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CHEM 3202 - Advanced Organic Chemistry 2 > pKa Values > Flashcards

pKa Values Flashcards

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1
Q

What is the pKa of a typical carboxylic acid?

A

5

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2
Q

What is the pKa of hydronium ion?

A

-1.74

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3
Q

What is the pKa of water?

A

15.74

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4
Q

What is the pKb of water?

A

-1.74

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5
Q

What is the pKb of hydroxide ion?

A

15.74

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6
Q

What is the pKa of HCl?

A

-7

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7
Q

What is the pKb of Cl- ion?

A

-7

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8
Q

What is the pKa of a typical phenol?

A

10

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9
Q

What is the pKb of a phenoxide?

A

10

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10
Q

What is the pKa of ammonium?

A

9.2

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11
Q

What is the pKb of ammonia?

A

9.2

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12
Q

What is the pKa of ammonia?

A

33

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13
Q

What is the pKb of an amide ion?

A

33

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14
Q

What is the pKa of a phenylketonium ion?

A

-6.2

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15
Q

What is the pKb of an aryl ketone?

A

-6.2

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16
Q

What is the pKa of an ketone?

A

19

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17
Q

What is the pKb of an enolate?

A

19

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18
Q

What is the pKa of sulfuric acid?

A

-3

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19
Q

What is the pKa of HBr?

A

-9.0

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20
Q

What is the pKa of perchloric acid?

A

-10.0

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21
Q

What is the pKa of a protonated sulfate?

A

1.99

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22
Q

What is the pKa of H3PO4?

A

2.12

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23
Q

What is the pKa of HF?

A

3.17

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24
Q

What is the pKa of H2PO4-?

A

7.21

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25
Q

What is the pKa of cyanide?

A

9.4

26
Q

What is the pKa of dihydroxyacetone?

A

10.3

27
Q

What is the pKa of HPO4 2-

A

12.32

28
Q

What is the pKb of perchlorate anion?

A

-10

29
Q

What is the pKb of bromide anion?

A

-9

30
Q

What is the pKb of the bisulfate anion?

A

-3

31
Q

What is the pKb of the chloride anion?

A

-8

32
Q

What is the pKb of water?

A

-1.74

33
Q

What is the pKb of the sulfate anion?

A

1.99

34
Q

What is the pKb of H2PO4 -?

A

2.12

35
Q

What is the pKb of a fluoride anion?

A

3.17

36
Q

What is the pKb of an acetate anion?

A

5

37
Q

What is the pKb of HPO4 2-?

A

7.21

38
Q

What is the pKb of ammonia?

A

9.2

39
Q

What is the pKb of cyanide?

A

9.4

40
Q

What is the pKb of a phenoxide?

A

10

41
Q

What is the pKb of carbonate ion?

A

10.3

42
Q

What is the pKb of phsophate anion?

A

12.32

43
Q

What is the pKb of hydroixde?

A

15.74

44
Q

What is the pKa of a sulfoxide?

A

35

45
Q

What is the pKa of an ether?

A

50

46
Q

What is the pKa of an n-alkane?

A

50

47
Q

What is the pKa of t-butane?

A

53

48
Q

What is the pKa of an alkene?

A

43

49
Q

What is the pKa of cp?

A

15

50
Q

What is the pKa of a nitroalkane?

A

10

51
Q

What is the pKa of a dinitroalkane (at same carbon)?

A

4

52
Q

What is the pKa of a trinitroalkane (at same carbon)?

A

0

53
Q

Does the pKa of acetic acid increase or decrease on the addition of an alpha-nitro group? (adjacent to carbonyl)

A

Decrease because you are adding an electron withdrawing group. You are also stabilizing the anion. Goes from 5 to 1.7.

54
Q

Does the pKa of a carboxylic acid increase or decrease by the addition of a quaternary amine alpha to the carbonyl?

A

It decreases because you are adding an electron withdrawing group alpha to the carbonyl. This makes the carbonyl carbon even more electron poor than it was before. Goes to 5 to 1.8.

55
Q

Does adding a nitrile group alpha to the carbonyl increase or decrease the pKa of a carboxylic acid group?

A

The nitrile carbon is realtively electron poor and withdraws electron density away from the carbon alpha to the carbonyl. This causes electron density to be withdrawn from the carbonyl carbon making it relatively electron poor resulting in an easier deprotonation. Goes from 5 to 2.4.

56
Q

Does adding an acetyl group alpha to the carbonyl of a carboxylic acid increase or decrease the pKa of the acid?

A

It decreases the pKa because the carbonyl carbon of the acetyl group is electron poor and withdraws the electron density away from the carbonyl carbon of the carboxylic acid group. This decreases the pKa from 5 to 3.6.

57
Q

Does the addition of CF3 groups to the hydroxyl carbon of an alcohol increase or decrease the pKa of the alcohol?

A

It decreases the pKa of the alcohol by withdrawing electron density from the hydroxyl carbon. This makes the hydroxyl carbon electron poor facilitating deprotonation. Goes from 15 to 12.4

58
Q

Does the addition of two CF3 groups increase or decrease the pKa of an alcohol? Is one or two better?

A

It decreases the pKa of the alcohol by withdrawing electron density away from the hydroxyl carbon making it relatively electron poor. Reduces the pKa from 15.5 to 9.3. Wrt/ one, decreases the pKa from 12.4 to 9.3.

59
Q

Does the addition of three CF3 groups increase or decrease the pKa of the corresponding alcohol when added to the hydroxyl carbon? Is 1, 2, or 3 better?

A

It decreases the pKa with respect to the corresponding acid. The three CF3 groups withdraw electron density from the hydoxyl carbon making the formation of the anion favourable. 3 is better than 2 which is better than 1. Goes from 15, 12.4, 9.3, and 5.4 respectively.

60
Q

If the distance increases from a carboxylic acid group from alpha, beta, to gamma, how does the pKa change if a chloro group is added?

A

Starts at 5 without any electron withdrawing groups attached at all. Then, goes to 2.8 if there is an alpha chloro. Then to 4.1 if there is a beta chloro. If the chloro group is gamma, there is essentially no effect on the acidity.

61
Q

How does the pKa of an alkane, alkene, and alkyne proton increase or decrease?

A

Decreases from alkane to alkene to alkyne, This is due to the hybridization of the orbitals corresponding to the proton. The more the s character, the more electronegative the orbital is. Therefore, alkynes are more likely to be deprotonated than an sp2 or an sp3. Goes from 50 to 44 to 25-26 respectively from sp3 to sp2 to sp3.

CHEM 3202 - Advanced Organic Chemistry 2 (1 decks)

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