"What is the mechanism of the chromium(VI) oxidation of alcohols? The first step is formation of an intermediate called a chromic ester; the oxidation state of chromium stays unchanged in this process. … The next step in alcohol oxidation is equivalent to an E2 reaction. Here water (or pyridine, in the case of PCC) acts as a mild base, removing the proton next to the alcohol oxygen. This proton is made unusually acidic by the electron-withdrawing power of the Cr(VI) (remember that it wants to become reduced!). HCrO3 is an exceptionally good leaving group, because the donation of an electron pair to chromium changes its oxidation state by two units, yielding Cr(IV)."
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K. Peter C. Vollhardt, Neil E. Schore (2011) Organic chemistry : structure and function 6th ed. Chapter 8. Hydroxy Functional Group : Alcohols. p. 303-304
https://en.wikiquote.org/wiki/Elimination_reaction
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Elimination reaction
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