4-Methylbenzaldehyde is the aromatic aldehyde with the formula CH3C6H4CHO. It is a colorless liquid. Commercially available, it may be prepared from the Friedel-Crafts formylation of toluene with carbon monoxide and hydrogen chloride under Gattermann-Koch conditions. 4-Methylbenzaldehyde has a cherry-like scent similar to benzaldehyde, and finds some use in the fragrance industry.
4-Methylbenzaldehyde is a precursor to terephthalic acid, which is used to make various plastics.
p-Tolualdehyde is used in the flavoring/fragrance industry because of its cherry/almond flavor/aroma and it is GRAS regulated for these purposes. Actual synthetic uses also include: Bicifadine, Enzacamene, Tolibut, Aptrol, 4-methylmethamphetamine, Wy-28342, PheTQS, & Imrecoxib (via the mandelic acid FGI to the phenylacetic acid). References