Acids and Bases

Question 1

For any amino acid, if the pH of the solution is LOWER than the pKa of the functional group:

Answer 1

The functional group will be protonated

Question 2

For any amino acid, if the pH of the solution is HIGHER than the pKa of the functional group:

Answer 2

The functional group will be deprotonated

Question 3

For any amino acid, nitrogen is ________ charged when protonated and ________ when deprotonated

Answer 3

For any amino acid, nitrogen is positively charged when protonated and neutral when deprotonated

Question 4

For any amino acid, oxygen is _______ when protonated and _________ charged when deprotonated

Answer 4

For any amino acid, oxygen is neutral when protonated and negatively charged when deprotonated

Question 5

What would the structure be if aspartic acid was placed in a solution with pH =13

Answer 5

The amine, carboxylic acid and R group all have a pKa value lower than pH of 13 so the resulting structure would be all of them in their deprotonated form
The amine will be deprotonated (-NH₂), having a neutral charge and both carboxylic acid groups will be deprotonated (-COO^-)

Question 6

acid-base reactions favor:

Answer 6

the formation of the weaker acid (higher pka): strong acids are highly reactive and will react to produce a weak (stable) conjugate base and vice versa

Question 7

ranking acids: CARDIO

Answer 7

Charge:
* acidity increases with increasing positive charge of an atom
* ex: OH^- < H₂O < H₃O⁺

Question 8

ranking acidity: CARDIO

Answer 8

Atom:
* acidity increases going down a column and from left to right on the periodic table
* going down = larger atomic radius = conjugate base can better stabilize the negative charge
* moving from left to right = higher EN = high electron density drawn from H = increasing acidity

Question 9

ranking acidity: CARDIO

Answer 9

Resonance delocalization
* resonance delocalization that increases the stability of a conjugate base will increase the acidity of a molecule

Question 10

ranking acidity: CARDIO

Answer 10

Dipole induction
* EN atoms on nearby carbons stabilize the conjugate base by pulling electron density towards themselves
* conjugate base stablization increases acidity