摘要:

The least-motion and non-least-motion energy profiles for the insertion reaction of singlet methylene into the hydrogen molecule have been calculated using the 6-31G* basis set and introducing the correlation energy with the Møller–Plesset perturbation theory and with the MC-SCF technique. From the results obtained the effect of geometry optimization including electron correlation on the shape of the energy surface is discussed. The building up of a bidimensional biconfigurational energy surface has permitted one to interpret the opening of the methylene angle during the least-motion process as a direct consequence of the change in the electronic configuration. The TC-SCF/6-31G* second order transition structure for this forbidden process has been directly located using gradient minimization methods.

ISSN:0008-4042    

DOI:10.1139/v87-330

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

X-ray single crystal analysis sheds further light on the structure of this new iminium salt. ATABNEP crystallizes in the monoclinic system, space groupP21and shows a very short value for the C—N distance in the iminium group, thus suggesting that the contribution of the carbonium ion form in this particular case is much lower than usual, a fact that can be considered a rationale for the reluctance of ATABNEP to undergo hydrolysis.

ISSN:0008-4042    

DOI:10.1139/v87-331

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Ionization efficiency curves of very high signal-to-noise ratio are presented for ethane and most fragment ions containing at least one carbon atom. These curves, which are produced by monoenergetic electron impact, extend up to 10 eV above the initial onsets. Novel structures are observed in most curves. Certain features appear at the same energy in several of the curves indicating that they belong to a common progenitor, eitheror, and not directly to the detected ions. These sets of structure are attributed to negative ion states (Feshbach resonances) and/or to Rydberg autoionizing states.

ISSN:0008-4042    

DOI:10.1139/v87-332

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The electrodeposition of cupric ferrocyanide from a solution of potassium ferrocyanide with the convection-free parallel plane horizontal electrodes with the cathode over the anode was followed by multiple beam laser interferometry as well as the conventional electrochemical instrumentation. It is considered that the cupric ion generated immediately reacts with ferrocyanide ion to form a conducting adhering precipitate layer. The initial resistance of this layer is low. Its resistance is constant with thickness until about 5 × 10−8 C mm2has been passed probably representing ~105molecular layers when the resistance begins to rise. A magnetic field of 0.47 T caused a slight decrease in the resistance of the cell probably due to slow rotation of the inhomogeneous paramagnetic solution. This coating may be useful as an electrode.

ISSN:0008-4042    

DOI:10.1139/v87-333

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The red shift observed in the absorption spectrum of 2,7-diaminofluorene (DAF) in ether and acetonitrile is either due to the proton-donating capacity of the solute or due to its dispersive interactions with the solvent and a blue shift in methanol and water is due to the proton-accepting nature of DAF. DAF acts as a proton donor inS1state in all solvents. The red shift in the fluorescence spectrum of the monocation of DAF relative to that of DAF is not because of the —NH2group becoming more basic but because of the large solvent relaxating in aqueous medium. On the other hand, the monocation of DAF in cyclohexane follows the normal blue shift in the fluorescence spectrum. pKavalues for the various prototropic reactions inS0andS1states are determined and discussed.

ISSN:0008-4042    

DOI:10.1139/v87-334

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

orthoIodophenoxy crotonates3e–7ecyclize to dihydrobenzo[b]furans1and9–12when subjected to lithium–iodine exchange at −100 °C. Naphtho[2,1-b]furan13can be similarly obtained from α-iodonaphthoxy crotonate8e. Methylation of this reaction mixtureinsituprovides a single diastereomer14; its relative configuration is assigned by1H nuclear magnetic resonance, and its formation rationalized by steric arguments. Diastereoselective deuteration is also observed in this case.

ISSN:0008-4042    

DOI:10.1139/v87-335

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The synthesis of the cleistanthane-type diterpene13(8-β(H), 14-β-ethyl, 13-methylene podocarpane), a dihydro epimer of the natural product6, is described. By comparison of the13C nuclear magnetic resonance spectral data of13and related compounds with those reported for6, the stereochemistry of the C-14 side chain of the latter was confirmed.

ISSN:0008-4042    

DOI:10.1139/v87-336

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Lithiation of 4-acetyl 2-chloro pyridine ethylene glycol ketal by exchange with lithium diisopropylamine (LDA) led to 4-acetyl 2-chloro 3-lithio pyridine ethylene glycol ketal. This lithio derivative was reacted with aromatic aldehydes giving the expected alcohols, which were reduced by triethylsilane and trifluoroacetic acid at room temperature. The resulting 4-acetyl 3-arylmethyl 2-chloro pyridine ethylene glycol ketals were hydrolysed and cyclized in acidic medium, leading to polycondensed heterocyclic systems that have a 1-chloro 5-methyl isoquinoline nucleus fused by its [g] bond to the starting aromatic aldehyde.

ISSN:0008-4042    

DOI:10.1139/v87-337

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

2-Methyl-4-phenylbutenolide (5) is prepared in a quantitative manner by an elimination of HBr from the corresponding bromolactones3. This reaction, induced by halide ions at 100 °C in polar aprotic solvents (DMF, DMSO), is accompanied by a bimolecular nucleophilic substitution. In these reactions, the solvent seems able to play an active role. A polar solvent induces the necessary activation of the substrate (by a prior strong polarization of the C—Br bond). In the absence of halide ions, a solvolytic reaction takes place. As soon as the elimination reaction produces enough halide ions, the bimolecular reaction takes over. The activation of the chlorolactones4is much more difficult than that of the bromolactones3; however, each elimination is of the E2ip type with some E2C type. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v87-338

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Treatment of nitrones (1a–d,26a,b,34,49) with potassium in tetrahydrofuran (THF) gives rise to radical anion (2a–d,27a,b,35,50) and dianion intermediates (3a–d,28a,b,36) through electron transfer reactions. These intermediates undergo further transformations to give a variety of products. Thus, the aldehydonitrones (1a–d) give the corresponding aldehydes (10a–c), carboxylic acids (25a–c), and azobenzenes (19a,d), whereas the ketonitrones (26a,b) give deoxygenation products (31a,b). The nitrone34gave a mixture of products consisting of benzoic acid (25a), dibenzyl (48), the dimeric product38, and tetraphenylpyrazine (46), whereas49did not give any isolable product. Cyclic voltammetric studies have been employed to measure the reduction potentials for both one-electron and two-electron transfer processes, leading to the radical anions and dianions respectively. These intermediates have been characterized through their electronic spectra and they were quenched by oxygen. Pulse radiolysis of the nitrones1a–d,26a,b,34, and49also gave the corresponding radical anions2a–d,27a,b,35, and50, characterized by their spectra.

ISSN:0008-4042    

DOI:10.1139/v87-339

出版商:NRC Research Press    

年代:1987

数据来源: NRC