Module 4D: Intermolecular Forces

Question 1

What is an intermolecular force? Is it a bond?

Answer 1

No, it is not a bond. It is an attraction d/t proximity in space.

weaker than intramolecular forces (ionic, covalent chemical bonds)

Question 2

How do we want drugs to interact with receptors?

Answer 2

Via intermolecular forces.

We do NOT want an actual chem bond formed, it will stay & never leave! :O

*we want the drug to “bind”, interact & release.

Question 3

Why can intermolecular forces seem very strong?

Answer 3

Due to the AMOUNT of interactions.

Question 4

What affects the strength of IF attractions?

Answer 4

1. Magnitude of charge (real or partial)
2. Distance

*attracted to each others partial charges.

Question 5

In polar bonds, are electrons shared equally?

Answer 5

No. This is what gives us a charge.

Based on electronegativity. F is the most.

Question 6

How do we measure distance btwn molecules?

*pm

Answer 6

Pm or picometer.

Question 7

How do solids keep their shape?

Answer 7

More intermolecular forces (amount) = very strong forces btwn particles (harder to break apart)

Question 8

What is a dipole moment?

Answer 8

Separation of charge.
The more atoms we have that share electrons UN-equally (polarity) the more partial charges are made.

*This can lead to an intermolecular force.

Question 9

Is water (H2O) polar?

Answer 9

• YES!
• the vectors add together = polar.

*vectors that move in diff directions cancel out = nonpolar (CO2)

Question 10

Application of IF

What is a liquids resistance to increase its surface area referred to as?

Answer 10

Surface tension!

To minimize surface area, liquids form spherical drops.

*unique property of water*

The stronger the intermolecular forces, the more energy required to increase the surface area.

Question 11

Application of IF

You get a corner of papertowel wet, you notice the towel gets more and more saturated upwards. What is this referred to as?

Answer 11

Capillary Action

results of cohesive & adhesive forces.

Question 12

Application of IF

What is the measurement of a liquids resistance to flow?

Or the amount of energy required to move an object thru fluid.

Answer 12

• Viscosity.
• Molecular size plays an important role. (think of Hct levels)

greater potential for more IF interactions (amount and strength)

Question 13

Applications of IF

When would we want a drug to covalently bind to a receptor?

Chemical/Irreversible bond.

Answer 13

Chemotherapy.

Question 14

What does drug-receptor binding help us determine about the drug? (3)

Answer 14

1. Efficacy
2. potency
3. toxicity (to a limited extent)

*different parts of drug will bind to diff parts of the receptor

Question 15

Do changes in phase break chemical bonds?

Answer 15

No.
Phase changes refer to changes in states of matter and the energy required.

Question 16

Application of IF

What is solubility based on?

Answer 16

Attractive forces of the solute & solvent. (polarity of each)

“Like dissolves like”

C-C = nonpolar bonds; if you try to put in polar environment, will not be happy.

Question 17

What is the weakest IF & also most common?

Answer 17

Van Der Walls

(London Dispersion)

two nonpolar molecules

Question 18

What IF is this?

Answer 18

Dipole-Dipole

occurs in all polar molecules

Question 19

What type of IF is this?

Answer 19

Hydrogen bonding.
H bond acceptors (F, O, N) & H bond donors (need a H+)

Very Strong!

Need both to create an H+ bond :)

Question 20

What are some examples of H+ bond donors.

4

Answer 20

1. Alcohols
2. Amines
3. Amides
4. Carboxylic Acid

Question 21

Examples of H+ bond acceptors?

Answer 21

Any functional group with O or N.

*Why we see a lot of N bonds in drugs.

Question 22

What is the rule in “Lipinski Rule of 5” pertaining to H bond donors?

Answer 22

No more that 5 H bond donors in a drug.

*violation of one rule predicts it is non-orally bioavailable

Question 23

What type of IF is this?

Answer 23

Ion-dipole

*pretty strong

Question 24

What is unique about this IF bond?

Electrostatic (Ion-Ion)

Answer 24

1. interaction btwn cation & anion portion
2. Effective at distances farther away than seen in other IF’s
3. persists longer than others

Question 25

What is the most rare, strongest & irreversible IF bond?

Answer 25

Covalent.

Seldomly formed.

Question 26

Label the types of IF.

You can do it!

Answer 26

VDW, D-D, HBD

Question 27

Label the IF.

You got this!

Answer 27

Hydrophobic = VDW
Ionic = Ion-Ion