摘要:

The infrared multiphoton chemistry of CF3D has been investigated in the ν2and ν5bands. The primary dissociation step forms DF and CF2. The major sink for the biradical is dimerization to form C2F4; this process preserves the13C/12C isotopic selectivity which is reasonably high (α ≈ 20). The isotopic selectivity for2H/1H is impaired by some scrambling reaction involving excited substrate. The possible nature of this scrambling reaction is discussed. In comparison with other CF3X systems (X = I, Br, Cl), CF3D is difficult to decompose, having low dissociation probability, and appears to decompose only after collisional activatio

ISSN:0008-4042    

DOI:10.1139/v79-519

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The pyrolysis of triethylgallium has been studied in a toluene carrier gas system in the temperature range of 464.7 to 700.7 K and a pressure range of 0.82 to 3.73 kPa. From the data obtained from this work, the following mechanism for the thermal decomposition of the metal alkyl is proposed:where [1] is the rate determining step. After runs below 606 K were corrected for the contribution of a concurrent residual reaction, a least-squares analysis of experimental results from 567 to 651 K based on both product and residual alkyl analysis gaveat 1.60 kPa.The rate constant,k1, is very slightly pressure-dependent as revealed by tests at 648.0 K (80% and 45% decomposition). Studies indicate there is no detectable surface catalysis effect. Similarly, no effect was observed for changes in concentration or contact time.The mechanism for the formation of polymeric gallium hydride in reaction [4] is not clearly defined and may consist of more than one step. Reaction [5] is slow but based on the C2H4:H2ratio must occur to a significant extent (40–80%) during a run. Further decomposition occurs between runs, causing a build-up of H2in the reaction vessel.Experimental data for the hydrogen abstraction by ethyl radicals from tolueneyield the equation

ISSN:0008-4042    

DOI:10.1139/v79-520

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The angular potential energy curves of theX2B1,A2A1,B2B2valence-shell and4Σg−,2Σg−(22B1),2Δg(22A1, 32B1), and2Σg+Rydberg states arising from πu23sconfigurations are calculated by configuration interaction techniques. The data obtained reproduce very satisfactorily allX2B1andA2A1characteristics deduced from experiments; they support the previous theoretical prediction of a small-angle2B2state but find a very low |Re′e′′|2value for the2B2–A2A1transition. The4Σg−as well as three of the above four doublet Rydberg multiplets are found to prefer linear (or nearly linear) geometry and larger NH separations (in the symmetric structure) than NH2in its ground state. A relatively large electronic transition moment for combination with bothX2B1andA2A1is calculated for the lowest Rydberg multiplet which lies roughly 5.3 eV above theA2A1state, while the intensity of transitions of the higher 3sstates is found to be considerably smaller. Finally it is pointed out that the former Rydberg transition fits in well with recent emission experiments in this wavelength region recently reported by Herzberg.

ISSN:0008-4042    

DOI:10.1139/v79-521

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The formation constants of nickel(II) and zinc(II) monothioacetylacetonates have been determined as 2.95 × 1012and 6.46 × 1010respectively. These are about 700 times more stable than the corresponding acetylacetonates. Both monothioacetylacetonats were more than 99% extracted into chloroform and ligand hydrolysis was not significant before completion of metal ion extraction.

ISSN:0008-4042    

DOI:10.1139/v79-522

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Sulfides are advanced as sulfonyl chloride precursors. SN2 cleavage of the intermediate sulfonium ions is discussed in conjunction with both the sulfohaloform pathway and our previous hypothesis that asymmetric chlorosulfonium chloride salts undergo Pummerer rearrangements which exhibit regioselectivity that can be anticipated on the basis of substituent electronegativity difference (ΔXp). Thioglycolic acid is developed as a new sulfur transfer agent for sulfonyl chloride synthesis.

ISSN:0008-4042    

DOI:10.1139/v79-523

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Carbon-13 nuclear magnetic resonance spectroscopy of caerulomycin A (1) produced by cultures ofStreptomycescaeruleushas shown that [1-13C]acetate labels C-2, C-4, and C-4′, whilst [1,2-13C]acetate enriches these carbons plus C-2′, C-3, C-3′, C-5′, and C-6′. The results establish that acetate is incorporated with little dilution at C-3 and C-4 in the substituted ring of1, whereas C-2, and C-2′ to C-6′ of the unsubstituted ring, are assembled from lysine via the symmetrical intermediate 2S,6S-diaminopimelic acid. The methoxyl carbon incorporates label fromDL-[3-13C]serine, but this precursor does not enrich C-5, C-6, or C-7 of the substituted ring, and the origins of these carbons remain undetermined.

ISSN:0008-4042    

DOI:10.1139/v79-524

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The equilibria [2]:for R = CH3, C2H5, and C6H5were studied in a pulsed electron beam high ion source pressure mass spectrometer. van't Hoff plots led to ΔH2values: (CH3), 24.6; (C2H5), 22.7; (C6H5), 21.9 kcal/mol. ΔHf(RC(OH)2+) were obtained from gas phase basicity ladders combined with the new ΔHf(t-butyl+) = 163 kcal/mol (Beauchamp). The ΔHf(RC(OH)2+) were: (CH3), 71.3; (C2H5), 63.6; (C6H5), 95.5 kcal/mol. Combination of ΔH2with ΔHf(RC(OH)2+) leads to ΔHf(RCO+): (CH3), 153.7; (C2H5), 144; (C6H5), 174.6 kcal/mol. These results are in agreement with selected data from appearance potentials. The energies and structures of the participants in reaction [2] were calculated by MINDO/3 and STO-3G. MINDO/3 gave good agreement with ΔH2. The establishment of the equilibria [2] was unusually slow. A study of the kinetics revealed thatk2fis approximately third order, unusually small, and has an unusually large negative temperature coefficient. Furthermore, reaction [2] was found to be catalyzed by RCOOH. An explanation of these observations is given by assuming that the proton shift RCO(OH2)+ → RC(OH)2+has a large activation energy barrier in the gas phase. This barrier is removed by formation of a hydrogen bonded complex with RCOOH.

ISSN:0008-4042    

DOI:10.1139/v79-525

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The reaction of α-copper(I)alkanephosphonates with methyl and ethyl oxalyl chlorides gives methyl or ethyl dialkylphosphonopyruvates which, submitted to reductive amination in ethanol at pH 6–7 with sodium cyanohydridoborate (NaBH3CN) and ammonia, or primary amines, lead to phosphonic amino esters; hydrolysis with diluted HCl gives phosphonic amino acids. These three reactions constitute a general way to β-phosphonoalanine and β-alkyl β-phosphonoalanine.

ISSN:0008-4042    

DOI:10.1139/v79-526

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The conformational properties of 1,3-dithia-5,6-benzocycloheptene (7) (2,4-benzodithiepin), three 2,2-dialkyl derivatives, and two monosubstituted derivatives (2-CH3and 2-OCH3) have been investigated by1H and13C dnmr methods. It is reported that the most stable conformation of the seven-membered ring is a chair on which, in the case of the monosubstituted compounds, the 2-CH3group adopts an equatorial position while the 2-OCH3group takes the axial position. Only for the 2,2-pentamethylene derivative (10) was a minor amount (13%) of TB form detected. These results are markedly different from those found previously for the oxygen analogs and the conformational effect of the cyclic heteroatoms will be discussed in terms of the anomeric and steric effects.

ISSN:0008-4042    

DOI:10.1139/v79-527

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

SeBr3AsF6and TeBr3AsF6were prepared from the elements and an excess of bromine and arsenic pentafluoride, as well as from Se4(AsF6)2and Te4(AsF6)2with excess bromine. SeBr3SbF6was prepared from Se4(SbF6)2and bromine, and TeBr3AsF6from tellurium tetrabromide and arsenic pentafluoride. Br3AsF6was found to oxidize arsenic trifluoride and sulphur dioxide to arsenic pentafluoride and SO2BrF respectively. Reaction pathways to the tribromochalcogen cations are discussed. Raman spectra of the tribromochalcogen salts were obtained. Assignments were confirmed, and force constants derived from normal coordinate analyses and compared with those derived for SBr3+, PBr3, AsBr3, and SbBr3.

ISSN:0008-4042    

DOI:10.1139/v79-528

出版商:NRC Research Press    

年代:1979

数据来源: NRC