1 / 14

Water and the Energy of Interaction of Solutes

Water and the Energy of Interaction of Solutes. Water is an unusual low molecular weight compound. M ~ 18. cf with ammonia (17), methane (16), hydrogen sulfide (34) Water has the highest boiling point by over 100  C (H 2 S ~ -61) Water has the highest dielectric constant  (~80)

callum-rocha
Download Presentation

Water and the Energy of Interaction of Solutes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Water and the Energy of Interaction of Solutes

  2. Water is an unusual low molecular weight compound • M ~ 18. cf with ammonia (17), methane (16), hydrogen sulfide (34) • Water has the highest boiling point by over 100 C (H2S ~ -61) • Water has the highest dielectric constant  (~80) • Water has a solid density lower than the liquid (~9%). • Water has a high viscosity • Water has a high surface tension

  3. Most of water’s properties stem from: • Its polarity (Exemplified by ) • High  reduces the attraction force between oppositely charged particles; F=k(q1q2)/ r2 • Its hydrogen bonding ability • Directionality  Structure (even in liquid state) • Acts as both donor and acceptor

  4. Hydrogen bonding • Partially covalent and partially electrostatic • Interatomic approach of H and acceptor is LESS than van der Waals distance but much more than covalent distance • OH ~0.19 nm, not 0.26 (vdW), but OH is 0.10 nm • Interaction energy is much less than that of covalent bonds.

  5. Si-O, ~200 kcal/mol C-F, ~125 kcal/mol C-X, ~80-100 kcal/mol, -X = -H, -OH, -NH2 etc C-NO, <50 kcal/mol H-bonds, charge-charge, other noncovalent Energy of interactions Bond Energy

  6. Noncovalent Interactions • charge-charge • longest range force, non-directional •  ~1/r • charge-(permanent)dipole • directional dependence •  ~1/r2 • Dipole-dipole • directional •  ~1/r3

  7. Noncovalent Interactions • Charge-induced dipole • depends on polarizibility of inducee •  ~1/r4 • Dipole-induced dipole • depends on polarizibility of inducee •  ~1/r5 • Dispersion • involves synchronization of fluctuating polarity •  ~1/r6

  8. Noncovalent Interactions • van der Waals repulsion • Overlap of outer electron clouds •  ~1/r12

  9. The Solvent Water • Hydration (polarity effect) • Water’s charged ends associate with charged solutes • Exchange of intramolecular/intrasolute H-bonds for intermolecular H-bonds with water

  10. H H O O H H Exchange of H-bonds H H G < 0

  11. The organization of aqueous compartments by hydrophobic entities • (It is said that) Water molecules are organized by hydrophobic surfaces, producing a decrease in entropy in the system (and an increase, by release of heat, in the universe). • The association of hydrophobic molecules/parts of molecules is energetically advantageous, because more water-water interaction is possible than if the molecules are separated in space

  12. Amphipathic structures (micelles) 2-D Micelle

  13. Amphipathic structures figure 12-4

  14. Chemical Reactions in Water

More Related