Towards a Comprehensive Hydride Donor Ability Scale

Rates of hydride transfer from several hydride donors to benzhydrylium ions have been measured at 20 °C and used for the determination of empirical nucleophilicity parameters N and s_N according to the linear free energy relationship log k_{20 °C}=s_N(N+E). Comparison of the rate constants of hydride abstraction by tritylium ions with those calculated from the reactivity parameters s_N, N, and E showed fair agreement. Therefore, it was possible to convert the large number of literature data on hydride abstraction by tritylium ions into N and s_N parameters for the corresponding hydride donors, and construct a reactivity scale for hydride donors covering more than 20 orders of magnitude.     

1,4,4a,10b-Tetrahydro-N,N-dimethyl-4-phenanthridinamines and 1,4,4a,5,6,10b-hexahydro-N,N-dimethyl-4-phenanthridinamines

Synthetic procedures to prepare the title compounds are described. Diels-Alder cycloaddition of β-nitrostyrene derivatives 5 to N,N-dimethyl-1,3-butadien-1-amine, 6 , gave 5-aryl-N,N-dimethyl-6-nitro-2-cyclohexen-1-amines 7. Reduction of 7 with zinc in acetic acid gave the diamino derivatives 8 . Schotten-Baumann acylation of 8 gave amides 9 . Treatment of 8 with alkyl isocyanates gave the aminourea derivatives 10 . Bischler-Napieralski cyclodehydration procudure of 9 and 10 gave 1,4,4a,10b-tetrahydrophenanthridinamines 3 and N⁶-alkyl-1,4,4a,10b-tetrahydro-N⁴,N⁴-dimethyl-4,6-phenanthridinediamines 11 , respectively. Condensation of diamines 8 with aryl aldehydes under azeotropic conditions gave imines 12 which on treatment with acids yielded 6-aryl-1,4,4a,5,6,10b-hexahydro-N,N-dimethyl-4-phenanthridinamines 4 . The stereochemistry of these materials is assigned from the proton magnetic resonance studies.     

Alternating copolymerization of methyl acrylate with donor monomers having a protected amine group

Attempts were made to copolymerize p-aminostyrene, p-acetamidostyrene, N-methyl-p-aceta-midostyrene, N-(4-vinylphenyl) phthalimide, N-vinyl succinimide, and N-vinyl phthalimide with methyl acrylate complexed with ethyl aluminum sesquichloride. Only reactions involving N-(4-vinylphenyl)phthalimide and N-vinyl phthalimide yielded alternating copolymers. N-vinyl succinimide gave nonalternating copolymers insoluble in common solvents and the other monomers did not copolymerize. In some cases, the conventional radical copolymers were prepared for comparison purposes. The reactivity ratios of the free-radical initiated copolymerization of methyl acrylate (I) with N-(4-vinylphenyl)phthalimide (II) were r₁ = 0.14 and r₂ 1.56. The alternating copolymers were studied by ¹H-NMR and ¹³C-NMR spectroscopy. The alternating copolymer of N-(4-vinylphenyl)phthalimide with methyl acrylate was hydrazinolyzed to form the alternating copolymer of methyl acrylate with p-aminostyrene. Hydrazinolysis of the alternating copolymer of methyl acrylate with N-vinyl phthalimide removed the phthalimide moiety and generated vinyl amine units which readily cyclized with neighboring methyl acrylate units to form copolymers that contained five-membered lactam rings. The infrared (IR) spectra of the hydrazinolyzed products contain bands due to amine or amide groups and are devoid of the characteristic bands of the phthalimide ring.     

N-Representability conditions generated by a one-particle grassmann factor of an antisymmetric function

N-representability conditions for a two-particle density operator implied by positive-semidefiniteness of the projection operator P^N+1(?¹ Λ Ψ^N) are derived and discussed. The operator P^N+1(?¹ Λ Ψ^N) projects onto an (N + 1)-particle antisymmetric function ?¹ Λ Ψ^N, the Grassmann product of a one-particle factor ?¹ and an N-particle factor Ψ^N. The polar subcone ??²_N(g, q) to the set of N-representable two-particle density operators ??²_N which corresponds to these conditions is found. It is shown that its extreme rays belong to two orbits for the action of the unitary group of transformations in one-particle Hilbert space. The facial structure of the convex set ??²_N exposed by elements of ??²_N(g, q) is analyzed. An example of the operator that changes the structure of its bottom eigenspace when the number of fermions N surpasses a certain value is noted. A new approach to the diagonal conditions for N-representability is found. It consists of the decomposition of the N-particle antisymmetric identity operator onto the mutually orthogonal projection operators.     

The Radical Anions of N,N′-Dicyanoquinone Diimines,a New Class of Electron Acceptors

The radical anions of 12 N,N′-dicyanoquinone diimines, a new class of electron acceptors, hace been characterized by their hyperfine data with the use of ESR and ENDOR spectroscopy. The largest coupling constant (0.30–0.45 mT), due to the two ¹⁴N nuclei in the exocyclic positions, gives rise to a conspicuous broadening of the peripheral ESR lines by an incomplete averaging of the hyperfine anisotropy. The most plausible interpretation of the experimental results for the radical anions of N,N′-dicyano- 1,4-benzoquinone diimine ( 1 ) and N,N′-Dicyano-9,10-anthraquinone diimine ( 9 ) is in terms of both ‘syn’- and ‘anti’-configurations contributing to the ESR and ENDOR spectra and having equal proton- and ¹⁴N-coupling constants. The π-spin distribution in the radical anions of N,N′-dicyanoquinone diimines is compared with those in the analogous ions of tetracyanoquinodimethanes and quinones.     

Oxidation of 9-benzyl-N-methylacridinium a highly efficient chemiluminescent reaction

9-Benzyl-N-methylacridinium iodide reacts with potassium persulphate inN,N-dimethylformamide to giveN-methylacridone and light with a quantum yield of over 8×10^–2 Einstein·mol^–1. Chemiluminescence also results on mere illumination of a 9-benzyl-N-methylacridinium salt solution.

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Oxydation von 9-Benzyl-N-methylacridinium—Eine hochwirksame Chemilumineszenz-Reaktion (Kurze Mitteilung)

Zusammenfassung 9-Benzyl-N-methylacridiniumjodid reagiert mit Kaliumpersulfat inN,N-Dimethylformamid zuN-Methylacridon und Licht mit einer Quantenausbeute von über 8×10^–2 Einstein·mol^–1. Chemilumineszenz tritt auch bei bloßer Belichtung einer Lösung von 9-Benzyl-N-methyl-acridiniumsalz auf.

     

Configurational degeneracy of a set of dipoles in a quasi-two-dimensional system

The purpose of this paper is to provide an exact evaluation of the configurational degeneracy when an arbitrary number (k) of dipoles are placed in a quasi-two-dimensional space (Q2D). This Q2D is made up of three contiguous diagonals 3 × N. Our Q2D space gives to the central sites of the lattice their full coordination number of nearest neighboring compartments. We are going to determine the exact configurational degeneracy W(k, N) when an arbitrary number k of the above mentioned particles are placed in this 3 × NQ2D space. We found that W(k, N) is exactly described by

Intermittent compression of N-alkyl-N,N-dimethylamine N-oxides encapsulated in a container with bis[2]catenane topology

Abstract

We report the encapsulation of a homologous series of N-alkyl-N,N-dimethylamine N-oxides in a molecular container with bis[2]catenane topology. N-oxides with short alkyl chains are co-encapsulated with one solvent molecule. Elongation of the alkyl chain from R = methyl to pentyl produced the progressive compression of the guest. The hexyl N-oxide reduces its compression by being singly encapsulated. Longer N-oxides (R = octyl to decyl) had to fold to adapt to the capsule’s dimensions and also experience a progressive compression. The mechanically interlocked nature of the container and the polar functionalisation of its cavity are responsible for the assembly of encapsulation complexes in solution displaying high packing coefficients (0.65–0.70). The high energy conformations adopted by the alkyl chains of the bound N-oxides are deduced from NMR experiments and molecular modelling studies.     

Methane Decomposition in a Barium Titanate Packed-Bed Nonthermal Plasma Reactor

The behavior of lattice oxygen species of the ferroelectric material during methane oxidation was investigated using a nonthermal plasma reactor packed with BaTiO ₃ pellets. Lattice oxygen species in BaTiO ₃ play an important role in the formation of N ₂ O and the oxidation of CH ₄ . The oxidation products such as CO and CO ₂ were formed from independent reaction pathways. Lattice oxygen species were able to preferentially oxidize the carbon species deposited on the pellet surface into CO. Also, N ₂ O and NO _x were independently formed in the N ₂–O ₂ reaction, suggesting that different oxygen species give N ₂ O and NO _x. N ₂ O was produced by the oxidation of molecular nitrogen with lattice oxygen species.     

Convenient Synthesis of a New Series of 3-Triazolonyl Iminocoumarins

3-Cyano-7-diethylamino-N-ethoxycarbonyl-iminocoumarin reacted with different hydrazines as N-nucleophiles to afford, in one step, a new series of 2-N-substituted 3-triazolonyl-iminocoumarins in good yields. In two cases, N-unsubstituted derivatives were also obtained. The structures of all the products obtained were confirmed by infrared, ¹H NMR, ¹³C NMR, and elemental analysis. The optical properties of three of these compounds in dichloromethane and ethanol were reported.     

Synthesis and Properties of a 2-Diazohistidine Derivative: A New Photoactivatable Aromatic Amino-Acid Analog

N^α[(tert-Butoxy)carbonyl]-2-diazo-L -histidine methyl ester 1 was synthesized starting from the corresponding L-histidine derivative. The physico-chemical properties of this new photoactivatable amino-acid derivative were established. The synthetic precursor of 1 , 2-amino-L -histidine derivative 3 , was best isolated and characterized as 2-amino-N^α-[(tert-butoxy)carbonyl]-N^τ-tosyl-L -histidine methyl ester ( 4 ). Selective deprotections of 4 (N^α-Boc, N^α-Tos, COOMe) were achieved, thus allowing the use of the corresponding products in peptide synthesis. The optically active dipeptides 8 and 9 were synthesized by coupling 2-amino-N^τ-tosyl-L -histidine methyl ester ( 5 ) with N-[(tert-butoxy)carbonyl]-L -alanine and N^α-[(tert-butoxy)carbonyl]-N^τ-tosyl-L -histidine ( 6 ) with L-alanine methyl ester, respectively. The question of selective diazotization of a 2-aminohistidine residue in a synthetic peptide was studied using competitive diazotizations between 2-amino-1H-imidazole and several amino-acid derivatives susceptible to undergo nitrosylation. The results show that synthetic photoactivatable peptides incorporating a 2-diazohistidine residue might become useful photoaffinity probes.     

Three new phosphoric triamides with a [C(O)NH]P(O)[N(C)(C)]2 skeleton: a database analysis of C—N—C and P—N—C bond angles

In N,N,N′,N′‐tetraethyl‐N′′‐(4‐fluorobenzoyl)phosphoric triamide, C₁₅H₂₅FN₃O₂P, (I), and N‐(2,6‐difluorobenzoyl)‐N′,N′′‐bis(4‐methylpiperidin‐1‐yl)phosphoric triamide, C₁₉H₂₈F₂N₃O₂P, (II), the C—N—C angle at each tertiary N atom is significantly smaller than the two P—N—C angles. For the other new structure, N,N′‐dicyclohexyl‐N′′‐(2‐fluorobenzoyl)‐N,N′‐dimethylphosphoric triamide, C₂₁H₃₃FN₃O₂P, (III), one C—N—C angle [117.08 (12)°] has a greater value than the related P—N—C angle [115.59 (9)°] at the same N atom. Furthermore, for most of the analogous structures with a [C(=O)NH]P(=O)[N(C)(C)]₂ skeleton deposited in the Cambridge Structural Database [CSD; Allen (2002). Acta Cryst. B 58 , 380–388], the C—N—C angle is significantly smaller than the two P—N—C angles; exceptions were found for four structures with the N‐methylcyclohexylamide substituent, similar to (III), one structure with the seven‐membered cyclic amide azepan‐1‐yl substituent and one structure with an N‐methylbenzylamide substituent. The asymmetric units of (I), (II) and (III) contain one molecule, and in the crystal structures, adjacent molecules are linked via pairs of N—H...O=P hydrogen bonds to form dimers.     

INDO Calculation of Spin Densities in Radical Cations of a Series of Substituted Nitro- and m-Dinitrobenzenes

The spin densities in radical cations of 22 substituted nitro- and m-dinitrobenzenes were calculated by the INDO method. For radical anions of substituted nitrobenzenes, a good linear correlation was obtained between the spin densities s_Ns_N and experimental hyperfine coupling constants with the nitrogen atoms of the NO₂ groups (a ^N): a ^N = K _N s _N s _N, where K _N = 428.58 (R ² = 0.96). For radical anions of substi- tuted m-dinitrobenzenes, no satisfactory agreement between the calculated and experimental a ^N constants was attained.     

Preparation of a thermally phase-separating copolymer,poly(N-isopropylacrylamide-co-N-acryloxysuccinimide), with a controlled number of active esters per polymer chain

N-isopropylacrylamide and N-acryloxysuccinimide have been copolymerized in various mixtures of terrahydrofuran and toluene using azobisisobutyronitrile as initiator. Polymerization has been conducted for 24 h at 50°C under a slightly positive pressure of nitrogen. The copolymers were assayed for active ester content by measuring the UV absorbance (259 nm) of N-hydroxysuccinimide anion, generated by reacting the copolymers with N-isopropylamine in dimethylformamide and dissolving the resulting mixture in 0.1M HEPES buffer, pH 7.5. The molecular weight and its distribution have been estimated by gel permeation chromatography. The active ester content was found to be equivalent to the comonomer feed ratio, and the major factor controlling the molecular weight was the ratio of tetrahydrofuran to toluene. Thus, the number of active esters per polymer chain could be controlled by adjustment of the comonomer feed ratio and the ratio of tetrahydrofuran to toluene. Monomer reactivity ratios for copolymerization of N-isopropylacrylamide with N-acryloxysuccinimide were also estimated. These copolymers are useful for immobilizing binding ligands such as antibodies for subsequent thermally induced precipitation immunoassays and bioseparation processes.     

Pyrrole Denitrogenation and Fragmentation of Tetramethylethylenediamine Promoted by a NbII Cluster

A nitrogen center was abstracted from a pyrrolyl ring to form the dinuclear nitrido- and dienyl-bridged complex 1 during the reaction of [{(tmeda)Nb^IICl}₂(μ-Cl)₃Li(tmeda)] with the lithium salt of 2,5-dimethylpyrrole (tmeda=N,N,N′,N′-tetramethylethylenediamine). A second product from this reaction is the amido-carbene-hydride niobium complex 2 , which likewise forms under C−N bond cleavage.     

Hydroacridines XXV [1]. First Synthesis of (4aα,8aα,9aβ,10aβ)-Tetradecahydroacridine and New Syntheses of (4aα,8aα,9aα,10aβ)- and (4aα,8aβ,9aα,10aβ)-Tetradecahydroacridine

Summary. On heating in dry DMSO, in the presence of potassium t-butoxide, the N-nitrosamine of (4aα,8aβ,9aβ,10aα)-tetradecahydroacridine is completely converted into the N-nitrosamine of (4aα,8aα,9aα,10aβ)-tetradecahydroacridine. Under similar conditions, the N-nitrosamine of (4aα,8aα,9aβ,10aα)-tetradecahydroacridine yields a ternary equilibrium mixture containing itself (19%), and the N-nitrosamines of (4aα,8aβ,9aα,10aβ)-tetradecahydroacridine (46%) and the so far unknown (4aα,8aα,9aβ,10aβ)-tetradecahydroacridine (35%). The resulting N-nitrosamines can be smoothly denitrosated to the corresponding secondary amines.     

Aggregate of a peptide-containing block copolymer with a lipase

The peptide-containing block copolymer poly(N-acetyliminoethylene)-block-poly(L -phenylalanine) (1) formed large water-soluble aggregates in water due to the hydrophobic and hydrogen-bonding character of the poly(L -phenylalanine) block. The solution properties of 1 were compared with those of the block copolymer poly(N-acetyliminoethylene)-block-poly(N-benzoyliminoethylene) (2) with an analogous structure. 1 formed aggregates even though the poly(phenylalanine) segment was short as compared with 2 in which hydrophobic interaction may be the only driving force to form aggregates. The aggregates have strong capability of incorporating Lipase P and largely increase the hydrolysis activity against p-nitrophenyl propionate as compared with that of free Lipase P.     

Ortho effects in organic molecules on electron impact. VI—Ortho effects of a carboxyl group in N-substituted anilines

The unusual fragments noticed in the mass spectra of N-benzyl- and N,N-dibenzylanthranilic acids have been explained on the basis of the ortho interaction of the carboxyl group with the N-benzyl- and N,N-dibenzyl moieties.     

Direct polycondensation of carbon dioxide with xylylene glycols: a new method for the synthesis of polycarbonates

This communication describes the direct polycondensation of carbon dioxide with p- and m-xylylene glycols using the system trisubstituted phosphine/carbon tetrahalide/base as a condensing agent. The polymerization reaction of carbon dioxide with p-xylylene glycol was carried out in the presence of the condensing agent in N,N-dimethylformamide. The yield was at most 81.0% obtained by using the condensing agent tributylphosphine/carbon tetrabromide/N-cyclohexyl-N′,N′,N″,N″-tetramethylguanidine (CyTMG). The structure of the product was determined by means of ¹H NMR, ¹³C NMR, and IR spectroscopy to be that of a polycarbonate. The molecular weight was estimated to be ca. 1 000–2 000 by ¹H NMR analyses.     

Neutral Pentacoordinate Silicon(IV) Complexes with a Tridentate Dianionic O,N,O or N,N,O Ligand,an Anionic PhX Ligand (X = O,S, Se), and a Phenyl Group: Synthesis and Structural Characterization in the Solid State and in Solution

A series of neutral pentacoordinate silicon(IV) complexes with a SiO₃NC, SiO₂SNC, SiO₂SeNC, SiO₂N₂C, SiOSN₂C, or SiOSeN₂C skeleton was synthesized and structurally characterized by multinuclear NMR spectroscopy in the solid state and in solution and by single‐crystal X‐ray diffraction. The compounds studied contain a tridentate dianionic O,N,O or N,N,O ligand, an anionic PhX ligand (X = O, S, Se), and a phenyl group. The structures, NMR spectroscopic parameters, and chemical properties of these silicon(IV) complexes were compared with those of related compounds that contain a tridentate dianionic S,N,O ligand instead of the O,N,O or N,N,O ligand.