Lecture 1

Question 1

5 types of Intermolecular Interactions (in order strongest to weakest)

Answer 1

Electrostatic (ion - ion)
Ion - Dipole (between ion and polar molecule)
Hydrogen Bonding
Dipole-Dipole (between two neutral polar molecules)
Van der Waals (transient dipoles that form due to constant electron motion, non polar interaction)

Question 2

What are the 3 requirements for hydrogen bonding to occur?

Answer 2

1) H must be bound to highly Eneg atom (FON)
2) Partially positive H has to be pointing at the lone pairs of FON
3) Three atoms (acceptor atom and donor atoms) have to be colinear

Question 3

What is a hydrogen bond donor? Acceptor?

Answer 3

Donor - donates the H atom

Acceptor - has lone pair that accepts H bond with H atom

Question 4

What conditions make a molecule hydrophilic? (3)

Answer 4

1) Charged or ionized groups on the molecule (can dissolve up to 20 carbons)
2) Small (low MW)
3) Hydrogen bonding functional groups: those that are both donor and acceptor can help dissolve up to 5 carbons per functional group

Question 5

What conditions make a molecule hydrophobic (4)?

Answer 5

1) Uncharged, non-ionized
2) High MW
3) Lack of dipole or hydrogen bonding functional groups
4) Presence of halogens

Question 6

Why are halogen atoms considered hydrophobic?

Answer 6

They are large (atomic radius) and they have lots of lone pairs of electrons, making them very polarizable, they have strong VDW interactions that contribute to hydrophobicity

Question 7

With regards to functions in the body, what happens to hydrophilic compounds upon ingestion?

Answer 7

They tend to dissolve and distribute in the bloodstream and are rapidly excreted, cannot easily pass through lipid bilayer so they are not well absorbed

Question 8

With regards to functions in the body, what happens to hydrophobic compounds upon ingestion?

Answer 8

Tend to pass well through biological membranes and penetrate fatty tissues, do not easily dissolve in blood and are more difficult to excrete

Question 9

pH in the blood? Stomach? Small intestine?

Answer 9

7.4, 1 - 2, 5 - 6

Question 10

Henderson - Hasselbach Eqn

Answer 10

pH = pKa + log (conj. base/conj. acid)
OR
pH = pKa + log (A-/HA)
OR
pH = pKa + log (B/BH+)

Question 11

If the pH of environment < pKa of compound, what will the the protonation state of the molecule?

Answer 11

The molecule will be protonated

• 1 pH unit from pKa = 91% protonated
• 2 pH unit from pKa = 99% protonated
• 3 pH unit from pKa = 99.9% protonated

Question 12

If the pH of environment > pKa of compound, what will the the protonation state of the molecule?

Answer 12

The molecule will be deprotonated
+1 pH unit from pKa = 91% deprotonated
+2 pH unit from pKa = 99% deprotonated
+3 pH unit from pKa = 99.9% deprotonated

Question 13

Describe the geometry and bonding character of the amide bond

Answer 13

• Flat due to partial delocalization of e- along amide bond

- Amide bond has partial double bond character