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Experiment 1:

Experiment 1:. STRUCTURE, INTERMOLECULAR FORCES, AND SOLUBILITY. OBJECTIVES. To investigate the effect of intermolecular forces (IMF) on the solubility of organic compounds in water using solubility testing. To study the polarity and solubility of various alcohols based on carbon chain length.

sigourney-emerson
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Experiment 1:

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  1. Experiment 1: STRUCTURE, INTERMOLECULAR FORCES, AND SOLUBILITY

  2. OBJECTIVES • To investigate the effect of intermolecular forces (IMF) on the solubility of organic compounds in water using solubility testing. • To study the polarity and solubility of various alcohols based on carbon chain length. • To understand how acid-base chemistry can affect the solubility of various organic solids.

  3. ROLE OF IMF • Physical state • solid, liquid & gas • Distillation • difference in BP • Extraction • difference in solubility • Chromatography • different IMF between analyte and stationary vs. mobile phase • Biology • secondary structure of proteins • DNA and DNA-RNA base pairing

  4. TYPES OF IMF • London Dispersion Forces • Dipole-Dipole Forces • Hydrogen Bonding • Acceptors • Donors • Ion-dipole Forces

  5. d - -------------- d - d + LONDON DISPERSION FORCES • London Dispersion Forces (LDF) = weakest intermolecular force. • Temporary attractive force. • Electrons are in constant motion, and are at times distributed unevenly about the nucleus. This results in the formation of a temporary dipole. • A second atom/molecule can be distorted by the appearance of the dipole in the first atom/molecule (electrons repel one another). This leads to an electrostatic attraction between the two atoms or molecules. d +

  6. LONDON DISPERSION FORCES • Dispersion forces are present between all molecules, whether they are polar or nonpolar. • The larger/heavier an atom is, the stronger the dispersion forces are. • Compounds which contain carbons and hydrogens ONLY possess LDF ONLY. LESS LDF MORE LDF

  7. DIPOLE - DIPOLE FORCES • Dipole moment(m):Electrostatic attraction between polar molecules. • Dipole moment = a measure of the unevenness of electron density in a bond or molecule. • It depends on both electronegativityof atoms and on molecular geometry.

  8. DIPOLE - DIPOLE FORCES • Dipole-dipole forces are present only in polar molecules. • They occur when the d+ end of one polar molecule is attracted to thed- end of another.

  9. HYDROGEN BONDING • Hydrogen bonds are a result of the large difference in electronegativity between H and N, O, or F. • They occur when the H of one molecule attached to an O or N is attracted to an O or N of a different molecule. • Some compounds have a H to donate to hydrogen bonding, while others can only accept a H from other compounds to form hydrogen bonds.

  10. HYDROGEN BONDING *** Notice that compounds containing an O or N with a H DIRECTLY bound to it are donors and acceptors!***

  11. ION-DIPOLE • An ion-dipole force exists between an ion and the partial charge on the end of a polar molecule. • They are especially important for solutions of ionic substances in polar solvents, such as NaCl in water.

  12. OVERVIEW • A: Test solubility of organic solvents in water. • B: Test solubility of alcohols in hexane and water. • C: Test solubility of organic solids in hexane, water, aqueous acidic, and aqueous basic solutions.

  13. Table 1.1: Miscibility of Organic Liquids and Water

  14. Table 1.2: Structure and Miscibility of Alcohols in hexane and water

  15. Acid-Base Chemistry

  16. Table 1.3: Structure and Solubility of Organic Solids

  17. IMF FLOW CHART Interacting molecules or ions NO NO YES NO Are polar molecules involved? Are ions involved? Are polar molecules and ions both present? YES DIPOLE-DIPOLE Ex: CH3Cl YES NO YES Are hydrogen atoms bonded to N, O, or F atoms? IONIC BONDING Ex: NaCl LDF ONLY Ex: CH3CH3 ION-DIPOLE Ex: NaCl in H2O NO YES HYDROGEN BOND Acceptor Ex: CH3OCH3 HYDROGEN BOND Donor Ex: H2O, NH3

  18. SAFETY CONCERNS • All solvents used in today’s lab are volatile. Wear safety goggles at all times, and use fume hoods. • Dichloromethane is carcinogenic in large amounts.

  19. WASTE DISPOSAL • Pour all liquid waste from this experiment into the container labeled “LIQUID ORGANIC WASTE”. • Do NOT pour any waste down the drain!

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