摘要:

N-Benzoylthiourea (pKHA10.9) and otherN-acylthioureas ionize in alkaline solution, and then are rapidly hydrolyzed to thiourea and a carboxylic acid. The rates become independent of hydroxide ion concentration when this exceeds about 0.1Mand point to a mechanism in which hydrolysis takes place by attack of an hydroxide ion on the un-ionized molecule ofN-acylthiourea. This mechanism accords with the Arrhenius parameters for the hydrolysis ofN-benzoylthiourea in 0.2Nsodium hydroxide, and with the Hammett ρ value of 0.10 for the hydrolysis ofm- andp-substitutedN-benzoylthioureas in 1.0Npotassium hydroxide.

ISSN:0008-4042    

DOI:10.1139/v74-109

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Lemmatoxin, one of the molluscicidal saponin components of the fruit ofPhytolaccadodecandra(endod), has been found to be a derivative of oleanolic acid substituted in the 3 position with a branched trisaccharide containing two glucose units and one galactose unit. A structure is proposed.

ISSN:0008-4042    

DOI:10.1139/v74-110

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

On treatment with hot formic acident-16-kaurene (4a) and the related ester4bgive a mixture containing 12-, 15- and 16-ent-beyerane derivatives (10a,1a;7a,12a;9a,11a) in which the last predominates, whileent-15-beyerene (5a) gives mainly the C-15 formate7a. In keeping with the anticipated longer lifetimes of the intermediate ions2and3in trifluoroacetic acid as compared with formic acid, reaction of4bin the former medium at room temperature affords a mixture containing1c,11c, and12c, in which the relative yield of the 12-substituted derivative (1c) is markedly increased. Treatment of methylent-trachyloban-19-oate (14) or methylent-15-atisen-19-oate (6b) under the same conditions gives a mixture similar to that obtained from4b.

ISSN:0008-4042    

DOI:10.1139/v74-111

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The existence of thermal transformations in silver and thallium chromate has been confirmed by differential thermal analysis, temperature-variable X-ray diffraction, and electrical conductivity measurements. The disputed transition ∼330 °C in Tl2CrO4has been shown to be due to lattice distortion. The subtle difference in behavior of the pre-annealed and un-sintered samples is brought out by a variety of experimental measurements. The high temperature structure of these chromates is hexagonal. The presence of small amounts of Tl in Ag2CrO4affects the transition temperature, enthalpy, and the order of the transformation.

ISSN:0008-4042    

DOI:10.1139/v74-112

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Molar excess free energies of the systems dimethylsulfoxide–water and propylene carbonate–water have been calculated from static vapor pressure measurements at 25 °C. Enthalpies of mixing at low water concentrations have also been determined. Possible association interactions in these systems are discussed.

ISSN:0008-4042    

DOI:10.1139/v74-113

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Crystals of the title compound are monoclinica = 9.801(2)b = 9.120(1)c = 8.026(2) Å, β = 107.45(1)°,Z = 2, space groupP21. The structure was determined by direct methods, and refined by electron-density and full-matrix least-squares procedures toR = 0.0325 for 1363 observed reflections. An attempt to determine the absolute configuration by use of the anomalous scattering of oxygen and carbon atoms has been made. The most important structural feature is delocalization in the cyclohexadiene ring. There are two intramolecular O—H … O hydrogen bonds, O … O distances 2.532(3) and 2.712(2) Å. The crystal structure consists of molecules linked by intermolecular O—H … O hydrogen bonds, O … O = 2.625(2)Å, to form continuous spirals about the 21axes.

ISSN:0008-4042    

DOI:10.1139/v74-114

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Crystals of the title compound, [N3P3(NMe2)6H]2CoCl4, are orthorhombic,a = 34.623,b = 13.964,c = 10.486 Å,Z = 4, space groupP212121. The structure was determined by Patterson and electron-density methods and refined by full-matrix least-squares procedures toR = 0.088 for 2178 observed reflexions. Both rings are slightly non-planar, with three distinct pairs of NP bonds: commencing at the protonated nitrogen atom, 1.68, 1.56, and 1.58 Å. The CoCl42−ion is tetrahedral and is hydrogen bonded to both rings, N—H … Cl = 3.32, 3.36 Å.

ISSN:0008-4042    

DOI:10.1139/v74-115

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

The infrared spectra of mixtures of propane-1-thiol and several oxygen-containing weak organic bases have been measured between 2500 and 2650 cm−1, in a 1:1 mixture of CCl3F and C2F4Br2at temperatures ranging from 20 to –190 °C. Association of thetype was observed between propane-1-thiol and 2-methyl-tetrahydrofuran, or cyclopentanone. This association is less important between the thiol and hexachloropropanone. In the case of a thiol–furan mixture association of thetype is strongly indicated.

ISSN:0008-4042    

DOI:10.1139/v74-116

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Natural abundance13C spectra of solvent coordinated to the cation have been observed in solutions of Mg(II) and Al(III) salts in alcohols. Carbon shielding changes induced by cations resemble those induced by electronegative substituents; a sign reversal between the β and γ positions is found in both instances. Solvent exchange rates correspond to those found by1H n.m.r.; this confirms that whole molecule exchange is dominant. Selective relaxation of the solvation shell signals at low temperatures reflects differences in conformational mobility within the solvation complex.

ISSN:0008-4042    

DOI:10.1139/v74-117

出版商:NRC Research Press    

年代:1974

数据来源: NRC

摘要:

Kinetic isotope effects have been determined for the E2 reaction of some 2-arylethyltrimethyl-ammonium ions with ethoxide in ethanol at 40°. The nitrogen effect, (k14/k15 − 1)100, decreased with increasing electron-withdrawing ability of theparasubstituent;i.e. 1.37, 1.33, 1.14, and 0.88 forp-OCH3,p-H,p-Cl, andp-CF3, respectively. Furthermore, the primary hydrogen–deuterium isotope effects increased for the same substituents, respectively;i.e.kH/kD = 2.64, 3.23, 3.48, and 4.16. A large positive ρ value of 3.66 was found as well as a small secondary α-deuterium effect of 1.02 forp-H. In addition, the nitrogen isotope effect decreased with increasing strength of the abstracting base for the reaction of ethyltrimethylammonium ion;i.e. 1.86 and 1.41 at 60° for reaction with EtO−–EtOH andt-BuO−–t-BuOH, respectively. The results are discussed in terms of recent theoretical treatments of the effect of base, substituents, and nature of the leaving group on the nature of the transition state for an E2 process. The conclusion is reached that any structural change which causes one bond (C—H) to be weakened more at the transition state will have a corresponding effect on the other bond

ISSN:0008-4042    

DOI:10.1139/v74-118

出版商:NRC Research Press    

年代:1974

数据来源: NRC