A reader on my website asked me the following question concerning Greek accents. I don't accurately know the answer and hope you can provide the proper grammatical reason:
"I would be most grateful if you could confirm whether or not the two articular verbal compound nouns (τὸ παρεῖναι, τὸ απείναι) are correct so far as their Greek accents is concerned. I want to be sure that when I put the neuter singular definite article τό in front of the two infinitives (παρεῖναι, απείναι) there is no alteration of their accentuation. Or is there?!
εἰμί, εἶναι, τὸ εἶναι
πάρειμι, παρεῖναι, τὸ παρεῖναι
ἄπειμι, απείναι, τὸ απείναι"

Are you working on Heidegger perhaps? Anyway, you are almost correct
τὸ παρεῖναι, τὸ ἀπεῖναι, εἰμί, εἶναι, τὸ εἶναι, πάρειμι, παρεῖναι, τὸ παρεῖναι, ἄπειμι, ἀπεῖναι, τὸ ἀπεῖναι.