Showing papers on "Substituent published in 1973"

Liquid crystal materials and devices

Abstract: OF THE DISCLOSURE A liquid crystal material which at least contains a compound having a molecular structure such that the material exhibits a liquid crystal phase, the molecular structure of the compound being selected from one of the following structures: the structure ; a simple ortho-substituted derivative of the structure ; and a derivative of the structure in which a simple bridging group is contained between two of the ortho-positions of the said structure wherein X and Y are different para-substituents of the kind which promote liquid crystal behaviour, the para-substituent X being a group selected from the following list: an alkoxy group having more than one carbon atom; an alkyl group; an acyloxy group; and an alkenyl group; and the para-substituent Y being selected from the following list: a cyano group; a benzene ring substituted in the para-position by a cyano group; and a plurality of directly para-linked benzene rings in which the end ring remote from the substituent X is substituted in the para-position by a cyano group. The material may be the said compound or it may be a multi-component solution or mixture containing it. The liquid crystal material may be nematic, smectic or cholesteric depending on the selection of the substituents X and Y. A device such as a twisted nematic effect device, incorporating the material may be operated at low temperatures. The material does not suffer from significant chemical and/or photochemical decomposition when used in a liquid crystal device.

NMR.‐Study of Nitrogen Inversion and Conformation of 1,5‐Dihydro‐isoalloxazines (‘Reduced Flavin’). Studies in the flavin series, XIX. Communication

Abstract: The pyramidal inversion of the N(5)-centre of several reduced flavins was measured by NMR. The inversion barrier was found to be ∼10 kcal/mol in acetone solutions and to be independent of the size of the N(5) substituent. An increase of the inversion barrier of ∼5 kcal/mol was observed in the case where the N(5) substituent could only be in axial position, and an increase of ∼3.5 kcal/mol was observed for an acyl-like N(5) substituent. In aqueous solution the inversion barrier increases by ∼3 kcal/mol. The stereochemistry of reduced flavin and its potential relevance in flavin-dependent biological dehydrogenations is discussed.

Fulvene, VII. Analyse der 13C‐ und 1H‐NMR.‐Spektren

Abstract: Carbon-13 and proton NMR spectra of pentafulvene and of a series of 6-substituted fulvenes have been analysed and assigned by homo- and heteronuclear double resonance and with the aid of iterative computation 13C and 1H chemical shifts are interpreted in terms of substituent effects and compared with π-electron charges calculated for the unsubstituted fulvene From 13C shifts a 10 percent contribution of dipolar structures to the electronic configuration of fulvene may be estimated All long-range proton-proton coupling constants including relative signs and some proton-carbon couplings in the fulvene spin system have been determined and assigned

Palladium-Catalyzed Coupling Reaction of Aromatic Compounds

Abstract: The oxidative coupling reaction of aromatic compounds proceeds catalytically with palladium salt under oxygen pressure. Yields and isomer distributions are attributed to the reaction variables such as temperature, additives, and the nature of the substituent on a benzene ring. Naphthalene was converted mainly into 1-substituted products and o-xylene into 4-substituted products. The coupling of diphenyl ether afforded diphenylene oxide with coupling dimers. An intramolecular two stage dehydrogenation process is proposed.

Methylene bis-phenol alkanoic acid compounds

Abstract: Novel compounds, useful as intermediates in the preparation of lubricant additives, are described by specified general formulae and as condensation products of (i) an alkyl-substituted monohydric phenol, phenol sulphide or alkylene bis-phenol in which the alkyl substituent contains at least 8 carbon atoms and (ii) a carbonyl-substituted compound selected from the group consisting of glyoxylic acid, pyruvic acid, levulinic acid, 3-oxoglutaric acid, 2-oxoglutaric acid and esters of such acids.

Investigations of Substituent Effects by Nuclear Magnetic Resonance Spectroscopy and All-valence Electron Molecular Orbital Calculations. II. 4-Substituted α-Methylstyrenes and α-t-Butylstyrenes

Abstract: Substituent-induced 1H chemical shifts (S.C.S.) for 19 4-substituted α-methyl- and α-t-butylstyrenes have been determined at infinite dilution in C6H12 and 13C S.C.S. have been determined for 0.4 M solutions in CCl4. S.C.S. are correlated with field and resonance substituent parameters and compared with charge densities determined by CNDO/2 MO calculations. The variation of S.C.S. with the dihedral angle, ρ, between phenyl and vinyl groups and the overall pattern of S.C.S. can be largely accounted for by a model of substituent effects based on field, resonance, and π polarization effects, with conjugative interactions varying as cos2ρ. Both 13C chemical shifts and charge densities indicate that the π polarization effect consists of two components: (1) a through-space polarization of the vinyl system by the polar C—X bond and (2) polarization of the entire conjugated styrene π electron system. However, significant deviations are noted for some of the 1H S.C.S. correlations. The CNDO/2 calculations indicate...

Stereochemical dependence of pharmacological activity in a series of optically active N-methylated barbiturates

Abstract: In a series of N-methylated barbiturates the nature of the cyclic hydrocarbon attached to C-5 does not influence the anesthetic potency ratio of the respective enantiomers. Anesthetic potency of the isomers, however, depends on the length of the aliphatic substituent at C-5. An exchange of methyl versus ethyl at this site causes a shift of the higher anesthetic potency from the (+)- to the (−)-isomer. A further lengthening of the aliphatic substituent at C-5—propyl instead of ethyl—in the C-5 phenyl-substituted derivative, changes the activity of the (+)-isomer qualitatively to a convulsant.

A Study of the Proton Nuclear Magnetic Resonance Spectra of Aryl and Mono- and Disubstituted N-Methylazoles

Abstract: Proton n.m.r. spectra of 111 substituted azoles are compared. The influence of the azole ring on the chemical shifts of substituent phenyl protons is discussed. A correlation between N-methyl chemi...

Steric effects in 31P NMR spectra: ‘Gamma’ shielding in aliphatic phosphorus compounds

Abstract: An examination of published 31P NMR spectral data for aliphatic phosphorus compounds has revealed that chain lengthening and branching effects on the chemical shift can be interpreted in terms similar to those used for 13C and 15N shifts. For six families of phosphorus compounds, a β-carbon substituent was shown to deshield phosphorus, while a γ-carbon caused shielding. The effects are additive, and good agreement was obtained between 31P shifts calculated with the appropriate constants and the experimental values. Shielding by γ-carbon is indicative of the operation of a steric influence on 31P chemical shifts, not heretofore articulated. The γ-effect is also useful in explaining the unusually large shielding found in six-membered cyclic phosphines.

Elimination–addition mechanism for the hydrolysis of carbamates. Trapping of an isocyanate intermediate by an o-amino-group

Abstract: The hydrolytic conversion of aryl carbamates to amines is base catalysed and evidence is presented that the process involves an E1cB elimination with the formation of isocyanate intermediates. Substituents in the leaving group (O-aryl ring) have a larger effect (ρ=+3·17) on the observed rate of hydrolysis than those in the N-aryl ring (ρ=+0·64) where the effects of a substituent are compensatory. Using N-(p-nitrophenyl)carbamates, it was possible to measure both the acidity of the carbamate (Ka1) and the rate of reaction of the carbamate anion (k2); k2 was sensitive to substituent effects (ρ=+2·90) for aryl carbamates indicating a high degree of acyl–oxygen bond cleavage in the transition state. A change in mechanism from E1cB to BAC2 attack by hydroxide ion was noted for poorer leaving groups. The pH profile for the conversion of p-nitrophenyl N-(o-aminophenyl)carbamates to o-phenyleneurea was interpreted to show that the o-amino-group traps an isocyanate intermediate after the rate determining E1cB elimination. Substituent effects for NN-disubstituted carbamates which hydrolyse via a BAC2 mechanism are also discussed.

Pharmaceutical compositions containing unsymmetrical esters of 1,4-dihydropyridine 3,5-dicarboxylic acid

Abstract: Pharmaceutical compositions containing unsymmetrical esters of 1,4-dihydropyridine 3,5-dicarboxylic acids as the active ingredient and methods of using same. The said ingredients are unsymmetrical 1,4-dihydropyridine 3,5-dicarboxylates which are substituted at position-4 of the dihydropyridine nucleus by phenyl which contains at least one nitro, cyano, azido, alkylthio, or alkylsulphonyl substituent. The compositions have a cardiovascular activity which makes them useful for effecting coronary vascular dilation and, also, they have utility in the treatment of hypertension.

Carbon-13 chemical shifts of substituted nortricyclenes

Abstract: 13C NMR spectra of a series of substituted nortricyclene derivatives have been measured, and the 13C chemical shifts interpreted in terms of α, β, γ and δ-effects. The nature of these substiuent shifts is discussed together with some analytical possibilities. The substituent shifts provide valuable data about the steric effects in strained molecules and can be used as increments for structural analysis, particularly for the determination of orientations of substituent groups.

Multifunctional lubricating oil additive

Abstract: The N-substituted, S-aminomethyl dithiophosphates, wherein said substituent is selected from the group consisting of hydrocarbyl, hydrocarbyl-substituted amines, and hydrocarbyl-substituted succinimides, are found to function as extreme pressure agents, oxidation inhibitors and ashless dispersants in lubricating oils.

Molecular orbital theory of the hydrogen bond. IV. The dimers ROH···OCH2

Abstract: Ab initio LCAO‐MO‐SCF calculations with a minimal STO‐3G basis set have been performed to determine the structures and energies of the dimers ROH···OCH2, where R may be H, or one of the isoelectronic substituents CH3, NH2, OH, or F. It is found that the order of hydrogen bond energies in the series parallels the order of sigma electron withdrawing ability of the substituent. Proton‐lone pair, dipole‐dipole, and long range interactions are discussed as factors which stabilize hydrogen bonded dimers. The structures of the dimers are analyzed in terms of a general hybridization model for the hydrogen bond.

Pyridopyrrolobenzheterocycles for combatting depression

Abstract: where X is O, S. S -> O, or SO2; n is 0 or 1; m is 0 or 1; the R''s are the same or different and are H or CH3, and one of them can be C2-C9 alkyl, phenyl, C7-C10 phenylalkyl, furyl, thienyl, pyridyl or substituted phenyl or phenylalkyl; when X is S, and m is 0, one R in the group -RCR- can be OCH3; when X is S and m is 1, the R in the group (CHR)mcan be OCH3; and R1is H, C1-C4 alkyl, C3-C5 alkenyl, C3-C5 alkynyl, C3-C6 cycloalkyl, C2-C4 alkoxycarbonyl, trifluoroacetyl, or substituted C1-C4 alkyl where the substituent is C3-C6 cycloalkyl, phenyl or substituted phenyl; and their pharmaceutically suitable salts. The compounds are useful as sedatives; some of them also exhibit antidepressant, antihypertensive and antibacterial activity. The compounds are prepared by cyclizing compounds of formula II wherein R2 is R1 or acyl. The latter compounds are prepared by reacting 4-piperidones with compounds of formula III in the presence of a reducing agent OR WITH COMPOUNDS OF FORMULA VI