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Assignment Range Comments CH3 CH2 CH C 5–35 ppm 5–45 ppm 25–60 ppm 30–60 ppm CH3, CH2, CH, and C can be differentiated by multipulse experiments (DEPT, APT), off-resonance decoupling, 2D CH correlation spectra, or based on relaxation times Lower shift values in three-membered rings CH3 CH2 CH 0.8–1.2 ppm 1.1–1.8 ppm 1.1–1.8 ppm Lower shift values in three-membered rings ...
The chemical shifts of sp3-hybridized carbon atoms can be estimated with the help of an additivity rule using the shift value of methane (-2.3 ppm) and increments (Z) for substituents in α, β, γ, and δ position (see next pages). Some substituents occupy two positions. Thus, the quaternary carbon atom c in the example given below is in δ position relative to the carbon atom a since the sp...
double bond equivalents ${\rm{ = 1 + \raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/ \kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} }}\sum_{\rm i}{\rm n}_{\rm i} ({\rm v}_{\rm i} - 2)$ ni: number of atoms of element i in molecular formula vi: formal valence of element i.
Fragmentation: Larger alkyl fragments (with Cn>4) are chiefly formed by direct cleavage. They dehydrogenate and undergo substantial H and skeleton rearrangements. Smaller alkyl fragments (C2 to C4) are mainly formed by secondary decomposition of higher alkyl fragments. Eliminations of groups from within the chain (and recombination of its ends) also occur.
The π→π* transition of conjugated double bonds is above ≈200 nm with typical intensities of the order of log ε ≈ 4. Its position can be estimated with the Woodward–Fieser rule. For cross-conjugated systems, the value for the chromophore absorbing at the longest wavelength has to be calculated.
The present data collection is intended to serve as an aid in the interpretation of molecular spectra for the elucidation and confirmation of the structure of organic compounds. It consists of reference data, spectra, and empirical correlations from 1H, 13C, 19F, and 31P nuclear magnetic resonance (NMR), infrared (IR), mass, and ultraviolet–visible (UV/Vis) spectroscopy. It is to be viewed as a supplement...
To estimate the 19F chemical shifts of substituted 6-ring heteroaromatics, the same increments, Zi, can be used as for substituted fluorobenzenes (see preceding page). However, different base values, Y (as given below), apply depending on the number and position of nitrogens and the position of the fluorine substituent in question.
This fourth edition of the highly successful and concise textbook contains about 20 % new data. Now included are chapters on 19F and 31P NMR as well as references to important Raman bands. With their unique approach of presenting - in the form of texts, tables, charts, and graphs - a succinct compilation of essential reference data for the interpretation of NMR, IR, UV/Vis, and mass spectra, the...
Die vorliegende Datensammlung soll bei der Interpretation von Molekülspektren zur Aufklärung und Bestätigung der Struktur organischer Verbindungen helfen. Sie besteht aus Referenzdaten, Spektren und empirisch gefundenen Regeln aus dem Bereich der 13C- und 1H-Kernresonanzspektroskopie (NMR), der Infrarotspektroskopie (IR), der Massenspektrometrie (MS) und der Spektroskopie im ultravioletten und sichtbaren...
Für Verbindungen, die ausschließlich C, H, O, N, S und Halogene enthalten, erlaubt das folgende Vorgehen eine schnelle und einfache Berechnung der Anzahl Doppelbindungsäquivalente: 1. O und zweiwertigen S aus der Formel entfernen 2. Halogene durch H ersetzen 3. Dreiwertigen N durch CH ersetzen 4. Der so erhaltene Kohlenwasserstoff CnHx wird mit dem gesättigten Kohlenwasserstoff CnH2n+2...
Fragmentierung: Größere Alkylfragmente (Cn>4) werden im Wesentlichen durch direkte Fragmentierung gebildet. Die Fragmente dehydrieren und zeigen umfangreiche Umlagerungen von H-Atomen und des Gerüsts. Dabei können sich Atomgruppen aus dem Inneren der Alkylkette unter Rekombination der Enden abspalten. Kleinere Alkylfragmente (C2 bis C4) werden meist durch Zerfall höherer Fragmente gebildet.
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