Transmission of polar effects arcoss the CH=CH link in styrylfuran system

1981 ◽  
Vol 46 (12) ◽  
pp. 3110-3114
Author(s):  
Viera Knoppová ◽  
Anton Beňo ◽  
Miloslava Dandárová ◽  
Jaroslav Kováč
Keyword(s):  
Thermodynamic Parameters ◽  
Substituent Effect ◽  
Nmr Spectra ◽  
Aldehyde Group ◽  
Point Of View ◽  
Polarographic Reduction ◽  
Transmission Coefficients ◽  
H Nmr ◽  
Polar Substituent ◽  
Kinetics Of

Transmission of polar substituent effect through the vinylidene grouping in 5-(4-X-styryl)-2-furaldehydes (X = H, Cl, Br, COOCH3, CN and NO2) was studied by polarographic reduction of the aldehyde group as well as by kinetics of their condensation with malononitrile. The obtained transmission coefficients π' were compared with the corresponding values for systems, containing other links between the benzene and furan nuclei. Thermodynamic parameters of the condensation with malononitrile were determined. The transmission of polar effects is discussed also from the point of view of 1H NMR spectra.

Kinetic and spectral studies on 5-phenoxy-2-furaldehydes and their condensation products

1981 ◽  
Vol 46 (2) ◽  
pp. 506-514 ◽  
Author(s):  
Viera Knoppová ◽  
Miloslava Dandárová ◽  
Jaroslav Kováč
Keyword(s):  
Substitution Reaction ◽  
Nmr Spectra ◽  
Furan Ring ◽  
Point Of View ◽  
Spectral Studies ◽  
Reaction Site ◽  
Cyclic Amines ◽  
H Nmr ◽  
Condensation Products ◽  
Kinetics Of

The base-catalyzed reaction of 5-(4- or 3-phenoxy)-2-furaldehydes (X = 4-OCH3, 4-CH3, 4-Cl, 4-NO2, 3-NO2, 4-Br, 4-COOC2H5, 3-NHCOCH3, 4-SCH3) with malonodinitrile in ethanol gave the corresponding condensation products. The course of the reaction has been monitored kinetically. The kinetics of the nucleophilic substitution reaction at the position 5 of the furan ring of the obtained 2-cyano-3-(5-X-phenoxy-2-furyl)acrylonitriles with secondary cyclic amines (piperidine, morpholine, pyrrolidine) has been studied. The effect of X across the oxygen bridge upon the reaction site is discussed from the point of view of kinetics of the reaction. 1H-NMR spectra of the starting aldehydes and of the formed condensation products have been measured.

Variable temperatures 1H NMR technique on the kinetics and thermodynamic parameters of equilibrium between the Z and E isomers in a stable phosphorus ylide involving an imidazole

RSC Advances ◽  
2016 ◽  
Vol 6 (52) ◽  
pp. 46345-46349 ◽  
Author(s):  
Elham Aghdaei ◽  
Sayyed Mostafa Habibi-Khorassani ◽  
Mehdi Shahraki
Keyword(s):  
Thermodynamic Parameters ◽  
1H Nmr ◽  
Nmr Spectra ◽  
Phosphorus Ylide ◽  
H Nmr ◽  
Kinetics Of ◽  
Kinetics And Thermodynamic

Analysis of 1H NMR spectra of a special ylide involving an imidazole at variable temperatures has been employed to study the kinetics of the interchangeable process in the equilibrium between the two Z- and E-isomers of a stable phosphorus ylide.

The 1H NMR spectra and the conformation of 1,6-anhydro-β-D-hexopyranoses and their triacetates

1979 ◽  
Vol 44 (6) ◽  
pp. 1949-1964 ◽  
Author(s):  
Miloš Buděšínský ◽  
Tomáš Trnka ◽  
Miloslav Černý
Keyword(s):  
Nmr Spectra ◽  
Chemical Shifts ◽  
Shift Reagent ◽  
Point Of View ◽  
Coupling Constants ◽  
Lanthanide Shift Reagent ◽  
Pyranose Ring ◽  
H Nmr ◽  
Vicinal Coupling Constants

The 1H NMR spectra of 1,6-anhydro-β-D-hexopyranoses and their triacetates, measured in hexadeuteriodimethyl sulfoxide or deuteriochloroform, confirmed the existence of these compounds in 1C4(D) conformations, with the pyranose ring partly planarized in dependence on the configuration of the substituents in positions C(2), C(3) and C(4). The effects of the substituents on the chemical shifts and the adjusted relationship for the dependence of vicinal coupling constants on the torsion angle are discussed in detail from the point of view of the determination of the configuration and the conformation of 1,6-anhydro-β-D-hexopyranoses and their derivatives. The 1H NMR spectra of triacetates were also measured in the presence of the lanthanide shift reagent, tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione) europium (III) [Eu.(FOD)3].

Stereochemistry and kinetics of amines addition to acetylenic esters

1991 ◽  
Vol 69 (9) ◽  
pp. 1445-1449 ◽  
Author(s):  
Saber M. Sharaf ◽  
Samir K. El-Sadany ◽  
Ezzat A. Hamed ◽  
Abdel-Hamid A. Youssef
Keyword(s):  
Key Words ◽  
Nucleophilic Addition ◽  
Nmr Spectra ◽  
Acetylenic Esters ◽  
H Nmr ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Step Mechanism

The reactions of a series of methyl para-substituted phenylpropiolates 1a–e with piperidine, morpholine, and diethylamine in methanol and dimethylformamide (DMF) have been studied and their rates measured. The products were methyl β-(N,N-dialkylamino)-p-substituted cinnamates 2–4a–e. 1H NMR spectra were used to determine the configuration of the products. The ρ values in methanol ranged between 0.34 and 1.24 whereas in DMF they were between 0.85 and 1.88. The values of ΔS≠ favor a bimolecular rate-limiting step mechanism. Key words: nucleophilic addition to acetylenic esters.

A study of reactions of 5-substituted furfurylidene derivatives with secondary amines

1985 ◽  
Vol 50 (2) ◽  
pp. 459-469 ◽  
Author(s):  
Katarína Špirková ◽  
Rudolf Kada ◽  
Jaroslav Kováč ◽  
Viera Knoppová ◽  
Miroslav Dzuroška ◽  
...  
Keyword(s):  
Nmr Spectra ◽  
Secondary Amines ◽  
H Nmr ◽  
Kinetics Of

The paper describes preparation of 5-bromo-, 5-nitro-, 5-phenylsulphonyl-, and 5-phenylthio-2-furfurylidene derivatives and investigation of their reactions with N-phenylpiperazine, morpholine, piperidine, and pyrrolidine. Kinetics of the reactions have been followed, and UV, IR, and 1H NMR spectra of the compounds produced are interpreted.

X+ transfer from the halonium ions of adamantylideneadamantane to acceptor olefins. The possibility of chiral induction in the transfer process

1997 ◽  
Vol 75 (12) ◽  
pp. 1844-1850 ◽  
Author(s):  
Alexei A. Neverov ◽  
Theresa L. Muise ◽  
R.S. Brown
Keyword(s):  
Nmr Spectra ◽  
Room Temperature ◽  
Reaction Rate ◽  
Methyl Groups ◽  
Kinetic Behavior ◽  
Methyl Group ◽  
Chiral Induction ◽  
H Nmr ◽  
Group 12 ◽  
Kinetics Of

The bromonium ion of adamantylideneadamantane (Ad=Ad-Br+) has been used to induce the bromocyclization of a 4-pentenyl glycoside (10) and a 5-hexenyl glycoside (11) in dichloroethane. The kinetics of these processes have been studied at 25 °C in the presence of varying [Ad=Ad] and, in the case of the transfer to 10, in the presence of pentanol. The second-order rate constants for bromocyclization of these two alkenes are (1.04 ± 0.06) × 10−1 M−1 s−1 and (5.34 ± 0.2) × 10−1 M−1 s−1, respectively, and in no case does added Ad=Ad or pentanol alter the reaction rate. The kinetic behavior is interpreted in terms of cyclization occurring directly from a 1:1 complex of Ad=Ad-Br+ and 10 or 11. The chiral induction for the bromocyclization of 10 promoted by AdAd-Br+ was measured at 20% e.e., the (−)-(S)-tetrahydrofurfuryl bromide being the dominant stereoisomer. Ad=Ad molecules substituted at one of the homoallylic carbons by an axial methyl group (12), or by two methyl groups (axial and equatorial), were synthesized and the 1H NMR spectra of their bromonium ions is given. These materials are not stable for prolonged times at room temperature. A limited kinetic study of the reaction of 12-Br+ and 4-pentenol indicated that the Br+ transfer is 500 times faster than the comparable transfer from Ad=Ad-Br+ to 4-pentenol. The possibility of using these materials to induce chiral bromocyclization is discussed. Keywords: bromonium ion, halonium, transfer, chiral, adamantylideneadamantane.

Substituent effect on solvolysis of 3-acetyl-1,3-diphenyltriazenes

1984 ◽  
Vol 49 (5) ◽  
pp. 1173-1181 ◽  
Author(s):  
Oldřich Pytela ◽  
Miroslav Pilný ◽  
Miroslav Večeřa
Keyword(s):  
Reaction Mechanism ◽  
Rate Constant ◽  
Substituent Effect ◽  
Aqueous Ethanol ◽  
Substituent Effects ◽  
Point Of View ◽  
Kinetics Of

Eleven symmetrically disubstituted 3-acetyl-1,3-diphenyltriazenes have been synthetized by anew method. The solvolysis kinetics of the title compounds has been measured in 20% aqueous ethanol at several temperatures. The results are discussed from the point of view of temperature and substituent effects on the solvolysis rate constant of the 3-acetyl-1,3-diphenyltriazenes and conclusions are drawn about the reaction mechanism.

1H NMR spectra and the conformation of 1,6 : 2,3- and 1,6 : 3,4-dianhydro-β-D-hexopyranoses and their derivatives

1979 ◽  
Vol 44 (6) ◽  
pp. 1965-1983 ◽  
Author(s):  
Miloš Buděšínský ◽  
Miloslav Černý ◽  
Tomáš Trnka ◽  
Soňa Vašíčková
Keyword(s):  
Hydrogen Bonds ◽  
1H Nmr ◽  
Torsion Angle ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Point Of View ◽  
Coupling Constants ◽  
H Nmr ◽  
Vicinal Coupling Constants ◽  
Intramolecular Hydrogen

The 1H NMR spectra of 1,6 : 2,3- and 1,6 : 3,4-dianhydro-β-D-hexopyranoses and their acetyl-, trichloroacetylcarbamoyl- and 2- or 4-deoxy derivatives were measured in hexadeuteriodimethyl sulfoxide or deuteriochloroform. In these solvents dianhydro derivatives assume the half-chair conformations 5H0 or 1H0 which are not distinctly affected by the presence of substituents. The effects of substituents on the chemical shifts and the adjusted relation for the dependence of the vicinal coupling constants on the torsion angle are discussed from the point of view of conformation and the interactions of the oxirane ring with the oxygen O(5) and O(6) of the 1,6-anhydropyranose skeleton. Intramolecular hydrogen bonds in free dianhydrohexopyranoses were measured and identified in tetrachloromethane solution.

Conformational structure of ethylene glycol dibenzoate. Vibrational and NMR spectra

1981 ◽  
Vol 46 (8) ◽  
pp. 1913-1929 ◽  
Author(s):  
Bohdan Schneider ◽  
Pavel Sedláček ◽  
Jan Štokr ◽  
Danica Doskočilová ◽  
Jan Lövy
Keyword(s):  
Ethylene Glycol ◽  
Vibrational Spectra ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Conformational Structure ◽  
Infrared And Raman Spectra ◽  
H Nmr ◽  
Liquid States ◽  
Crystalline Forms ◽  
C Nmr

It was found that three crystalline forms of ethylene glycol dibenzoate can be prepared. Infrared and Raman spectra of these three forms, as well as of the glassy and liquid states, were measured. From 3JHH coupling constants obtained by analysis of the 13C satellite band of the -CH2- group in 1H NMR spectra, and from the 3JCH coupling constants of the -CO.O.CH2- fragment obtained by analysis of the carbonyl band in 13C NMR spectra it was found that in the liquid state the -CH2-CH2- group exists predominantly in the gauche conformational structure, and the bonds C-O-C-C assume predominantly a trans orientation. The results of the analysis of NMR and vibrational spectra were used for the structural interpretation of conformationally sensitive bands in vibrational spectra of ethylene glycol dibenzoate.

Preparation and absolute configuration at C(20) of 21-nor-5α-chol-22-en-24→20-olide derivatives

1981 ◽  
Vol 46 (4) ◽  
pp. 917-925 ◽  
Author(s):  
Vladimír Pouzar ◽  
Miroslav Havel
Keyword(s):  
Absolute Configuration ◽  
Nmr Spectra ◽  
Lithium Salt ◽  
H Nmr ◽  
Chemical Correlation ◽  
Unsaturated Lactones

Reaction of the aldehyde I with the lithium salt of 1-(2-tetrahydropyranyloxy)-2-propyne yielded the compounds II and IV. From the compound II the lactone XII was prepared via the intermediates III and X, the lactone XVIII was prepared from the substance IV via the intermediates V and XVI. The unsaturated lactones XII and XVIII were also prepared by sulfenylation and dehydrosulfenylation of the saturated lactones XIII and XIX. Based on chemical correlation and 1H-NMR spectra analyses of the compounds II and IV, the lactone XII was assigned the 20R-configuration whereas the lactone XVIII was allotted the 20S-configuration.

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