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Hello, thanks for your help. I'm now studying English infinitival clauses, especially how they form interrogative sentences. As you know, we can say "You don't remember what to buy." or "What did you remember to buy?" as interrogative forms of "You remembered to buy that novel." Then, how about the following sentences in (1)-(4), which contain the internal subect "her" in the infinitival clause. I'd appreciated if you native speakers would tell me if they are grammatical or not. Thank you.

(1) You didn’t want her to buy this novel.

(2) You didn’t want her to buy what? (as an “echo question” as in “You bought what?”)

(3) You didn’t want what (for) her to buy.

(4) What did you want (for) her to buy?
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You don't remember what to buy.-- An odd statement. 'Didn't' is the expected.

(2) You didn’t want her to buy what?- -Fine and natural.

(3) You didn’t want what (for) her to buy.-- No good.

(4) What did you want her to buy?-- OK as amended.

Any other questions?
Comments  
Thank you for your quick and kind reply! This will certainly help my study. For the time being, I have no question about this. Thanks a lot!