Tieftemperatur ¹³C‐NMR.‐Spektren von ¹³C‐und ⁶Li‐markierten Chlor‐, Brom‐ und Jod‐Lithium‐Carbenoiden. Vorläufige Mitteilung

Abstract

Low Temperature 13 C‐NMR. Spectra of 13 C‐ and 6 Li‐Labelled Chloro‐, Bromo‐, and Iodo‐lithiumcarbenoids The 13 C‐NMR. spectra of tetrahydrofuran solutions of 16 chloro‐, bromo‐, and iodo‐ 6 lithio‐ and ‐ 7 lithio‐carbenoids with 13 C‐labelled methane, ethane, ethylene, and cyclopropane C‐skeletons have been measured at temperatures around − 100° (for examples see Fig. 1 and 2 ). Invariably, the exchange of hydrogen or halogen by lithium causes deshielding (Δδ, see Table 1 ) of the 13 C‐signal by up to 289 and 434 ppm, respectively, and decrease of 1 J ( 1 H, 13 C) and 1 J ( 13 C, 13 C) couplings (see Table 2 ) with the C‐atom of up to 104 and 30 Hz, respectively. The 1 J ( 6 Li, 13 C) and 1 J ( 7 Li, 13 C) coupling of ca. 17 and 45 Hz, respectively, obtained in ten cases (Table 1) is independant of the substitution pattern of the C‐skeleton and of the particular halogen atom.