Unit 1 Flashcards

1
Q

diastereotopic hydrogens

A

chemically nonequivalent and thus give different chemical shifts in NMR and typically occur in
1.) Chiral molecules (not considered in this course)
2.) Rings
3.) Double Bonds

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2
Q

more electronegative atoms have a () frequency

A

higher

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3
Q

aldehyde and carboxylic acid chemical shift

A

9-12 region

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4
Q

aromatic hydrogens

A

6.5 - 8 region

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5
Q

hydrogens on alkene

A

4.5 - 6.5 region

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6
Q

how do pi electrons shield protons

A

magnetic field is going in different directions

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7
Q

what percentage of hydrogens are in an alpha and beta state

A

50% alpha
50% beta

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8
Q

the alpha state is aligned with () and () in energy

A

magnetic field, lower

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9
Q

the beta state is aligned () and () in energy

A

against the magnetic field, higher

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10
Q

splitting when equivalent

A

(N+N+1)

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11
Q

splitting when nonequivalent

A

(N+1)(N+1)

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12
Q

what splitting pattern does a doublet of doublet result in

A

1:1:1:1

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13
Q

aryl

A

H’s on benzene

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14
Q

axial and equatorial hydrogens are chemically different - why do we only see 1 signal (as a singlet) for cyclohexane

A

chair conformer innerconversion

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15
Q

wet sample

A

the exchangeable H appears as a singlet and it no longer splits adjacent H signals

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16
Q

how many resonance structures does benzene have

A

2 equivalent

17
Q

how many sp2 hybridized carbons does benzene have

18
Q

what are the criteria for aromaticity

A

1.) cyclic
2.) planar
3.) continuous ring of p orbitals
4.) (4n+2) pi electrons –> odd number of electron pairs

19
Q

anytime you see an Sp3, what can can you automatically classify the molecule as

A

nonaromatic –> not continuous loops of p orbitals

20
Q

what hybridization is C+

21
Q

what do you use to rank pKa

A

conjugate base of molecules

22
Q

after 7 carbons in a ring, what happens to the shape

A

the ring often buckles and are no longer planar

23
Q

non-aromatic compounds

A

do not fit the criteria for aromaticity

24
Q

antiaromatic compounds

A

fit all the criteria for aromaticity except they have an even number of electron pairs

25
steps for ranking pKa
1.) draw conjugate base (as pKa increases, acidity decreases) 2.) look at aromaticity to determine acidity Most: aromatic Least: antiaromatic
26
going downhill to lower energy is more/less feasable
more
27
Al, B, C+
all sp2
28
diene
recieves bond
29
dienophile
give bond
30
dine and dienophile combine to form what
2 new c-c bonds and a cyclohexane ring
31
molecular orbitals in diels alder
HOMO of diene overlaps with LUMO of dienophile
32
order of reactivity of diene molecules in a diels alder rxn
locked cis>trans>cis&trans>locked trans
33
1-substituted dienes produce what major product
ortho
34
2-substituted dienes produce what major product
para
35
diels alder stereochemistry
the stereochemical relationship of groups is retained from reactant to product ex: groups that are cis on the dienophile are cis in the product
36
substitution with () on diene speed up the rate of reaction
EDG
37
substitution with () on dienophile speed up rate of rxn
EWG