adverbs - Is "'as' + article + adjective + noun + 'as'" grammatically correct?

1. The sentiments expressed in the tweets can be as accurate a measure as is found with traditional telephone surveys.

The sentence above is grammatically correct.
I wonder if it is still ok when I write like this,

2. The sentiments expressed in the tweets can be as an accurate measure as is found with traditional telephone surveys.

Why is it grammatical or ungrammatical?

Plus, even if the second sentence is ungrammatical, can it be accepted in ordinary conversation? Thank you!