EFFECTS ON THE N.M.R. SPECTRA OF THE STEREOCHEMISTRY OF 3,4-DIARYLADIPIC ESTERS AND 1,2-DIARYLCYCLOPENTANES

1964 ◽  
Vol 42 (4) ◽  
pp. 867-877 ◽  
Author(s):  
D. Y. Curtin ◽  
S. Dayagi
Keyword(s):  
Methyl Ester ◽  
Trans Isomer ◽  
Alternative Explanation ◽  
Ring Current ◽  
Effect Of Temperature ◽  
Aromatic Rings ◽  
Benzene Rings ◽  
Cis And Trans ◽  
Related Compounds

Examination of the n.m.r. spectra of cis- and trans-1,2-diphenylcyclopentane and 3,4-diphenylcyclopentanone substituted in the para positions of both rings with methoxyl, methyl, and chloro substituents has shown that the previous explanation (1) of the effect of temperature on the n.m.r. spectra of 1,2-diphenylcyclopentane and 3,4-diphenylcyclopentanone (unsubstituted) was incorrect. The n.m.r. spectra provide no evidence of restriction of rotation of the aromatic rings of these compounds. An alternative explanation is offered.Comparison of the spectra of the compounds above and those of meso- and dl-3,4-diphenyl-adipic esters with the para substituents mentioned leads to the observation that in the dl-adipates and the cis-cyclopentanes the position of absorption of the protons ortho to the central structure (HR) is shifted to higher field compared to the corresponding meso or trans isomer by an amount ranging from 0.2 to 0.7 p.p.m. The protons ortho to the substituent X (HX) are also shifted to higher field but by only about 0.1 p.p.m.Shifts of the benzylic protons of the trans-cyclopentanes and cyclopentanones to higher field amount to 0.3–0.6 p.p.m. in agreement with previous work (1, 34). The corresponding shift of the benzylic protons of the meso-adipic esters is only 0.1–0.2 p.p.m. The methylene protons and the methyl ester protons of the meso-adipates are also shifted to higher field by about 0.3 and 0.2 p.p.m. respectively.These shifts seem adequately explained in terms of ring current effects of the benzene rings and lead to the possibility of obtaining detailed information concerning the stereochemistry of such substances. They are of immediate value in making configurational assignments to related compounds.

The High Resolution NMR Spectra of Pesticides. II. The DDT-Type Compounds

1969 ◽  
Vol 52 (5) ◽  
pp. 1074-1092 ◽  
Author(s):  
L H Keith ◽  
A L Alford ◽  
A W Garrison
Keyword(s):  
Nuclear Magnetic Resonance ◽  
High Resolution ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Aromatic Rings ◽  
Nuclear Magnetic Resonance Spectra ◽  
High Resolution Nmr ◽  
Related Compounds ◽  
Deshielding Effect

Abstract The high resolution nuclear magnetic resonance spectra of the DDT class of pesticides and related compounds are discussed, including a study of the resonances of the aromatic protons as they are affected by various substiluents. The CCl3 moiety on the α-carbon strongly deshields the ortho protons on the aromatic rings, and this deshielding effect is greatly enhanced by substitution of a chlorine ortho rather than para on the aromatic ring. These deshielding effects are explained by a consideration of the electronegativity of the substituents and the stereochemistry of the molecule. The chemical shifts and coupling constants are tabulated.

scholarly journals N′-(3-Hydroxybenzylidene)-4-methylbenzohydrazide

2012 ◽  
Vol 68 (6) ◽  
pp. o1816-o1816
Author(s):  
Ji-Lai Liu ◽  
Ming-Hui Sun ◽  
Jing-Jun Ma
Keyword(s):  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Title Compound ◽  
Crystal Packing ◽  
Aromatic Rings ◽  
Π Interactions ◽  
Compound C ◽  
Centroid Distance ◽  
Benzene Rings

The title compound, C15H14N2O2, was obtained from the reaction of 3-hydroxybenzaldhyde and 4-methylbenzohydrazide in methanol. In the molecule, the benzene rings form a dihedral angle of 2.9 (3)°. In the crystal, N—H...O and O—H...O hydrogen bonds link the molecules into layers parallel to (101). The crystal packing also exhibits π–π interactions between the aromatic rings [centroid–centroid distance = 3.686 (4) Å].

scholarly journals Reaction of cis- and trans-Dichlorotetra(Dimethylsulfoxide)Ruthenium(II) With the Antiviral Drug Acyclovir

2000 ◽  
Vol 7 (6) ◽  
pp. 325-334 ◽  
Author(s):  
Aglaia Koutsodimou ◽  
Giovanni Natile
Keyword(s):  
Trans Isomer ◽  
Early Stage ◽  
Antiviral Drug ◽  
Metallic Substrate ◽  
Purine Base ◽  
Coordination Environment ◽  
Molar Ratios ◽  
Discrete Amount ◽  
Cis And Trans ◽  
Cis Isomer

NMR was used to investigate the reaction of cis- and trans-[RuCl2(DMSO)4] with the antiviral drug acyclovir, a guanine derivative containing the acyclic (2-hydroxo) ethoxymethyl pendant linked to N(9). Studies were performed in aqueous solutions at ambient temperature and at 37 °C, and at various molar ratios. Both isomers yielded two compounds, a monoadduct and a bisadduct, the relative yields being dependent upon the metal to ligand concentration ratios. The products derived from the two Ru isomers displayed identical NMR spectra, suggesting that they have the same coordination environment, however the rate of formation of the monoadduct was higher in the case of the trans isomer than in the case of the cis isomer, while the rate of conversion of the monoadduct into the bisadduct appeared to be similar in both cases. As a consequence in the case of the trans isomer there is accumulation of monoadduct in the early stage of the reaction, whose concentration afterwards decreases with the progress of the reaction. As for platinum, also for ruthenium the preferred binding site is N(7) of the purine base, however, in the case of ruthenium a discrete amount of bisadduct is formed even in the presence of an excess of metallic substrate with respect to the acyclovir ligand; under similar conditions a platinum substrate would have given, nearly exclusively, the monoadduct.

scholarly journals How Aromatic Are Molecular Nanorings? The Case of a Six-Porphyrin Nanoring

2021 ◽  
Author(s):  
irene casademont-reig ◽  
Raúl Guerrero-Avilés ◽  
Eloy Ramos-Cordoba ◽  
Miquel Torrent-Sucarrat ◽  
Eduard Matito
Keyword(s):  
Low Temperatures ◽  
Ring Current ◽  
Computational Method ◽  
Oxidation States ◽  
Aromatic Rings ◽  
Persistent Currents ◽  
Conjugated Molecules ◽  
Strong Magnetic Fields ◽  
The Poor ◽  
Computational Calculations

<div> <div> <div> <p>Large conjugated rings give rise to novel promising structures that can sustain persistent currents at low temperatures even in the presence of strong magnetic fields. One of the most interesting such molecules was recently synthesized [Anderson et al., Nature, 2017, 541, 3512] in the form of a six-porphyrin nanoring structure, which, according to the authors, in its +6-oxidation state (c-P66+) sustained an aromatic ring current involving 78π electrons; one of the largest aromatic rings ever produced. In this paper, we have provided compelling evidence that this molecule is not aromatic, as it was incorrectly inferred from computational calculations that suffer from large delocalization errors. A thorough analysis of four oxidation states of the six-porphyrin nanoring re- veals that the main reason behind the poor aromaticity of these nanorings is the low delocalization in the transition from the porphyrins to the bridging butadiyne linkers, which disrupts the overall conjugated circuit. These results highlight the importance of choosing an adequate computational method to study large conjugated molecules and the appropriate aromaticity descriptors to identify the part of the molecule that is responsible for the loss of aromaticity. We believe the strategy here employed will be helpful in designing new large aromatic molecular nanorings. </p> </div> </div> </div>

scholarly journals Crystal stucture of methyl 2-({[2-(methoxycarbonyl)phenyl]carbamoyl}amino)benzoate

2015 ◽  
Vol 71 (5) ◽  
pp. o297-o298 ◽  
Author(s):  
Hasna Yassine ◽  
Mostafa Khouili ◽  
Lahcen El Ammari ◽  
Mohamed Saadi ◽  
El Mostafa Ketatni
Keyword(s):  
Hydrogen Bonds ◽  
Dihedral Angle ◽  
Title Compound ◽  
Molecular Conformation ◽  
Dihedral Angles ◽  
Aromatic Rings ◽  
Compound C ◽  
Benzene Rings

In the title compound, C17H16N2O5, the dihedral angles between the central urea [N—C(=O)—N] fragment and its attached benzene rings are 20.20 (14) and 24.24 (13)°; the dihedral angle between the aromatic rings is 42.1 (1)°. The molecular conformation is consolidated by two intramolecular N—H...O hydrogen bonds, which both generateS(6) rings. In the crystal, inversion dimers linked by pairs of C—H...O interactions generateR22(14) loops. The dimers are linked by further C—H...O interactions into (011) sheets.

Structure et réactivité. IV. Diastéréosélectivité de la réduction de cétones par le borohydrure de sodium. De l'influence de l'effet de champs de substituants polaires éloignés

1979 ◽  
Vol 57 (21) ◽  
pp. 2823-2826 ◽  
Author(s):  
Jean-Pierre Aycard ◽  
Ronald Lafrance ◽  
Bernard Boyer
Keyword(s):  
Trans Isomer ◽  
Cyano Group ◽  
Specific Effect ◽  
Group Effect ◽  
Stable Isomer ◽  
Free Enthalpy ◽  
Steric Strain ◽  
Experimental Values ◽  
Cis And Trans

The cyano group effect on diastereoselectivity is studied through the reduction of cis and trans 3-R 4-cyano cyclohexanones with NaBH4; the diastereoselectivity (zero for R = H) is 74 and 62% respectively (R = CH3) and 74 and 50% (R = (CH3)3C), the more stable isomer being always the major one. These stereoselectivities are rationalized from the experimental values of free enthalpy between conformers and from the diastereoselectivities of the 3-t-butyl (and 4-t-butyl) cyclohexanones, cis 3,5-dimethyl and 3,3,5-trimethyl cyclohexanones, without taking account of a cyano group specific effect. The decrease in diastereoselectivity for R = (CH3)3C (trans isomer) is associated with deformation induced by steric strain between the substituents.

[1H,15N] N.M.R. Kinetic Studies of Reactions of cis- and trans-[PtCl2(15NH3)(c-C6H1115NH2)] with Guanosine 5'-Monophosphate

1999 ◽  
Vol 52 (3) ◽  
pp. 173 ◽  
Author(s):  
Sarah J. Barton ◽  
Kevin J. Barnham ◽  
Abraha Habtemariam ◽  
Urban Frey ◽  
Rodney E. Sue ◽  
...  
Keyword(s):  
Trans Isomer ◽  
Active Metabolite ◽  
Kinetic Studies ◽  
Trans Influence ◽  
Trans Complex ◽  
Kinetics Of Reaction ◽  
Cis And Trans ◽  
Kinetics Of ◽  
Cis Isomer ◽  
Amine Ligand

cis-[PtCl2(15NH3)(c-C6H11NH2)] is an active metabolite of the oral platinum(IV) anticancer drug cis,trans,cis-[PtCl2(CH3CO2)2(NH2)(c-C6H11NH2)]. Since it is likely that guanine bases on DNA are targets for this drug, we have analysed the kinetics of reaction of this platinum(II) metabolite with guanosine 5′-monophosphate (5′-GMP) at 310 K, pH 7, using [1H, 15N] n.m.r. methods. Reactions of the trans isomer are reported for comparison. The reactions proceed via aquated intermediates, and, for the cis isomer, the rates of aquation and substitution of H2O by 5′-GMP are 2-5 times faster trans to the amine ligand (c-C6H11NH2) compared to trans to NH3 for both the first and second steps. For the trans complex, the first aquation step is c. 3 times faster than for the cis complex, as expected from the higher trans influence of Cl¯, whereas the rate of the second aquation step (trans to N7 of 5′-GMP) is comparable to that trans to NH3. These findings have implications for the courses of reactions with DNA.

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