15N NMR study of azo-hydrazo tautomerism: Past and present

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F62690094%3A18470%2F23%3A50019968" target="_blank" >RIV/62690094:18470/23:50019968 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S014372082200818X" target="_blank" >https://www.sciencedirect.com/science/article/pii/S014372082200818X</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.dyepig.2022.110896" target="_blank" >10.1016/j.dyepig.2022.110896</a>

Jazyk výsledku

angličtina

Název v původním jazyce

15N NMR study of azo-hydrazo tautomerism: Past and present

Popis výsledku v původním jazyce

5N NMR data (1J(15N, 1H) coupling constants and 15N chemical shifts) seem to be the most suitable ones to characterize azo-hydrazo tautomerism quantitatively. The reason is that nitrogen atoms of –Ndouble bondN−/−NH-N = fragments are directly involved in azo-hydrazo equilibrium.First data was measured and published in 1970 and 15N selectively enriched compounds had to be prepared since electro magnets were used in NMR spectrometers at that time providing very low resonance frequencies (from 60 to 100 MHz for protons) and have had, consequently, very low sensitivity. Moreover, a choice of 15N enriched 15N anilines was very limited and these compounds were relatively very expensive.At present, the situation is completely different. There has been a huge increase of NMR spectrometer frequencies used for measurement of NMR spectra and even routinely used NMR spectrometers having 400–600 MHz proton frequencies are sufficiently sensitive to provide 1J(15N, 1H) coupling constants and 15N chemical shifts at the natural abundance level of 15N. Inverse detection of resonances is now routinely used. The lower magnetogyric ratio of appropriate nucleus the higher signal enhancement is achieved: this is the very case of the 15N isotope. Theoretical enhancement factor obtained for inverse detection of 15N compared with direct one is ca 300! Application of cryoprobes where electronics is chilled either by liquid nitrogen or even liquid helium reducing electric noise allows to reduce time of accumulation from 8 to 16 times!Some representative examples are presented both from past to present demonstrating the fact that thorough analyses of NMR spectra allow determining the proper constitutions of compounds studies and excluding the wrong ones.

Název v anglickém jazyce

15N NMR study of azo-hydrazo tautomerism: Past and present

Popis výsledku anglicky

5N NMR data (1J(15N, 1H) coupling constants and 15N chemical shifts) seem to be the most suitable ones to characterize azo-hydrazo tautomerism quantitatively. The reason is that nitrogen atoms of –Ndouble bondN−/−NH-N = fragments are directly involved in azo-hydrazo equilibrium.First data was measured and published in 1970 and 15N selectively enriched compounds had to be prepared since electro magnets were used in NMR spectrometers at that time providing very low resonance frequencies (from 60 to 100 MHz for protons) and have had, consequently, very low sensitivity. Moreover, a choice of 15N enriched 15N anilines was very limited and these compounds were relatively very expensive.At present, the situation is completely different. There has been a huge increase of NMR spectrometer frequencies used for measurement of NMR spectra and even routinely used NMR spectrometers having 400–600 MHz proton frequencies are sufficiently sensitive to provide 1J(15N, 1H) coupling constants and 15N chemical shifts at the natural abundance level of 15N. Inverse detection of resonances is now routinely used. The lower magnetogyric ratio of appropriate nucleus the higher signal enhancement is achieved: this is the very case of the 15N isotope. Theoretical enhancement factor obtained for inverse detection of 15N compared with direct one is ca 300! Application of cryoprobes where electronics is chilled either by liquid nitrogen or even liquid helium reducing electric noise allows to reduce time of accumulation from 8 to 16 times!Some representative examples are presented both from past to present demonstrating the fact that thorough analyses of NMR spectra allow determining the proper constitutions of compounds studies and excluding the wrong ones.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10401 - Organic chemistry

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2023

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Dyes and pigments

ISSN

0143-7208

e-ISSN

1873-3743

Svazek periodika

209

Číslo periodika v rámci svazku

B

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

7

Strana od-do

"Article Number: 110896"

Kód UT WoS článku

000913167600004

EID výsledku v databázi Scopus

2-s2.0-85142311251