Question

If you are restless, there is no solution except to concentrate.
to concentrate- infin.
used as an adverb?

Answer 1

Since "except" is used as a preposition in this sentence, the infinitive "to concentrate" must be a noun, used as the object of the preposition.

http://dictionary.reference.com/browse/except

Answer 2

Would this sentence not have an infinitive if it is part of a prep. phrase?

Answer 3

This sentence does have an infinitive. As I said, it's used as as a noun, the object of the preposition.

Remember that infinitives used as nouns can be subjects, direct objects, and objects of a preposition.

Answer 4

Thank you! :)

Answer 5

You're welcome. :-)