Big-O of 2^(100n)

I'm having some trouble figuring this one out. Basically I'm wondering if the constant multiple c is a multiple of n or a multiple of the whole function?

For example, if it were O(2^n) would you put the constant multiple next to n so it could be:

2^100n

or

do you have to put the constant multiple outside of the whole function so it would be:

100 * 2^n

Thanks for any help!

By the way this question is relating to a larger question:

You have functions f and g such that f(n) is O(g(n))

- 2^(f(n)) is O(2^(g(n))) : True or False?

I'm currently saying False because if f(n) = 100n and g(n) = n so f(n) is O(n)

then

no constant multiple C * 2^n will produce an upper bound for 2^(100n)