m-Fluorotoluene → 2-Fluoro-4-methylbenzaldehyde

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100.89 g of aluminum chloride (mol. Wt. 133.34; 756.6 mmol) and about 503.54 g of 3-fluorotoluene (mol. Wt. 110.13; 4,572 mmol) were charged to a 2 liter Parr®-brand 4522 stainless steel reaction vessel. To this mixture was added 5 drops of concentrated HCl. The vessel was sealed, heated to 60° C., and purged three times with carbon monoxide with the pressure of the vessel increased to 200 psi for each purging. After the third purge, the vessel was vented and a final introduction of CO was made at a pressure of about 200 psi, the pressure at which the reaction was maintained for the total reaction time of about 17 hours (the reaction temperature was maintained at 60° C. for the duration as well). Once the reaction was complete, the resultant mixture (exhibiting a dark orange color) was poured into about 500 mL of ice water (which turned the solution a yellow color), to which was added 500 mL of cyclohexane. The top, organic layer was removed and washed three times with water using a separatory funnel and dried over magnesium sulfate. The residual organic phase was then distilled under vacuum to remove excess cyclohexane, 3-fluorotoluene, and left about 79.65 g of a benzaldehyde mixture consisting of 4-fluoro-2-methylbenzaldehyde (88.4%) and 2-fluoro-4-methylbenzaldehyde (11.6%) (mol. Wt. 138.14; 576.6 mmol; yield of approximately 76.2%).

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