# Distinguishing atom types

How does one recognize lipophilic points, hydrogen bond acceptors and hydrogen bond donors in organic molecules? For example, provided this SMILES instance

O=C1NC(=O)SC1Cc3ccc(OCCN(c2ncccc2)C)cc3


I know it contains 2 lipophilic points, 5 hydrogen bond acceptors and 1 hydrogen bond donor. How can I determine them?

• Can you draw a molecular structure from this SMILES, to begin with? I, for one, can't. Human readability was never the primary objective of this format. – Ivan Neretin Feb 15 '17 at 19:55
• @IvanNeretin, check the updated question, please. This is rosiglitazone (en.wikipedia.org/wiki/Rosiglitazone). – Rail Suleymanov Feb 15 '17 at 19:59
• Thank you, that's much better. (Not sure if the SMIILES is still needed, BTW.) Now, all hydrogen atoms attached to N or O are hydrogen bond donors, and all N or O atoms with lone pairs are acceptors. – Ivan Neretin Feb 15 '17 at 20:07
• @IvanNeretin, could you clarify the statement about "lone pairs", please? And one more question: do I get it right that lipophilic atoms are all remaining non-ring atoms that are nor H-bond donors, nor H-bond acceptors? – Rail Suleymanov Feb 15 '17 at 20:14
• What's unclear about that? As to what constitutes a lipophilic point in your definition, I'm not sure. – Ivan Neretin Feb 16 '17 at 6:07