scholarly journals The alkyl group is a -I + R substituent

2018 ◽  
Vol 28 (4) ◽  
Author(s):  
Luis Salvatella
Keyword(s):  
Alkyl Group ◽  
Dipole Moments ◽  
Substituent Effects ◽  
Uv Spectra ◽  
Substitution Effects ◽  
Resonance Effects ◽  
Alkyl Groups ◽  
Alkyl Substitution ◽  
Donor Substituent ◽  
Electron Donor Substituent

Electronic substituent effects are usually classified as inductive (through σ-bonds) and resonance effects (via π-bonds). The alkyl group has been usually regarded as aσ -electron donor substituent (+I effect, according to the Ingold’s classification). However, a σ-withdrawing, π-donor effect (-I + R pattern) allows explaining the actual electron-withdrawing behavior of alkyl groups when bound to sp³ carbon atoms as well as their well-known electron-releasing properties when attached to sp² or sp atoms. Alkyl substitution effects on several molecular properties (dipole moments, NMR, IR, and UV spectra, reactivity in gas phase and solution) are discussed.

The Alkyl Inductive Effect, II Theoretical Calculation of Inductive Parameters

1979 ◽  
Vol 34 (2) ◽  
pp. 321-326 ◽  
Author(s):  
Harry F. Widingand ◽  
Leonard S. Levitt
Keyword(s):  
Electric Field ◽  
Alkyl Group ◽  
Bond Model ◽  
Chemical Effects ◽  
Alkyl Groups ◽  
Alkyl Substitution ◽  
Internal Induction ◽  
Experimental Values ◽  
Physical And Chemical ◽  
Calculated Distance

AbstractThree models of alkyl groups, “derealization”, “through-the-bond”, and “electric field” models, are presented, all of which enable the calculation of σI (R) from first principles, and excellent agreement is demonstrated for the calculated and experimental values of σI (R) . For the “delocalization” model it is found that - σI (R) = 0.0455 + 0.0232(1-1/n), where n is the number of C atoms in an n-alkyl group, and for an infinite C-chain R group, σI( R∞) is - 0.0687, identical to the value found b y a different method in Part I of this series. The “through-the-bond” model gives - σI(R) = - 0.0559 +, where Ci is the number of C-atoms in the i th position from X in RX; and for the “electric field” model, we obtain - σI(R) = 0.0463 + 0.0102 , where di is the calculated distance from C1 to Cn in the most probable conformation of the R-group. It is concluded that Taft's σI(R) values have a real significance whether or not the physical and chemical effects of alkyl substitution reside ultimately in an internal induction mechanism, or in alkyl group polarization by charged centers in the molecule, or a combination of the two.

Effect of Alkyl Group Structure on Cure Characteristics of N,N-Dialkylthio-Carbamyl-N′,N′-Dialkylsulfenamide Vulcanization Accelerators

1974 ◽  
Vol 47 (4) ◽  
pp. 906-910 ◽  
Author(s):  
R. D. Taylor
Keyword(s):  
Carbon Atom ◽  
Steric Hindrance ◽  
Alkyl Group ◽  
Group Structure ◽  
Substituent Effects ◽  
Steric Effects ◽  
Alkyl Groups ◽  
Inductive Effects ◽  
Cure Rates ◽  
Alpha Carbon

Abstract Wide variations in scorch times and cure rates can be attained with tetraalkylthiocabamylsulfenamides through variation in alkyl groups. Substituent effects are substantial on either the carbamate nitrogen or on the sulfenamide nitrogen. Both inductive effects and steric effects influence the scorch times and cure rates. Positive inductive effects shorten scorch times and increase cure rates. Steric hindrance at the sulfenamide nitrogen increases the scorch time. Branching at the carbon atom beta to the nitrogen has a larger effect on scorch time than branching at the alpha carbon. Thiocarbamylsulfenamides can give appreciably higher cure rates and cure efficiencies than their benzothiazole sulfenamide analogs.

Correlation between Alkyl Cation Affinities and Proton Affinities—A Means to Rationalise Alkyl Group Substituent Effects

2000 ◽  
Vol 6 (2) ◽  
pp. 131-134 ◽  
Author(s):  
Einar Uggerud
Keyword(s):  
Linear Relationship ◽  
Alkyl Group ◽  
Substituent Effects ◽  
Alkyl Substituent ◽  
Thermochemical Data ◽  
Proton Affinities ◽  
Alkyl Groups ◽  
Substituent Constants ◽  
Straight Lines ◽  
Methyl Cation

Using literature thermochemical data it is demonstrated that the known linear relationship between proton affinities and methyl cation affinities can be extended to other alkyl groups (ethyl, i-propyl, t-butyl). It is suggested that the slopes of the straight lines can be used to define a new set of alkyl substituent constants.

scholarly journals N/N Bridge Type and Substituent Effects on Chemical and Crystallographic Properties of Schiff-Base (Salen/Salphen) Niii Complexes

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 616 ◽  
Author(s):  
Cynthia S. Novoa-Ramírez ◽  
Areli Silva-Becerril ◽  
Fiorella L. Olivera-Venturo ◽  
Juan Carlos García-Ramos ◽  
Marcos Flores-Alamo ◽  
...  
Keyword(s):  
Substituent Effects ◽  
Planar Geometry ◽  
X Ray ◽  
Half Wave ◽  
Square Planar ◽  
Bridge Type ◽  
Aliphatic Bridge ◽  
Aromatic Bridge ◽  
Donor Substituent ◽  
Electron Donor Substituent

In total, 13 ligands R-salen (N,N’-bis(5-R-salicylidene)ethylenediamine (where R = MeO, Me, OH, H, Cl, Br, NO2) and R-salphen (N,N’-bis(5-R-salicylidene)-1,2-phenylenediamine (where R = MeO, Me, OH, H, Cl, Br) and their 13 nickel complexes NiRsalen and NiRsalphen were synthesized and characterized using IR (infrared) spectroscopy, mass spectrometry, elemental analysis, magnetic susceptibility, NMR (nuclear magnetic resonance), UV-vis (ultraviolet-visible) spectroscopy, cyclic voltammetry, and X-ray crystal diffraction. Previous studies have shown that all complexes have presented a square planar geometry in a solid state and as a solution (DMSO). In electrochemical studies, it was observed that in N/N aliphatic bridge complexes, the NiII underwent two redox reactions, which were quasi-reversible process, and the half-wave potential followed a trend depending on the ligand substituent in the 5,5’-R position. The electron-donor substituent—as -OH, and -CH3 decreased the E1/2 potential—favored the reductor ability of nickel. The crystals of the complexes NiMesalen, NiMeOsalen, NiMeOsalphen, and Nisalphen were obtained. It was shown that the crystal packaging corresponded to monoclinic systems in the first three cases, as well as the triclinic for Nisalphen. The Hirshfeld surface analysis showed that the packaging was favored by H∙∙∙H and C∙∙∙H/H∙∙∙C interactions, and C-H∙∙∙O hydrogen bridges when the substituent was -MeO and π-stacking was added to an aromatic bridge. Replacing the N/N bridge with an aromatic ring decreased distortion in square-planar geometry where the angles O-Ni-N formed a perfect square-planar.

Kinetic study of hydrolysis of benzoates. part xxvii. ortho substituent effect in alkaline hydrolysis of phenyl esters of substituted benzoic acids in aqueous Bu4NBr

2009 ◽  
Vol 74 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Vilve Nummert ◽  
Mare Piirsalu ◽  
Signe Vahur ◽  
Oksana Travnikova ◽  
Ilmar A. Koppel
Keyword(s):  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Pure Water ◽  
Substituent Effects ◽  
Benzoic Acids ◽  
Resonance Effects ◽  
The Media ◽  
Substituted Benzoic Acids ◽  
Hydrolysis Of ◽  
Ortho Substituent

The second-order rate constants k (in dm3 mol–1 s–1) for alkaline hydrolysis of phenyl esters of meta-, para- and ortho-substituted benzoic acids, X-C6H4CO2C6H5, have been measured spectrophotometrically in aqueous 0.5 and 2.25 M Bu4NBr at 25 °C. The substituent effects for para and meta derivatives were described using the Hammett relationship. For the ortho derivatives the Charton equation was used. For ortho-substituted esters two steric scales were involved: the EsB and the Charton steric (υ) constants. When going from pure water to aqueous 0.5 and 2.25 M Bu4NBr, the meta and para polar effects, the ortho inductive and resonance effects in alkaline hydrolysis of phenyl esters of substituted benzoic acids, became stronger nearly to the same extent as found for alkaline hydrolysis of C6H5CO2C6H4-X. The steric term of ortho-substituted esters was almost independent of the media considered. The rate constants of alkaline hydrolysis of ortho-, meta- and para-substituted phenyl benzoates (X-C6H4CO2C6H5, C6H5CO2C6H4-X) and alkyl benzoates, C6H5CO2R, in water, 0.5 and 2.25 M Bu4NBr were correlated with the corresponding IR stretching frequencies of carbonyl group, (ΔνCO)X.

scholarly journals Effects of substituents on the 1H-NMR chemical shifts of 3-methylene-2-substituted-1, 4-pentadienes

2003 ◽  
Vol 68 (7) ◽  
pp. 525-534 ◽  
Author(s):  
Natasa Valentic ◽  
Gordana Uscumlic
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Electronic Effects ◽  
Resonance Effects ◽  
Charge Densities ◽  
Linear Free Energy ◽  
Energy Relationships ◽  
Consistent Picture ◽  
Vinyl Group ◽  
Proton Chemical Shifts

The principle of linear free energy relationships was applied to the 1H chemical shifts of the ?-vinyl proton atoms of 3-methylene-2-substituted-1,4-pentadienes. The correlations of the proton chemical shifts with Swain and Lupton substituent parameters provide a mutually consistent picture of the electronic effects in these compounds. The overall pattern of proton chemical shifts can be largely accounted for by a model of substituent effects based on field, resonance and ? polarization effects. Owing to the particular geometric arrangement of the vinyl group in 3-methylene-2-substituted-1,4-pentadienes, the ?-vinyl protons HB and HC have different sensitivities to polar and resonance effects. The different sensitivities of the 1H chemical shifts to resonance effects reveals some effects not predicted by the model outlined above. Evidence is presented that demonstrates that both the 1H and 13C chemical shifts for these compounds reflect their ground-state charge densities.

The Hantzsch pyrrole synthesis

1970 ◽  
Vol 48 (11) ◽  
pp. 1689-1697 ◽  
Author(s):  
M. W. Roomi ◽  
S. F. MacDonald
Keyword(s):  
Carboxylic Acids ◽  
Ethyl Acetoacetate ◽  
Alkyl Group ◽  
Ethyl Esters ◽  
Hantzsch Synthesis ◽  
Butyl Esters ◽  
Alkyl Groups

Ethyl esters of 2-alkyl- and 2,4-dialkylpyrrole-3-carboxylic acids are obtained generally by extensions of the Hantzsch synthesis, benzyl and t-butyl esters when the 2-alkyl group is methyl. Hemopyrrole is obtained from butanal and ethyl acetoacetate in three steps. Pyrroles bearing higher alkyl groups or carbobenzoxy groups are reductively alkylated like the corresponding methylpyrroles and carbethoxy derivatives; t-butyl esters do not survive.

scholarly journals Cytotoxicity against HL60 Cells of Ficifolidione Derivatives with Methyl, n-Pentyl, and n-Heptyl Groups

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4081
Author(s):  
Hisashi Nishiwaki ◽  
Megumi Ikari ◽  
Satomi Fujiwara ◽  
Kosuke Nishi ◽  
Takuya Sugahara ◽  
...  
Keyword(s):  
Insecticidal Activity ◽  
Alkyl Group ◽  
Caspase 3 ◽  
Biological Activities ◽  
Mosquito Larvae ◽  
Leukaemia Cell ◽  
Leukaemia Cell Line ◽  
Hl60 Cells ◽  
Flow Cytometric ◽  
Alkyl Groups

Ficifolidione, a natural insecticidal compound isolated from the essential oils of Myetaceae species, is a spiro phloroglucinol with an isobutyl group at the C-4 position. We found that ficifolidione showed cytotoxicity against cancer cells via apoptosis. Replacement of the isobutyl group by n-propyl group did not influence the potency, but the effect of the replacement of this group by a shorter or longer alkyl group on the biological activity remains unknown. In this study, ficifolidione derivatives with alkyl groups such as methyl, n-pentyl, and n-heptyl group—instead of the isobutyl group at the C-4 position—were synthesized to evaluate their cytotoxicity against the human promyelocytic leukaemia cell line HL60 and their insecticidal activity against mosquito larvae. The biological activities of their corresponding 4-epimers were also evaluated. As a result, the conversion of the isobutyl group to another alkyl group did not significantly influence the cytotoxicity or insecticidal activity. In HL60 cells treated with the n-heptyl-ficifolidione derivative, the activation of caspase 3/7 and the early stages of apoptosis were detected by using immunofluorescence and flow cytometric techniques, respectively, suggesting that the cytotoxicity should be induced by apoptosis even though the alkyl group was changed.

Sign in / Sign up

Export Citation Format

Share Document