Would you explain to me why some of the following sentences (a,b,c and d) are correct, and other (e and f) are wrong.
a) I went to the post office for some stamps. "for + noun phrase" is okay; "for something".
b) I went to the post office to buy some stamps. infiinitive of purpose is ok
c) I went to the post office because I wanted to buy some stamps.
Conjunction 'because + sentence explains the reason/the purpose.
d) I went to the post office in order to buy some stamps.
'in order' is also used to explain the reason.
e) I went to the post office for to buy some stamps.
This is nonstandard English.It's sometimes when people want to effect a really casual style of speaking but there's simply no need for both 'for' and 'to',
f) I went to the post office for buying some stamps.
We just don't use ' for + [verb+ing]' to state the purpose/reason.
Thanks in advance.
Student or Learner