Organic Chemistry Chapter 12 Oxygen and Sulfur in

Part 02 Intermolecular Forces of Attraction 2

1. IMFA - intermolecular force of attraction - any attraction that exists between two

2. Types of IMFA in Organic Molecules a. London Forces b. Dipole-Dipole c. Hydrogen

a. London Forces - IMFA between nonpolar molecules - all organic molecules containing C

- the greater the size of the molecule containing only C and H, the

Example: - propane molecules are larger than ethane molecules - LF will be greater

b. Dipole-Dipole Attractions - any organic molecule containing a C bonded to an O

Example: 2 -propanone - the C-O bond is polar - primary IMFA is dipole-dipole

c. Hydrogen Bonding - any organic molecule containing an H bonded to a F,

Example: 1 -propanol - contains a H bonded to an O - IMFA is

Example: Name the following molecule. Show all the IMFA between the following molecules. Which

H H NH 2 H C C C H H H OH London Forces.

3. Physical Properties All of the following physical properties are directly related to IMFA

3. a. b. c. d. e. f. g. h. Physical state at room temp

Example: Which of the following liquids is more volatile? Explain. H OHH H C

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Organic Chemistry Chapter 12 Oxygen and Sulfur in Organic Compounds 1

Part 02 Intermolecular Forces of Attraction 2

1. IMFA - intermolecular force of attraction - any attraction that exists between two or more molecules 3

2. Types of IMFA in Organic Molecules a. London Forces b. Dipole-Dipole c. Hydrogen Bonding 4

a. London Forces - IMFA between nonpolar molecules - all organic molecules containing C and H will always be nonpolar or have a nonpolar part and attract each other with London Forces 5

H d+ H C H H LF H d- d+ H C H d. H When the molecules are close, their electron clouds experience a momentary shift of electrons producing an instantaneous dipole. 6

- the greater the size of the molecule containing only C and H, the greater the London forces 7

Example: - propane molecules are larger than ethane molecules - LF will be greater between the propane molecules H H H C C C H d+ H H H dd+ H C C H dd+ H H d+ H C C C H H H d- H H H 8

b. Dipole-Dipole Attractions - any organic molecule containing a C bonded to an O will have a polar area - primary IMFA between these molecules will be dipole-dipole 9

Example: 2 -propanone - the C-O bond is polar - primary IMFA is dipole-dipole d- H O H H C C C H d+ H H 10

c. Hydrogen Bonding - any organic molecule containing an H bonded to a F, O or N will have a highly polar area - primary IMFA between these molecules will be hydrogen bonding 11

Example: 1 -propanol - contains a H bonded to an O - IMFA is hydrogen bonding H H C C C O H H d+ H H C C C O H H d- 12

Example: Name the following molecule. Show all the IMFA between the following molecules. Which is the dominant IMFA? 13

H H NH 2 H C C C H H H OH London Forces. Hydrogen Bonding H H NH 2 H C C C H H H OH 1 -amino-1 -pentanol 14

3. Physical Properties All of the following physical properties are directly related to IMFA 15

3. a. b. c. d. e. f. g. h. Physical state at room temp Melting point Boiling point Volatility Viscosity Density Solubility Surface Tension 16

Example: Which of the following liquids is more volatile? Explain. H OHH H C C C H H H The IMFA between 2 -propanol molecules is H-bonding. The IMFA between two pentane molecules is LF. Since LF are very weak, pentane is more volatile. 17