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Medicinal Chemistry > Aromatics > Flashcards

Aromatics Flashcards

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1
Q

What is phenyl?

A

C6H5

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2
Q

What is benzyl?

A

C6H5CH2

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3
Q

Describe benzene structure

A

Planar

120 degrees = sp2

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4
Q

What are the significant features of benzene?

A

C-C bond length = 140pm
More stable than predicted
Hydrogenation of cyclohexene = 120kJmol-1

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5
Q

What is significance of hydrogenation of cyclohexene = 120kJmol-1?

A

Calculated value of benzene = 210kjMOL-1

Difference = empirical resonance energy

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6
Q

LEARN WHELAND INTERMEDIATE + GRAPH

A

NOTES

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7
Q

What drives the process?

A

Energy from complete formation of new bond attack E+

Delocalisation of charge of Wheland intermediate

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8
Q

What are the different benzene reactions?

A

Nitration
Sulfonation
Halogenation
Friedel Crafts

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9
Q

What is general nitration?

A

Warm benzene with concentrated mix of HNO3 + H2SO4

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10
Q

What is the E+ for nitration?

A

NO2+

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11
Q

What is the overall equation for nitration?

A

HNO3 + 2H2SO4 ⇆ NO2+ + H3O+ + 2HSO4-

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12
Q

What happens in nitration mechanism?

A

Nitronium cation attack pi system, forming sigma complex

= loses H+

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13
Q

What is required for sulfonation?

A

Concentrated H2SO4

150 degrees

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14
Q

What is the equation for sulfonation?

A

2H2SO4 ⇆ SO3 + H3O+ + HSO4-

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15
Q

What can benzenesulfonic acid be isolated by + why important?

A

NaOH

Sodium benzenesulfonate can be converted to benzene sulfonyl

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16
Q

What is the equation for benzenesulfonic acid + NaOH?

A

Sodium benzenesulfonate + H2O

17
Q

What is needed for halogenation?

A

AlCl3 or FeCl3 = chlorine

FeBr3 = bromine

18
Q

What happens to halogenation if there is no Lewis acid catalyst?

A

Very slow

19
Q

What happens to Fe catalyst in halogenation?

A

React in situ with X2 to form FeX3

20
Q

Why are iodine or fluorine not used?

A

Present problems

= too reactive

21
Q

What is the equation for with iodine?

A

2H+ + I2 + H2O —-> 2H2OI+

Benzene + H2OI+ —-> Iodobenzene + H3O+

22
Q

What are the Friedel Crafts reactions?

A

Alkylation

Acylation

23
Q

What is needed for Friedel Crafts reactions?

A

Lewis acid catalyst

24
Q

What are the three type of precursor for alkylation?

A

Alkyl halide
Aliphatic
Alkenes

25
Q

What is the most stable alkyl carbocation?

A

Methyl = most stable
Primary
Secondary
Tertiary = least stable

26
Q

What is used in monoalkylation?

A

Excess of benzene

27
Q

What can you alkylation with?

A

Alcohols

Alkenes

28
Q

What is the general equation for acylation?

A

Benzene —-> ketone + HCl
AlCl3
Acid chloride

29
Q

Why is H2O + acid added at end of reaction?

A

Hydrolyse Lewis acid + liberate ketone

30
Q

Does acylation take place more rapidly than alkylation?

A

YES

Medicinal Chemistry (19 decks)

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