Sorry if the question is very straight forward but am a newbie to shell scripting. I am trying to write something like this :
for i in {1..20} do curl \"
Your quoting is not correct. You don't need double quotes around the second $i because the whole thing is already surrounded in double-quotes.
$i
Change it to the following:
for i in {1..20} do curl "something $i ........ -d 'something $i something'" done