Electronegativity, acids, and bases. IV. Concerning the inductive effect of alkyl groups

1971 ◽  
Vol 36 (1) ◽  
pp. 204-205 ◽  
Author(s):  
James E. Huheey
Keyword(s):  
Inductive Effect ◽  
Alkyl Groups ◽  
Acids And Bases

Échelles pKHB et enthalpique du pouvoir accepteur de liaison hydrogène de thioéthers, thiols et disulfures

2005 ◽  
Vol 83 (2) ◽  
pp. 138-145 ◽  
Author(s):  
Christian Laurence ◽  
Michel Berthelot ◽  
Karine Evain ◽  
Bertrand Illien
Keyword(s):  
Hydrogen Bond ◽  
Inductive Effect ◽  
Resonance Effect ◽  
Substituent Effects ◽  
Hydrogen Bond Acceptor ◽  
Frequency Shifts ◽  
Ir Spectrometry ◽  
Distinctive Features ◽  
Alkyl Groups ◽  
Polarizability Effect

The hydrogen bond acceptor (HBA) strength of 31 tetrahedral sulfur bases (thioethers, thiols, disulfides) has been measured by IR spectrometry from: (i) their 1:1 complexation constants with 4-fluorophenol in CCl4 at 25 °C (the pKHB scale); (ii) their HB enthalpies; and (iii) the frequency shifts, Δν(OH), of the ν(OH) band of 4-fluorophenol hydrogen bonded to sulfur. The comparison of the pKHB, ΔH°, and Δν(OH) scales points to their distinctive features. The HBA strength depends on: (i) the nature of the atomic site: oxygen bases are always stronger than sulfur bases, in agreement with the hard and soft acids and bases principle; (ii) the functionality of this atom (for sulfur bases: phosphine sulfur > thioamide > thioketone > thioether > thiol > isothiocyanate ~ disulfide); and (iii) the substituent effects on the function. The main substituent effects are: (i) the polarizability effect of alkyl groups; (ii) the field-inductive effect; (iii) the resonance effect; and (iv) the cyclization effect, which changes the percentage of the s character of sulfur lone pairs. In addition to the attachment to the sulfur atom, IR spectra show the attachment of 4-fluorophenol to the chlorine of MeSCH2Cl and MeSCH2CH2Cl, and the interaction to the π cloud of PhSMe, Ph2S, PhCH2SMe, and EtSCH=CH2. Key words: hydrogen bond, thioethers, thiols, disulfides, pKHB scale.

Assessing the Effect of Ligand Proximity on Chiroptical and Other Properties in Cobalt(III) Model, Tyrosine-Like Complexes

1995 ◽  
Vol 60 (12) ◽  
pp. 2097-2106 ◽  
Author(s):  
František Jursík ◽  
Ronald D. Archer
Keyword(s):  
Amino Acid ◽  
Inductive Effect ◽  
Lewis Acidity ◽  
Side Chain ◽  
Ground State Structure ◽  
Amino Acid Side Chain ◽  
State Structure ◽  
Reduction Potentials ◽  
Alkyl Groups ◽  
C Nmr

A series of new cobalt(III) octahedral complexes of the general formula Na[Co(ohb-aa)2] (ohb-aa = N-(o-hydroxybenzyl)amino acid anion); amino acid = glycine, (S)-α-alanine, α-aminoisobutyric acid, (S)-valine, (S)-norvaline and (S)-leucine) were prepared by the charcoal catalyzed reaction of the appropriate ligand with [Co(NH3)6]3+ in alkaline aqueous solution. Complexes obtained have, regardless of the amino acid used, the same facial all-trans symmetry (CoN2O4 chromophore) with the vicinal effects as the entire source of the optical activity. 13C NMR spectra reveal that the leucine derivative has, due to the steric reasons, a different ground state structure. Absorption maxima reflect a positive inductive effect from the amino acid side chain carbon atoms. Complexes of the ligands bearing electrophobic alkyl groups exhibit more negative E1/2 in comparison with the glycine derivative, reduction of which occurs at a more positive potential. Reduction potentials do not correlate with cobalt(III) Lewis acidity modulated by ligands.

The Alkyl Inductive Effect. I. Relations between σI*, σ* and ρI ρ* for H and Alkyl Groups; σI Values from the Size and Branching of R

1979 ◽  
Vol 34 (1) ◽  
pp. 81-85 ◽  
Author(s):  
Leonard S. Levitt
Keyword(s):  
Inductive Effect ◽  
Simple Relation ◽  
Previous Estimate ◽  
Polar Substituent ◽  
Alkyl Groups ◽  
Substituent Constants ◽  
Reaction Constants

Abstract For alkyl groups it is shown that new inductive substituent constants, σI (R), can be calculated accurately from previously obtained polar substituent constants, σ*(R), from the simple relation σI(R) = σI (Me) [I-2σ* (R)]. In similar fashion, the two reaction constants are related by ρI/ρ* = σ* (H)/σI (Me) = 10.6. Many new σI values are presented for groups for which no previous estimate has been available. The attentuation of σI (R) with alkyl size for n-alkyl groups is shown to be a function of the number of C atoms, nc: σI(R) = -0.137 nc/(2nc + 1). The effect of branching of R is also discussed.

Kinetics and Mechanism of the Heterogeneous Oxidation of N-Substituted-p-Phenylenediamines over Supported Zinc Oxide

2002 ◽  
Vol 216 (2) ◽  
Author(s):  
Ibrahim A. Salem
Keyword(s):  
Zinc Oxide ◽  
Inductive Effect ◽  
Initial Rate ◽  
Kinetics And Mechanism ◽  
Heterogeneous Oxidation ◽  
Initial Concentration ◽  
First Order ◽  
Alkyl Groups ◽  
Rate Of Reaction ◽  
Decreasing Ph

The kinetics and mechanism of the oxidation of some N-substituted-p-phenylenediamines over ZnO supported with some transition metal sulfates were investigated at 25 °C. The rate of reaction decreased in the following order; N,N,N´,N´-tetramethyl-p-phenylenediamine, TMPPD > N,N-diethyl-p-phenylenediamine, DEPPD > N,N-di-methyl-p-phenylenediamine, DMPPD, due to the positive inductive effect of alkyl groups. For the oxidation of DEPPD, the rate of reaction was observed to have the order: Cu(II) > Fe(III) > Ni(II) > Cr(III) > Mn(II) > Co(II). The initial rate of reaction was decreased with decreasing pH as a result of the protonation of the diamine nitrogen atoms. Also, it follows a first order dependence of the initial concentration of the diamine and attained a maximum at higher concentrations. Moreover, it increased with increasing amount of the oxidant. Greater amounts, however, reduced the rate of reaction as a result of the adsorption of the formed p-semiquinonediimine, S

Synthesis, Structure and Reactivities of Pentacoordinated Phosphorus–Boron Bonded Compounds

2020 ◽  
Author(s):  
Nathan O'Brien ◽  
Naokazu Kano ◽  
Nizam Havare ◽  
Ryohei Uematsu ◽  
Romain Ramozzi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ring Expansion ◽  
Bicyclic Compound ◽  
Compound A ◽  
Ligand System ◽  
Large Bulk ◽  
Rearrangement Reaction ◽  
Hydride Abstraction ◽  
Pentacoordinated Phosphorus ◽  
Acids And Bases

<div>The isolation and reactivities of two pentacoordinated phosphorus–tetracoordinated boron bonded compounds were</div><div>explored. A strong Lewis acidic boron reagent and electron-withdrawing ligand system were required to form the</div><div>pentacoordinated phosphorus state of the P–B bond. The first compound, a phosphoranyl-trihydroborate, gave a THF</div><div>stabilised phosphoranyl-borane intermediate upon a single hydride abstraction in THF. This compound could undergo a</div><div>unique rearrangement reaction, that involved a two-fold ring expansion, to give an unusual fused bicyclic compound or it</div><div>could act as a mono-hydroboration reagent. The hydroboration reactivity of the intermediate was found to be more reactive</div><div>towards alkynes over alkenes with good to moderate regioselectivity towards the terminal carbon. The second compound,</div><div>a phosphoranyl-triarylborate, was found to have a vastly different reactivity to the trihydroborate as it was highly stable</div><div>towards acids and bases. This is thought to be due to the large bulk around the P–B bond as shown in the crystal structure</div>

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