Fast pyrolysis of lignocellulosic biomass, utilizing moderate temperatures ranging from 400 to 600 degrees C, produces a primary liquid product (pyrolytic bio-oil), which is potentially compatible with existing petroleum-based infrastructure and can be catalytically upgraded to fuels and chemicals. In this work, experiments were conducted with a micropyrolyzer coupled to a gas chromatography-mass spectrometry/flame ionization detector system to investigate fast pyrolysis of neat cellulose and other glucose-based carbohydrates. A detailed mechanistic model building on our previous work was developed for fast pyrolysis of neat glucose-based carbohydrates by integrating updated findings obtained through experiments and theoretical calculations. The model described the decomposition of cellulosic polymer chains, reactions of intermediates, and formation of a range of low molecular weight compounds at the mechanistic level and specified each elementary reaction step in terms of Arrhenius parameters. The mechanistic model for fast pyrolysis of neat cellulose included 342 reactions of 103 species, which included 96 reactions of 67 species comprising the mechanistic model of neat glucose decomposition.