The best choice for a BSc in Chemistry in my opinion would be Jadavpur University. This is one of the best universities in Kolkata second only to IISER in terms of quality of education offered. The chemistry department of JU specifically is the best among other science departments. It has the most learned and experienced faculty pool of around 36 full-time qualified professors. Its infrastructure is better than most colleges in Kolkata.
There is a downside to JU considering its high involvement in politics. However, individually you can refrain from being involved, which won’t affect your academics much. Nevertheless, as a science student, you will hardly get time to involve yourself in anything non-academic like politics.
St Xaviers College too is a decent choice followed by Presidency University. Next comes St Xavier's College. And then Presidency University.
While the general preference order would be JU>St Xaviers>Presidency University, the final decision will depend on your personal goals and inclinations.
Jadavpur University is a top-notch university for pursuing B.Sc. But, I will suggest you join ST. Xavier’s. The reason behind this is that it has recently fallen trap to a huge amount of politics, which students rather should not be part of.
On the other hand, if considering St. Xavier’s, then it is completely not part of any of it. Alongside that, if you search for the best college for B.Sc in India, then St. Xavier’s will be among the top 5.
In fact, the major upside is that if you are planning further for your higher studies as well, like M.Sc or MBA, then you can similarly find various kinds of privileges in XLRI itself. But if you want to do MSc then, most students join IIT or IISc.
So, consider all these factors, and choose the institute that works best for you.