Inductive Effect Of Methyl Group Research Articles

Inductive effect of methyl group in a series of methylated indoles: A graph theoretical analysis in the light of density functional theory and correlation with experimental charge transfer transition energies

The inductive effect of methyl group has been quantified by expressing highest occupied molecular orbital (HOMO) and HOMO–1 energies of indole and a series of methylated indoles using a combination of graph theory (GT) and the Coulson–Longuett–Higgins perturbation method. By correlating these expressions with the corresponding Kohn–Sham orbital energies of the indoles obtained by density functional theory (DFT) calculation at the B3LYP/6–31+ +G(d,p) and M06–2X/6–31+ +G(d,p) levels of theory, the inductive effect parameter h Me has been estimated; the Coulomb integral α of π-conjugated carbon atom also comes out from the analysis. A correlation of the GT results with the HOMO and HOMO–1 energies obtained by the HF/STO–3G method yield almost the same values of h Me and α. Finally, when these estimated h Me and α are used to calculate the vertical ionization potentials of the methylated indoles in the series, an excellent correlation with experimental charge transfer transition energies of their molecular complexes with tetracyanoethylene is obtained which complies with Mulliken’s theory of charge transfer.

Inductive effect of methyl group in the light of HMO and DFT methods

Inductive effect parameter h Me of methyl group and the Coulomb integral α of sp 2 hybridized carbon have been estimated from the HOMO energies of a series of methylbenzenes calculated by DFT/B3LYP method using the basis sets 6-31++G ∗∗ and 6-311+G(2d,p). By correlating the DFT results with those from Coulson–Longuet-Higgins perturbation method in HMO formalism and with charge transfer transition energies of three series of CT complexes of methylbenzenes, it is established that the fundamental concepts used by organic chemists and the simple Hückel method still serve as a useful and easy alternative to the present-day computer-intensive methods in explaining experimental trends at least for π-conjugated systems. The parameter ( h Me) value has been shown to be transferable from one series of compounds to another. Further it has been shown that h Et is about 15% higher than h Me, which is supported by the experimental observation that ethyl group exerts greater +I effect than methyl.

Kinetics and mechanism of oxidation of dimethyl and diphenyl sulfoxides by tetrabutylammonium tribromide

The kinetics of oxidative conversion of dimethyl and diphenyl sulfoxides to corresponding sulfones with environmentally benign tetrabutylammonium tribromide was investigated in 50% v/v aqueous acetic acid medium. The reactions were carried out under pseudo first-order conditions keeping an excess of sulfoxides over that of the oxidant. The tribromide ion, , was found to be the active species of the oxidant. The electrophilic attack of the ion on the nucleophilic sulfur of the sulfoxide leads to the formation of a complex between the reactants in a prior equilibrium. The complex formed undergoes rate-determining hydrolysis to yield sulfone as the product. The complex formation was kinetically verified by the Michealis—Menten plot. The formation constants for the complexes and the rate constant for the slow hydrolysis step were determined by studying the reaction at four different temperatures. The values of observed rate constant and the complex formation constant for dimethyl sulfoxide were found to be comparatively greater than that of diphenyl sulfoxide due to the positive inductive effect of methyl groups. The thermodynamic parameters with respect to the slow step of the reaction were determined and the values support the proposed mechanism.

Inductive effect of methyl groups on acidopentaaminecobalt(III) complexes

Electron spectroscopy for chemical analysis (ESCA) was performed for [Co(NH 3) 5Cl](ClO 4) 2, trans-[Co(NH 3) 4(NH 2CH 3)Cl](ClO 4) 2, [Co(NH 2CH 3) 5Cl](ClO 4) 2 and trans-[Co(NH 3) 4(NH 2CH 3)(OSO 3)](ClO 4) complexes. Comparison of the results for the complexes [Co(NH 3) 5Cl](ClO 4) 2 and trans-[Co(NH 3) 4(NH 2CH 3)Cl](ClO 4) 2 shows clearly the electronic influence (+I effect) of the methylamine group on the cobalt and through this on the chlorine atom in trans position. Comparison of [Co(NH 2CH 3) 5Cl](ClO 4) 2 with trans-[Co(NH 3) 4(NH 2CH 3)Cl](ClO 4) 2 shows that methylation of the four cis-NH 3 ligands does not produce a proportional decrease in the binding energy of the cobalt atom, while the electron density of the chloro ligand is not affected. For the complex trans-[Co(NH 3) 4(NH 2CH 3)(OSO 3)](ClO 4) the +I effect is almost completely compensated by the presence of the sulfato group in trans position. Acid dissociation constants are also reported for [Co(NH 3) 5(OH 2)] 3+ and trans-[Co(NH 3) 4(NH 2CH 3)(OH 2)] 3+ ions. The implications of these results for the mechanism of the acid and base hydrolysis reactions of acidopentaaminecobalt(III) complexes are discussed. The preparation of the trans-[Co(NH 3) 4(NH 2CH 3)(OSO 3)](ClO 4) complex through the trans-[Co(NH 3) 4(NH 2CH 3)(SO 3)] + precursor is also described.

Electronic Structure of Poly(dimethylsilane) and Polysilane Studied by XPS, UPS, and Band Calculation

Abstract The valence electronic structures of poly(dimethylsilane)(PDMS) (Si(CH3)2)n and polysilane (SiH2)n were studied. PDMS was experimentally studied by X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS), and band calculations were performed for both compounds. The observed spectral features and calculated band structures were assigned and discussed through a comparison with theoretical and experimental results for oligomers and other polymers. These analyses have demonstrated how the electronic structures of these compounds are correlated through factors such as (i) change in the chain length, (ii) methylation, and (iii) the substitution of Si by C. PDMS has a small ionization energy (5.9 eV) almost as low as that of poly(p-phenylene) (5.6 eV). This small value comes from the combined contribution from the small electronegativity of silicon, σ-conjugation, and the inductive effect of methyl groups. The small ionization energy and large σ-conjugation explain the reported high conductivity of PDMS and its derivatives upon acceptor doping.

ChemInform Abstract: THE ELECTROCAPILLARY BEHAVIOUR AND THE CORROSION‐INHIBITIVE NATURE OF SOME ORGANIC SULPHUR COMPOUNDS

Abstract The effects of different organic radicals attached to the sulphide group in dimethyl sulphide,di- n -butyl sulphide, di-phenyl sulphide and thiophene on their electrocapillary behaviour with mercury surface and on their corrosion inhibitive nature with respect to steel in 1N sulphuric acid have been examined. It has been found that (i) there is a qualitative correlation between the electrocapillary behaviour and corrosion inhibitive effect of only some of these sulphides, (ii) the inductive effect of methyl groups enhances the effectiveness of the sulphur atom both in its adsorption on mercury surface and in corrosion- inhibition and (iii) the direct linkage of the sulphur atom to aromatic groups or its incorporation in the aromatic ring brings down the electrocapillary adsorption and the corrosion inhibitive effects of the organic sulphides.

The Electrocapillary Behaviour and the Corrosion-Inhibitive Nature of some Organic Sulphur Compounds

The effects of different organic radicals attached to the sulphide group in dimethyl sulphide,di- n-butyl sulphide, di-phenyl sulphide and thiophene on their electrocapillary behaviour with mercury surface and on their corrosion inhibitive nature with respect to steel in 1N sulphuric acid have been examined. It has been found that (i) there is a qualitative correlation between the electrocapillary behaviour and corrosion inhibitive effect of only some of these sulphides, (ii) the inductive effect of methyl groups enhances the effectiveness of the sulphur atom both in its adsorption on mercury surface and in corrosion- inhibition and (iii) the direct linkage of the sulphur atom to aromatic groups or its incorporation in the aromatic ring brings down the electrocapillary adsorption and the corrosion inhibitive effects of the organic sulphides.

Studies in nuclear magnetic resonance spectroscopy. Part VII. 13C and 1H spectra of aliphatic ketones and secondary alcohols. The negative inductive effect of methyl groups

13 C and 1H N.m.r. parameters have been obtained for the series of aliphatic ketones, acetone to 2,2,4,4-tetramethylpentan-3-one, and secondary alcohols, propan-2-ol to 2,2,4,4-tetramethylpentan-3-ol. The downfield shift of the carbinol carbon atoms with increasing substitution is explained in terms of a negative inductive effect (–l) of a methyl group. These shifts can be predicted by use of a modification of a known empirical relationship. The resonances of the carbonyl carbons of the ketones also move downfield with increasing substitution as shown previously. Values of J(CH) for the α-positions of the ketones were found to be insensitive to methyl substitution. However, the geminal HH coupling constants for the α-positions were found to be greater in ethyl ketones (Jav–17·6 Hz) than in methyl ketones (Jav–14·5 Hz), indicating that ethyl ketones exist predominantly in a conformation in which the methyl group eclipses the plane of the carbonyl double bond. Populations of conformations of the secondary alcohols have been determined from the values of the vicinal coupling constants. From these populations, values of the carbinol methine proton chemical shift have been estimated from additivity relations and shown to agree closely with the observed values.

On the Inductive Effect of Methyl Groups Bonded to Saturated Systems1

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOn the Inductive Effect of Methyl Groups Bonded to Saturated Systems1V. W. Laurie and J. S. MuenterCite this: J. Am. Chem. Soc. 1966, 88, 12, 2883–2884Publication Date (Print):June 1, 1966Publication History Published online1 May 2002Published inissue 1 June 1966https://doi.org/10.1021/ja00964a069RIGHTS & PERMISSIONSArticle Views64Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (283 KB) Get e-Alerts Get e-Alerts