In an emergency, is mouthwash as effective as disinfectant for a scratch or graze?

Orally: If the problem is in the mouth, it would be better than nothing. Advise visit a dentist to visually inspect the damage

Skin scratch: I would use an ointment or even flush with clean water before pouring mouthwash onto an external wound. The mouthwash may irritate the damaged tissue.

Scratches: For most superficial minor scratches and scrapes to the skin, cleansing adequately with soap and water is usually sufficient. There is no emergency and using something like Neosporin or Bacitracin with a band-aid or gauze bandage in a reasonable amount of time.