Exchange of amide protons with deuterium results in changes of 13 C chemical shifts for carbon atoms near the site of substitution (CH{N and N{C|O). There is a measurable decrease in the isotopic shifts of CH{N for cycloalkylacetamides as ring size increases from 3 to 8 and for lactams as ring size
First experimental determination of two-bond 13C isotopic effects on 1H NMR chemical shifts
✍ Scribed by Juan Félix Espinosa; Teodor Parella
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- French
- Weight
- 174 KB
- Volume
- 49
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
For the first time, a simple NMR methodology is proposed for the accurate determination of the effect of the substitution of 12 C by 13 C on the chemical shifts of protons separated by two-bonds in small molecules in their natural abundance.
📜 SIMILAR VOLUMES
Two-bond deuterium-induced isotope effects ('A) have been studied in several neutral x-systems (64dimethylfulvene, cyclohexene and cyclohexa-1,ldiene). Isotope effects on the 13C shifts of adjacent carbons are invariably to higher field, and vary from -84 to -139 ppb. In combination with literature
## Abstract A series of intramolecularly hydrogen‐bonded enamines, enols and enethiols with ester carbonylic, ketonic carbonylic, thioester carbonylic, nitro and sulphoxide acceptors were investigated to obtain ^13^C chemical shifts and deuterium isotope effects. Results from 33 new compounds and s
## Abstract The one‐ and two‐bond ^13^C isotope shifts, typically −1.5 to −2.5 ppb and −0.7 ppb respectively, in non‐cyclic aliphatic systems and up to −4.4 ppb and −1.0 ppb in glucose cause effects that need to be taken into account in the adaptive NMR spectral library‐based quantification of the
17O chemical shifts were measured in 40 enamines activated in the b-position by CxO, COO, NO 2 , SO and groups. Data for the oxygen-containing series of o-hydroxyacyl aromatics are also included for com-SO 2 parison. Intramolecular hydrogen bonding in the enamines is discussed in terms of the accept