Here is a map of ORD

http://www.aa.com/i18n/aboutUs/where...rminal_ORD.jsp

A previously mentioned, your GRB flight will most likely depart out of the G terminal. I've found that I can cover the distance between terminals in under 10 minutes. Depending on where your seats are on the TUS flight, this begins to look like a very tight connection. Also, delays into O'Snare are not uncommon. Personally, I would book a longer connection, if possible.