Showing papers on "Substituent published in 1974"

Photoelectron Spectra of Substituted Benzenes

Abstract: Photoelectron spectra were measured in the region between 6 and 21 eV for aniline, N,N-dimethylaniline, phenol, anisole, benzonitrile, acetophenone, nitrobenzene, and their methyl derivatives. The observed spectra were interpreted in terms of their MO’s obtained by the CNDO/2 and EHMO methods, the methyl-substituent effect and the steric hindrance effect being considered. Both effects are essential for the reliable assignment of the observed photoelectron spectra. We found a general tendency that the interaction of the doubly degenerate highest occupied orbitals (e1g) of the benzene ring with the highest occupied orbital of a substituent group is important for the interpretation of the observed lower energy (7∼12 eV) bands. The only exceptional case is the nitrobenzenes in which the lowest vacant orbital of the substituent group is rather close to the highest occupied orbitals of the benzene ring and the interaction between them is important. The effects of the substituent groups upon the observed photoel...

13C Nuclear Magnetic Resonance Studies. 38. Examination of the Long-range Shielding Effects of the Hydroxyl Group in Alicyclic Systems

Abstract: The substituent effects of the hydroxyl group on the 13C shieldings of the trans-decalols and the 10-methyl-trans-decalols have been determined. The shifts for the carbons three and four bonds from...

1,2,3-Triazoles

Abstract: Publisher Summary This chapter focuses on the chemistry of monocyclic1,2,3-triazoles as much of the chemistry of benzotriazoles and other fused systems has little in common with monocyclic triazole chemistry and provides a broad survey of methods of synthesis and reactions of triazoles. There has been considerable interest in 1,2,3-triazoles as light stabilizers and as optical brightening agents. They are also used as precursors for azapurines and similar heterocyclic systems that are potential carcinostatic agents. Three recognized classes of 1,2,3-triazoles are 1 H -, 2 H -, and 4 H -1,2,3-triazoles. Triazoles unsubstituted on nitrogen can be regarded either as 1 H - or as 2 H -derivatives, depending upon what tautomer is preferred. The first two classes can be regarded as aromatic systems whereas the third, the 4 H -system, cannot. This is reflected in the abundance of examples of 1 H - and 2 H -triazoles and the rarity of 4 H -triazoles. The thermal cycloaddition of azides to acetylenes is the most versatile route to 1 H -1,2,3-triazoles because of the wide range of substituents that can be incorporated into the acetylene and azide components. The base-catalyzed condensation of azides with activated methylene compounds is a well-established route to 1 H -triazoles and is the best route to triazoles bearing a 5-amino or hydroxy substituent and an aryl or carbonyl-containing function in the 4-position. The structure and spectroscopic and physical properties of triazole are discussed in the chapter.

A 13C-NMR and IR study of isocyanides and some of their complexes

Abstract: 13C chemical shifts and 1J(14N13C) coupling constants as well as stretching frequencies of the isocyano group are reported for some representative aliphatic, unsaturated and aromatic isocyanides and for two copper(I) isocyanide complexes. The results are discussed in terms of the inductive and mesomeric substituent effects on the polarisation and charge density of the CNC bonds. The marked solvent effect on the chemical shifts of the isocyano carbon hampers comparison of our data with previously reported data. The hydrogen bonding shift of this carbon in water or methanol is much smaller than previous data suggest.

Phytosterol side chain biosynthesis.

Abstract: The typical plant sterols contain a substituent at C-24 of the side chain. This can be a methylene, ethylidene, methyl, or ethyl group; with the last three groups, all possible isomers have been reported in nature. The C-24 alkyl groups are derived by a transmethylation reaction from methionine. The details of several distinct alkylation mechanisms, which are now recognized in a range of lower and higher plants, have been reviewed. The operation of these different routes may have some phylogenetic significance.

Process for the production of polymeric hydrocarbons having reactive silyl end groups

Abstract: Polymeric hydrocarbons having reactive silyl end groups are produced by conducting a catalyzed ring opening polymerization of a cyclic olefin in the presence of, or reacting with a polymeric hydrocarbon having an unsubstituted non-conjugated ethylenic double bond in a polymer unit thereof, an organic silicon compound having at least one nonconjugated unsubstituted double bond or a polymeric hydrocarbon having a non-conjugated unsubstituted terminal double bond, with an organic silicon compound having at least one organic group, bound to the silicon atom by a carbon-silicon bond, which contains at least one unsubstituted, non-conjugated acyclic double bond and having at least one silicon atom bearing, via a carbon-silicon bond, at least one substituent which is readily removable by hydrolysis.

Scale inhibition and corrosion inhibition

Abstract: A method of inhibiting corrosion and scale formation in an aqueous system is disclosed which comprises the step of treating the said system with 0.1 to 500 parts per million by weight of the total aqueous content of the said system, of a composition which may additionally include zinc and which comprises a polymer selected from the group consisting of: Polymers having recurring units of the formula: ##EQU1## WHEREIN M + may be H + , alkali metal cation, or quaternary ammonium cation of the formula: ##EQU2## wherein for all of the above formulas, R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently selected from the group consisting of hydrogen, alkyl of from one to 10 carbon atoms, and substituted alkyl of from one to 10 carbon atoms, where the substituent is hydroxyl; carbonyl; and carboxylic acid groups, and alkali metal ion and ammonium salts thereof; and Wherein n is an integer of from 2 to 100; and polymers having recurring units of the formula: ##EQU3## WHEREIN R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 are each independently selected from the group consisting of hydrogen, alkyl of from one to 10 carbon atoms, and substituted alkyl of from one to 10 carbon atoms, where the substituent is hydroxyl; carbonyl; and carboxylic acid groups, and alkali metal ion and ammonium salts thereof; Wherein p is an integer of from 1 to 6; Wherein m is an integer of from 2 to 100; and Wherein n is an integer of from 2 to about 100, provided that, n not equal to m, the lesser of m or n is multiplied by a factor such that n = m.

Substrate Specificity of the Purified Primary Alcohol Dehydrogenases from Methanol-Oxidizing Bacteria

Abstract: Hyphomicrobium strain WC, Pseudomonas strain TP-1, and Pseudomonas strain W1 are capable of growth on methanol as the sole source of carbon and energy. Methanol-grown cells of each organism contain a primary alcohol dehydrogenase that has been purified to homogeneity. Each enzyme has a molecular weight of 120,000 and shows an in vitro requirement for phenazine methosulfate and ammonium ions for enzymatic activity. Normal aliphatic alcohols are oxidized rapidly by each enzyme. The presence of a methyl group on the carbon atom adjacent to the primary alcohol group lowers the enzymatic activity. This effect is reduced as the methyl substituent is moved further away from the hydroxyl group. The effect of other substituents on enzymatic activity is reported. Methanol, formaldehyde, and to a limited extent acetaldehyde are oxidized by the primary alcohol dehydrogenases. Higher aldehydes are not oxidized. A possible explanation for this specificity, with regard to aldehydes, is presented in terms of degree of hydration of the aldehyde.

The Mechanism of the Transition Metal-catalyzed Reaction of 1,1′-Carbonyldipyrazoles with Aldehydes and Ketones

Abstract: The metal-catalyzed reaction of 1,1′-carbonyldipyrazoles with aldehydes or ketones to give 1,1′-alkylidenedipyrazoles and carbon dioxide, the latter being derived from the amide carbonyl group as shown by labeling experiments, is sensitive to electronic and to steric substituent effects. Under comparable reaction conditions, 1,1′-carbonyldiimidazole, N-acetylpyrazole, and 1-pyrazole-N,N-diethylcarbonamide do not react with acetone while pyrazole-1-carbo(N′-phenylhydrazide) yields an anilino isocyanate dimer. These results are interpreted in terms of a mechanism that involves coordination of the metal ion at the 2,2′-nitrogen atoms of the pyrazole rings and heterolytic cleavage of an amide bond, followed by formation of a carbamate intermediate, decarboxylation, and metal ion exchange. Unsymmetrically substituted 1,1′-carbonyldipyrazoles were found to equilibrate thermally with their respective symmetrical analogs by an intermolecular exchange mechanism.

A Carbon-13 Nuclear Magnetic Resonance Investigation of Some Substituted Methyl Phenyl Sulfides, Sulfoxides, and Sulfones

Abstract: Carbon-13 chemical shifts for 33 methyl phenyl sulfides, sulfoxides, and sulfones are reported. Observed trends are discussed in terms of the steric and electronic influences of the substituent gro...

Restricted Rotation Involving the Tetrahedral Carbon. X. Barriers to Rotation of Methyl Groups in 9-Methyltriptycene Derivatives.

Abstract: Several 9-methyltriptycene derivatives have been synthesized and the PMR spectra examined at low temperatures. The compounds which have a methoxy or a methyl group at a peri position showed only broadening of methyl signals, whereas those with a chlorine at a peri position and another substituent at some other peri position showed a splitting of methyl signals. The compounds which have a halogen atom at a peri position are the intermediary cases in a sense that they show separation of the signal into two with 1 : 2 relative intensities but fail to show fine splittings. Activation parameters for the rotation were obtained by total line shape analysis. Substituent effects have been discussed.

Carbon magnetic resonance studies of some phenyl, furyl and thienyl organometallics. Some comments on carbon-metal scalar coupling

Abstract: 13C chemical shift variations within a series of phenyl, furyl and thienyl Group IVB organometallics appear to be best understood in terms of the usual alkyl and aryl substituent effects on 13C chemical shifts and not variations in dπ ?pπ metal-aryl interactions. Large changes in 13C-metal scalar coupling constants have been observed suggesting that other factors besides the s-character of the carbon-metal bond is responsible in determining the coupling constant.

Mass spectra of monosubstituted trans‐stilbenes

Abstract: The mass spectra of twenty-eight monosubstituted trans-stilbenes in ortho, meta, para and alpha positions with N(CH3)2, NH2, OCH3, OH, Br, Cl, F, CH3, COOH, CN and NO2 groups as substituents have been studied. A detailed fragmentation pathway is given for stilbene. This fragmentation, characteristic for most of the substituted stilbenes, takes place either from the molecular or from the [M - Substituent] ion. In o-nitro-, o-methoxy-,α-carboxyl- and α-methylstilbene, however, rearrangement reactions prior to fragmentation influence the fragmentation pattern.

Characterization of branched chain fatty acids from subcutaneous triacylglycerols of barley-fed lambs.

Abstract: The fatty acids of subcutaneous triacylglycerols (containing ca. 11% of branched chain components) from lambs fed on barley-rich diets were fractionated by treatment with mercuric acetate and by urea adduct formation to yield concentrates rich in the branched chain components, all of which were saturated. The concentrates were subjected to analysis by high resolution gas liquid chromatography in conjunction with mass spectrometry. The branched chain fatty acids consisted of a complex mixture of mono-, di-, and trimethyl substituted components. The greater part of the mixture comprised monomethyl substituted acids of chain length 10–17 carbon atoms. Within each of these molecular species, a number of positional isomers was identified, notably in respect of methyltetradecanoic acid (methyl substituent on carbon 2, 4, 6, 8, 10, and 12) and methylhexadecanoic acid (methyl substituent on carbon 2, 4, 6, 8, 12, and 14). Homologous series also could be recognized of one of which all eight members from 4-methyldecanoic acid to 4-methylheptadecanoic acid were identified; together they accounted for ca. 39% of the branched chain fatty acids which were sampled for mass spectrometry. The dibranched acids identified consisted of five members of a homologous series, ranging in chain length from 11–15 carbon atoms and with substituent methyl groups at positions 4 and 8. Though the identity of only one tribranched acid (2,6,10-trimethyltetradecanoic acid) was established, others also apparently were present in the mixture. The probable involvement of methylmalonate in the biosynthesis of these branched chain acids is discussed briefly, with particular reference to the availability of vitamin B12 in relation to the activity of methylmalonyl coenzyme A mutase.

The Crystal and Molecular Structure of Ethyl Chlorophyllide a.2H(2)O and Its Relationship to the Structure and Aggregation of Chlorophyll a.

Abstract: Determination of the crystal structure of ethyl chlorophyllide a·2H2O by single crystal x-ray diffraction techniques has provided the first detailed molecular structural data available for a magnesium-containing derivative of chlorophyll. At the same time the aggregation observed in this structure serves as the basis for a model of chlorophyll aggregation in vitro and in vivo. The magnesium atom in ethyl chlorophyllide is displaced 0.4 A from the plane of the chlorin ring in the same direction as the methyl ester substituent. A water molecule occupies the fifth coordination site. A second water molecule is hydrogen bonded to the coordinated water molecule and also to the carbonyl oxygen atom of the methyl ester. Hydrogen bonds between the water molecules and carbonyl oxygen atoms link the chlorophyllide molecules into a two-dimensional aggregate of crosslinked one-dimensional polymers. The relationship of this aggregate to aggregates of chlorophyll both in vitro and in vivo is discussed, as is the efficiency of exciton transport within the polymer.

Carbon-13 nuclear magnetic resonance spectra of some substituted pyrroles

Abstract: The 13C n.m.r. spectra of 55 pyrroles have been recorded and assigned. The pyrrole ring carbon chemical shifts can be predicted, to ca. 0·5 p.p.m., on the basis of additive substituent effects together with contributions due to adjacent substituents (steric compression shifts) and in the case of carbonyl functions in the α-positions, an additional ‘conjugation effect’. The substituent chemical shift parameters obtained are analogous to those for substituted thiophens, and are compared with those obtained from ethylenes and benzene derivatives. The C(2) substituents affect mainly C(3) and C(5)(apart from the directly bonded carbon) and the C(3) substituents mainly C(2), and these directive effects may be rationalised by accepted resonance considerations. The steric compression effects parallel those found for other aromatic and olefinic systems; a buttressing effect of the next-but-one substituent was also identified. Novel conjugation effects were manifest for two α-carbonyl substituents at all the ring carbons.