Brainscape's Knowledge GenomeTM

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


See full index

Chemistry Module 6 > 6.1.1 Aromatic Compounds > Flashcards

6.1.1 Aromatic Compounds Flashcards

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

Aliphatic

A

Straight or branched chain organic substancex

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

Aromatic/arene

A

Includes one of more rings of six carbons with delocalised bonding

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

Benzene structure

A

C6H6
Carbon to 2 carbons and one hydrogen by single covalent sigma bonds
One unused electron in each C atom in a p orbital, perpendicular to plane of ring
6 p electrons are delocalised into a ring above and below carbon atoms

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

Kekule model

A

Alternate single and double covalent bonds

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

What type of molecule is benzene what does this suggest

A

Planar

All C-C bonds are the same and have a length and bond energy between a CC single and CC double

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

HCC bond angle in benzene

A

120 degrees

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

What is delocalisation energy

A

Increase in stability connected to delocalisation

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

Enthalpies of hydrogenation

A

Would expect when 3 double bonds for the hydrogenation to be 3 times greater
Real amount is less as 6 pi electrons are delocalised
Delocalised is more thermodynamically stable

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

Evidence for why benzene has a delocalised structure

A

Bond length intermediate between short C=C and long C-C
🔼H hydrogenation less exothermic than expected when compared to that of Kekule structure
Only reacts with Br2 at high temp or presence of halogen carrier
Doesn’t undergo addition reactions

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

Reactions of benzene

A

Doesn’t undergo addition reactions as they’d have to break delocalised system
Electrophillic substitution

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

Toxicity of benzene

A

Benzene is a carcinogen
Methylbenzene less toxic and reacts more readily as methyl side group releases electrons into delocalised ring, more attractive to electrophiles

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

Nitration of benzene

A 
Benzene to nitrobenzene 
Conc nitric scid 
Conc sulfuric acid catalyst 
Electrophillic substitution 
Uses NO2+ as electrophile
50 degrees temp
Reacts slowly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Bonding in delocalised

A

Draw hexagon with p orbitals above and below
Show overlap
Then draw ring

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

Enthalpy of hydrogenation

A

Enthalpy change when one mole of unsaturated compound reacts with an excess of hydrogen to become fully saturated

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

Nitration full stages

A 
1. Create electrophile: 
HNO3 + H2SO4 -> NO2+ +H2SO4- +H2O
2. Dative covalent bond (mechanism)
3. Catalyst regenerated:
H+ + HSO4- -> H2SO4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Halogenation

A 
Benzene to bromobenzene 
Bromine
Iron 3 bromide catalyst (FeBr3)
Electrophillic substitution 
Can be done with chlorine with (AlCl3 or FeCl3)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

naming aromatic compounds

A

if group is: alkyl, halogen, nitro then added as a prefix ___ benzene
if group is: amine,ester, alcohol or ketone then phenyl___

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

which groups get ___benzene

A

alkyl
halogen
nitro

19
Q

which groups get phenyl ___

A

amine
ester
alcohol
ketone

20
Q

Halogenation full stages

A 
1. Create electrophile:
AlBr3 + Br2 -> AlBr4- + Br+
2. Dative covalent bond forms unstable intermediate
3. Catalyst regenerated:
H+ + AlBr4- -> AlBr3 + HBr
21
Q

which category of reactions are alkylation and acylation?

A

Friedel Crafts

22
Q

Alkylation

A

benzene to alkyl benzene
chloroalkane in the presence of anhydrous aluminium chloride catalyst
heat under reflux
electrophillic substitution

23
Q

Alkylation full steps

A 
1. Create electrophile:
AlCl3 + CH3Cl -> AlCl4- + CH3+
2. Accepts lone pair, dative covalent bond is formed 
3. Catalyst is regenerated
AlCl4- + H+ -> AlCl3 + HCl
24
Q

Acylation

A

benzene to phenyl ketone
acyl chloride in the presence of anhydrous aluminium chloride catalyst
heat under reflux at 50 degrees
electrophilic substitution

25
Q

Acylation full steps

A 
1. Create electrophile
AlCl3 + CH3COCl -> AlCl4- + CH3CO+
2. Forms a dative covalent bond
3. Catalyst regeneration: 
AlCl4- + H+ -> AlCl3 + HCl
26
Q

naming acyl chlorides

A

look like a carboxylic acid but have Cl in replacement of OH
Name carbon chain first (ethanoyl) then place “chloride” on the end

27
Q

phenol definition

A

aromatic compound where a hydroxyl (OH) group is directly bonded to the benzene ring

28
Q

phenols as acids

A

very weakly acidic

weaker than carboxylic acids

29
Q

reactions: phenols vs carboxylic acids

A

both: react with sodium metal and sodium hydroxide (metals and strong bases)
carboxylic acids: react with sodium carbonate (weak base)
phenols: bromine

30
Q

phenols in water, proof of weak acid

A

less soluble in water than alcohols due to non-polar benzene ring
dissolved in water partially dissociates to form phenoxide ion and a proton
as it only partially dissociates phenol is a weak acid

31
Q

phenols reaction with alkalis

A

forms a salt (sodium phenoxide) and water in neutralisation reactions
acid + alkali -> salt + water
C6H5OH + NaOH -> C6H5 O- Na+ + H2O
if more than one OH then excess alkali, put alkali on each

make sure ions aren’t bonded but just next to each other

32
Q

phenols reactions with metals

A

need to balance this equation
acid + metal -> salt + hydrogen
phenol + sodium -> sodium phenoxide + hydrogen

33
Q

bromination with phenol

A

Br2
room temperature
decolourised water forms a white ppt

34
Q

bromination with phenol full steps

A

max 3 bromine added

decolarised water forms a white ppt

35
Q

why is phenol more reactive with bromine than benzene

A

one of the lone pairs of electrons on p orbital of oxygen atom in OH is partially delocalised into the ring
increases the electron density
electrophile is more polarised
so can react more readily

36
Q

nitration with phenol

A

reacts with dilute nitric acid
at room temperature
adds to carbon 2,4 or 6

37
Q

nitration of phenol full steps

A

react with dilute nitric acid
forms 2-nitrophenol or 4-nitrophenol
2 nitro is more common as 6 would be the same as 2 is the second carbon was free
also forms water

38
Q

effect of electron donating

A

increases electron density

39
Q

effect of electron withdrawing

A

decreases electron density

40
Q

electron donating

A

side chains increase the density
allow electrophiles to react faster, activating groups
in OH and NH2 the O and the N lone pairs overlap the ring
substitute onto position 2,4,6
2,4 directing

41
Q

electron withdrawing

A

side chains decrease density
slow electrophile reactions, de-activating groups
NO2, the O is more electronegative so electrons are drawn away from the ring
groups direct substitution to 3 and 5
3-directing

42
Q

2,4-directing

A

OH
NH2
F, Cl, Br
R (carbon chain)

43
Q

3-directing

A

NO2
COOH
CHO
COOR (ester)

Chemistry Module 6 (10 decks)

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