Now let's say that instead of drinking the alcohol, you inject pure ethanol straight into a vein [**]. For example, say you inject 2.5 ounces of ethanol (the amount of alcohol in 5 ounces of 100 proof moonshine) right into the bloodstream. The big difference is the time. Instead of it taking an hour for the alcohol to absorb, the alcohol is all there instantly. That's 60 grams of alcohol straight into a bloodstream containing approximately 5 liters (5,000 grams) of blood. There will be a moment or two where the blood alcohol concentration is 60 / 5,000 - a toxic, possibly fatal level - before that alcohol diffuses into the water and fat of the entire body and falls by a factor of 10 to 60 / 50,000 [***].
So to answer your question, there really isn't any chemical difference between drinking and injecting alcohol. In both cases you have ethanol molecules flowing in the bloodstream. But there is a big time difference. And because of the time difference you would need to be extremely careful in the amount injected. A mistake could be fatal. It would be good to apply the "don't try this at home" rule.