The conformational properties of seven-membered heterocycles: 1,3-dioxacyclohept-5-ene and its 2-substituted derivatives

1981 ◽  
Vol 59 (15) ◽  
pp. 2283-2289 ◽  
Author(s):  
R. St-Amour ◽  
M. St-Jacques
Keyword(s):  
Low Temperature ◽  
Dynamic Properties ◽  
Substituent Effects ◽  
Dynamic Processes ◽  
Stable Conformation ◽  
Spectral Changes ◽  
Conformational Properties ◽  
C Nmr

1,3-Dioxacycloheptene and its 2-CH3, 2-OCH3, 2-t-Bu, and 2,2-dimethyl derivatives were studied by 1H and 13C dnmr methods. Substituent effects and the interpretation of spectral changes in 13C nmr at low temperature allow the determination of the most stable conformation of these compounds (TB for 1–4b and C for 5b) and the characterization of the dynamic processes observed for 2b, 4b, and 5b. The differences between the conformational and dynamic properties of the above compounds and their benzo analogs are rationalized in terms of different torsional interactions in the two series.

Nuclear magnetic resonance characterization of the ring conformations of monosubstituted derivatives of 1,3-dioxa-5,6-benzocycloheptene

1983 ◽  
Vol 61 (1) ◽  
pp. 109-115 ◽  
Author(s):  
R. St-Amour ◽  
M. St-Jacques
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Substituent Effects ◽  
Steric Effects ◽  
Slow Exchange ◽  
Conformational Properties ◽  
Derivatives Of ◽  
Ring Conformations ◽  
Twist Boat

The conformational properties of 2-alkyl (Me, Et, i-Pr, and t-Bu) and 2-phenyl derivatives of 1,3-dioxa-5,6-benzocycloheptene (1) were studied by 13C dnmr. Analysis of slow exchange spectra at 100.6 MHz indicates that all derivatives except tert-butyl exist in an equilibrium of chair (major) and twist-boat (minor) conformations. Substituent effects on the position of the equilibrium are rationalized in terms of steric effects.

On the Characterization of Dynamic Properties of Random Processes by Spectral Parameters

2000 ◽  
Vol 67 (3) ◽  
pp. 519-526 ◽  
Author(s):  
G. Petrucci ◽  
M. Di Paola ◽  
B. Zuccarello
Keyword(s):  
Dynamic Properties ◽  
Time Derivative ◽  
Wide Band ◽  
Random Processes ◽  
Spectral Parameters ◽  
Unambiguous Determination ◽  
Power Spectral ◽  
Bandwidth Parameter

This paper deals with the general problem of directly relating the distribution of ranges of wide band random processes to the power spectral density (PSD) by means of closed-form expressions. Various attempts to relate the statistical distribution of ranges to the PSD by means of the irregularity factor or similar parameters have been done by several authors but, unfortunately, they have not been fully successful. In the present study, introducing the so-called analytic processes, the reasons for which these parameters are insufficient to an unambiguous determination of the range distribution and the fact that parameters regarding the time-derivative processes are needed have been explained. Furthermore, numerical simulations have shown that the range distributions depend on the irregularity factor and bandwidth parameter of both the process and its derivative. These observations are the basis for the determination of accurate relationships between range distributions and PSDs. [S0021-8936(00)02903-2]

scholarly journals The Electrophoretic and Spectroscopic Characterization of Hgb M

Blood ◽  
1958 ◽  
Vol 13 (10) ◽  
pp. 936-949 ◽  
Author(s):  
PARK S. GERALD
Keyword(s):  
Relative Concentration ◽  
Spectroscopic Characterization ◽  
Spectroscopic Studies ◽  
Spectral Curves ◽  
Spectral Changes ◽  
Electrophoretic Behavior ◽  
Patient Reported ◽  
High Concentrations

Abstract The hemoglobin (hgb) from a patient with Hgb M disease was resolved into two components by starch block electrophoresis (at pH 7.0-7.2) of the oxidized hemolyzate. One component was identified electrophoretically and spectroscopically as Hgb A, and the other as Hgb M. Methods for the determination of the relative concentration of Hgb M were given. In the patient reported, Hgb M was found to comprise approximately 30 per cent of the total hgb. Spectroscopic studies of electrophoreticably isolated Hgb M demonstrated that both the methgb and the cyanmethgb form were abnormal in their spectral curves. The reactions of the methgb form with low and high concentrations of cyanide were found to differ. The nature of the spectral changes were such as to indicate that some of the heme groups of the methgb form react abnormally and others apparently normally. The electrophoretic behavior of the patient’s hemolyzate after treatment with various combinations of cyanide and ferricyanide was consistent with this hypothesis. The differing reactivity of the heme groups was explained in the light of the biochemical genetics of the abnormal hemoglobins.

Substituent effects of phosphorus-containing groups on aromatic reactivity. Determination of substituent constants by 13C nuclear magnetic resonance spectroscopy

1977 ◽  
Vol 55 (21) ◽  
pp. 3681-3685 ◽  
Author(s):  
Tomasz A. Modro
Keyword(s):  
Substituent Effects ◽  
Resonance Spectroscopy ◽  
Benzene Derivatives ◽  
13C Nuclear Magnetic Resonance ◽  
Phosphorus Containing ◽  
Substituent Constants ◽  
Parameter Approach ◽  
Reactivity Determination ◽  
C Nmr

13C nmr spectra have been obtained for a series of benzene derivatives substituted with phosphorus-containing groups of the type PZ2, P(O)Z2, and P(S)Z2. Inductive and resonance substituent constants were determined from the shielding of meta and para carbon atoms according to the dual-substituent parameter approach. Possible mechanisms of substituent effects of PIII and PV derived functional groups are discussed and in some cases compared with effects of the analogous nitrogen derivatives.

scholarly journals Preparative Capillary GC for Characterization of Five Dracocephalum Essential Oils from Mongolia, and their Mosquito Larvicidal Activity

2016 ◽  
Vol 11 (10) ◽  
pp. 1934578X1601101
Author(s):  
Gülmira Özek ◽  
Nurhayat Tabanca ◽  
Mohammed M. Radwan ◽  
Sanduin Shatar ◽  
Altaa Altantsetseg ◽  
...  
Keyword(s):  
Essential Oils ◽  
Larvicidal Activity ◽  
System Structure ◽  
Capillary Gc ◽  
Adulticidal Activity ◽  
Fraction Collector ◽  
First Time ◽  
C Nmr

The chemical composition and mosquito larvicidal and adulticidal activity of five essential oils (EOs), Dracocephalum ruyschiana L. (DR), D. foetidum Bunge (DF), D. moldavica L. (DM), D. fruticulosum Steph. ex Willd. (DFr) and D. peregrinum L. (DP) were evaluated. Simultaneous GC-FID and GC-MS analyses revealed in the EOs of DR, DF and DM an unidentified compound (1) ([M+122], 5.4%, 57.9% and 74.0%, respectively). Therefore, we aimed to isolate compound 1 using Preparative Capillary GC (PCGC) connected to a Preparative Fraction Collector (PFC) system. Structure determination of 1 was determined by 1H- and 13C-NMR as p-mentha-1,8-dien-10-al (1, limonen-10-al). Other detected major constituents were thymol (34.0%) and carvacrol (6.1%) in DR; limonene (28.8%) in DF; cis-chrysanthenol acetate (29.1%) and trans-verbenol (5.0%) in DFr; and linalool (17.9%), trans-β-bergamotene (7.9%), (E)-nerolidol (7.7%) and eugenol (5.5%) in DP. The DFr, DP, DR and DM EOs produced 100% mortality to 1st instar larvae of Aedes aegypti L. at 250 ppm and DR and DM EO exhibited the strongest activity and killed 100% 1st instar larvae at 62.5 ppm. No adulticidal activity was observed against female Ae. aegypti. In the scope of the present study, for the first time isolation of limonen-10-al (1) from DR, DM, and DP EOs and larvicidal activity of five Dracocephalum EOs were reported.

Determination of the stable conformation of GABAA-benzodiazepine receptor bivalent ligands by low temperature NMR and X-ray analysis

2004 ◽  
Vol 14 (6) ◽  
pp. 1465-1469 ◽  
Author(s):  
Dongmei Han ◽  
F.Holger Försterling ◽  
Xiaoyan Li ◽  
Jeffrey R. Deschamps ◽  
Hui Cao ◽  
...  
Keyword(s):  
Low Temperature ◽  
Benzodiazepine Receptor ◽  
Bivalent Ligands ◽  
Stable Conformation ◽  
X Ray

Low temperature carbon-13 magnetic resonance detection of axial conformers in vinyl- and formylcyclohexane: a deshielding γ–gauche effect

1982 ◽  
Vol 60 (23) ◽  
pp. 2908-2913 ◽  
Author(s):  
G. W. Buchanan
Keyword(s):  
Magnetic Resonance ◽  
Low Temperature ◽  
Substituent Effects ◽  
Free Energies ◽  
Gauche Effect ◽  
High Preference ◽  
Resonance Detection ◽  
C Nmr

Using 50.3 MHz 13C nmr at 173 K, distinct resonances for axial conformers of vinyl- and formylcyclohexane have been obtained. Substituent effects for axial and equatorial substitution of these groups have been derived. A deshielding γ–gauche effect was found for the axial substituent carbon of formylcyclohexane, a result attributed to the high preference for rotamers in which the formyl proton does not sterically interfere with syn-axial protons at C-3 and C-5 of the ring. Conformational free energies for the vinyl and formyl groups have been estimated to be 1.49 and 0.84 kcal/mol respectively.

Synthesis and characterization of Δ-cis(N)-trans(O5)-RR sodium bis-((S)-α-alaninato-N-monopropionato)cobaltate(III) isomer

1986 ◽  
Vol 51 (10) ◽  
pp. 2109-2115
Author(s):  
Bohumil Hájek ◽  
Jana Ondráčková ◽  
František Jursík
Keyword(s):  
Absolute Configuration ◽  
Synthesis And Characterization ◽  
Mutual Position ◽  
Molecular Models ◽  
Visible Absorption ◽  
The Absolute ◽  
Circular Dichroïsm ◽  
C Nmr

Of the 12 possible diastereoisomers only Δ-cis(N)-trans(O5)-(RR)-Na[Co(alamp)2] isomer was isolated. Possible reasons explaining stereospecific coordination of ligand are discussed in terms of steric intra- and interligand interactions arising from the mutual position of -CH3 and N-CH2-CH2- groups. These exclude all isomers with SS or RS configuration of secondary nitrogen atoms. For the determination of the absolute configuration visible absorption, 1H, 13C NMR, circular dichroism and molecular models were employed.

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