if I have concentrated acetic acid (99%) what are the out put gases during electrolysis?
Upon electrolysis, organic acids will lose the carboxyl group and dimerize.
This is known as the Kolbe electrolysis:
https://en.wikipedia.org/wiki/Kolbe_electrolysis
In the case of electrolysis of acetic acid, ethane and $\ce{CO2}$ will be formed.