Search results for "Substituent"

Partition Behavior of Anilines in Bulk‐Phase and High‐Performance Liquid Chromatographic Systems: Influence on Correlation with Biological Constants

1992

Abstract The partition behavior of a mixed series of ring‐substituted anilines in reversed‐phase high‐performance liquid chromatographic systems is substantially different from that observed in a classical bulk‐phase partition system with n ‐heptane as the aprotic reference solvent. On the basis of the equivalence of each ring substituent in the p ‐straight‐chain methylene groups (ν value) as a function of the fraction of organic solvent (acetonitrile or methanol) in the mobile phase, the biased partition behavior for imperfect homologues and heterologues is verified relative to that of perfect homologues. This behavior was tentatively attributed, mainly, to differences in the hydrogen bond…

13C NMR, 1H NMR and IR spectra of a series of monochloroesters of aliphatic short chain carboxylic acids

1981

Abstract 13 C chemical shifts for 14 isomeric monochloroesters of aliphatic carboxylic acids from propanoic acid to hexanoic acid have been determined. Comparisons are made with the literature values for methyl monochloro-octanoate isomers. Substituent effects for all positions are given. Characteristic IR absorption bands are presented and comparisons are made with regard to the isomeric structure. Connections are suggested between observed trends in IR absorption frequencies and some “abnormal” chlorine substituent effects on 13 C chemical shifts. 1 H NMR spectra of these compounds are considered.

Measured and Calculated Oxidation Potentials of 1-X-12-Y-CB11Me10– Anions

2012

Cyclic voltammetry of 31 icosahedral carborane anions 1-X-12-Y-CB(11)Me(10)(-) at a Pt electrode in liquid SO(2) revealed a completely reversible one-electron oxidation even at low scan rates, except for the anions with Y = I, which are oxidized irreversibly up to a scan rate of 5.0 V/s, and the anion with X = COOH and Y = H, whose oxidation is irreversible at scan rates below 1.0 V/s. Relative reversible oxidation potentials agree well with RI-B3LYP/TZVPP,COSMO and significantly less well with RI-BP86/TZVPP,COSMO or RI-HF/TZVPP,COSMO calculated adiabatic electron detachment energies. Correlations with HOMO energies of the anions are nearly as good, even though the oxidized forms are subjec…

Mono- and di-bridged heterobimetallic systems from group 5 hydride phosphido and hydride phosphino metalloligands. Crystal structure of Cp2Ta(H)( μ-H…

1997

Abstract The trihydrides Cp2MH3 (M  Nb, Ta) react with chlorophosphines PR2Cl (R  Me, Ph) affording phosphonium salts [Cp2MH2(PR2H)]+, Cl− (2 (a, b) 2′ (a, b)). Depending on the metal (Nb or Ta) and on the nature of the phosphine substituent (Me or Ph), deprotonation of these salts leads to hydride phosphino Cp2MH(PR2H) (3 (a, b) 3′a) or hydrided phosphido Cp2 TaH2(PPh2) (4′b) metalloligands. These two kinds of complexes are able to bind [M′(CO)5] or [M′(CO)4] (M′  Cr, Mo, W) organometallic fragments to give mono- or di-bridged heterobimetallic systems. The crystallographic analysis of Cp2Ta(H)(μ-H)(μ-PMe2)Cr(CO)4 (7′aCr) is reported and discussed.

2018

The title compound, C24H22N2OP2, is an asymmetrically substituted hydrazine derivative bearing a phosphoryl and a phosphanyl substituent. The PNNP backbone has a torsion angle of −131.01 (8)°. In the crystal, molecules form centrosymmetric dimers by intermolecular N—H...O hydrogen bonds, which are further linked into a three-dimensional network by weak C—H...O and C—H...π interactions.

The synthesis and X-ray study of (η6-benzamide)- and (η6-phenylacetamide)tricarbonyl chromium complexes. Structural effects of the substituent

1994

(η6-Benzamide)tricarbonylchromium and tricarbonyl(η6-phenylacetamide)chromium (1 and 2) have been synthesized from the corresponding amides and chromium hexacarbonyl. Decalin, a mixture of decalin and butyl acetate, and neat butyl acetate have been used as the reaction media. The first system gave best yields. Both amide complexes form adducts with non-complexed molecules of the type [(CO3)CrL] · L through hydrogen bonds, suggested on the basis of 1H and 13C NMR spectroscopy. Similar associations by hydrogen bonds exist in the solid state structure of 3 and 4. The π-donor-acceptor abilities of the substituents on the rings are discussed on the basis of geometrical parameters and 13C NMR dat…

1,5-Dimethyl-2-nitrimino-1,2-dihydropyridine

2006

Methyl­ation of 5-methyl-2-nitramino­pyridine provides the title compound, C7H9N3O2, as the only product. The mol­ecule consists of two planar fragments, viz. an aromatic ring and a nitrimino substituent. The NNO2 group is twisted by 17 (2)° out of the plane of the pyridine ring. Despite a small torsion angle between these fragments, the geometry of the mol­ecule indicates the participation of the π-electrons in the C—N bond. The hydrogen bonds in the crystal structure seem to be too weak to generate any deformations observed in the mol­ecule.

15N NMR: Substituent effect analysis inpara-andmeta-substituted phenylhydrazines

1994

15N NMR spectra of phenylhydrazine and of 14 para- and meta-substituted phenylhydrazines were measured at natural isotope abundance in DMSO-d6 solution. The substituent present exerts a larger influence on the chemical shift of the nitrogen atom directly bound to the aromatic ring (N-1) than on the second one (N-2), which shows an attenuated and inverted trend. The chemical shifts of N-1 and N-2 give a good cross correlation in both series of compounds if p-NO2 and m-F derivatives are excluded from the correlations of para- and meta-substituted phenylhydrazines, respectively. Moreover, N-1 SCS values show good linear correlations with Hammett substituent constants, with SCSs of directly bou…

A computational and conceptual DFT study on the mechanism of hydrogen activation by novel frustrated Lewis pairs.

2015

A computational and conceptual density functional theory (DFT) study on the mechanism of molecular hydrogen activation by a set of three frustrated Lewis pairs (FLPs) was performed at the ωB97X-D/6-311G(d,p) level of theory. A reduced model and other two prototypes derived from experimental data, based on the donor nitrogen and acceptor boron atoms, were used. Analysis based on the energy results, geometries and the global electron density transfer at the TSs made it possible to obtain some interesting conclusions: (i) despite the well-known very low reactivity of molecular hydrogen, the catalytic effectiveness of the three FLPs produces reactions with almost unappreciable activation energi…

A versatile methodology for the controlled synthesis of photoluminescent high-boron-content dendrimers.

2013

Fluorescent star-shaped mol- ecules and dendrimers with a 1,3,5-tri- phenylbenzene moiety as the core and 3 or 9 carborane derivatives at the pe- riphery, have been prepared in very good yields by following different ap- proaches. One procedure relies on the nucleophilic substitution of Br groups in 1,3,5-tris(4-(3-bromopropoxy)phe- nyl)benzene with the monolithium salts of methyl and phenyl-o-carborane. The second method is the hydrosilylation reactions on the peripheral allyl ether functions of 1,3,5-tris(4-allyloxy-phe- nyl)benzene and 1,3,5-tris(4-(3,4,5-tris- AAA with suitable carboranyl-silanes to produce different generations of dendrimers decorated with carboranyl fragments. This ap…