摘要:

One of the classical problems in mass spectrometry is the structure and formation of the C7H7+and XC7H6+ions which are generated in the mass spectra of alkylbenzenes and many other aromatic compounds. The intermediacy of both symmetrical tropylium ion structures and unsymmetrical benzyl ions has been postulated using a number of different approaches. We have investigated this problem using ion kinetic energy spectroscopy, a relatively new technique, with the isomeric fluorobenzenes and benzyl fluoride as model compounds. Our results indicated incomplete substituent (i.e. fluorine) scrambling in the first field-free region of the mass spectrometer and thus incomplete equilibration in the decomposing FC7H6+ions and these conclusions are in contrast to results obtained using other techniques.

ISSN:0008-4042    

DOI:10.1139/v74-139

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The substituent effects of the hydroxyl group on the13C shieldings of thetrans-decalols and the 10-methyl-trans-decalols have been determined. The shifts for the carbons three and four bonds from the site of substitution depend strongly on their orientation with respect to the hydroxyl group. While the latter have not been widely recognized, these δ effects are valuable for spectral analysis and stereochemical assignments since these range up to 3.4 p.p.m. In direct contrast to the well established trends for γ effects, steric crowding of δ nuclei causes marked downfield shifts. The corresponding effects in several steroids are illustrated.

ISSN:0008-4042    

DOI:10.1139/v74-140

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Aromatic hydrazonyl halides (1), treated successively with triethylamine and hydrogen sulfide – triethylamine, giveN-aryl-N′-thioaroylhydrazines (3) as primary products, which can be isolated in many cases. Depending on conditions, further reaction may occur to givesym-hydrazonyl sulfides.Bothsymandunsym-hydrazonylsulfides are available from reaction of appropriate hydrazonyl halides andN-aryl-N′-thioaroylhydrazines in presence of triethylamine.The product of oxidation ofN-phenyl-N′-thiobenzoylhydrazine under various conditions is confirmed as the corresponding hydrazonyl disulfide rather thanN-phenyl-N'-thiobenzoyldiimide.

ISSN:0008-4042    

DOI:10.1139/v74-141

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Rates of acid-catalyzed hydrolysis of the benzylic amino group in stereoisomers of 4-arylamino-1,2,3,4-tetrahydroquinaldines have been determined by n.m.r. spectroscopy. Those isomers which have a pseudo-axial leaving group react more rapidly than those with a pseudo-equatorial leaving group, forming in each case the isomer with a pseudo-axial hydroxyl group as the kinetically controlled product. This product is converted in time to an equilibrium mixture of the two stereoisomeric alcohols. The reaction is inhibited by excess acid and appears to proceed through an intermediate carbonium ion which is stabilized by the heterocyclic nitrogen atom.

ISSN:0008-4042    

DOI:10.1139/v74-142

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Borane in tetrahydrofuran was found to reduce acetals and ketals to ethers, generally in good yield and under mild and convenient conditions. Cyclic acetals and ketals were converted by this reagent into hydroxy ethers. The mechanism appeared to resemble that of reduction with LiAlH4–AlCl3.

ISSN:0008-4042    

DOI:10.1139/v74-143

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The radiochemical yields of [Cp50Fe(CO2]• in neutron-irradiated [CpFe(CO)2]2and [CpFe(CO)2]I are 6.9 and 14.8%, respectively. Other prominent products are [CpFe(CO)2]2-59Fe,59Fe(CO)5, and59FeCp2, in both target compounds.Thermal treatment at 75 °C increases the yields of59Fe(CO)5, and of the radioactive target compound in both cases, and does not affect the yields of the other two products. The radioactive radical [Cp59Fe(CO)2]• is stable to 75° in the solid [CpFe(CO)2]2, and on dissolution is rapidly scavenged by iodine transfer from carrier [CpFe(CO)2]I.It is suggested that complex molecular products are not reformed following the nuclear activation, but are rather preserved during and despite the nuclear reaction. An effective "hot zone" need not contain more than two or three molecules.Production of [Cp59Fe(CO)2]• and [Cp59Fe(CO)2]2is observed in neutron irradiated solutions of Fe(CO)5and benzene with either FeCp2or C5H6.

ISSN:0008-4042    

DOI:10.1139/v74-144

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The second moment and spin lattice relaxation times have been obtained forcis-diaquotetramminecobalt(III)sulfate between 77 and 310 °K. The results suggest that one of the ammine ligands is unique, reorienting more slowly at a given temperature than the others. Both water ligands undergoC2- jumps. Although whole ion rotation does not occur libration does, and the second moment is interpreted in terms of such a torsional motion.

ISSN:0008-4042    

DOI:10.1139/v74-145

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The results of calculations indicate that a previously proposed model for the transition state in "borderline" substitution reactions can be generalized and, as a result, the observed differences in the carbon-13 and deuterium isotope effects of SN1, SN2, and "borderline" reactions rationalized. Although the conclusions may apply more generally, the standard reaction investigated is the solvolysis of benzyl bromide. The importance of resonance interaction with the phenyl ring, the significance of the product- or reactant-like character of the transition state, and the influence of the magnitude of force constants in determining isotope effects are examined. The temperature dependence of kinetic isotope effects in solvolysis is also investigated.

ISSN:0008-4042    

DOI:10.1139/v74-146

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The relaxation kinetics of the reaction of iodide with cobalamin (vitamin B12) were studied on a high pressure laser temperature jump apparatus in aqueous solution at 25° and ionic strength 0.2 M. Analysis of the pressure dependence of the formation and dissociation rate constants gave their respective volumes of activation to be: ΔVf* = 5.50 ± 0.8 cm3mol−1and ΔVd* = 11.5 ± 1.6 cm3mol−1The positive activation volume for formation of the complex, ΔVf*, after appropriate correction for the volume change due to formation of an outer sphere complex, is consistent with a dissociative type mechanism in which the metal ion – water bond is stretched in the activated complex.

ISSN:0008-4042    

DOI:10.1139/v74-147

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The spectra of the complexes involving a water molecule and a proton acceptor molecule are obtained by using ternary mixtures water – base – carbon tetrachloride. The vibrational assignment of these spectra is performed through a prior calculation and by examining the shape of the absorptions and their frequencies according to the base. With the complexes HOH … B, it is observed that the bands related to thev(011) combinations, which involve the free OH group, are narrower thanv(110) and have always a larger extinction coefficient. In the 7000–7300 cm−1region, the most intense absorption is thev(101) combination with the weak bases, but the &([a-z]+);(002) overtone with the strong ones.

ISSN:0008-4042    

DOI:10.1139/v74-148

出版商:NRC Research Press    

年代:1974

数据来源: NRC