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CHM 241 Dr. Erb > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

Ka

A

equilibrium constant for the reaction between an acid and water, tells us how many reactants are going to products

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2
Q

Ka value range

A

10^-50 to 10^10

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3
Q

how to get pKa from Ka

A

-log(Ka)

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4
Q

range of pKa values

A

-10 to 50

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5
Q

relationship between Ka and pKa

A

indirect

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6
Q

what do small or large pKa’s indicate?

A

small pKa=stronger acid

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7
Q

tendency of strong acids

A

they really want to give away a proton

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8
Q

acidity/basicity of alcohols

A

very basic

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9
Q

acidity/basicity of amines

A

almost almost basic unless theyre cations

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10
Q

pattern of strength of conjugate acids

A

strong acids result in weaker conjugate bases and vice versa

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11
Q

which acid will equilibrium favor and why?

A

formation of the weaker acid because it has a more stable base, so it goes from stronger to weaker acids, the acid with the most stabilized negative charge

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12
Q

how can you find the difference in number of molecules and products?

A

subtracting the pKa’s: the result it the exponent of 10

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13
Q

Ka of a reaction that is likely to happen

A

large Ka

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14
Q

arrows in an acid/ base reaction

A

2 arrows, one starting at a lone pair and another starting at a bond

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15
Q

which acids/bases will always be on the same side of the equilibrium and why?

A

the strong acids and bases are always on the same side, opposite from the weak acids and bases due to the driving force for stronger acids to become more stable and less reactive

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16
Q

direction of reaction in terms of pKa

A

low to high pKa

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17
Q

what role does resonance play in stability

A

resonance is a stabilizing factor because it delocalizes pi electrons

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18
Q

A in ARIO

A

Atom: the type of atom carrying a charge. When looking across the periodic table, the more electronegative atom that has the negative charge is more stable. When going down the periodic table, the larger atoms are better able to stabilize electron density. Stability indicates strength

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19
Q

which atoms are better at stabilizing negative charges?

A

more electronegative atoms

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20
Q

why are larger atoms better at stabilizing electron density?

A

it can spread out the density more among its larger area

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21
Q

R in ARIO

A

Resonance stabilizes formal nergative charges. more resonance = stability

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22
Q

how does localization relate to stability?

A

indicates stability

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23
Q

I in ARIO

A

Induction: stabilizes a negative formal charge by spreading it out. indicated by electronegativity differnces

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24
Q

induction vs resonance

A

induction is the pulling of electrons through sigma bonds, resonance moves electrons through a pi system

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25
Q

why is resonance more stabilizing than induction?

A

resonance pulls electrons through pi systems whereas induction occurs in sigma bonds

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26
Q

O in ARIO

A

Orbital: type of orbital affects the stability of a formal charge. SP orbitals are the most electronegative because they have the most S character and are closest to the nucleus, and therefore more stable

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27
Q

relationship between orbitals and energy level and stability

A

more s character=lower energy level and more stable

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28
Q

What does ARIO tell you?

A

which molecule has the lower pKa

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29
Q

biggest ARIO exceptions

A

alkynes vs amines: where N- is less important than the orbital(ARIO out of order), then
acetylene vs ammonia

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30
Q

trends in charged conjugate bases

A

other than HCl and H2SO4, neutral conjugate bases will be more stable than a negatively charged conjugate base

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31
Q

charges of acids and bases

A

Bases: neutral or negative
Acids: neutral or positive

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32
Q

What outweighs A in ARIO?

A

charges

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33
Q

counterions

A

spectator ions

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34
Q

lewis acid/base definition

A

Acid: accepts electron pair
Base: donates a pair of electrons

acids dont always fit bronsted lowry defintion

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35
Q

why are lewis acids and bronsted acids sometimes different?

A

lewis acids include compounds with unfilled valence orbitals

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36
Q

saturated hydrocarbons

A

dont contain pi bonds, not very reactive

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37
Q

-ane

A

suffix for saturated hydrocarbons

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38
Q

which prefixes are ignored with ordering alphbetically

A

iso- and cyclo-

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39
Q

how do you know which parent chain to pick if there are 2 that are the same length?

A

choose the one with the most substituents, if substituents are the same either one is fine

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40
Q

1 carbon atom prefix

A

meth

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41
Q

2 carbon atom prefix

A

eth

42
Q

3 carbon atom prefix

A

prop

43
Q

4 carbon atom prefix

A

but

44
Q

5 carbon atom prefix

A

pent

45
Q

6 carbon atom prefix

A

hex

46
Q

7 carbon atom prefix

A

hept

47
Q

8 carbon atom prefix

A

oct

48
Q

9 carbon atom prefix

A

non

49
Q

10 carbon atom prefix

A

dec

50
Q

suffix for substituent side chains

A

-yl

51
Q

where do the numbers come from when naming substituents?

A

which number carbon they come from

52
Q

how do you number a parent chain?

A

If one substituent is present: number the parent chain so that the substituent has the lowest locant possible

If multiple substituents: number the parent chain to give the first substituent the lowest number possible

If there is a tie: give second locant lowest # possible

if all locants are tied: give lowest locant to substituent that comes first in the alphabet

53
Q

how does cyclo- get alphabetized when naming molecules?

A

according to “C”, not the substituent name

54
Q

what is the fastest way to identify if 2 molecules are identical or not?

A

name them

55
Q

conformation

A

differential rotations of the same molecule due to single bonds

56
Q

what is misleading about molecules drawn on paper?

A

they are not stagnant. They are always rotating, vibrating, stretching or in other motion

57
Q

What points of view do you get from wedge-and-dash structures, sawhorse structures and newman projections?

A

Wedge and dash: from the side

Sawhorse: rotates the molecule from the side

Newman: looks at a molecule head-on, straight down a C-C bond

58
Q

Where are wedges and dashes drawn in Newman projections

A

always on the same side of the bond

59
Q

Which conformations are most/least stable and why?

A

staggered conformation is the most stable because the dihedral angle gives maximum separation between bonds and electrons pairs that are repelling each other.

60
Q

Torsional angle

A

60 staggered conformation angle, most stable and lowest energy

61
Q

torsional strain

A

raises energy and decreases stability of a molecule because it takes more energy to keep the smaller bond angles together since electrons repel each other. also can be defined as the difference in energy between staggered and eclipsed formations

62
Q

eclipse formation

A

0 degree bond angles, highest possible newman projection energy figure, perfect overlap, has torsional strain

63
Q

how are are the staggered and eclipsed forms related to each other in ethane?

A

they are degenerate

64
Q

hyperconjugation

A

An occupied bonding MO and an unoccupied antibonding MO overlap and the opposite charge difference is diffused, stabilizing the molecule. not a large stabilization

65
Q

does H or C have a higher electronegativity?

A

C

66
Q

where do wedges go on Newman projections?

A

the right side

67
Q

steric strain

A

a type of strain resulting from groups bumping into each other, staggered and eclipse formation can have steric strain

68
Q

what decides magnitude of steric strain?

A

size of colliding molecules

69
Q

gauche interaction

A

type of steric strain in staggered formations

70
Q

anti group

A

group where methyl groups are as far apart as possible, most stable steric strain, have no torsional strain or steric strain

71
Q

why do anti group have no torsional strain?

A

it is staggered

72
Q

Why do staggered groups have no steric stain?

A

methyl’s are too far apart, no Gauche

73
Q

what kind of strain is an overlap of two H’s?

A

torsional strain

74
Q

what kind of strain is overlap of an H and CH3

A

torsional strain and an insignificant amount of steric agree

75
Q

what kind of strain are gauche interactions?

A

steric strain only

76
Q

how does strain affect the energy of a molecule

A

it raises the energy of the molecule

77
Q

angle strain

A

molecules that can’t get close to their ideal bond angle, straining the bonds, unique to rings, comes from poor orbital overlap

78
Q

most stable form of cycloalkanes

A

not flat to optimize bond angles

79
Q

what type of angle strain is in smaller rings?

A

they are more compressed/pushed together than they would like to be

80
Q

What type of angle strain is in larger rings?

A

they are wider than they want to be

81
Q

which rings have the least angle strain?

A

5 and 6 C rings, 6(cyclohexane) specifically

82
Q

what type of strain does a flat ring worsen?

A

increase torsional and angle strain

83
Q

what allows benzene rings to be flat?

A

the atoms are SP2

84
Q

Why are big rings more stable than smaller rings(except for 5 and 6 C rings)?

A

big rings have more opportunity to orient themselves to optimize bonds

85
Q

cyclopropane

A

highly reactive, has severe angle and torsional strain, eclipsed, nearly flat because of restriction of having only 3 carbons

86
Q

cyclobutane

A

significant angle strain and some torsional strain, eclipsed

87
Q

cyclopentane

A

very little angle strain, has 1 C atom where torsional strain occurs

88
Q

envelope formation

A

ideally stable formation of cyclopentane where 1 C atom is elevated upwards

89
Q

what makes cyclohexane slightly more stable than cyclopentane?

A

cyclopentane has the torsional strain in 1 C atom that cyclohexane does not have

90
Q

what characteristic makes rings good antibiotics?

A

they are more ready to burst/open up easily

91
Q

chair conformation

A

optimally stable conformation of cyclohexane with zero angle strain

92
Q

What is required for no angle strain?

A

109.5 degree bond angles

93
Q

what is required for no torsional strain?

A

all adjacent C-H bonds must be staggered

94
Q

how do you know which direction to draw axial substituents?

A

draw them in the direction their angle points

95
Q

what happens when a ring flips?

A

everything that is axial becomes equitorial and vice versa, ONLY C-C double bonds rotate

96
Q

why do equitorial formation tend to be more stable?

A

axial groups are closer together so anything bigger than an H causes steric strain

97
Q

explain the name 1, 3-diaxial strain

A

the steric straining substituents interact with substituents that are 3 carbons away

98
Q

what type of interactions is a 1,3-diaxial strain

A

gauche interaction between two non-H groups

99
Q

what type of interaction is a substituent in am equatorial position?

A

anti interaction

100
Q

What decides the amount of steric strain between 2 groups?

A

size, larger groups crowd more

101
Q

how do you know which proton is the most acidic in a molecule?

A

the most acidic protein creates the most stable base when it is removed

CHM 241 Dr. Erb (4 decks)

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