Anionic cis-trans isomerisation of dimethyl perfluoro-(4-methyl-2-pentene)dioate

1980 ◽  
Vol 45 (12) ◽  
pp. 3360-3369 ◽  
Author(s):  
Oldřich Paleta ◽  
Jiří Svoboda ◽  
Václav Havlů ◽  
Václav Dědek
Keyword(s):  
Proton Transfer ◽  
Title Compound ◽  
Heterogeneous System ◽  
Equilibrium Mixture ◽  
Potassium Fluoride ◽  
Side Product ◽  
Solvation Effect ◽  
Aprotic Solvents ◽  
Reaction Conditions ◽  
Dipolar Aprotic Solvents

Potassium fluoride induced cis-trans isomerisation of the title compound I was investigated. The isomerisation takes place in a heterogeneous system and is enabled by solvation effect of dipolar aprotic solvents. Dimethyl 2,3,3,4-tetrafluoro-2-trifluoromethylpentanedioate (II) is formed as side product by proton transfer from the solvent to the intermediate 1,3-bis(methoxycarbonyl)perfluoro-1-butanide (III). The mechanism was deduced from the reaction conditions and results of the isomerisation. Composition of the equilibrium mixture of cis- and trans-isomer (Ia, Ib, respectively) studied in the interval 2-75 °C, shows an extreme. In the interval 2-30 °C the reaction Ia → Ib appears to be exothermic (ΔH = -21.2 kJ mol-1), in the interval 35-47 °C the enthalpy equals practically zero and in the maximum of the curve at 42.5 °C the entropic factor ΔS = 2.82 J mol-1 K-1. In the interval 50-75 °C the reaction is endothermic (ΔH = 15.2 kJ mol-1). In this context the effect of steric interactions between the substituents -COOCH3 and -CF(CF3)COOCH3, as well as of the so called cis-effect in 1,2-dihalogenoethylenes, on the Ia ##e Ib equilibrium are discussed.

Ionic dimerisation of methyl trifluoropropenoate

1980 ◽  
Vol 45 (2) ◽  
pp. 415-422 ◽  
Author(s):  
Oldřich Paleta ◽  
Václav Havlů ◽  
Václav Dědek
Keyword(s):  
Proton Transfer ◽  
Potassium Fluoride ◽  
Complete Conversion ◽  
Reaction Conditions ◽  
Kinetically Controlled

Dimerisation of methyl trifluoropropenoate (I) in solvents in the presence of potassium fluoride affords stereoisomeric dimethyl perfluoro-(4-methyl-2-pentene)dioates (III), the ratio of which depends on the reaction conditions. The reaction is accompanied by formation of methyl 2,3,3,3-tetrafluoropropenoate (IV), arising by proton transfer from the solvent to the carbanionic intermediate. Under suitable conditions complete conversion of the propenoate can be achieved and the dimer is obtained in 80-90% yield. Principal steps of the dimerisation were proved and the formation of configurational isomers is discussed in terms of kinetically controlled reaction.

Kinetics and isotope effects of the proton transfer reactions between 1-(4-nitrophenyl)-1-nitroethane to phenyltetramethylguanidine in dipolar aprotic solvents

1984 ◽  
Vol 62 (5) ◽  
pp. 954-957 ◽  
Author(s):  
Arnold Jarczewski ◽  
Przemyslaw Pruszynski ◽  
Mohammed Kazi ◽  
Kenneth T. Leffek
Keyword(s):  
Proton Transfer ◽  
Transfer Reaction ◽  
Isotope Effects ◽  
Proton Transfer Reaction ◽  
Transfer Reactions ◽  
Aprotic Solvents ◽  
Enthalpy Of Activation ◽  
Proton Transfer Reactions ◽  
Carbon Acid ◽  
Dipolar Aprotic Solvents

The carbon acid 1-(4-nitrophenyl)-1-nitroethane reacts with phenyltetramethylguanidine in the aprotic solvents acetonitrile, benzonitrile, and chlorobenzene in a bimolecular proton transfer reaction. The primary isotope effects, kH/kD, for these reactions at 25 °C are 8.5 ± 0.4, 6.1 ± 0.4, and 16 in acetonitrile, benzonitrile, and chlorobenzene respectively. The magnitude of the isotope effects on the enthalpy of activation [Formula: see text] are 2.3 ± 0.2, 1.6 ± 0.7, and 4.2 ± 0.6 kcal mol−1, which indicates a contribution from proton tunnelling to the reaction rate of the normal substrate.

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).

Ionic dimerisation of trifluoropropenenitrile and its addition reactions with methyl trifluoropropenoate

1980 ◽  
Vol 45 (2) ◽  
pp. 406-414 ◽  
Author(s):  
Jiří Svoboda ◽  
Oldřich Paleta ◽  
Václav Dědek
Keyword(s):  
Reaction Mechanism ◽  
Proton Transfer ◽  
Substituent Effect ◽  
Solvent Molecule ◽  
Addition Product ◽  
Potassium Fluoride ◽  
Relative Reactivity ◽  
Addition Reactions ◽  
Tertiary Amines ◽  
Optimum Conditions

Dimerisation of trifluoropropenenitrile (I) in the presence of potassium fluoride and tertiary amines afforded a mixture of stereoisomeric perfluoro-4-methyl-pentenedinitriles (II), higher-boiling compounds, and 2,3,3,3-tetrafluoropropanenitrile (III) which arises by proton transfer from the solvent molecule. Under optimum conditions, product II was obtained in about 50% yield. Reaction of the nitrile I with methyl trifluoropropenoate (IV) gave, besides the dimers II and V, the product of addition of the nitrile I to the propenoate, IV, i.e. methyl 4-cyanoperfluoro-2-pentenoate (VI), and the addition product of the propenoate IV to the nitrile I, i.e. methyl 4-cyanoperfluoro-2-methyl-3-butenoate (VII). The relative reactivity if I and IV is discussed. The ratio of stereoisomers in II, V, VI and VII indicates that the magnitude of the steric substituent effect, operating in the reaction mechanism, decreases in the order -CFCF3.(COOCH3) > -CFCF3(CN) > -COOCH3 > -CN.

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%.

Electron-transfer reactions in non-aqueous media. VII. Reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ by copper(I) in dimethyl sulfoxide-water mixtures

1983 ◽  
Vol 36 (10) ◽  
pp. 1923 ◽  
Author(s):  
JMB Harrowfield ◽  
L Spiccia ◽  
DW Watts
Keyword(s):  
Electron Transfer ◽  
Dimethyl Sulfoxide ◽  
Aqueous Media ◽  
Mixed Solvents ◽  
Transfer Reactions ◽  
Aprotic Solvents ◽  
Aqueous Mixtures ◽  
Electron Transfer Reactions ◽  
Dipolar Aprotic Solvents ◽  
Sphere Mechanism

Previous work on the reduction of a series of cobalt(III) complexes by iron(II) in dipolar aprotic solvents and in aqueous mixtures has been extended to reduction by copper(I). The greater stability of copper(I) to disproportionation in these media has permitted the study of the reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ in range of solvents over a number of temperatures with a precision not possible in previous studies in water. The results are consistent with an inner-sphere mechanism in which the copper(I) reductant is preferentially solvated by dimethyl sulfoxide to the exclusion of water in mixed solvents.

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