There were two Confederate infantry units designated the 5th. One was the 5th Alabama Infantry Battalion, the other was the 5th Alabama Infantry Regiment.

For info. on the Battalion, go to:http://history-sites.com/civilwar/units/5albn/5alhist.htm

For info. on the Regiment, go to: http://www.civilwarhome.com/5alainf.htm

As a side note, I am writing a history of the 5th Alabama Infantry Regiment and will gladly any specific questions you may have.