摘要:

Bromination ofp-cresol, 2-bromo-p-cresol, 3,4-dimethylphenol, and mesitol in trifluoromethanesulfonic acid gives as the main product the bromo derivative with brominemetato hydroxyl, a result attributed to the intermediate formation of a bromodienone and its rearrangement. Phenol does not givem-bromophenol in trifluoromethanesulfonic acid. 4-Bromo-2,4,6-trimethylcyclohexa-2,5-dienone rearranges to 3-bromomesitol in trifluoromethanesulfonic acid and, similarly, 2,4,6-tribromo-4-methylcyclohexa-2,5-dienone rearranges to 2,3,6-tribromo-4-methylphenol. Under appropriate conditions debromination of bromodienones is competitive with rearrangement. Tetramethylammonium bromide in trifluoromethanesulfonic acid is an effective reagent for isomerization and disproportionation of bromophenols. Tetramethylammonium iodide in trifluoromethanesulfonic acid is an effective reagent for selective debromination of bromophenols at theorthoandparapositions.

ISSN:0008-4042    

DOI:10.1139/v83-183

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The preparation of various deuterium labelled 9- and/or 10-oxygenated derivatives of geraniol, geranial, nerol, and neral is described. Wittig reaction of the tetrahydropyranyl ethers of (E)- and (Z)-1,1-dideutero-6-(triphenylphosphonium)-3-methyl-2-hexen-1-ol iodides (23and24) with the tetrahydropyranyl ethers of hydroxyacetone and 1,3-dihydroxyacetone afforded, after deprotection, C-1 dideuterated 9-hydroxygeraniol, 9-hydroxynerol, 9,10-dihydroxygeraniol, and 9,10-dihydroxynerol of high isomeric purity. Selective oxidation of these products allowed for the preparation of the corresponding derivatives possessing an aldehyde functionality at C-9 or C-1 and C-9. Wittig reaction of23and24with pyruvaldèhyde dimethyl acetal followed by acidic hydrolysis afforded C-1 dideuterated 10-oxogeraniol and 10-oxonerol, oxidation of which yielded C-1 deuterated 10-oxogeranial and 10-oxoneral. Wittig reaction of (E)- and (Z)-1,1-dideutero-6-(triphenyl-phosphonium)-3-methyl-2-hexen-1-ol iodides (49and50) with 1,1,3,3-tetraethoxyacetone afforded C-1 dideuterated 9,9,10,10-tetraethoxygeraniol and 9,9.10,10-tetraethoxynerol, oxidation of which provided C-1 deuterated 9,9,10,10-tctraethoxygeranial and 9,9,10,10-tetraethoxyneral.

ISSN:0008-4042    

DOI:10.1139/v83-184

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Tritium isotope fractionation in the exchange reaction between methanol and hydrogen sulphide has been studied in the gaseous phase over the temperature range 283–373 K. It was found that the heavier isotope accumulates in methanol and that the tritium–protium isotope effect characterizing the exchange reaction studied reaches large values: from 2.70 at 373 K to 3.72 at 283 K. The temperature dependence can be described by the simple relation: In α = −0.1221 + 431.5/T. Using observed vibrational frequencies, theoretical fractionation factors could be calculated and good agreement with the experimentally determined values was observed. The results presently obtained were also compared with those obtained for the CH3SH–H2S system.

ISSN:0008-4042    

DOI:10.1139/v83-185

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Fluorimetric titrations were carried out for various forms of 9-phenanthrylaminc and pKa* values were determined. An unusual behaviour observed in the fluorimetrie titration of the neutral form at moderate proton concentration is due to the quenching of the S1state of PNH2by H+.

ISSN:0008-4042    

DOI:10.1139/v83-186

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Surface tensions of aqueous solutions of cyclopropane, cyclobutane, cyclopentane, and cycloheptane carboxylic acids, and of cyclopentaneacetic and cyclopentanepropionic acids were measured at 25 °C by the drop volume method. The Traube constants for calculation of standard free energies of adsorption were estimated from second and third degree polynomial least-squares analyses, from nonlinear least-squares analysis using the Szyszkowsky equation, and graphically.The standard free energies of adsorption at the air/solution interface of cycloalkane and cycloalkanealkyl carboxylic acids are less negative than those of the corresponding straight chain acids, but not by a constant amount; the standard free energy of the CH2group in a cycloalkane ring is −2.5 kJ mol−1as compared to a value of −3.3 kJ mol−1for straight chain acids.

ISSN:0008-4042    

DOI:10.1139/v83-187

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

We find that the product from the interaction of 6,7-dimethoxy-3-isochromanone and hydrazine, followed by treatment of the intermediate hydrazide with mineral acid, is not 6,7-dimethoxy-1,3-dihydro-3-(2H)isoquinolone as stated in the literature, but rather bis-2,2-(6,7-dimethoxy-1,4-dihydro-3(2H)isoquinolonyl). An explanation of the formation of this product is provided.

ISSN:0008-4042    

DOI:10.1139/v83-188

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The lithium and sodium salts of 1,2-diaminoethane, 1,3-diaminopropane, n-butylamine, and the lithium salt of isobutylamine were studied as potential reagents for isomerization of triple bonds in alkyn-1-ols. The sodium salts of the diamines afforded high yields of the ω-alkyn-1-ol. Somewhat surprisingly, the sodium salt of n-butylamine also effects isomerization to the terminal position. The lithium salt of 1,3-diaminopropane gave the highest conversion of 2- to 3-alkyn-1-ol. A novel, selective rearrangement of one triple bond of a diynol, a 2, ω- to 3, ω-diyn-1-ol isomerization, was incorporated into a synthesis of the insect sex pheromone 3,13-octadecadienol acetate.

ISSN:0008-4042    

DOI:10.1139/v83-189

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Rate constants for the overall rearrangement of the 2,2-dimethyl-3-buten-1-yl radical to the 1,1 -dimethyl-3-buten-1-yl radical,kC=C, have been measured from −145 °C to −101 °C by kinetic epr spectroscopy and at 40 °C by spin trapping with 1-methyl-4-nitroso-3,5-diphenylpyrazole. The temperature dependence can be represented bywhere θ = 2.3RT kcal mol−1. This rearrangement, which must proceed via a 2,2-dimethylcyclopropylcarbinyl radical as an intermediate, is one of the fastest rearrangements involving a primary alkyl radical. At 25 °C,kC=C = 4.3 × 107 s−1, which makes this rearrangement about 10 000 times faster than the rearrangement of the simplest homoallyl radical, 3-buten-1-yl. This rate enhancement is attributed to steric acceleration of ring closure by thegemdimethyl groups (Thorpe–Ingold effect).

ISSN:0008-4042    

DOI:10.1139/v83-190

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

abinitioMolecular orbital calculations at the STO-3G and STO-3G* levels on H2S2, (CH3)2S2, (CH3CH2)2S2, andL-cystine show that the minimum energy conformation occurs at the angle at which the S—S overlap population is at a maximum. In agreement with experiment, the calculations favour a disulfide dihedral angle close to 90°. The variation of the S—S overlap population is essentially independent of substituents, whereas thecisbarrier to rotation about the S—S bond increases relative to thetransbarrier as the size of the substituents increases. These observations lead to the conclusion that electronic effects determine the disulfide dihedral angle and that both steric and electronic effects control the relative magnitude of thecisandtransbarriers.

ISSN:0008-4042    

DOI:10.1139/v83-191

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Heterogeneous termination reactions in the pyrolysis of ethane have been investigated by three methods, involving measurements of the reductions in the steady state rates of formation of C2H4and C4H10and of the reduction in the induction period in the presence of active surfaces. Equations were developed for the approach of the concentration of C2H5to its steady state value when both first and second order termination reactions occur. Experiments have been performed at about 904 K with from 2.8 × 10−4to 2.3 × 10−3 mol L−1of C2H6in the presence of surfaces of SiO2, PbO, KCl, and C. Data from the literature have been reinterpreted. The data may be most simply explained if the main surface termination on most surfaces is first order with respect to gaseous C2H5. Collisional termination probabilities, γ, for this reaction were calculated to be: KCl, 905 K, 3 × 10−4; C, 903 K, 3 × 10−4; SiO2, 894 K, 6 × 10−5; 823 K, 10−5; PbO, 833 K, 6 × 10−5; Pyrex, 833 K, 4 × 10−6.

ISSN:0008-4042    

DOI:10.1139/v83-192

出版商:NRC Research Press    

年代:1983

数据来源: NRC