syntax - "If" and "Whether" - Is interrogative IF always replacable by WHETHER?

I am asking here specifically about if and whether when they introduce embedded questions (or to be more tachnically accurate, subordinate interrogative clauses):

• I don't know if Bob's here.


• I don't know whether Bob's here.

In the sentence above we can freely replace if with whether. There are some situations in which the reverse does not apply. We cannot always replace whether with if. For example in standard English, we cannot normally use if after a preposition:

• The question of whether he is actually eligible didn't arise.


• *The question of if he is actually eligible didn't arise.

We cannot usually use interrogative-if directly followed by or not:

• It's unclear whether or not he's a real elephant.



• *It's unclear if or not he's a real elephant.

There are several more examples. However, what I want to know is:

• Are there any examples where we can use interrogative-if but we can't use whether?

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^{Edit note: There is an if that we find in conditionals that can't be replaced by whether. However, this is conditional, not interrogative, if.}