摘要:

The relationship between Taft and Kirkwood–Westheimer equations has been derived with the use of the modified MacInnes equation.

ISSN:0008-4042    

DOI:10.1139/v78-124

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The energy transfer efficiency ratio, ETE=(σhΔEh/σxΔEx), for hydrocarbons dissolved in liquid xenon has the following values: ethane, 96; propane, 180;n-butane, 485; ethylene, 193; propylene, 255;cis-butene-2, 425;trans-butene-2, 665. The large increase on going from propane to butane is attributed to the energy absorption capability of the C2H5groups through rotation about the central bond in butane. The presence of a double bond in the molecule enhances ETE, presumably through the participation of transient negative ion states in the energy transfer process. Thecis–transeffect in butene-2 is still not understood.

ISSN:0008-4042    

DOI:10.1139/v78-125

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Ethylene, propylene,cis-butene-2,trans-butene-2, ethane, propane, andn-butane were added to xenon at 168 and 192 K. At concentrations up to 4 mol%, electrons were scattered by one hydrocarbon molecule at a time and a gas phase model was used to estimate the scattering cross sections. The values for thermal electrons were, in Å2: ethane, 2.7; propane, 4.6;n-butane, 7.2; ethylene, 4.7; propylene, 5.4;cis-butene-2, 7.4;trans-butene-2, 9.4. The scattering cross sections of the hydrocarbons dissolved in liquid xenon were about half of those in the gas phase, where comparisons could be made.The mobility of electrons in pure xenon decreases with increasing electric field strength, due to heating of the electrons by the field. Addition of a small amount of hydrocarbon increases the mobility at high fields, eightfold by 4% of ethylene, propylene, orcis-butene-2 at 23.4 kV/cm and 192 K. The scattering cross sections of the hydrocarbons are two orders of magnitude larger than the effective cross section of liquid xenon, and the collisions with the hydrocarbons tend to prevent the electrons from becoming heated.Electrons begin to form localized states in solutions containing 10 mol% hydrocarbon, or 20 mol% in the case of ethane. The mobility decreases approximately exponentially with concentration above these thresholds. The values of μ0for these exponential regions reflect the different scattering coefficients of the hydrocarbons: μ = μ0exp (−Eμ/RT). The values ofEμincrease with molecular size in a series, and are greater for olefins than for alkanes. For the C2and C3hydrocarbonsEμincreases linearly with the mol fraction of hydrocarbon.cis-Butene-2 shows anomalous behaviour, as found earlier for electrons in the pure compound.

ISSN:0008-4042    

DOI:10.1139/v78-126

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Ammonium tetrachloroaluminate crystallizes in the orthorhombic Systema = 11.022(6) Å,b = 7.072(3) Å,c = 9.257(5) Å,Z = 4, space groupPnma. The structure was determined by direct methods from diffractometer data and refined by full-matrix least-squares procedures to finalRandRwvalues of 0.053 and 0.069 respectively, for 596 reflections withI > 2σ(I). Hydrogen atoms were not observed. Al—Cl bond lengths are similar to those of other alkaline chloroaluminate salts (Li+, Na+, NO+). The salt is isostructural with NH4ClO4.Crystals and polycrystalline samples of this compound have been studied by Raman scattering above 10 K, and infrared spectra of specimens of a polycrystalline sample have been recorded in Nujol and a fluorolube above 80 K. Both methods enabled us to observe the bands corresponding to the ν1(A2), ν3, and ν4(F2) vibration modes of the ammonium ion but the infrared spectra contain no band due to combination modes involving the librations of this ion. Nuclear magnetic second moment remains equal to 4 G2over the range 298–80 K. These spectroscopic results, compared to those of other ammonium salts, indicate that the ammonium ion seems to be freely rotating.The four characteristic bands of the AlCl4−tetrahedral anion have been studied by Raman scattering in the 298–10 K temperature range.

ISSN:0008-4042    

DOI:10.1139/v78-127

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The microwave rotational spectrum of methylthioacetonitrile has been studied in the frequency range 18–37 GHz. The spectrum found is that of thegaucheconformer. The non-observation of the spectrum of thetransconformer indicates that its abundance is less than about 5%. The rotational and centrifugal distortion constants for the ground vibrational state of thegaucheconformer are:A = 7715.123 MHz,B = 2641.756 MHz,C = 2174.538 MHz,DK = 0.6824 MHz, DJK = −2.52 kHz, andDJ = 1.96 kHz. The observed rotational constants are compatible with a dihedral angle of 66 ± 5° and a CSC angle of 104 ± 2°. The dipole moment of thegaucheconformer has been determined as 3.02 D. Vibrational satellites due to S—CH2torsion have been observed and a torsional frequency of 101 cm−1has been estimated from relative intensity measurements.

ISSN:0008-4042    

DOI:10.1139/v78-128

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

A study of solutions of the oxalate complexes of berylium by ir and Raman spectrometry has demonstrated the formation of three complexed species: BeC2O4, Be(C2O4)22−, and Be3(OH)3(C2O4)33−regardless of the ratio used. Each complex is characterized by specific vibrational frequencies which are independant of the pHof the solution. It was possible to determine the concentration of each species as a function of pH, as well as its stability constant, by measuring the intensifies of certain characteristic bands in the Raman scattering spectrum. [Journal translation]

ISSN:0008-4042    

DOI:10.1139/v78-129

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Examination of unreacted sodium borohydride after reduction of ketones by mixtures of NaBH4and NaBD4shows that it is still isotopically pure and that no detectable species NaBHnD4−nhave been formed. Disproportionation of intermediates back to NaBH4therefore plays no significant role in the reduction.

ISSN:0008-4042    

DOI:10.1139/v78-130

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The stereoisomers of 2-methyltetrahydropyran-4-ol have been separated and identified by carbon-13 and proton nmr analysis of the trideuteriomethyl-2,6,6-trideuterio analogue. Stereoisomeric product ratios of reduction of 2-methyltetrahydropyran-4-one (1) by NaBH4, KBH4, L-Selectride, K-Selectride, and LiBH(nBu)3have been determined and compared with reductions of 3-methylcyclohexanone. Product ratios in the reduction of the two substrates by the borohydride reducing agents are similar but are quite different in the reduction by the Selectride reducing agents,1being reduced by Selectride to give 73%equatorialalcohol. Two possible mechanisms of reduction of1are proposed, involving intramolecular assistance by the cyclic ether oxygen.

ISSN:0008-4042    

DOI:10.1139/v78-131

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The addition of the pseudohalogen iodine nitrate (IONO2) to the endocyclic alkenic bond in benzyl 2-O-benzyl-3,4-dideoxy-α-D-glycero-pent-3-enopyranoside (3) is described. The stereochemistry and regiochemistry of addition were elucidated by chemical degradation,1Hmr spectroscopy, mass-spectral analysis, and polarimetry. A synthetic route to 4′-thiocordycepin (20) from compound3, by way of the intermediacy of the preponderant iodine nitrate adduct of3, namely, benzyl 2-O-benzyl-3-deoxy-3-iodo-4-O-nitro-β-L-lyxopyranoside (4), is also described.

ISSN:0008-4042    

DOI:10.1139/v78-132

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The series of cyclopropyl ketones1–6was irradiated in methanol. Cyclopentanones1and2gave mainly products of type I reaction whereas ketones3,5, and6gave type II products. Formation of type II products can arise by two different mechanisms. One involves the intermediacy of a dienol which can be trapped with methanol-OD. Photochemical degradation of the cyclopentanones was slower than the corresponding cyclohexanones.

ISSN:0008-4042    

DOI:10.1139/v78-133

出版商:NRC Research Press    

年代:1978

数据来源: NRC