Pharmaceutically acceptable salts and polymorphic forms of hydrocodone benzoic acid enol ester and processes for making same

A process for the preparation of the following compound:

• wherein the compound is a polymorphic form of hydrocodone benzoic acid enol ester, wherein the polymorphic form is Form I and Form I has an x-ray powder diffraction pattern comprising peaks at about the following 2θ values:
• 9.05, 12.32, 13.16, 14.94, and 18.57 comprising the steps of:
• (a) preparing a mixture comprising hydrocodone free base and either benzoic anhydride or benzoyl chloride and,
• (b) heating the mixture to a temperature in the range of about 80° C. to about 160° C.