摘要:

Interaction of diethyl, triethyl,n-butyl, di-n-butyl and tri-n-butyl amines as n-donor with benzonitrile as π-acceptor has been studied inn-hexane. The formation of weak electron donor–acceptor (EDA) complexes is proposed to explain the spectroscopic behavior of the mixtures. An iterative procedure was used to obtain values of stability constants (K) and extinction coefficients (ϵ). The fact that from the new absorption observed for these systems a value ofKand a finite constant value of ϵ could be determined gives proof of the existence of EDA complexes. This conclusion is further supported by the temperature effect observed. Correlations of the experimental data with amine structure and other types of amine complexes were found.

ISSN:0008-4042    

DOI:10.1139/v81-189

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The reaction of naphtho[1,2-b]thiophene with an aromatic hydrocarbon in the presence of aluminum chloride at 20 °C gave either a 3-aryl-2,3-dihydronaphtho[1,2-b]thiophene by addition to the 2,3-bond or 2,3-dihydronaphtho[1,2-b]thiophene as a result of hydride abstraction.Occasionally 2-aryl-2,3-dihydronaphtho[1,2-b]thiophenes were obtained. At higher temperatures 2-arylnaphtho[1,2-b]thiophenes and 2,3-dihydronaphtho[1,2-b]thiophene were isolated. Attempts are made to rationalize the formation of these products in terms of protonation of naphtho[1,2-b]thiophene by moist aluminum chloride and reaction of the resulting electrophile with an aromatic substrate.

ISSN:0008-4042    

DOI:10.1139/v81-190

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The synthesis of 5,5-dimethyl-2-tert-butyl-(1a), -2-triméthylsilyl-(1b), and -2-trimethylgermyl-(1c) cyclohexanones is described as well as those of 2,2-dimethyl-5-tert-butyl-(2a), -5-trimethylsilyl-(2b), and -5-trimethylgermyl-(2c) cyclohexanones. The stereochemistry of the reduction of these ketones by different hydrides is examined. This latter reaction competes with the cleavage reaction of the C—M bond in the case of β-substituted ketones (M = Si, Ge).

ISSN:0008-4042    

DOI:10.1139/v81-191

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Infrared multiphoton dissociation of pentafluoroiodoethane leads to a complex array of reaction products. For photolysis in the v4band the reaction mechanism involves C2F5—I bond cleavage followed by thermal dissociation of C2F5radicals. For irradiation within the v3band at high fluence, efficient secondary photolysis of C2F5radicals is postulated. At lower fluences the dissociation is isotopically selective leading to C4F10enriched in carbon-13.

ISSN:0008-4042    

DOI:10.1139/v81-192

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Adenine (HAd) reacts with CH3HgX (X = NO3, ClO4) in basic aqueous solution to form a compound [CH3HgAd]•H2O, which crystallizes in the monoclinic space groupC2/c, witha = 19.796,b = 7.119,c = 16.471 Å, β = 128.83°, and Z = 8. The CH3Hg+group is linearly bonded to N(9) of deprotonated adenine and the molecules are held in pairs by twohydrogen bonds. With excess adenine, higher complexes of the formula [(CH3Hg)nAd]Xn−1(wheren = 2, 3) are formed, in which positions N(9) (deprotonated), N(7), and N(3) are successively filled. Compounds [(CH3Hg)3(Ad-H)]X have been obtained at high pH by substitution of H(9) and an amino hydrogen, and with coordination of a third CH3Hg+group probably to N(7). Complexation leads to significant changes in the infrared spectra and the 1750–1250 cm−1regions are correlated with the substitution patterns. The structures are discussed in connection with the basicity of the donors in adenine and the basicity changes of the remaining donors when other atoms are already involved in coordination.

ISSN:0008-4042    

DOI:10.1139/v81-193

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Ab initioMRD-CI calculations have been carried out to nearly full-CI accuracy for several large AO basis sets (includingffunctions) for the potential curves of the BH2molecule in itsX2A1andA2B1electronic states. A two-dimensional vibrational treatment of the bending modes in this system has been performed employing a variational method which takes account of both Renner–Teller coupling and large-amplitude motion. The resulting structural data agree to within 0.002 Å and 2° of measured bond distance and angles and the computed bending frequencies are found to be in error by less than 30 cm−1; in addition predictions of the as yet unobserved stretching frequencies are also reported for both electronic states. In the best theoretical treatment thev2′′ = 0 → v2′ = 1 transition energy to the linear upper state is calculated to be 4145 cm−1, in excellent agreement with the corresponding value of 4190 cm−1obtained by extrapolation of the three higher-energy band frequencies actually observed by Herzberg and Johns provided a renumbering of these levels (namely asv2′ = 9, 11, and 13) is undertaken relative to the originally preferred experimental interpretation. It is also pointed out that some of the earlier reported discrepancies between calculation and experiment regarding transition energies in this band system are actually due to a misinterpretation of the definition of the experimental fitting parameterT00in previous theoretical work.

ISSN:0008-4042    

DOI:10.1139/v81-194

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The13C nmr spectra of some 23-hydroxy spirostane sapogenins fromSolanum hispidumPers., mostly as their acetates, have been studied. The effect of different orientations of the substituents at C-23 and C-25 as well as that due to change in the stereochemistry at C-22 have been discussed. The unexpected absence of the γgeffect of the axial 23-OH on C-25 in hispigenin (5), a 22βO-spirostane derivative, presumably results from ring F deformation brought about by the steric interaction between 20-Me and 23-OH groups.

ISSN:0008-4042    

DOI:10.1139/v81-195

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The synthesis and complexation of the novel tridentate chelating anionic organogallate ligands [Me2Ga(N2C5H7)(OCH2CH2SR)]−(R = Et or Ph) have been investigated. A variety of octahedral molybdenum, tungsten, and manganese carbonyl compounds have been studied in which the organogallate ligand (R = Et) is in thefaccoordination mode. In addition tetrahedral "Cu•PPh3" and "Ni(NO)" complexes have been characterized which display fluxional behaviour in solution. The dearth of derivatives available using the ligand where R = Ph is attributed to steric factors.

ISSN:0008-4042    

DOI:10.1139/v81-196

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The thermal decomposition of maleic anhydride has been studied in the gas phase in a static system at temperatures from 645 to 760 K and pressures from 0.7 to 20 Torr. The first-order rate constant for the homogeneous unimolecular reaction,is described by the Arrhenius parameters logA(s−1) = 14.33 (±0.3), andE = 60.9 (± 1) kcal/mol. The reaction appears to proceed through a concerted mechanism rather than a biradical one.The photochemical decomposition, studied at wavelengths from 220 to 350 nm, yielded the same products. At 300 nm and below, the decomposition was unaffected by pressure, but at longer wavelengths collisional quenching was observed. Weak light emission was observed on excitation between 350 and 380 nm. The absorption spectrum was measured from 250 to 400 nm, and three overlapping transitions, π*←π, π*←n+, and π*←n−, can be distinguished. The mechanism of the photolysis is discussed and it is concluded that it probably proceeds through internal conversion to a vibrationally excited ground state.

ISSN:0008-4042    

DOI:10.1139/v81-197

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Several 1-aryl-3-(2-haloethyl)triazenes have been synthesized and characterized spectroscopically as well as by their esterification of 3,5-dinitrobenzoic acid. Their rates of decomposition in aqueous media at pH7 were determined polarographically employing the electrochemically active triazene moiety. In two selected cases the rates of decomposition increase markedly with lowered pH in the range 9.3 to 4.65. The products of aqueous decomposition, both volatile and involatile, were identified and quantitated by gc and gc–ms. Discrimination between alternative decomposition pathways was possible by the preparation and use of selectively deuterated triazenes. The data are consistent with initial protonation of the triazene and generation therefrom of a 2-haloethyl cation (or its kinetic equivalent) which is subject to rearrangements detected by deuterium scrambling. A second competing pathway involves cyclization of the triazene to a 1-aryl-1,2,3-triazoline intermediate which is then subject to nucleophilic opening at two sites with attendant loss of nitrogen. The effects of structural changes in the triazenes on their modes of decomposition and generation of electrophiles should assist in the interpretation of their antitumor effects.

ISSN:0008-4042    

DOI:10.1139/v81-198

出版商:NRC Research Press    

年代:1981

数据来源: NRC