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Organic Chemistry > Exam 2 (Ch 3, 5, 14, 15) > Flashcards

Exam 2 (Ch 3, 5, 14, 15) Flashcards

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1
Q

what is a bronsted acid

A

proton donor

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2
Q

what is a bronsted base

A

proton acceptor

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3
Q

what does a bronsted acid look like

A

H attached to EN atom

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4
Q

what can a bronsted acid do?

A

stabilize a negative charge

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5
Q

what do you look for when looking for bronsted bases?

A

a negative charge and localized lone pairs

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6
Q

what is a conjugate acid

A

a protonated base

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7
Q

what is a conjugate base

A

a deprotonated acid

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8
Q

what do strong bases form?

A

weak conjugate acids

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9
Q

what do strong acids form?

A

weak conjugate bases

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10
Q

why do strong acids form weak conjugate bases?

A

because they really want to give up that proton, don’t want it back

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11
Q

why do strong bases form weak conjugate acids?

A

because they really want to take a proton, don’t want to give it up once they get it

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12
Q

what does the equilibrium of an acid-base reactio always favor?

A

the side with the higher, more positive pka value (weaker acid and weaker base)

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13
Q

when using ARIO to analyze the strength of an acid or determine equilibrium, what are you comparing?

A

the stability of the conjugate base

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14
Q

what is the ability to stabilize a negative charge proportional to?

A

the stability of a conjugate base which leads to a stronger acid!

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15
Q

what does ARIO stand for?

A

Atom: electronegativity and size
Resonance
Induction
Orbital

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16
Q

which is better able to stabilize a negative charge, resulting in a more stable conjugate base and a stronger acid, sp or sp3 hybridized orbital? why?

A

sp hybridized is better because more s character holds negative charge closer to nucleus = more stable

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17
Q

when identifying the most acidic hydrogen in a compound, what 3 atoms do you look for attached hydrogens on first? how do you find if those 3 are not present?

A

Sulfur, Oxygen, and Nitrogen; if not present, look for resonance, induction, or hybridized orbitals

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18
Q

define constitutional isomers

A

same molecular formula, different connectivity

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19
Q

define stereoisomers

A

same MF, same connectivity, different spatial arrangement

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20
Q

what are the 3 types of stereoisomers?

A
  1. ring
  2. double bond
  3. chirality stereoisomers
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21
Q

how do you assign configuration for ring stereoisomers?

A

cis: all wedges or all dashes, groups on same side
trans: wedge and dash mixed up, groups on different sides

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22
Q

is there any rotation in ring stereisomers? why or why not?

A

no rotation, bonds locked into place

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23
Q

how do you assign configuration for double bond stereoisomers?

A

cis: 2 identical groups on SAME side of double bond
trans: 2 identical groups on OPPOSITE side of double bond

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24
Q

are double bonds rotatable? why or why not?

A

no rotation, P orbitals must remain parallel so pi bond doesn’t break

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25
Q

how do you assign configuration of 2 identical groups are on the same END of a double bond? is cis/trans stereoisomerism possible here?

A

no cis/trans!
Z: 2 higher priority groups on the same side of DB (like cis)
E: 2 higher priority groups on opposite side of DB (like trans)

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26
Q

what determines higher priority?

A

larger atomic number

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27
Q

how do you assign R/S configuration of chiral centers?

A
  1. assign priority to each of the 4 groups
  2. make sure lowest priority is on a dash!!
  3. draw path from 1-2-3
    clockwise: (R)
    counterclockwise: (S)
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28
Q

how do you assign D/L configuration for Fischer projections?

A

analyze bottom-most carbohydrate
OH on Left: L
OH on right: D

29
Q

do chiral molecules have an optical rotation value?

A

yes!

30
Q

what do chiral molecules possess?

A

non super-imposable mirror images

31
Q

what is an enantiomer?

A

a chiral compound’s one non super-imposable mirror image

32
Q

when do chiral molecules exist?

A

when a carbon is attached to 4 DIFFERENT groups

33
Q

what is a racemic mixture?

A

a 50/50 mixture or both enantiomers of a compound (usually costs too much to separate. so lump all together and you’re fine)

34
Q

what are the only 2 differences between enantiomers?

A
  1. optical rotation of each

2. how each interacts with other molecules (smell and thalidimide babies)

35
Q

what are diastereomers?

A

non super-imposable and also NOT mirror images

36
Q

which can be distinguised by chemical properties: enantiomers or diastereomers?

A

diastereomers

37
Q

what are meso compounds?

A

possess a chiral center but also have a plane of symmetry, so ACHIRAL

38
Q

do meso compounds have optical rotation?

A

nope!

39
Q

what does NMR stand for?

A

Nuclear Magnetic Resonance

40
Q

what does NMR mean?

A

nucleus of an atom is in a magnetic field and it resonates by absorbing radiofrequency

41
Q

what kind of nuclei can spin? (2)

A
  1. odd atomic number
  2. odd mass number
    just need to have one
42
Q

what is it called when a nucleus can spin?

A

NMR active

43
Q

what is the most commonly observed NMR nucleus?

A

hydrogen

44
Q

how many allowed spin states does hydrogen have?

A

2

45
Q

what is Bo?

A

an external magnetic field

46
Q

in the presence of Bo, describe the 2 spin states of hydrogen

A

+1/2: the alpa spin state, lower in energy because flows with current of Bo
-1/2: the beta spin state, higher in energy because flows against current of Bo

47
Q

what increases as Bo increases?

A

the energy gap (delta E) between alpha and beta spin states

48
Q

how do you calculate number of allowed spin states?

A

2I + 1

49
Q

what does the energy of radiofrequency match?

A

the change in energy between alpha and beta spin states

50
Q

what can the energy of radiofrequency do? what is this called?

A

spin flip! excite a nucleus from alpha to beta spin state

51
Q

in what state is the nucleus during/after a spin flip from radiofrequency energy?

A

resonating/in resonance

52
Q

define shielding

A

electrons create opposing magnetic field that partially cancels out the external magnetic field (Bo)

53
Q

what does shielding do to the felt Bo, the change in energy, and the radiofrequency?

A
  1. decreases felt Bo by nucleus
  2. decreased change in energy
  3. decreases the radiofrequency energy required to excite a nucleus from alpha to beta spin state
54
Q

define deshielding

A

withdrawal of electron density via induction from electronegative atoms

55
Q

what does deshielding do to the felt Bo, the change in energy, and the radiofrequency?

A
  1. increases the felt Bo
  2. increases change in energy
  3. increases the radiofrequency energy required to excite a nucleus from alpha to beta spin state
56
Q

what is anisotropy?

A

when the electrons in pi bonds create magnetic fields that either oppose (shield) or reinforce (deshield) the external magnetic field (Bo)

57
Q

name 3 functional groups where anisotropy can occur

A
  1. alkenes
    2 carbonyls
  2. benzene rings
58
Q

what does anistropy explain?

A

the large deshielded chemical shift of benzenes and aldehydes

59
Q

what allows NMR differentiation?

A

the different electronic environments of each hydrogen nucleus in a compound

60
Q

what is splitting?

A

when NMR peaks appear anywhere from a singlet to a dectet, caused by the small magnetic field created by the neighboring hydrogen atoms that either shieldor deshield Bo

61
Q

what is integration?

A

the amount of hydrogen atoms that produce an NMR signal

62
Q

how to you determine splitting pattern?

A

N+1 (neighboring H atoms +1)

63
Q

what is the most common molecular weight of Cl in NMR?

A

35

64
Q

what is the most common molecular weight of Br in NMR?

A

79

65
Q

what does a quartet usually indicate structurally?

A

a H next to CH3

66
Q

what does 3H usually indicate structurally?

A

methyl (CH3)

67
Q

what does 2H usually indicate structurally?

A

CH2 group

68
Q

what does 6H usually indicate structurally?

A

2 identical CH3 groups

Organic Chemistry (5 decks)

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