Effects Of Phenyl Substituents Research Articles

ChemInform Abstract: Effects of Phenyl Substituents on the Geometry and Charge Density of Vinylacetylene.

ChemInformVolume 20, Issue 22 Physical Organic Chemistry ChemInform Abstract: Effects of Phenyl Substituents on the Geometry and Charge Density of Vinylacetylene. R. DESTRO, R. DESTRO Dip. Chim. Fis. Elettrochim., Centro CNR, Univ. Milano, 20133 Milano, ItalySearch for more papers by this authorF. MERATI, F. MERATI Dip. Chim. Fis. Elettrochim., Centro CNR, Univ. Milano, 20133 Milano, ItalySearch for more papers by this authorE. ORTOLEVA, E. ORTOLEVA Dip. Chim. Fis. Elettrochim., Centro CNR, Univ. Milano, 20133 Milano, ItalySearch for more papers by this author R. DESTRO, R. DESTRO Dip. Chim. Fis. Elettrochim., Centro CNR, Univ. Milano, 20133 Milano, ItalySearch for more papers by this authorF. MERATI, F. MERATI Dip. Chim. Fis. Elettrochim., Centro CNR, Univ. Milano, 20133 Milano, ItalySearch for more papers by this authorE. ORTOLEVA, E. ORTOLEVA Dip. Chim. Fis. Elettrochim., Centro CNR, Univ. Milano, 20133 Milano, ItalySearch for more papers by this author First published: May 30, 1989 https://doi.org/10.1002/chin.198922060Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume20, Issue22May 30, 1989 RelatedInformation

The effects of phenyl substituents on the geometry and charge density of vinylacetylene

A quantitative description of conjugative interactions between the phenyl rings and the butenyne fragment in phenyl-substituted vinylacetylenes is presented in terms of the properties of the electronic charge distribution at the critical points of the CC bonds. The structure of one of the two molecules investigated has been determined by X-ray single-crystal analysis as part of this study, while the other was apparently the only one available from the literature for phenyl-substituted vinylacetylenes. The study includes a topological analysis of the unsubstituted parent compound, whose CC bond ellipticities show unchanged values when calculated for three different models of the molecular geometry.

ChemInform Abstract: A THEORETICAL STUDY ON THE PHOTOISOMERIZATION OF THIOPHENE

The photoisomerization of thiophene (3–5 and 2–4 transpositions of carbon atoms) has been studied with ab initio SCF and CI calculations. A possible reaction mechanism from the lowest excited singlet state 1B2 of thiophene can be proposed from potential surface via Dewar thiophene. The 1B2 state of thiophene would easily convert to the biradical intermediate by almost one step. The internal conversion of this species to the S0 state would cause to the transposition of carbon atoms. The effect of phenyl substituent is also discussed.

A comparison of methyl and phenyl substituent effects on the gas phase basicities of amines and phosphines

The proton affinities of phenyl phosphine and cyclohexylphosphine were measured by determining the equilibrium constants of proton transfer equilibria with a pulsed electron beam high ion source pressure mass spectrometer. These proton affinities combined with values for methyl and phenyl phosphines and the analogous amines provide an interesting comparison of the methyl and phenyl substituent effects on the basicities of phosphine and ammonia. Methyl substitution increases the basicity of both ammonia and phosphine; however, the increase is significantly larger for the phosphine. Phenyl substitution increases the basicity of ammonia and phosphine and the increase for phosphine is very much larger. Calculations at the STO-3G, 4-31G, STO-3G*, and 4-31G* (* with d orbitals) for PH3, MePH2, PhPH2, the protonated species, and the nitrogen analogues predict proton transfer reaction energies in good agreement with the experimental results. A shortening of the C—P bond is predicted for protonation of MePH2 and particularly PhPH2, while a lengthening of the C—N bond is predicted for the corresponding nitrogen compounds. The much stronger increase in proton affinity of the phosphines caused by phenyl substitution is due to the stabilization of the phenyl phosphonium ion by π donation from the phenyl group to the empty orbitals of phosphorus in the [Formula: see text] group; in contrast, in the amines, it is the free base aniline which is stabilized by conjugation of the nitrogen lone pair with the aromatic ring. This stabilization of the free base is less important in phenyl phosphine. The participating empty orbitals of phosphorus in the conjugation of phenyl with [Formula: see text] in phenyl phosphonium are mostly π* with some -πd participation. The stabilization of the aniline free base contributes considerably more than the conjugation in the phosphonium ion, to the phenyl substituent difference for the amines and phosphines. The factors involved in the bigger substituent effect of methyl in the phosphines are somewhat similar to those for phenyl: stabilization of the methyl amine by conjugation of the nitrogen lone pair with empty orbitals of CH3 and stabilization of the [Formula: see text] by hyperconjugation. An alternate description can be given in terms of hybridization changes.

A theoretical study on the photoisomerization of thiophene

The photoisomerization of thiophene (3–5 and 2–4 transpositions of carbon atoms) has been studied with ab initio SCF and CI calculations. A possible reaction mechanism from the lowest excited singlet state 1B2 of thiophene can be proposed from potential surface via Dewar thiophene. The 1B2 state of thiophene would easily convert to the biradical intermediate by almost one step. The internal conversion of this species to the S0 state would cause to the transposition of carbon atoms. The effect of phenyl substituent is also discussed.

ChemInform Abstract: ELECTRONIC EFFECTS IN TRANSITION‐METAL PORPHYRINS. 4. EFFECT OF UNSYMMETRICAL L PHENYL SUBSTITUTION ON THE NMR SPECTRA OF A SERIES OF METAL‐FREE AND ZINC TETRAPHENYLPORPHYRINS

AbstractDie metallfreien Verbindungen (I) wurden nach einer abgewandelten Literaturmethode durch Reaktion von Pyrrol und je einem Äquivalent p‐Diethylaminobenzaldehyd und p‐Chlorbenzaldehyd in Propionsäure unter Rückfluß dargestellt.

An examination of the 13C NMR phenyl substituent effect in branched and non‐branched alkyl systems

AbstractLiterature and unpublished data on alkylbenzenes have been analysed to give phenyl substituent effects. The effects have been determined for non‐α‐branched, α‐branched and α,α‐branched alkyl groups.

The effect of phenyl substituents on elimination stereochemistry: A mechanistic manifold in alkoxide promoted decomposition of 1-phenyl-1-propyltrimethylammonium ion

Reactions of the positionally isomeric 1-phenyl-1-propyl (I) and 1-phenyl-2-propyltrimethylammonium (II) ions with CH3OK-CH3OH, t-C4H9OK-t-C4H9OH and t-C4H9OK-C6H6 systems have been investigated with aid of the deuterated analogues erythro-2-D-I, threo-2-D-I, 1-D-I and threo-1-D-II. A least five mechanistic components (anti-β-elimination, syn-β-elimination, α',β-elimination, Sommelet-Hauser rearrangement and SN2substitution) have been found to participate in the reaction of the quaternary compound I, in proportions varying greatly with base-solvent combination. The corresponding reactions of the isomeric compound _____CHYBI_CISLO_____ proceeded in a more simple manner, without the intervention of ylide pathways in the olefin as well as in the amine formation. The stereochemistry of β-elimination determined for the two phenyl-substituted 'onium compounds has been compared with that reported previously for structurally related aliphatic analogues. The anomalously low propensity for syn-elimination as well as the anomalously high values of trans/cis-olefin ratios in anti-elimination stigmatizing the presence of phenyl substituents are proposed to originate from a lack of base-approach hindrance in the reaction.

Effect of phenyl substituents on the hydrolyses of trifluoroacetanilides catalyzed by imidazolyl cation and hydroxide ion

Effect of phenyl substituents on the hydrolyses of trifluoroacetanilides catalyzed by imidazolyl cation and hydroxide ion

14N nuclear quadrupole resonance in the barbiturates

The 14N nuclear quadrupole resonance frequencies at 77 K are reported for several barbiturates. Differences between charge densities in the π and various σ orbitals at the nitrogen site are obtained. The charge distributions are correlated with various substituents, and are discussed with emphasis on the effects of phenyl substituents, hydrogen bonding, and formation of the sodium salt.

Carbon acids. 12. Acidifying effects of phenyl substituents

Carbon acids. 12. Acidifying effects of phenyl substituents

Stable carbocations. CLXXXI. Dihydrodibenzotropylium and dibenzotropylium ions. Neighboring methyl, cyclopropyl, and phenyl substituent effects in geometrically constrained systems

Stable carbocations. CLXXXI. Dihydrodibenzotropylium and dibenzotropylium ions. Neighboring methyl, cyclopropyl, and phenyl substituent effects in geometrically constrained systems

Conformational Analysis of cyclotrisilazanes by the NMR method

Abstract1H NMR spectra of substituted cyclotrisilazanes are discussed in terms of conformational analysis. Experimental spectra are consistent with an equilibrium involving chair conformers, following from simulating the effect of phenyl substituents and the temperature dependence of methyl proton chemical shifts. The barrier to chair‐chair interconversion in hexamethyl‐cyclotrisilazane is estimated. An analysis is carried out of the shielding of non‐equivalent methyl groups in substituted cyclotrisilazanes.