Indirect Speech/whether-if

Question

We say: I don't know whether he is right.

Is it acceptable to say: I don't know he's right or wrong.

Answer 1

You should say, "I don't know if he's right or wrong."

Answer 2

We use "if" or "whether" to introduce clauses after verbs of doubting:

I don’t know if I can drive. My foot really hurts.

Look at If or whether: indirect questions at the Cambridge Dictionary.

I don't know whether he is right or not

I don't know whether he is right or wrong