25°C and λmax is different from that observed for dimeric cupric halides complexes of substituted pyridine N-oxides. In these complexes the substituent effect transmits to the bridging oxygen atom in the superexchange pathway. As compared with the parent complex (H), methyl, chloro and benzo groups weakened the magnetic interaction but nitro group strengthened it. An interpretation of the substituent effect is given...

Structural effects in reactions of organophosphorus compounds. I. Reactions of phosphorus oxychloride with hindered phenols

Abstract: 2,6-Dialkyl-phenols exhibit little steric hindrance on reaction with phosphoryl chloride unless the alkyl substituent is bulky (i.e. t-butyl). Where bulky substituents are present reaction with phosphoryl chloride occurs only in the presence of Friedel–Crafts type catalysts after either a dealkylation or a rearrangement of the ortho-placed alkyl groups, followed by O-phosphorylation, has occurred.

The mass spectra of some alkyl and aryl oxazoles

Abstract: The mass spectra of a variety of alkyl and aryl oxazoles have been determined and the spectra analyzed with the aid of deuterium labelling and high resolution mass spectrometry. In contrast to the corresponding benzenoid compounds, the mass spectra of isomeric alkyl oxazoles are distinctive and in this respect are akin to those of the corresponding pyridines. Further analogy to the pyridines is suggested by the unfavorable nature of a carbonium ion adjacent to the 2-position and this effect may be used to locate alkyl substituents attached to the oxazole nucleus. The loss of carbon monoxide from the molecular ions of 2,5-disubstituted oxazoles probably occurs with ring opening and migration of the C-5 substituent (e.g.Br) to the C-4 position.

The electron distribution at the nitrogen atom in substituted pyridines and related compounds as measured by their 14N quadrupole coupling constants

Abstract: The measurements of 14N pure quadrupole resonance spectra of symmetrical azabenzenes and their analysis in terms of the electron distribution around the nitrogen atom has been extended to the two asymmetric diazabenzenes, pyrimidine and pyridazine, and to a variety of substituted pyridines. The coupling constants of unsymmetric compounds, i.e. compounds where the two nitrogen sigma bonds are not equivalent, cannot be analysed completely but yield values of the difference between the pi population and the average sigma population, including the lone-pair. Within these limits the electron distributions are in good agreement with those expected from simple molecular orbital theory. The results for the substituted pyridines show very strikingly the expected effect of substituents and the expected differences between the same substituent either ortho or para to the nitrogen atom on the one hand or meta on the other.

Structural requirements for active intestinal sugar transport. The involvement of hydrogen bonds at C-1 and C-6 of the sugar

Abstract: 1. A series of d-galactose derivatives substituted at C-1 and C-6 were tested for active accumulation by everted segments of hamster and rat intestine. 2. d-Galactose and 6-deoxy-6-fluoro-d-galactose were accumulated far more rapidly than 6-deoxy- and 6-chloro-6-deoxy-d-galactose, and this is interpreted as due to hydrogen-bonding at C-6 during the transport process. 3. 6-Bromo-6-deoxy- and 6-deoxy-6-iodo-d-galactose were not actively transported, indicating that the allowed size of substituent at C-6 lies between that of chlorine and bromine atoms. 4. Similar results were obtained at C-1. Both methyl α-d-galactopyranoside and methyl β-d-galactopyranoside were well transported, but methyl β-d-thiogalactopyranoside and 1-deoxy-d-galactose were not transported; d-galactopyranosyl fluoride was transported, but only poorly. Again hydrogen-bonding is suggested. 5. It is proposed that d-glucose is the ideal structure for active transport and that binding occurs at C-1, C-2, C-3, C-4 and C-6. Loss of two or more of these bonds usually causes loss of active transport. 6. By plotting Lineweaver–Burk plots of the rates of transport of the galactose derivatives, the apparent V and Km values were obtained. With hamster intestine both these values were very reproducible. Contrary to expectation, V varied for different sugars. 7. The Ki of some of the analogues modified at C-1 and C-6 was determined with methyl α-d-glucoside as substrate. 8. An attempt to alkylate the carrier by using methyl 3,4-anhydro-α-d-galactoside was unsuccessful. There was no evidence that this compound was bound to the carrier.