Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Organic Chem Is Killing Me > Arenes > Flashcards

Arenes Flashcards

You may prefer our related Brainscape-certified flashcards:
Periodic Table flashcards Chemistry 101 flashcards AP® Chemistry flashcards Organic Chemistry 101 flashcards
1
Q

[ARENES] What does aromatic compound mean?

A

cyclically conjugated
stability more than hypothetical localised structure due to delocalisation
its usually benzene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

[ARENES] Formula of benzene ring?

A

C6H6
When the ratio of C:H is close to 1:1, its safe to assume a benzene ring is in the structure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

[ARENES] C-C bond length in benzene?

A

all same length 0.140nm
longer than C=C but shorter than C-C, hence partial double bond character

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

[ARENES] Enthalpy difference in theoretical and actual arenes

A

Hypothetical enthalpy is higher(less stable) than the actual of benzene.
Difference in energy is known as resonance energy.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

[ARENES] Why does benzene not react like an alkene and undergo addition?

A

They undergo substitution reactions instead.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

[ARENES] Resonance hybrid structure of Benzene?

A

Each C atom is sp2 hybridised

BONDS:
C has 3 sp2 hybrid orbitals in trigonal planar, hence 180°
2 overlap head on with other sp2s from other C atoms to make 2 ring C-C bonds
last 1 overlap head on with 1s in H

DELOCALISED pi e CLOUD: one more unhybridised p orbital, perpendicular to molecular plane (it just sticks out)
All the unhybridised p orbitals overlap side on with neighbouring p orbitals, forming a cyclic delocalised pi e cloud

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

[ARENES] What are the physical properties of arenes? (no explanation just yes/no answers)

  • boiling/melting points
  • Solubility in polar/non-polar solvents
  • density compared to H2O
  • Type of molecular attraction
  • colour of flame
A

bp/mp are low, usually in liquid form
bp increase with Mr, more e, larger polarisibility or e cloud, stronger idid
mp trend irregular as it depends on molecular symmetry

Soluble in polar, not soluble in non-soluble

less dense than water, immiscible

idid foa

smoky, luminous orange flames

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

[ARENES] Bp/mp of arenes

A

Bp increases with Mr
more e
more polarisible e cloud
stronger idid

Mp depends on molecular symmetry but generally low

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

[ARENES] Solubilty of arenes in polar/H2O

A

Insoluble
energy formed by pd-id btwn water/polar and arene
insufficient to overcome
idid btwn arene and ion-dipole interaction/pdpd btwn H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

[ARENES] Solubilty of arenes in non-polar

A

Soluble
energy formed by idid btwn water/non polar and arene
sufficient to overcome
idid btwn arene and non polar solvent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

[ARENES] Density of arene

A

less dense than h2o and immiscible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

[ARENES] Type of flame of burning arene

A

Smoky, luminous orange flame
due to high C:H

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

[ARENES] Reactivity and site of attack of benzene vs cyclohexene (Alkene)

A

C=C highly susceptible to electrophilic attack

pi e cloud is susceptible
Resonance stabilisation of benzene
less reactive towards electrophiles than alkene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

[ARENES] What type of reaction and why?
Arene with halogen

A

Substitution to preserve resonance stabilised ring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

[ARENES] Site of electrophilic attack when halogen is added to arene?

A

pi electron cloud

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

[ARENES] alkene vs arene
reactivity with halogens

A

arene less reactive with halogen
resonance stabilisation
delocalise pi e
less reactive to electrophiles

17
Q

[ARENES] Types of electrophilic substitution reactions that can happen to an arene ring

A

Electrophilic substitution:

  1. Halogenation
  2. Nitration
  3. Friedel-crafts Alkylation

Friedel-crafts acylation (NOT TESTED DONT EVEN BOTHER)

18
Q

[ARENES] Requirement for electrophilic substitution in Arenes

A

Strong electrophile

19
Q

[ARENES] Electrophilic substitution in arenes (general eqn)

A
20
Q

[ARENES] Slow and fast steps of electrophilic substitution in arenes
and why is that step the rate determining step (RDS)?

A
  1. Generate strong electrophile (fast)
  2. Electrophilic attack of E+ on benzene ring forms resonance-stabilised arenium ion (slow)
  3. Deprotonation and regen benzene ring (fast)

RDS (step 2) due to destruction of aromaticity of benzene ring

21
Q

[ARENES] Steps of electrophilic substitution in arenes and fast/slow steps

A
  1. Generation of strong electrophile (slow)
  2. Electrophilic attack on benzene ring to from resonance-stable arenium ion (slow/RDS)
  3. Deprotonation and regeneration of benzene ring
22
Q

[ARENES] Reagent and conditions for Nitration of arenes

A

conc HNO3
conc H2SO4 catalyst
kept under 55c, exothermic, must cool

23
Q

[ARENES] Eqn/mechanism for Nitration of arenes

A

conc HNO3
conc H2SO4 catalyst
kept under 55c, exothermic, must cool

24
Q

[ARENES] Reagent and conditions for Halogenation of arenes

A

X2 (Cl/Br)
Lewis acid catalyst ANHYDROUS AlX3, FeX3
(if there is water present it will (hydrolyse) incapacitate the catalyst so dont do that)
room temp

25
Q

[ARENES] Mechanism for Halogenation of arenes

A

Electrophilic sub

26
Q

[ARENES] Reagent and conditions for Friedel-crafts alkylation of arenes

A

RX, excess benzene
Lewis acid catalyst AlX3, FeX3
room temp

27
Q

[ARENES] Difference between 3 types of electrophilic substitution in arenes

A

Nitration: Nitrate added to benzene ring
Halogenation: Halogen added to benzene ring
Friedel-crafts alkylation: R added to benzene ring while X (halogen) joins the removed H to form HX

28
Q

[ARENES] Requirement of halogenation of arene

A

Lewis acid acting as a halogen carrier
anhydrous FeX3, AlX3,
or finely divided Fe which converts to FeX3 anyway lmao

29
Q

[ARENES] Nitration in arenes eqns

A
30
Q

[ARENES] Summary of electrophilic substitution reactions of benzene

A
31
Q

[ARENES] Substituent on benzene ring determines

A
  • reactivity
  • orientation
32
Q

[ARENES] Substituents effect on reactivity

A

ACTIVATING GROUPS
increase rate of electro sub

DEACTIVATING GROUPS
decrease rate of electro sub

33
Q

[ARENES] Substituents effect on reactivity

A

ACTIVATING GROUPS
increase rate of electro sub

DEACTIVATING GROUPS
decrease rate of electro sub

34
Q

[ARENES] Effect on reactivity for activating groups

A

increase electo sub
activating groups
donate e density to benzene ring
increase avail of pi electron cloud
stabilises arenium intermediate
by dispersing pos charge
lowering EA
more susceptible to electro attack

35
Q

[ARENES] Effect on reactivity for deactivating groups

A

decrease electo sub
deactivating groups
withdraw e density from beznene ring
decrerase avail of pi electron cloud
destabilises arenium intermediate
by intensify pos charge
raising EA
less susceptible to electro attack

36
Q

[ARENES] Types of reactions on benzene (aromatic vs aliphatic portion)

A 
Aromatic portion (benzene ring): electrophilic sub
Aliphatic (side group): FRS, side chain [O]
37
Q

[ARENES] Compare products of benzene vs methylbenzene for halogenation and nitration

A

Benzene just adds the NO2 or X anywhere

Methylbenzene NO2/X attaches to 2-/4- position
RELATIVE TO CH3
aka adjacent or opposite

38
Q

[ARENES] Side chain FRS mechanism

A

UV light
Limited Cl
Excess of methylbenzene

39
Q

[ARENES] Side chain oxidation

A

Acidified KMnO4, heat
methybenzene to
benzoic acid (-CO2H)
benzaldehyde (-CHO)

Organic Chem Is Killing Me (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions