摘要:

Crystals of 1,1′-bi(3,3,4,4-tetrafluoro-2-diphenylphosphinocyclobutene) are monoclinic,a = 10.398(1),b = 18.484(1),c = 15.984(1) Å, β = 107.76(1)°,Z = 4, space groupP21/c. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a finalRof 0.042 andRwof 0.057 for 4226 reflections withI ≥ 3σ(I). The molecule has acisoidconfiguration about the central C—C bond, the angle between the two cyclobutene rings being 34.3°. The overall molecular symmetry is approximatelyC2with a P … P separation of 3.661(1) Å. Bond lengths and angles in the molecule are generally in good agreement with accepted values.

ISSN:0008-4042    

DOI:10.1139/v77-429

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Crystals of phenylboronic acid are orthorhombic,a = 17.9049(7),b = 115.3264(5),c = 9.8113(2) Å,Z = 16, space groupIba2. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a finalRof 0.031 andRwof 0.041 for 1409 reflections withI ≥ 3σ(I). The asymmetric unit consists of two independent molecules linked by a pair of O—H … O hydrogen bonds. Each dimeric unit is also hydrogen bonded to four other such units (at) to form an infinite array of layers which stack along thecaxis. Mean bond lengths corrected for libration (rms deviations from the mean in parentheses) are: O—B, 1.371(7), B—C, 1.565(3), and C—C(phenyl), 1.394(11) Å.

ISSN:0008-4042    

DOI:10.1139/v77-430

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

125Te Mössbauer data for frozen solutions of tellurium in HSO3F and in oleum are reported together with data for solid samples which may have contained the Te42+, Tenn+, and Te62+cations. The data demonstrate that the quadrupole splitting reflects the sequential oxidation of the tellurium through the steps Te → Te42+ → Tenn+ → Te(II) → Te(IV) → TeO2. The quadrupole splittings for samples identified as containing Te42+are consistent with a unit quadrupole splitting of 12 mm s−1for125Te.

ISSN:0008-4042    

DOI:10.1139/v77-431

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Crystals of tricyclohexylphosphine sulphide, C18H33PS, are orthorhombic,a = 10.906(2),b = 15.836(2), c = 10.362(2) Å,Z = 4, space groupPn21a. The structure was solved by direct methods and refined by full-matrix least-squares procedures to a finalRωof 0.058 for all 1209 reflexions with sin θ/λ ≤ 0.5377.Although second harmonic generation unambiguously established the correct space group asPn21a, parameters reported here refer to the centrosymmetric space groupPnma. The geometry at phosphorus is approximately tetrahedral with an average P—C distance of 1.838(2) Å. Angles at phosphorus range from 105.4° to 113.2°. The P=S bond length of 1.966(2) Å is one of the longest bonds of this type so far reported. Rigid body analysis of thermal parameters suggests that the 'true' bond lengths are even longer.

ISSN:0008-4042    

DOI:10.1139/v77-432

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The kinetics of the reaction of mercuric acetate with alkenes in methanol can be measured directly by observing the ultraviolet absorbance of the solution at 265 nm. For more reactive alkenes stopped flow techniques are required, but for less reactive substrates conventional spectrophotometers are adequate. The measured rates are in satisfactory agreement with values obtained by other methods. The rates of several cyclopropylalkenes were measured in this way, and relative reactivities of some of the same substrates were obtained by the competition method. Rates obtained by both methods are in qualitative agreement, and show very high reactivity for the cyclopropylalkenes. These rates are analyzed by comparison with model reactions involving open ions (acid-catalyzed hydration) and bridged ions (sulfenyl halide addition). The comparisons suggest that the oxymercuration of alkenes not substituted with strongly resonance electron-donating substituents, for example ethylene, proceeds through bridged rate-determining transition states that put very little positive charge on carbon, but that when strongly resonance electron-donating substituents such as cyclopropyls are present, the rate-determining transition state resembles an open carbonium ion.

ISSN:0008-4042    

DOI:10.1139/v77-433

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The study of the reaction of formation of the diacetoacetylium ion from CH3COX (X = Cl or Br) and the Lewis acids AlCl3, AlBr3, and GaCl3shows that the counterion is always the tetrahalogenometallate. In the solid tetrachloroaluminate the cation is a monomer with a double minimum type of intramolecular hydrogen bond:vO—H—O = vO—D—O = 1400 cm−1;dO—O = 2.48 Å. An identical behaviour is observed with the tetrabromoaluminate, but the structure of the diacetoacetylium sstetrachlorogallate is more complicated.

ISSN:0008-4042    

DOI:10.1139/v77-434

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The alkaloids (±)-nupharamine and (±)-3-epinupharamine were synthesized using 3-acetylfuran as the starting material. The conditions for stereoselective reduction of pyridine derivatives are described.

ISSN:0008-4042    

DOI:10.1139/v77-435

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Racemic 3-epinupharamine hydrobromide (C15H26BrNO2) crystals are monoclinic, space groupC2/c, witha = 18.163(3),b = 13.346(2),c = 13.847(2) Å, β = 100.36(1)°, Z = 8. The X-ray analysis proved the structural identity of the compound obtained by the total synthesis with the natural 3-epinupharamine. The empirical criterion indicating the axial or equatorial orientation of theC-methyl group on the basis of the direction of changes of the chemical shifts recorded in benzene solutions does not hold for the piperidine system investigated.Les cristaux du bromhydrate d'épi-3 nupharamine racémique (C15H26BrNO2) sont monocliniques, groupe d'espaceC2/caveca = 18.163(3),b = 13.346(2),c = 13.847(2) Å, β = 100.36(1)°,Z = 8. L'analyse par rayons-X a démontré l'identité structurale du composé obtenu par synthèse totale avec l'épi-3 nupharamine naturel. Les critères empiriques permettant de déterminer l'orientation axiale ou équatoriale des groupesC-méthyles en se basant sur la direction des changements dans les déplacements chimiques enregistrés en solutions benzéniques ne peuvent être utilisés dans le système pipéridine étudié. [Traduit par le journal]

ISSN:0008-4042    

DOI:10.1139/v77-436

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Crystals of dodecamethylcyclohexaphosphazene are triclinic,a = 13.898(1),b = 8.690(1),c = 10.790(1) Å, α = 109.84(1), β = 92.01(1), γ = 106.39(1)°,Z = 2, space group. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a finalRof 0.034 andRwof 0.042 for 4217 reflections withI ≥ 3σ(I). The unit cell contains two independent centrosymmetric molecules which are virtually identical. The 12-membered rings have the 'double tub' conformation. Bond lengths not involving hydrogen have been corrected for libration. Weighted mean bond lengths (rms deviations from the mean in parentheses) are: P—N, 1.593(6), C—P, 1.808(4), and C—H, 0.95(6) Å.

ISSN:0008-4042    

DOI:10.1139/v77-437

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The behavior of hydrogen atoms in the fragmentation of CH3CD3has been studied by use of a monoenergetic electron beam. Ionization efficiency curves for ions (m/e3, 4, 15 to 18, 26 to 33) from CH3CD3have been measured over ranges of 12 to 30 eV near their appearance thresholds. Mass spectra over various ranges ofm/ehave been measured at several electron energies. It has been found that at least two processes participate in the formation of C2X4+and CH3+(X = H or D) and the rates of these processes depend on the energy of electron beam. The formations of C2X2+and X2+are independent of the electron energy.

ISSN:0008-4042    

DOI:10.1139/v77-438

出版商:NRC Research Press    

年代:1977

数据来源: NRC