摘要:

The Seebeck coefficient, ϵT, of the thermocell Ag(T)/AgNO3in NaNO3 − KNO3/Ag (T + ΔT) was measured as a function of silver nitrate concentration and temperature. Extrapolation of the results to unit mole fraction,N, of AgNO3gave the value ϵT0 = − 277.5 − 0.136T°C (µV deg−1).For several mixed melts of AgNO3and an alkali nitrate the functionwas calculated and shown to be linear inN.Pwas extrapolated to finite values for the pure alkali nitrates.

ISSN:0008-4042    

DOI:10.1139/v71-333

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A flash photolysis apparatus coupled with a fast response conventional sector field mass spectrometer for the rapid time resolved detection of short-lived neutral transients is described. The utility of the apparatus is illustrated by the detection of the Fe(CO)(NO)3intermediate with a half-life of ~0.1 s in the flash photolysis of Fe(CO)5in the presence of NO.

ISSN:0008-4042    

DOI:10.1139/v71-334

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The fluorescence of chloropentafluoroacetone in the gas phase at 23 °C is quenched by the addition of certain olefins. The quenching rate constants of 17 unsaturated hydrocarbons for the first excited singlet state of chloropentafluoroacetone are reported. The molecules are divided into two classes on the basis of their quenching abilities, (a) olefins with only electron-withdrawing substituents and (b) olefins with electron-donating substituents. It is shown that the quenching by molecules in the latter group can be quantitatively correlated with the ionization potential (i.p.) of the quenching molecule. The relation is logk = 18.0 − 0.79 (i.p.),i.e. a type of linear free energy relation is obeyed. This implies that the quenching by molecules containing only electron-donating substituents involves a charge-transfer complex.

ISSN:0008-4042    

DOI:10.1139/v71-335

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Electron spin resonance spectroscopy has been used to study triple ions formed between pyrazine and tetramethylpyrazine and the cations Li+, Na+, K+in dimethoxyethane, tetrahydrofuran, and 2-methyl-tetrahydrofuran. Differential line-broadening effects are reported within the hyperfine splitting patterns of the alkali metals incorporated into the triple ions, and a possible application of such effects to the study of ionic association is described.

ISSN:0008-4042    

DOI:10.1139/v71-336

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

trans-2-Acetamidocyclohexanol (1;n = 2, R = CH3) on addition to thionyl chloride in chloroform at 0° was converted rapidly and quantitatively toD,L-2-methyl-4,5-cis-cyclohexanoöxazoline hydrochloride (2;n = 2, R = CH3) judging from shifts in the methyl proton resonances of the n.m.r. spectra of the amide and the reaction solution. The intermediate chlorosulfinate was estimated to have a half-life of less than 2.25 min. The oxazoline salt was isolated in 98% yield by sublimation of the crude productin vacuoand was identified by its i.r. and n.m.r. spectra and by its facile and almost quantitative hydrolysis tocis-2-aminocyclohexanol hydrochloride. The oxazoline salts2(n = 1, R = CH3,andn = 2, R = C6H5,) were readily obtained in 95 % yield or better by the same general method and it was shown that thetrans-2-acetamidocyclanols are the preferred starting materials for conversion tocis-2-aminocyclanol derivatives by the thionyl chloride inversion reaction. The oxazoline bases4(n = 1, R = CH3,andn = 2, R = CH3,) were readily obtained in high yield from the corresponding salts and differences in the i.r. and n.m.r. spectral characteristics of the salts and bases are reported.

ISSN:0008-4042    

DOI:10.1139/v71-337

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Lead(II) and cadmium(II) each form a 1:1 complex with DTPA. Nuclear magnetic resonance (n.m.r.) spectroscopy was used to show that each complex has three metal–nitrogen bonds and labile metal–oxygen bonds to terminal acetate groups. The latter lead to proton equivalence for the methylene protons of the terminal acetate groups of the lead complex, and near equivalence for those of the cadmium complex. The central carboxylate group is coordinated to the lead but not to the cadmium. Protonation occurs below pH5.5 for the lead complex and occurs predominantly at a terminal nitrogen atom with consequent breaking of the metal–nitrogen bond. In the cadmium complex protonation occurs below pH5 at the terminal nitrogen, breaking the metal–nitrogen bond, and also to almost the same extent at the central, uncoordinated carboxylate group. These differences in behavior of the lead and cadmium complexes are attributed to differences in ionic size. Possible structures are proposed and allowances are made for the possibility of coordination number greater than six. In the protonated complexes, structures and interconversion of protonated forms are discussed in the light of the observed simplification of the n.m.r. spectra.

ISSN:0008-4042    

DOI:10.1139/v71-338

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Nuclear magnetic resonance (n.m.r.) spectroscopy was used to determine the preferred protonation sites in TTHA. For its 1:1 complex with Pb(II) the following equilibrium constants for protonation were obtained (triethylenetetraaminehexaacetic acid ≡ H6A)The non-protonated complex is considered to have four coplanar (or nearly coplanar) metal–nitrogen bonds with the center carboxylate groups coordinated above and below this plane, and with the terminal carboxylate groups playing only a small part in the coordinate bonding. The first and second protonations of the complex occur preferentially at the terminal and center nitrogen atoms, respectively, on the same side of the complex, accompanied by breaking of the respective metal–nitrogen bonds. This causes partial unwrapping of the complex from one side. Rapid interconversion between configurations in which unwrapping and rewrapping occurs first from one side of the molecule and then from the other leads to simplified n.m.r. spectra.

ISSN:0008-4042    

DOI:10.1139/v71-339

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Proton nuclear magnetic resonance (n.m.r.) spectroscopy and the pHdependence of the chemical shifts of the nonlabile protons have been used to determine the preferred protonation sites in tetraethylenepentaamineheptaacetic acid (TPHA). The nitrogen atoms are protonated more readily than the carboxylate groups with the sequence of protonation dependent on electrostatic interactions. The 1:1 Pb(II)–TPHA complex which is not protonated for solution conditions from pH10 to 14, has five metal–nitrogen bonds. The coordinate bonds are labile so that rapid interconversion between nonequivalent configurations produces an average configuration in which the protons of the acetate groups exhibit single n.m.r. peaks. Protonation of the complex probably occurs in three stages. From pH10 to pH8 the preferred protonation sites are the terminal nitrogen atoms with the attendant elimination of the metal–nitrogen bonds. Increasing the acidity to pH4 causes all but the central nitrogen site to be protonated. Below pH4 the central nitrogen atom becomes protonated and causes further unwrapping of the complex.

ISSN:0008-4042    

DOI:10.1139/v71-340

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Three new sesquiterpene lactones, dihydro-β-cyclopyrethrosin (3), chrysanin (4), and chrysanolide (5) were isolated from the flowers ofChrysanthemum cinerariaefoliumand their structures determined by physical and chemical methods. The configuration at C-1 of pyrethrosin (2) was established asRby its conversion to dihydro-β-cyclopyrethrosin (3), a hydrogenation product of β-cyclopyrethrosin (1), which had the C-1 hydroxyl group assigned by the Horeau procedure and Brewster's benzoate method. The preparation and properties of the C-11 epimers,12and17, of dihydropyrethrosin are reported and their stereochemistry established.

ISSN:0008-4042    

DOI:10.1139/v71-341

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A study has been made of the 100 MHz p.m.r. spectra of a number of pyrimidine nucleosides in aqueous solution. Long-range five-bond spin–spin coupling interactions between the H-5 and H-1′ hydrogens were noted in uridine, 2′-deoxyuridine, 6-azauridine, and 6-azacytidine and rationalized by a predominantlyanticonformation for each nucleoside. The absence of a detectable five-bond coupling in orotidine suggested that thesynconformation is preferred in this instance. The relative magnitudes of the four-bond and five-bond interactions in uridine and pseudouridine were shown to be consistent with the calculated mobile π-bond orders of the C6—N1and C6—C5bonds of the uracil base.

ISSN:0008-4042    

DOI:10.1139/v71-342

出版商:NRC Research Press    

年代:1971

数据来源: NRC