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  • 1
    ISSN: 1434-4475
    Keywords: 13C Incremental system ; Substituted benzenes and naphthalenes ; INEPT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The aryl13C chemical shifts of Cl-substituted 4-amino-, 4-diazonium-N,N-dimethylanilines, N,N-dimethylanilines and differently substituted naphthalenes were assigned by means of different NMR methods. The assignments were compared with chemical shifts obtained by using empirical additivity relationship for mono substituted aromatic substances. As a means of substitutent interactions, the chemical shift difference between calculated and experimental values (Δδ c i ) has been used. In the presence of remarkable steric and electronic substituent interactions, large deviations from additivity (Δδ c i values up to 15.4 ppm) were found. Which originate primarily from steric interactions between the substitutents. In order to account therefore, correction increments have been developed by employing the Δδ c i values obtained from 1,2-disubstituted benzenes or naphthalenes. The13C chemical shifts of more than seventy substituted benzenes and naphthalenes have been predicted. The results corroborate that reasonable calculation of chemical shifts in sterically hindered benzenes is possible by using the extended additivity rule. The Δδ c i values are much lower and allow reasonable structural assignments. For external users of this incremental system, a computer program for IBM compatible PC/AT was developed. By means of this program, the13C chemical shifts for different benzenes and naphthalenes with or without 1,2-disubstituted correction increments will be calculated and the corresponding spectrum displayed. The program can assist the successful assignment of experimental13C chemical shifts.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0009-2940
    Keywords: Borate lithium (dimethylamino)trihydrido- ; TMEDA complex ; Dioxane complex ; 12-Crown-4 complex ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Li(Me2NBH3) (1) was prepared by deprotonation of Me2NH BH3 with LiBu and its solubility determined in various solvents. Compound 1 is unstable in most ethereal solvents and decomposes in a reversible reaction into LiH and Li-(Me2N—BH2—NMe2—BH3) (2). Five solvates of 1 were characterised by X-ray structure analysis. Li(Me2NH3) · TMEDA is a dimer in the solid state, and two units are connected to one another by B—H…Li bonds. The crystal structure of Li(Me2NBH3) · 0.5 dioxane is represented by layers consisting of tetrameric Li(Me2NBH3) units connected via dioxane molecules. Each Li atom is coordinated to one oxygen atom, one nitrogen atom, and two hydrogen atoms. Also Li(Me2NBH3) · 0.5 O2C3H6 forms an extended layer, however with pentacoordinated Li atoms which bear one oxygen, one nitrogen, and three hydrogen atoms. A similar layer structure was also found for Li(Me2NBH3) · O3C3H6 where each Li atom is bound to two oxygen atoms of different trioxane molecules, one nitrogen atom, and two hydrogen atoms. Finally, Li(Me2NBH3) · 12-crown-4 retains its molecular integrity in the solid state. Its Li atom is pentacoordinated by four oxygen atoms and one nitrogen atom.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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