3,4-Dimethylbenzaldehyde (3,4-DMB) is a benzaldehyde derivative. It is the OH radical initiated oxidative degradation product of trimethylbenzene. The rate coefficient of the gas-phase reaction between 3,4-DMB and OH radical is 24. 6±4. 0×10-12cm3molecule-1s-1. The vibrational analysis of 3,4-DMB based on FT-IR spectra, FT-Raman spectra, ab initio and density functional theory (DFT) calculations have been reported. It is formed as an intermediate during the transformation of furfural into gasoline-range fuels using ZSM(Zeolite Socony Mobil)-5-based catalysts.