Influence of molecular structure on helicoidal structure and NMR spectra of chiral liquid crystalline esters

Three-ring chiral liquid crystalline compounds, forming antiferroelectric phase, differing in the structure of alkyl chain and in the substitution of benzene ring by fluorine atoms were studied. The measurements of helical pitch, based on the selective light reflection phenomenon, were performed as well as 1H and 13C NMR spectra at room temperature were registered. The influence of molecular structure as well as the type of helicoidal structure on the chemical shift of signals coming from chiral center was observed. Keywords: liquid crystals, helicoidal structure, nuclear magnetic resonance, antiferroelectric phase

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Influence of alkyl chain length and fluorine atoms substitution on infrared spectra of chiral liquid crystalline esters

Bulletin of the Military University of Technology ◽

10.5604/01.3001.0010.5391 ◽

2017 ◽

Vol 66 (3) ◽

pp. 63-74

Author(s):

Anna Drzewicz ◽

Marzena Tykarska ◽

Magdalena Żurowska

Keyword(s):

Molecular Structure ◽

Infrared Spectroscopy ◽

Liquid Crystals ◽

Infrared Spectra ◽

Crystalline Phase ◽

Liquid Crystalline ◽

Alkyl Chain ◽

Alkyl Chain Length ◽

Rigid Core ◽

Helicoidal Structure

The infrared spectra were registered for series of three-ring liquid crystalline esters, differing in the structure of alkyl chain, in the substitution of benzene ring by fluorine atoms and in the type of helicoidal structure in the chiral smectic CA phase with antiferroelectric properties. The influence of molecular structure on the shift of signals coming from carbonyl group, located in the rigid core, was observed. Keywords: liquid crystals, helicoidal structure, chiral smectic CA phase, antiferroelectric crystalline phase, infrared spectroscopy

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Koenigs-Knorr Synthesis of Natural and Potential Metabolites of Cholesteryl Hexosides

Revista de Chimie ◽

10.37358/rc.08.10.1987 ◽

2008 ◽

Vol 59 (10) ◽

Author(s):

Silvia Iga ◽

Dumitru Petru Iga ◽

Nicoleta Florentina Predescu ◽

Adrian Iga ◽

Alina Nicolescu

Keyword(s):

High Temperature ◽

Spectroscopic Data ◽

Nmr Spectra ◽

Room Temperature ◽

General Scheme ◽

Chlorosulfonic Acid ◽

13C Nmr Spectra ◽

1H And 13C Nmr ◽

Characteristic Methods ◽

Per Se

The following glycosides of cholesterol have been synthesized: a-D-galactofuranoside, �-D-glucopyranoside, bis-sulfo-3,6-b-D-glucopyranoside. 1-a-Bromides of protected sugars were used as glycosylation donors: tetra-O-benzoyl-D-galactofuranosyl and tetra-O-acetyl-D-glucopyranosyl. Peracylated sugars, i. e., precursors of sugar bromides, were synthesized in conditions that preferentially facilitated the envisaged ring: room temperature for pyranosic ring, high temperature for furanosic one. Constantly, cadmium carbonate was used as promotor. As a general scheme of work, glycosylation mixture was submitted to Zemplen saponification and the obtained glycolipids have been separated by characteristic methods. The glucoside of cholesterol was sulfated with chlorosulfonic acid in pyridine. Neutral or acidic glycolipids were characterized per se by chromatographic and chemical means as well as by IR spectroscopy. Sulfatide and galactocerebroside of rat brain and ganglioside GM4 of rooster testis were used as reference compounds. Alternatively, the synthesized glycosides were peracetylated and their 1H and 13C NMR spectra registered. New NMR spectroscopic data are presented for cholesteryl-a-D-galactofuranoside and -bis-sulfo-6-b-D-glucopyranoside.

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The molecular structure and vibrational, 1H and 13C NMR spectra of lidocaine hydrochloride monohydrate

Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy ◽

10.1016/j.saa.2015.07.060 ◽

2016 ◽

Vol 152 ◽

pp. 92-100 ◽

Cited By ~ 6

Author(s):

Hassan M. Badawi ◽

Wolfgang Förner ◽

Shaikh A. Ali

Keyword(s):

Molecular Structure ◽

13C Nmr ◽

Nmr Spectra ◽

Lidocaine Hydrochloride ◽

13C Nmr Spectra ◽

1H And 13C Nmr ◽

Hydrochloride Monohydrate

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Synthesis of Novel N-Acylhydrazones and Their C-N/N-N Bond Conformational Characterization by NMR Spectroscopy

Molecules ◽

10.3390/molecules26164908 ◽

2021 ◽

Vol 26 (16) ◽

pp. 4908

Author(s):

Rubina Munir ◽

Noman Javid ◽

Muhammad Zia-ur-Rehman ◽

Muhammad Zaheer ◽

Rahila Huma ◽

...

Keyword(s):

13C Nmr ◽

Nmr Spectra ◽

Room Temperature ◽

Aromatic Aldehydes ◽

Spectral Studies ◽

13C Nmr Spectra ◽

1H And 13C Nmr ◽

Mass Spectral ◽

Nmr Techniques ◽

Ft Ir

In this article, a synthesis of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides and their structural interpretation by NMR experiments is described in an attempt to explain the duplication of some peaks in their 1H- and 13C-NMR spectra. Twenty new 6-methyl-1H-pyrazolo[3,4-b]quinoline substituted N-acylhydrazones 6(a–t) were synthesized from 2-chloro-6-methylquinoline-3-carbaldehyde (1) in four steps. 2-Chloro-6-methylquinoline-3-carbaldehyde (1) afforded 6-methyl-1H-pyrazolo[3,4-b]quinoline (2), which upon N-alkylation yielded 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetate (3). The hydrazinolysis of 3 followed by the condensation of resulting 2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazide (4) with aromatic aldehydes gave N-acylhydrazones 6(a–t). Structures of the synthesized compounds were established by readily available techniques such as FT-IR, NMR and mass spectral studies. The stereochemical behavior of 6(a–t) was studied in dimethyl sulfoxide-d6 solvent by means of 1H NMR and 13C NMR techniques at room temperature. NMR spectra revealed the presence of N’-(benzylidene)-2-(6-methyl-1H-pyrazolo[3,4-b]quinolin-1-yl)acetohydrazides as a mixture of two conformers, i.e., E(C=N)(N-N) synperiplanar and E(C=N)(N-N)antiperiplanar at room temperature in DMSO-d6. The ratio of both conformers was also calculated and E(C=N) (N-N) syn-periplanar conformer was established to be in higher percentage in equilibrium with the E(C=N) (N-N)anti-periplanar form.

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Some Considerations Regarding the 1H and 13C Spectra of 4-(1-azulenyl)-2,6-bis(2-heteroaryl-vinyl)- pyrylium and Pyridinium and their Corresponding Pyridines

Revista de Chimie ◽

10.37358/rc.18.1.6045 ◽

2018 ◽

Vol 69 (1) ◽

pp. 64-69

Author(s):

Liviu Birzan ◽

Mihaela Cristea ◽

Constantin C. Draghici ◽

Alexandru C. Razus

Keyword(s):

Double Bond ◽

13C Nmr ◽

Nmr Spectra ◽

Chemical Shifts ◽

Pyridinium Salts ◽

13C Nmr Spectra ◽

1H And 13C Nmr ◽

Pyrylium Salts

The 1H and 13C NMR spectra of several 2,6-diheteroarylvinyl heterocycles containing 4-azulenyl moiety were recorded and their proton and carbon chemical shifts were compared with those of the compounds without double bond between the heterocycles. The influence of the nature of central and side heterocycles, molecule polarization and anisotropic effects were revealed. The highest chemical shifts were recorded for the pyrylium salts and the lowest at pyridines, but in the case of the pyridinium salts, the protons chemical shifts at the central heterocycle are more shielded due to a peculiar anisotropy of the attached vinyl groups.

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