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2023-2024 > Organic II - Aromaticity > Flashcards

Organic II - Aromaticity Flashcards

1
Q

What is the simplest aromatic hydrocarbon (or arene)?

A

Benzene

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2
Q

How many degrees of unsaturation does benzene have?

A

4

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3
Q

Is benzene highly unstaturated? Why or why not?

A

It is unsaturated because it has 4 degrees of unsaturation.

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4
Q

List some saturated hydrocarbons.

A

Alkenes, alkynes and dienes.

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5
Q

What kind of reactions do saturated carbons go through?

A

Addition reactions.

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6
Q

How does benzene react with bromine?

A

Reacts with bromine only in the presence of FeBr3 (lewis acid) and results in substitution, not addition.

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7
Q

What does a low heat of hydrogenation of benzene mean?

A

Benzene is stable (more than conjugated polyenes).

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8
Q

Define annulenes.

A

Hydrocarbon with alternating single and double bonds.

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9
Q

Give examples of annulenes.

A

Cyclobutadiene, [4]annulene
Benzene, [6]annulene
Cyclooctatetraene, [8]annulene

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10
Q

Why is cyclooctatetraene less stable than benzene?

A

Because it can’t form resonance structures.

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11
Q

Cyclooctatetraene with Br2 and CCl4 goes through which reaction and produces what?

A

Addition reactions and produces constitutional isomers. (Ring is changed/touched)

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12
Q

Styrene with Br2 and CCl4 goes through which reaction?

A

Bromination on the non-cyclic bond. (Ring is untouched)

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13
Q

To have pi MOs what needs to happen with the carbons in benzene?

A

Each carbon is sp2 hybridized.

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14
Q

6 p-orbitals give rise to __ pi MOs, __ bonding and __ antibonding.

A

6;3;3

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15
Q

What is the best indication of aromaticity?

A

The presence of a ring current produced by circulating pi electrons.

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16
Q

For a compound to be aromatic, it must have _________ pi electrons.

A

4n + 2
n is the indicator of aromaticity.
Hukcle # = 2, 6, 10, 14

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17
Q

What are the values for aromaticity of the Huckle Rule?

A

2, 6, 10, 14…

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18
Q

If a compound have 3 double bonds, how many pi bonds and pi-electrons does it have?

A

3 pi bonds and 6 pi-electrons.

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19
Q

Do lone pairs count as pi-electrons?

A

Yes.

20
Q

Why is pyrrole (C4H4NH) aromatic?

A

Because the lone pair on the nitrogen is delocalized.

21
Q

Is the N-protonated pyrrole aromatic or nonaromatic? Why?

A

Nonaromatic because the nitrogen is sp3.

22
Q

What does PAH represent?

A

Polyaromatic hydrocarbons

23
Q

As the number of fused aromatic rings increases, what happens to the resonance energy per ring?

A

It decreases, so compound becomes more reactive and can undergo addition reactions.

24
Q

A compound that is classified as “anti-aromatic” has unusual _________.

A

instability

25
Q

Is cyclobutadiene aromatic, anti-aromatic or non-aromatic?

A

Anti-aromatic.

26
Q

Is cyclooctatetrane aromatic, anti-aromatic or non-aromatic?

A

Non-aromatic.
(Can form tub formation)

27
Q

What is an aromatic compound?

A

A cyclic, planar, completely conjugated compound with 4n + 2 pi-electrons.

28
Q

What is an anti-aromatic compound?

A

A cyclic, planar, completely conjugated compound
with 4n pi-electrons.

29
Q

What is a non aromatic compound?

A

A compound that lacks either one of the following requirements for aromaticity; cyclic, planar, and completely conjugated

30
Q

How many basic nitrogens does pyrimidine (C4H4N2) have?

A

2

31
Q

How many of purine’s (C5H4N4) nitrogen’s is not basic?

A

1

32
Q

What is the relationship between pKa value and base/acid?

A

The lower the pKa value, the weaker the base/stronger acid.

33
Q

Two p orbitals of similar phase overlap side-by-side forms…

A

a pi bonding MO.

34
Q

Two p orbitals of opposite phase overlap side-by-side forms…

A

a pi anti-bonding MO.

35
Q

F attached to a benzene is called…

A

Fluorobenzene

36
Q

NO2 attached to a benzene is called…

A

Nitrobenzene

37
Q

CH3 attached to a benzene is called…

A

Toulene

38
Q

OH attached to a benzene is called…

A

Phenol

39
Q

NH2 attached to a benzene is called…

A

Anniline

40
Q

SO3H attached to a benzene is called…

A

Benzene-sulfonic acid

41
Q

OCH3 attached to a benzene is called…

A

Anisole

42
Q

COOH attached to a benzene is called…

A

Benzoic acid

43
Q

COCH3 attached to a benzene is called…

A

Acetophenone

44
Q

Dimethylbenzenes are often called…

A

Xylenes

45
Q

1,3-dimethylbenzene is also called…

A

meta-xylene

46
Q

Of the 3 groups, which is the highest ranked?
Alcohol
Halogen
Methyl/Ethyl

A

Alcohol

2023-2024 (18 decks)

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