Quiz 3

Question 1

Arenes

Answer 1

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

Question 2

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

Answer 2

Benzene will be the parent

Question 3

What is the subtiuent name for benznes?

Answer 3

phenyl/ Ph

Question 4

Ortho
Meta
Para

Answer 4

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

Question 5

Why is benzene so stable?

Answer 5

Bc of its 6 overlapping p orbitals + resonance too

Question 6

What are the two requirments to be an aromatic

Answer 6

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

Question 7

Huckles rule

Answer 7

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

4n+2

Question 8

True or false?

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

Answer 8

false, all 6 are in bonding MOs

Question 9

Frost Circles

Answer 9

A way to estimate the number of MOs in a ring

Question 10

True or False?

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

Answer 10

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

Question 11

Anti aromatic

Answer 11

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

Question 12

Non aromatic

Answer 12

• 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

Question 13

carbocations open up p orbitals, carbanions —-

Answer 13

fill p orbitals

Question 14

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-?

Answer 14

Yes!

Question 15

How can aromaticity affect acidity?

Answer 15

Aromaticity can stabilize which makes weak bases/ strong acids

Question 16

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

Answer 16

Lost stability

Question 17

Why is the benzylic position so good for reactions?

Answer 17

bc it is resonance stabilized

Question 18

What benzylic reaction can extend the conjugation?

Answer 18

Elimination

Question 19

True or False?

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

Answer 19

False, with no proton it will not oxidize

Question 20

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

Answer 20

hydrogenation reaction

Question 21

Electrophilic Aromatic Substituion (EAS)

Answer 21

replacement of one of the aromatic protons with an electrophile

ex: sulfonation, halogenation, nitration

Question 22

What does it mean to say aromatic moitey preserved?

Answer 22

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

Question 23

mechanism of Halogenation by EAS

Answer 23

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

Question 24

What are FeBr3 and AlBr3 classified as?

Answer 24

Lewis acids that make the electrophile more electrophilic

Question 25

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

Answer 25

the arrow starts at a bond, not a lp

Question 26

sigma complex

Answer 26

resonance stabilized carbocation

Question 27

Sulfonation by EAS

Answer 27

1. nuc attack 2. pt 3. pt - using conc. H2SO4 + SO3----SO3H | extra pt step unique to sulfonation

Question 28

Why is SO3 so electrophilic?

Answer 28

Bc its pi bonds have inefficent overlap

Question 29

# True or False concentrated SO3 promotes sulfonation

Answer 29

false, concentrated H2SO4 promotes sulfonation

Question 30

Nitration by EAS

Answer 30

1. nuc attack 2. pt - HNO3 + H2SO4----NO2

Question 31

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

Answer 31

HCl + Zn/Fe

Question 32

Friedel Crafts- Alkylation

Answer 32

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

Question 33

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

Answer 33

2 or 3 to prevent rearrangments

Question 34

# True or false? FC alkylation can occur without the lewis acid under very harsh conditions

Answer 34

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

Question 35

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

Answer 35

there will be rearrangements and a mixture of products

Question 36

What are the three complications with FC alkylation?

Answer 36

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

Question 37

Friedel Crafts Acylation

Answer 37

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

Question 38

Acyl group

Answer 38

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

Question 39

Acylation is --- prone to polyacylation and rearrangements

Answer 39

NOT

Question 40

Clemmensen reduction

Answer 40

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