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Dehydration reactions play a key role in the conversion of biomass derivatives to valuable chemicals, such as alcohols to alkenes. Both Lewis and Brønsted acid-catalyzed dehydration reactions of biomass-derived alcohols involve transition states with carbenium ion characteristics. In this work, we employed high-level ab initio theoretical methods to investigate the effect of molecular structure on the physicochemical properties of a set of alcohols that appear to control dehydration chemistry. Specifically, we calculated the carbenium ion stability (CIS, alkene-binding H + ) and proton affinity (PA, alcohol-binding H + ) of various C2−C8 alcohols to show the effect of alcohol size and degree of primary heteroatom substitution on the properties of the reactive species. Our results show a strong linear correlation between CIS and PA, following the substitution order of the reacting alcohols (i.e., primary < secondary < tertiary). Additionally, the calculated binding free energy (BE) of water on the formed carbenium ions was found to be exothermic and to decrease in magnitude with increasing alcohol substitution level. We demonstrate that the CIS and/or the PA are excellent structural descriptors for the alcohols and, most importantly, they can serve as reactivity descriptors to screen a large number of alcohols in the conversion of biomass-based alcohols involving the formation of carbenium ions. We demonstrate this concept in both Lewis and Brønsted acid-catalyzed dehydration reactions. ■ INTRODUCTIONGlobal primary energy consumption, including commercial renewable energy, increased by 5.6% in 2010, reaching its highest value since 1973. China accounted for 20.3% of the total global energy consumption, followed closely by the United States at 19%. 1 The depleting fossil fuel resources and increasing pollution and global warming concerns require the utilization of alternative and sustainable methods for the production of energy and chemicals. 2 Biomass is an abundant and inexpensive resource with a worldwide production of 560 billion tons of carbon. 3 Biomass-derived energy represents ∼14% of the world's primary energy supply with 25% usage in developed and 75% usage in developing countries. The total sustainable worldwide biomass energy potential is ∼2.47 × 10 13 kJ/m 2 , corresponding to a third of the current total global energy consumption. 4 The abundant quantity of biomass and its sustainable nature make it a plausible alternative source of energy and chemicals production (ethanol, lactic acid, acetone, etc.).Glucose and fructose (major sugars), polyols, and simpler alcohols can be derived from cellulosic biomass processing and further converted into valuable chemicals. For instance, glucose can be reduced to sorbitol, which in turn can be converted to simpler alkanes such as hexane and used as a fuel, through a series of catalyzed dehydration and hydrogenation reactions. 5 Several processes currently exist to convert carbohydrates to liquid fuels. These include (among others) the formation of bio-oils by liq...