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Pharmaceutical Chemistry > Exam I: EWG, EDG, Acid-Base Chem > Flashcards

Exam I: EWG, EDG, Acid-Base Chem Flashcards

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1
Q

What effects do functional groups have on drugs activity in the body?

A
  1. Drug transport through the body
  2. Mechanism to bind to receptors
  3. How it causes a biological response
  4. How it undergoes metabolism
  5. How it is excreted
  6. Drug stability during storage
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2
Q

Tautomerization is the equilibrium reaction between a ____ their less stable ____ .

A

Tautomerization is the equilibrium reaction between a Keto their less stable Enol.

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3
Q

What is the field effect?

A

Polarization experience through space rather than bonds

ex. An oxygen atom on a carbonyl can pull electron density from a nitrogen a few carbons away

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4
Q

What is the inductive effect?

A

Polarization due to the electronegativity difference between bonded atoms

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5
Q

How can an alkyl group contribute to delocalizing a neighboring positive charge? What is this process called?

A

An alkyl can break a hydrogen bond so that the newly freed electrons can stabilize a cation

This is called hyperconjugation.

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6
Q

Alkyl groups are EWG or EDG? Why?

A

Alkyl groups are electron donating groups through induction.

There is a partial negative charge on the carbon due to its pull on electron density from bonded hydrogen atoms.

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7
Q

-CH3, -CH2, CH, C-R. Which group would be the best electron donating group?

A

-CH3 because it has the greatest number of hydrogen bonded to it

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8
Q

-NO2, -F, CO2H. Put in order from most to least EWG.

A

-NO2 > CO2H > F

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9
Q

Would a ketone or a carboxylic acid have greater electron withdrawing potential? Why?

A

A ketone would have greater electron withdrawing potential.

Carbonyls attached to electronegative heteroatoms have weaker withdrawing power due to resonance which decreases the positive charge that builds on the carbonyl carbon.

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10
Q

Put the halogens in order of withdrawing power (-I, -Br, -F, -Cl). Explain this order.

A

-F > -Cl > -Br > -I

Larger atoms have lower electronegativity due to less shielding of the positive charge of the nucleus.

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11
Q

What type of environment do drugs exert their biological activity?

A

Aqueous

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12
Q

Bronsted and Lowry acid and base

A

Acid - Donates proton (hydrogen)

Base - Accepts proton (hydrogen)

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13
Q

Do strong or weak hydrogen bonds make strong acids? What heteroatoms typically form the weakest bonds with hydrogen?

A

Weak hydrogen bonds make stronger acids

Oxygen, sulfur, nitrogen and phosphorus tend to form the weakest bonds to hydrogen

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14
Q

If a compound (not an atom) is not an acid nor a base then it is considered positive, negative or neutral?

A

Neutral

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15
Q

Lewis acids and bases

A

Lewis acid - electron acceptor (electrophile)

Lewis base - electron donor (nucleophile) - must have a lone pair

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16
Q

What is the equation for Ka?

A

Ka = [H+][A-]/[HA]

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17
Q

What is the equation for pKa?

A

pKa = -log(Ka)

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18
Q

Highest possible Ka value? Lowest possible pKa value?

A

Ka = 1 for the dissociation of hydronium ion (H3O+)

pKa = 0

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19
Q

High Ka –> Strong or weak acid?

A

High Ka = strong acid

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20
Q

Low pKa –> Strong or weak acid?

A

Low pKa = strong acid

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21
Q

What is the Kw of autoionization of water forming H3O+ and OH-?

A

1 x 10^-14

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22
Q

What are the three equations for gibbs free energy discussed? Two are ΔG = and one is pKa =.

A

ΔG = -RTlogKa

ΔG = Total energy of products - Total energy of reactants

pKa = ΔG/RT

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23
Q

Value for R gas constant. Include units.

A

1.987 cal/mol⋅K

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24
Q

Unit for temperature in gibbs free energy equations. Conversion to this unit.

A

Kelvin (K)

T(°C) + 273.15 = T(K)

25
Q

Gibbs free energy and pKa are _____ related?

A

Gibbs free energy and pKa are proportionally related

↑ ΔG = ↑ pka

26
Q

F3CO2H vs H3CO2H. Which is a stronger acid?

A

F3CO2H is a stronger acid

27
Q

In water what are the ranges for pka and pkb?

A

0 - 14

28
Q

High kb = Strong or weak base?

A

Strong base

29
Q

Low pkb = Strong or weak base?

A

Strong base

30
Q

pH can be compared to pka and pkb. (True/False)

A

False

pH can only be compared to pKa

31
Q

If pkb (base) = 4, what is the pka of the conjugate acid?

A

pka + pkb = 14 therefore, pka = 10

32
Q

In a molecule there are two substituents. Group 1 (pka = 9) - Group 2 (pka 4). Which group would donate a proton first?

A

Group 2 because it is more acidic

33
Q

In a molecule there are two substituents. Group 1 (pkb = 5) - Group 2 (pkb = 10). Which group would gain a proton first?

A

Group 1 because it is more basic

34
Q

What is a salt?

A

A salt forms when an acid reacts with a base

Ionized form

35
Q

Why are a vast majority of drugs in the salt form?

A

Charged compounds typically have good water solubility

Usually have a crystalline structure

Good bioavailability

36
Q

What is the henderson-hasselbalch equation?

A

pka = pH + log[HA]/[A-}

37
Q

What is the percent ionization equation? Define what an ionized molecule is.

A

%ionization = [ionized]/[ionized+nonionized]

The ionized molecule has a charge does not matter if it is the acid or base form

NH4+ (Ionized acid) - OH- (ionized base)

38
Q

What equation is used to find the concentrations of the ionized and nonionized molecules?

A

Henderson-hasselbalch equation

pka = pH + log[HA]/[A-}

39
Q

What are the steps to find the percent of acetic acid ionized at pH 5? Given acetic acid pka = 4.

A
  1. Write down the equation to visual the ionized form
    AcOH –> AcO- + H+
  2. Use pka = pH + log[HA]/[A-} to find the concentrations
    AcOH/AcOH- = 1/10
  3. Calculate the percent ionization
    10/1+10 x 100% = 90.9%
40
Q

What are the pH within the following body compartments: stomach, intestine (duodenum), intestine (lower ileum), circulating fluids (i.e. plasma, CSF)?

A

Stomach - pH 1

Intestine (duodenum) - pH 5

Intestine (lower ileum) - pH 8

Circulating fluids - pH 7

41
Q

pka of water H-OH without any added groups?

A

pka 14

42
Q

pkb of ammonia H-NH2 without any added groups?

A

pkb 5

43
Q

How do electron withdrawing groups affect acid-bases?

A

EWG can stabilize conjugate bases of an acid so the acid becomes stronger (lower pKa)

44
Q

Put these EWG in order from strongest. Carbonyl, sulfonyl, aryl.

A
  1. Sulfonyl SO2
  2. Carbonyl CO
  3. Aryl = phenyl group
45
Q

Why is aniline (benzene with -NH2) a weaker base than ammonia (NH3)?

A

EWG delocalize lone pairs weakening the basicity of aniline

46
Q

Why does acetamide behave as an acid?

A

Acetamide H3C C=O NH2

Carbonyl delocalizes the lone pair on the nitrogen giving it a positive charge through resonance

47
Q

Use the pka-pka scale to determine the pka or pkb of ph-o-ph.

A

This compound is neither an acid nor a base because there is no hydrogen to donate or any available lone pairs to accept a hydrogen.

48
Q

Reference notes on how to determine pka of a compound that must be converted to conjugate acid or base to solve.

A

Beneath “how could you predict the pka for this compound?”

Note: to predict pka/pkb the compound must be neutral (no charge)

49
Q

Why are imines (H3C C=NH CH3) less basic than amines (-NH2)?

A

Sp2 orbitals are smaller than sp3 orbitals

Sp2 orbitals have greater shielding of the positive charge of the nucleus

Imines have a greater hold on their electrons than amines

50
Q

Is N(CH3)3 an acid or a base? Compare to ph-o-ph

A

This is a base.

Note that nitrogen is not a highly electronegative atom so a hydrogen atom can be added to nitrogen and acquire a positive charge

ph-o-ph is a neutral compound because oxygen is too electronegative to donate electrons to a hydrogen and acquire a positive charge

51
Q

Effect of H or Alkyl (-CH3) to pka? As first and second group.

A

H or Alkyl (-CH3) groups do not have an affect on pka

H2O and Ethanol have the same pka

52
Q

Effect of aryl, C=C (double bond), C=N, N=N, C (triple bond)? As first and second group.

A

First group - 5

Second group - 2

(toward pka end) = more acidic

53
Q

Effect of C=O or Ar C=O? As first or second group.

A

First group - 10

Second group - 5

(toward pka end) = more acidic

54
Q

Effect of SO2 or ArSO2? As first or second group.

A

First group - 15

Second group - 7

(toward pka end) = more acidic

55
Q

pka/pkb of aniline

A

pkb 10

56
Q

pka/pkb of MeSo2-NH2

A

pka 9

57
Q

In amidine, which nitrogen is more basic (imine or amine)?

A

The imine nitrogen is the stronger base because resonance stabilizes the conjugate acid

See note for a visual or write down the reaction

58
Q

If an EWG like a carbonyl is added to the imine nitrogen in amidine, what would happen to the pkb? Increase or decrease?

A

The nitrogen would become less basic so the pkb would increase

Pharmaceutical Chemistry (3 decks)

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