1. A Creative Chemistry PowerPoint Presentation By Nigel Saunders Copyright © 2003 Nigel Saunders, all rights reserved Permission is granted for personal and educational use only. Commercial copying, hiring, lending is prohibited. Introduction to hydrogen bonding

2. Hydrogen bonds What are they? A special case of permanent dipole- dipole interactions They are stronger than van der Waals forces. Molecules with hydrogen bonds have higher boiling points than molecules that don’t.

3. Hydrogen bonds What do you need? A hydrogen atom covalently bonded to an electronegative atom … N, O or F. If only one of these conditions is met, you don’t get hydrogen bonding. A lone pair of electrons on the electronegative atom.

4. Hydrogen bonds Give me an example! This does not have any hydrogen bonds. Carbon is not very electronegative, and it has no lone pairs of electrons in methane. methane, CH 4 …

5. Hydrogen bonds Give me a real example! This does have hydrogen bonds. Nitrogen is very electronegative, and it has one lone pair of electrons in ammonia. ammonia, NH 3 …

6. Hydrogen bonds Give me another example! This has not one, but two hydrogen bonds. Oxygen is very electronegative, and it has two lone pairs of electrons in water. water, H 2 O …

7. Hydrogen bonds Remember, you need: A hydrogen atom covalently bonded to an electronegative atom … N, O or F. If only one of these conditions is met, you don’t get hydrogen bonding. A lone pair of electrons on the electronegative atom.