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443-82-3

Example 5: Synthesis of 2,3-dimethylfluorobenzene 1. Diazotization reaction: 2,3-dimethylaniline (2.3 g, 0.02 mol) was slowly added to Et3N-3HF (30 cm3) at 0 °C. Subsequently, sodium nitrite (2.0 g, 0.03 mol) was added in batches with the aid of ultrasound and significant gas release was observed for about 25 min. The reaction mixture gradually changed from clear to yellow and finally to dark color due to tar generation. 2. Post-treatment: the brown reaction mixture was poured into water (150 cm3) and extracted with ether (180 cm3 x 2). The remaining tar-like substance was transferred to Soxhlet extractor and extracted continuously with ether (30cm3) for 24 hours. All the ether extracts were combined and dried with magnesium sulphate and subsequently the ether was removed by fractional distillation to give a brown oily substance. 3. purification: the above oily substance was distilled at 142-143°C (atmospheric pressure) to give 1-fluoro-2,3-dimethylbenzene (1.47 g, 63.4% yield) as a clear liquid. 4. Characterization: - 1H NMR (CDCl3) δ: 2.18 (d, J = 2.0 Hz, 3H, 2-CH3), 2.28 (s, 3H, 3-CH3), 6.88 (t, J = 7.6 Hz, 1H, 6-H), 6.91 (d, J = 7.6 Hz, 1H, 4-H), 7.03 (q, J = 8.0 Hz and J = 6.0 Hz, 1H, 5 -H). - 19F NMR (CDCl3) δ: 118.3 (tq, J = 7.6Hz and J = 2.0Hz, 1-F). - Mass spectrum: molecular ion peak at m/z 124, and fragmentation peaks at m/z 109, 101, 96, 86, 83 and 77, consistent with the expected fragmentation pattern of 1-fluoro-2,3-dimethylbenzene.