Assignment of chemical shifts in benzohydroxamic acid and structure of its silylated derivatives by <sup>15</sup>N enrichment

Schraml, Jan; Blechta, Vratislav; Soukupová, Ludmila; Karban, Jindřich; Mindl, Jaromír

doi:10.1002/mrc.1217

Cited by 3 publications

(6 citation statements)

References 15 publications

(18 reference statements)

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“…Similar absolute values of these couplings were found in benzohydroxamic acid 1 J( 15 N-1 H) = 102.2 Hz, 1 J( 15 N-13 C) = 13.7 Hz, and 2 J( 15 N-13 C) = 11.2 Hz but in its disilylderivatives, which have Z-benzohydroximic structure, the 1 J( 15 N-13 C) coupling was estimated to be <0.6 Hz while 2 J( 15 N-13 C) = 10.6 Hz, and 3 J( 15 N-13 C) = 3 Hz. [8] …”

Section: Introductionmentioning

confidence: 97%

¹⁵N¹H and ¹⁵N–¹³C couplings in ¹⁵N‐enriched dihydroxamic acids

Schraml

Cígler

2008

Magnetic Reson in Chemistry

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(15)N-enriched dihydroxamic acids (HONHCO(CH(2))(n)CONHOH, n = 0, 1, and 2) were prepared and their spectra NMR ((1)H, (13)C, (15)N) recorded in dimethyl sulfoxide (DMSO) solutions with the aim of determining (15)N coupling constants ((15)N-(1)H and (15)N-(13)C). The results supplement chemical shifts published earlier and yield additional support to the structural conclusions derived from other NMR parameters. Notably, no trace of hydroximic structures could be found in the (15)N NMR spectra of these acids. The values of (15)N-(13)C coupling constants backed by theoretical calculations support the assignments made earlier for all of the major conformers and for the minor conformer of succinohydroxamic acid. The enrichment revealed that the minor component of malonodihydroxamic acid solution previously considered to be the ZE conformer is in fact the monohydroxamic acid (HOOC-CH(2)-CO-NH-OH).

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Section: Introductionmentioning

confidence: 97%

¹⁵N¹H and ¹⁵N–¹³C couplings in ¹⁵N‐enriched dihydroxamic acids

Schraml

Cígler

2008

Magnetic Reson in Chemistry

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“…Under these conditions, the OH line remains unresolved. 7 In other cases (such as the 2-chloro derivative), the splitting becomes visible on both lines at lower temperature, 283 K.…”

Section: Preliminary Experimentsmentioning

confidence: 96%

“…Hence following the reasoning of other investigators, 5 this observation is taken as an indication that each of the acids is present as only one conformer. Extending the assignment of NH and OH proton lines in benzohydroxamic acid 7 to all the acids studied here, the chemical shifts follow a simple Hammett-type dependence that will be further discussed below. In view of these dependences, it is reasonable also to assume that the ring substitution in para or meta position has little effect on the conformer preferences.…”

Section: Solution Chemical Shiftsmentioning

confidence: 96%

“…The CP/MAS spectra (the carbonyl carbon around υ165) support the hydroxamic structure only partially; in hydroximic structures (silylated hydroximic acids 30 ) the carbon would resonate around υ155 but could reach υ164 depending on geometry (E or Z isomers) and substitution. 7,31 …”

Section: Solid-state and Solution Structurementioning

confidence: 98%

“…5 Therefore, we have undertaken a study of the NMR spectra of ringsubstituted benzohydroxamic acids with particular attention to proton exchange. The study was facilitated by the recent confirmation 7 of the assignment of the NH and OH proton lines in the 1 H NMR spectrum.…”

Section: Introductionmentioning

confidence: 99%

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Ring‐substituted benzohydroxamic acids: ¹H, ¹³C and ¹⁵N NMR spectra and NHOH proton exchange

Schraml

Tkadlecová

Pataridis

et al. 2005

Magnetic Reson in Chemistry

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NMR spectra (1H, 13C, 15N) of para- and meta-substituted benzohydroxamic acids were studied in dry dimethyl sulfoxide solutions. The 13C chemical shifts were very close to those found by cross-polarization magic angle spinning in solids, the hydroxamic (not hydroximic) structure of which is unambiguous. The hydroxamic structure of these acids in DMSO solutions was proved independently by their 15N chemical shifts. The 15N and 1H chemical shifts of the NH-OH fragment showed excellent mutual dependences and dependences on the nature of the ring substituent. According to these dependences and ab initio energy calculations, all the acids assume the same Z conformation. Proton exchange between hydroxamic OH and NH groups in DMSO proceeded by both intra- and intermolecular exchange and the rates did not exhibit any simple relationship to the substituent constants.

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15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

Marek¹,

Lyčka²,

Kolehmainen³

et al. 2007

COC

133

110

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Since our previous review article (Curr. Org. Chem. 2002, 6, 35), significant improvements and an array of 15 N NMR applications in structural analysis have been published. This report aims to update coverage of improvements in methodology and various types of applications published over the period 2001 -2005. Substantial progress in cryogenic probe technology and the commercial availability of cryoprobes have facilitated the measurement of 15 N NMR parameters.The number of solid-state applications has increased significantly during the past few years. In contrast to our previous review, this article covers 15 N solid-state studies. The 15 N NMR chemical shifts of organic molecules are routinely measured by using cross-polarization magic-angle spinning (CP/MAS) techniques. The principal values of the chemical shift tensors can also be determined. 1 H-15 N and 2 H-15 N distance measurements made by means of 1 H detection are currently used in NMR crystallography.User friendly quantum chemical programs allow for the routine calculation of 15 N chemical shielding and indirect spinspin coupling constants, especially using density functional theory (DFT).Applications of 15 N NMR spectroscopy in various fields of chemistry are summarized here. Major sections represent tautomerism, complexation, protonation, and hydrogen bonding. The other topics comprise N-alkylation, N-oxidation, regioisomerism, and changes in configuration or conformation.

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Assignment of chemical shifts in benzohydroxamic acid and structure of its silylated derivatives by ¹⁵N enrichment

Cited by 3 publications

References 15 publications

¹⁵N¹H and ¹⁵N–¹³C couplings in ¹⁵N‐enriched dihydroxamic acids

¹⁵N¹H and ¹⁵N–¹³C couplings in ¹⁵N‐enriched dihydroxamic acids

Ring‐substituted benzohydroxamic acids: ¹H, ¹³C and ¹⁵N NMR spectra and NHOH proton exchange

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

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Assignment of chemical shifts in benzohydroxamic acid and structure of its silylated derivatives by 15N enrichment

Cited by 3 publications

References 15 publications

15N1H and 15N–13C couplings in 15N‐enriched dihydroxamic acids

15N1H and 15N–13C couplings in 15N‐enriched dihydroxamic acids

Ring‐substituted benzohydroxamic acids: 1H, 13C and 15N NMR spectra and NHOH proton exchange

15N NMR Spectroscopy in Structural Analysis: An Update (2001 - 2005)

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Product

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Assignment of chemical shifts in benzohydroxamic acid and structure of its silylated derivatives by ¹⁵N enrichment

¹⁵N¹H and ¹⁵N–¹³C couplings in ¹⁵N‐enriched dihydroxamic acids

¹⁵N¹H and ¹⁵N–¹³C couplings in ¹⁵N‐enriched dihydroxamic acids

Ring‐substituted benzohydroxamic acids: ¹H, ¹³C and ¹⁵N NMR spectra and NHOH proton exchange