Influence of substituents in the 3-position of cyclohexene oxides on the rates of their reactions with hydrogen chloride in low polarity aprotic solvents

1978 ◽  
pp. 627 ◽  
Author(s):  
Giuseppe Bellucci ◽  
Giancarlo Berti ◽  
Giovanni Ingrosso ◽  
Antonio Vatteroni ◽  
Giovanni Conti ◽  
...  
Keyword(s):  
Hydrogen Chloride ◽  
Aprotic Solvents ◽  
Cyclohexene Oxides ◽  
Influence Of Substituents

Cyclization of Substituted Phenyl N-(2-Hydroxybenzyl)carbamates in Aprotic Solvents. Synthesis of 4H-1,3-Benzoxazin-2(3H)-ones

2000 ◽  
Vol 65 (8) ◽  
pp. 1262-1272 ◽  
Author(s):  
Jaromír Mindl ◽  
Oldřich Hrabík ◽  
Vojeslav Štěrba ◽  
Jaromír Kaválek
Keyword(s):  
Reaction Mechanism ◽  
Transition State ◽  
Convenient Method ◽  
The Other ◽  
Aprotic Solvents ◽  
Phenoxy Group ◽  
Kinetics Of ◽  
Influence Of Substituents ◽  
Electron Withdrawing Substituents

The kinetics of cyclization of substituted phenyl N-(2-hydroxybenzyl)carbamates and their N-methyl analogs, prepared by the reaction of 2-(aminomethyl)phenols with substituted phenyl chloroformates, was studied in dioxane or toluene at the temperatures 110-180 °C. Electron-withdrawing substituents in the leaving phenoxy group strongly accelerate the rate of cyclization (ρ = 2.45 ± 0.15) while the substituents in the other ring have virtually no effect. The cyclization was catalyzed with triethylamine in toluene but not in dioxane. On the basis of these results, the most convenient method for preparation of substituted 4H-1,3-benzoxazin-2(3H)-ones was a one-hour reflux of substituted 4-nitrophenyl N-(2-hydroxybenzyl)carbamates in dioxane. Based on the influence of substituents, solvents (dioxane and toluene) and triethylamine, the reaction mechanism and structure of the transition state were proposed.

Solvation of ions by dipolar aprotic solvents and water. A CNDO/2 study

1985 ◽  
Vol 50 (11) ◽  
pp. 2493-2508 ◽  
Author(s):  
Petr Kyselka ◽  
Zdeněk Havlas ◽  
Ivo Sláma
Keyword(s):  
Binary Mixtures ◽  
Quantum Chemical ◽  
Chemical Method ◽  
Molecular Structures ◽  
Dimethyl Sulphoxide ◽  
Ternary Mixtures ◽  
Aprotic Solvents ◽  
Quantum Chemical Method ◽  
Solvation Of Ions ◽  
Dipolar Aprotic Solvents

Solvation of Li+, Be2+, Na+, Mg2+, and Al3+ ions has been studied in binary mixtures with dimethyl sulphoxide, dimethylformamide, acetonitrile and water, and in ternary mixtures of the organic solvents with water. The CNDO/2 quantum chemical method was used to calculate the energies of solvation, molecular structures and charge distributions for the complexes acetonitrile...ion (1:1, 2:1, 4:1), dimethyl sulphoxide...ion (1:1), dimethylformamide...ion (1:1), and acetonitrile (dimethyl sulphoxide, dimethylformamide)...ion...water (1:1:1).

Oxidation of (1-hydroxybenzyl)ferrocene and its derivatives substituted in phenyl ring with bis(triphenylsilyl) chromate

1982 ◽  
Vol 47 (12) ◽  
pp. 3375-3380 ◽  
Author(s):  
Jaroslav Holeček ◽  
Karel Handlíř ◽  
Milan Nádvorník ◽  
Milan Vlček
Keyword(s):  
Linear Dependence ◽  
Rate Constants ◽  
Oxidation Rate ◽  
Phenyl Ring ◽  
Equilibrium Constants ◽  
Aprotic Solvents ◽  
Protonation Equilibrium ◽  
Oxidation Of Alcohols ◽  
Hammett Σ Constants ◽  
Sulphuric Acid Medium

Kinetics have been studied of oxidation of (1-hydroxybenzyl)ferrocenes substituted in phenyl ring with bis(triphenylsilyl) chromate in benzene solutions as well as protonation of these alcohols in sulphuric acid medium. Logarithms of the oxidation rate constants (kobs, 20-40 °C) and those of the protonation equilibrium constants (KR+, 25 °C) show linear dependence on the Hammett σ constants, the ρ constant values being -0.86 to -0.40 and -2.50, respectively. These negative values suggest that the both processes are influenced by the same effects and confirm the mechanism proposed earlier for oxidation of alcohols with ferrocenyl substituent by action of bis(triphenylsilyl) chromate in aprotic solvents.

Chlorination of 2,4,6-trichlorophenol in acidic aqueous medium

1985 ◽  
Vol 50 (8) ◽  
pp. 1842-1851 ◽  
Author(s):  
Petr Švec
Keyword(s):  
Reaction Mechanism ◽  
Aqueous Medium ◽  
Hydrogen Chloride ◽  
Reaction Medium ◽  
Model Experiments ◽  
Sulfuric And Hydrochloric Acids

The course of chlorination of 2,4,6-trichlorophenol (I) in water and approximately 20% sulfuric and hydrochloric acids has been investigated. In all these media the reaction gives primarily 2,4,6,6-tetrachloro-2,4-cyclohexadienone (II) which is subsequently chlorinated under formation of polychlorinated alicyclic ketones or isomerized to give the more stable 2,4,6,6-tetrachloro-2,5-cyclohexadienone (III), the precursor of further arising chlorinated 1,4-benzoquinones. The ratio of the arising polychlorinated alicyclic ketones to chlorinated 1,4-benzoquinones is significantly influenced by concentration of hydrogen chloride in the reaction medium. On the basis of model experiments, the reaction mechanism of exhaustive chlorination of 2,4,6-trichlorophenol has been suggested.

1H and 13C NMR spectra of 2,2’-disubstitutedtrans-azobenzenes suitable for preparation of metallized azo dyes

1991 ◽  
Vol 56 (10) ◽  
pp. 2160-2168 ◽  
Author(s):  
Josef Jirman
Keyword(s):  
Nmr Spectra ◽  
Electron Pair ◽  
Phenyl Group ◽  
Aprotic Solvents ◽  
1H And 13C Nmr ◽  
Predominant Form ◽  
Rapid Equilibrium ◽  
Dipolar Aprotic Solvents ◽  
Free Electron Pair ◽  
C Nmr

The 1H and 13C NMR spectra have been measured of six trans-azobenzenes substituted at 2 and 2’ positions with substituents favourable for complex formation with a metal (OH, NH2, NHCOCH3, COOH). From the standpoint of NMR such substituted trans-azobenzenes are present in solution in a rapid equilibrium following from rotation around the bond between C-1 of phenyl group and N atom of azo linkage. The predominant form has the substituent in the syn-position with respect to the free electron pair of the nearer azo nitrogen atom. The equilibrium is affected by dipolar aprotic solvents (such as hexadeuteriodimethyl sulfoxide) by decreasing the presence of the predominant form by 1 to 11%.

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