(1) One grammar book says that a sentence like No. 2 IS
BUT it is NOT idiomatic. That is, native speakers have
decided that the order of No. 1 SOUNDS better to them.
(2) Some more examples:
How excellent a view.
So sweet a story.
Too great a sacrifice.
Such an expression.
Such a good friend.
(3) This book says that "a so sweet story"/ "a how excellent view" and
other expressions in "correct" order would sound "awkward" and
"ridiculous" to the ears of native speakers.
(4) Learners should just accept these exceptions (such as "many a
boy") as IDIOMS.
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