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Ochem 2 > Quiz 4 > Flashcards

Quiz 4 Flashcards

1
Q

How can you tell if a group is an activating group?

A

if you draw the resonance structures and find a negative charge within the ring

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1
Q

Activating groups

A

electron donating groups that increase the rate of electrophilic aromatic substitution

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2
Q

True or false

Most activators are ortho para directors?

A

True

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3
Q

If your substiuent on the ring is very small what can be said about the directing of an activating group

A

it may favor ortho over para bc there are more ortho positions and less steric hinderence to consider

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4
Q

Deactivating groups

A

ewg that lower the rate of EAS by making the ring less nucleophilic

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5
Q

If the resonance structures feature a — charge on the ring it is likely a deactivator

A

positive

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6
Q

Most deactivators are — directing

A

meta

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7
Q

Why are halogens the exception to the deactivating meta directing rule?

A

Bc they deactivate by induction, not by resonance

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8
Q

halogens are electron withdrawing by — and — — by resonance

A

induction, electron donating

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9
Q

a lp at the benzylic position that only participates in resonance inside the ring

A

strong activators

ex: oxygen

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10
Q

a lp at the benzylic position that can resonate both inside and outside the ring

A

moderate activator

ex: ester or amide with e- connected to ring

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11
Q

akyl chains that donate electron density via hyperconjugation, not resonance

A

weak activators

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12
Q

Examples of strong deactivators

A

NO2, CX3, any + charged N

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13
Q

Moderate deactivators

A

carboxylic acids, ketones, aldehydes, where the pi bond to an electronegative atom is part of the conjugation of the ring

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14
Q

Weak deactivators

A

halogens that are deactivators by induction, not resonance

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15
Q

If the directing effects of the substients on the ring do not agree how do you know what directing effects to follow?

A

You follow the directing of the strongest activator

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16
Q

Blocking group

A

a group that can be easily added and taken off to help control the placement of new substituents on a ring

ex: sulfonation is often used

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17
Q

True or false?

Nitration cannot be done on a ring that has a amide group attatched

A

false, nitration cannot be done on a ring that has a nitro or alcohol group attatched bc it will react instead of the ring

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18
Q

In what order should you place a methyl group and a nitrogroup on a ring

A

methyl group first bc friedel crafts will not react with a deactivated ring

wait to install deactivator last

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19
Q

Nucleophilic aromatic substitution (NAS)

A

ring acts as electrophile and is attacked by nucleophile

20
Q

What are the three conditions for NAS

A
  1. must have nitro group/ strong deactivator
  2. must have good leaving group
  3. leaving group cannot be meta to nitrogroup, must be ortho or para
21
Q

Mechanism of NAS

A
  1. nuc attack on ring
  2. Loss of a leaving group on ring
22
Q

Meisenheimer complex

A

intermediate of NAS, resonance stabilized carbanion

23
Q

the ewg during NAS acts as an electron density — —to kick off leaving group

A

holding place

24
Q

Elimination addition

A

addition of a group to a benzene without a NO2 group under high pressure and temperature (350 C)

25
Q

What is the mechanism of EA

A
  1. proton transfer to create anion
  2. loss of a a leaving group that forms benzyne
  3. nucleophilic attack by added group
  4. proton transfer to restore aromaticity
26
Q

What is the key intermediate of Electrophilic addition

A

benzyne

27
Q

True or False?

The triple bond in the benzyne intermediate is not a true triple bond?

A

true, it is better explained as a di radical

28
Q

O3, DMS splits a double bond and adds Os on the end

A

ozonolysis

29
Q

Pcc/ Chromic acid
- with secondary and primary alcohols

A
  1. primary alchols can be oxidized to aldehydes by PCC
  2. secondary alchols can be oxidized to ketones by PCC or chromic acid
30
Q

terminal alkyne + R2BH and H2O2

A

antimarkovnkov addition to create a aldehyde

31
Q

H2SO4, H2O and internal alkyne

A

markonikov addition to produce ketone

32
Q

Why are aldehydes more reactive than ketones?

A

Bc they do not have weakly activating aklykl groups on both sides like a ketone does

33
Q

True or False?

With a strong nucleophile and good leaving group a nucleophilic addition reaction will occur

A

False, you need a poor LG so the mechansim can proceed

34
Q

If you have a poor nucleophile what is needed to proceed with NA?

A

Acid catalysis to make the electrophile very strong

35
Q

Hydrate

A

two hydroxyl groups attatched to the same C

36
Q

Acetal

A

two ether groups attatched to the same C

37
Q

What is the first part of acetal formation?

A

the formation of the hemiacetal
1. pt
2. nuc attack
3. pt

38
Q

What is the main intermediate for NA?

A

A hemiacetal

39
Q

What is the second part of acetal formation

A

formation of the acetal
1. pt
2. nuc attack
3. LLG
4. pt

40
Q

Acetals can be used as — — if you want to selectivley reduce a C=O bond

A

blocking groups

41
Q

primary amines make —-

A

imines

42
Q

Secondary amines make —-

A

enamines

43
Q

What is the key intermediate of imine formation?

A

carbinolamine
- neutral intermedaite

44
Q

Mechanistic steps for formation of the imine intermediate (carbinolamine)

A
  1. nuc attack
  2. proton transfer
  3. proton transfer
45
Q

Mechanistic steps to second part of imine formation

A
  1. proton transfer
  2. LLG
  3. proton transfer
46
Q

The formation of thioacetals is directly analogus to what other process?

A

acetal formation

47
Q

Thioacetals when treated with —- – will yield an alkane

A

Raney Ni

reagents: acid + dithiol and Raney Ni

48
Q

Wolf Kishner reduction

A

Heat + base to completely remove/ reduce an imine

Ochem 2 (7 decks)

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