Substituent‐Induced chemical shifts of 2‐phenylthiazolidines—<sup>1</sup>H NMR study

Umarani, R.

doi:10.1002/mrc.1260280902

Cited by 3 publications

(2 citation statements)

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“…The above situation describes that the reactions (eqs. [3] and [4]) are stoichiometrically termolecular but kinetically second order and the expected rate equation is then eq. [ 5 ] , where a is the concentration of the nucleophiles (PT), b is the concentration of the EBA or PB, and x is the concentration of EBA or PB reacted in time t. The rate constants for various meta-and para-substituted 2-phenylthiazolidines reveal that electrondonating substituents increase the reaction rate while electron-attracting substituents decrease it.…”

Section: Resultsmentioning

confidence: 99%

Structure–reactivity correlations of substituted 2-phenylthiazolidines

Umarani¹,

Radhakrishnan²

1992

Can. J. Chem.

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R. UMARANI and G. RADHAKRISHNAN. Can. J. Chem. 70, 2009 (1992. Systematic investigations of the kinetics of the reactions of ethyl bromoacetate (EBA) and of picryl bromide (PB) with 2-phenylthiazolidines (PT) in 100% ethanol were undertaken at 30, 35, 40, and 45°C. The most incisive information concerning the Hammett equation comes from the extensive studies on the substituted 2-phenylthiazolidines, establishing linear Hammett plots with negative p values. The kinetic data, plotted in a Bransted fashion against pK, of the corresponding thiazolidinium ions, yield linear relationships. The activation parameters were computed. The linear relationships between AHf and ASf signify a consistent mechanism throughout the series. [Traduit par la redaction]

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Section: Resultsmentioning

confidence: 99%

Structure–reactivity correlations of substituted 2-phenylthiazolidines

Umarani¹,

Radhakrishnan²

1992

Can. J. Chem.

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“…The data still fitted well with the experimental values but the correlation worsened on going from chlorine to bromine and iodine. Umarani,11 in a study of 2-phenylthiazolidines, again correlated the SCS of several different substituents to the Hammett coefficients and the Swain-Lupton reactivity models. Including the halogens gave much poorer correlation coefficients for this system.…”

Section: Introductionmentioning

confidence: 97%

¹H chemical shifts in NMR. Part 20 — Anisotropic and steric effects in halogen substituent chemical shifts (SCS), a modelling and ab initio investigation

Abraham

Mobli

Smith

2004

Magnetic Reson in Chemistry

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The 1H NMR spectra of 1-halonaphthalenes were recorded and assigned. These data together with the known 1H chemical shifts of the halobenzenes and of H-5 in 4-halophenanthrenes were used to investigate different models of halogen SCS using the CHARGE program. Good agreement was obtained with the observed shifts for the fluoro compounds, but a new model which included the anisotropy of the C-X bond (X = Cl, Br, I) and steric and electric field effects was required to give an accurate description of the observed chemical shifts for the other halogens. A previous observation of an anomalous 1H SCS on the meta protons in halobenzenes was further investigated using the 1-halonaphthalenes plus the observed 1H shifts of a number of 2-substituted bromobenzenes. The meta SCS of the bromo substituent in the bromobenzenes was only observed on H-5. When a substituent was attached to C-2, H-3 showed no appreciable effect. This remarkable effect was investigated by CHARGE and GIAO calculations and shown to be due to the pi-electron system. It was reproduced in CHARGE as a gamma effect from the C-X carbon atom. The observed 1H chemical shifts in the above compounds were compared with those calculated by CHARGE, the GIAO technique and by the ACD database program. The recommended ab initio basis set for the iodo compounds (Lan12DZ) gave very poor calculated shifts, which suggests that 1H chemical shifts of fourth-row atoms when calculated with the GIAO technique should be viewed with caution. In contrast, the recommended 6-31G** basis set with the B3LYP technique in the Gaussian98 program gave calculated values in reasonable agreement with the observed data, as did the ACD package. These different prediction methods were compared by pie charts, scatter plots and r.m.s. errors and the CHARGE program was shown to be more accurate for the compounds considered here than the other two methods. The different philosophies of these programs are discussed together with the results obtained.

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Substituent‐induced chemical shift ¹³C NMR study of substituted 2‐phenylthiazolidines

Umarani

1992

Magnetic Reson in Chemistry

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The analysis of the 13C NMR chemical shifts of 16 substituted 2‐phenylthiazolidines shows that the 1,3‐thiazolid‐2‐yl group exerts a deshielding effect at the ipso carbon (C‐1′) and shielding effects at the ortho and para positions of the benzene ring (C‐2′ and C‐4′), and that the transmission of the resonance effect from the substituents in the phenyl ring to the benzylic carbon (C‐2) in the thiazolidine heterocycle is diminished by the polarizable nitrogen and sulphur atoms.

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Substituent‐Induced chemical shifts of 2‐phenylthiazolidines—¹H NMR study

Cited by 3 publications

References 7 publications

Structure–reactivity correlations of substituted 2-phenylthiazolidines

Structure–reactivity correlations of substituted 2-phenylthiazolidines

¹H chemical shifts in NMR. Part 20 — Anisotropic and steric effects in halogen substituent chemical shifts (SCS), a modelling and ab initio investigation

Substituent‐induced chemical shift ¹³C NMR study of substituted 2‐phenylthiazolidines

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Substituent‐Induced chemical shifts of 2‐phenylthiazolidines—1H NMR study

Cited by 3 publications

References 7 publications

Structure–reactivity correlations of substituted 2-phenylthiazolidines

Structure–reactivity correlations of substituted 2-phenylthiazolidines

1H chemical shifts in NMR. Part 20 — Anisotropic and steric effects in halogen substituent chemical shifts (SCS), a modelling and ab initio investigation

Substituent‐induced chemical shift 13C NMR study of substituted 2‐phenylthiazolidines

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Substituent‐Induced chemical shifts of 2‐phenylthiazolidines—¹H NMR study

¹H chemical shifts in NMR. Part 20 — Anisotropic and steric effects in halogen substituent chemical shifts (SCS), a modelling and ab initio investigation

Substituent‐induced chemical shift ¹³C NMR study of substituted 2‐phenylthiazolidines