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Ochem 2 > Quiz 3 > Flashcards

Quiz 3 Flashcards

1
Q

Arenes

A

class of compounds with a fully conjugated pi system in a closed ring

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2
Q

What is the parent compound for a benzene ring + less than 6 carbon chain

A

Benzene will be the parent

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3
Q

What is the subtiuent name for benznes?

A

phenyl/ Ph

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4
Q

Ortho
Meta
Para

A

Ortho: no carbons between substituents
Meta: one carbon between subtiuents
Para: two carbons between subtituents

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5
Q

Why is benzene so stable?

A

Bc of its 6 overlapping p orbitals + resonance too

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6
Q

What are the two requirments to be an aromatic

A
  • overlapping p orbitals in a conjugated ring
  • odd number of pi bonds (huckles rule)
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7
Q

Huckles rule

A

a compound can be aromatic only if it has 2,3,10,14…. pi electrons

4n+2

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8
Q

True or false?

In a benzene ring three electrons are in anti bonding MOs and three are in bonding MOs

A

false, all 6 are in bonding MOs

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9
Q

Frost Circles

A

A way to estimate the number of MOs in a ring

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10
Q

True or False?

You want all of your electrons in non bonding and bonding MOs

A

false, you want them in bonding, not non bonding which are unstable MOs

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11
Q

Anti aromatic

A
  • smaller than 5 atoms w/ no conjugation or not enough p orbitals
  • most unstable
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12
Q

Non aromatic

A
  • 6 atoms or larger than can change shape to overlap orbitals but not enough p e-
  • unstable but not as unstable as anti aromatic compounds
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13
Q

carbocations open up p orbitals, carbanions —-

A

fill p orbitals

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14
Q

If a N has no double bonds attatched it, can its lone pair participate in resonance and be counted towards the number of pi e-?

A

Yes!

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15
Q

How can aromaticity affect acidity?

A

Aromaticity can stabilize which makes weak bases/ strong acids

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16
Q

If you undergo a proton transfer that causes a molecule to go from aromatic to non aromatic have you gained or lost stability?

A

Lost stability

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17
Q

Why is the benzylic position so good for reactions?

A

bc it is resonance stabilized

18
Q

What benzylic reaction can extend the conjugation?

A

Elimination

19
Q

True or False?

You dont need a benzylic proton to oxidze a alkyl chain on a benzene?

A

False, with no proton it will not oxidize

20
Q

What reaction can selectively reduce pi bonds on a benzylic chain?

A

hydrogenation reaction

21
Q

Electrophilic Aromatic Substituion (EAS)

A

replacement of one of the aromatic protons with an electrophile

ex: sulfonation, halogenation, nitration

22
Q

What does it mean to say aromatic moitey preserved?

A

It starts aromatic and ends aromatic even if aromaticity is changed intermediatley

23
Q

mechanism of Halogenation by EAS

A
  1. nuc attack
  2. pt
    - FeBr3/AlBr3 + Br2
24
Q

What are FeBr3 and AlBr3 classified as?

A

Lewis acids that make the electrophile more electrophilic

25
Q

What is unique about the proton transfer step in halogenation by EAS

A

the arrow starts at a bond, not a lp

26
Q

sigma complex

A

resonance stabilized carbocation

27
Q

Sulfonation by EAS

A
  1. nuc attack
  2. pt
  3. pt
    - using conc. H2SO4 + SO3—-SO3H

extra pt step unique to sulfonation

28
Q

Why is SO3 so electrophilic?

A

Bc its pi bonds have inefficent overlap

29
Q

True or False

concentrated SO3 promotes sulfonation

A

false, concentrated H2SO4 promotes sulfonation

30
Q

Nitration by EAS

A
  1. nuc attack
  2. pt
    - HNO3 + H2SO4—-NO2
31
Q

What is used to reduce a nitro group to an amino group on a benzene?

A

HCl + Zn/Fe

32
Q

Friedel Crafts- Alkylation

A

addition of an akyl group to a benzene ring using an akly halide + lewis acid + benzene ring

33
Q

What is the preferred conjugation of aklyl halides for friedel crafts alkyklation?

A

2 or 3 to prevent rearrangments

34
Q

True or false?

FC alkylation can occur without the lewis acid under very harsh conditions

A

False, with out the lewis acid there will be no reation

35
Q

What happens if you have a primary halide for a FC alkylation?

A

there will be rearrangements and a mixture of products

36
Q

What are the three complications with FC alkylation?

A
  1. polyalkylation can occur
  2. some rings are too deactivated to be added to
  3. If the halide on the akyl chain is attatched to an sp2 carbon there will be no reaction
37
Q

Friedel Crafts Acylation

A

addition of an acyl group to a benzen ring using an acid halide + lewis acid + benzene ring

38
Q

Acyl group

A

C=O bond connected to an alkyl chain or aryl group

39
Q

Acylation is — prone to polyacylation and rearrangements

A

NOT

40
Q

Clemmensen reduction

A

using HCl + Zn to reduce the product of FC acylation so it is only an akyl chain

Ochem 2 (7 decks)

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