Example 2: General procedure for synthesizing 2-fluoro-1,3-dimethylbenzene from 2,6-dimethylaniline
The diazotization of 2,6-dimethylaniline (2.3 g, 0.02 mol) was carried out in an Et3N-3HF system under the same conditions as for 2,4,6-trimethylaniline in Example 1. Upon initial addition of sodium nitrite (2.0 g, 0.03 mol), the color of the reaction mixture gradually changed from yellow to red. A small amount of tar is generated during the reaction, which can be easily separated by solvent extraction. The post-treatment was consistent with the description of 2,4,6-trimethylaniline. The organic layer was extracted from the aqueous phase using diethyl ether (150 mL), and the organic extract was dried over magnesium sulfate and fractionated by solvent to give an orange colored oil. The oily substance was distilled at 141-143 °C and atmospheric pressure to give the colorless liquid 1-fluoro-2,6-dimethylbenzene (2.0 g, 86.3% yield). The distillation process was completed in 1 hour.
The 1H NMR (CDCl3) spectrum of the product showed: δ 2.25 (2-CH3 and 6-CH3, d, J = 2.0 Hz, 6H); δ 6.91 (3-H and 5-H, dd, J = 8.3 Hz and J = 6.5 Hz, 2H); and δ 7.01 (4-H, t, J = 8.0 Hz, 1H).19F NMR (CDCl3) spectrum was found to be at δ 122.5 (1-F, ts, J = 6.5 Hz and J = 2.0 Hz) showed signals. Mass spectrometry analysis showed the molecular ion peak at m/z 124 and characteristic fragmentation peaks of 1-fluoro-2,6-dimethylbenzene were observed at m/z 109, 103, 96, 89, 83 and 77.
