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Flashcards in Aromatic Chemistry Deck (27)
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1

What is benzenes formula and structure

C6H6

Ring

2

What is another name for arenes

Aromatic compounds

3

What is the most common type of reaction of benzene

Substitution

4

What is the shape of benzene

Flat, regular hexagon
Bond angle = 120

5

What is the bond length between adjacent C atoms

Intermediate between C-C and C=C

6

What happens to the 4th electron in the p orbital of each C atom in benzene

It delocalises to form rings of electron density above and below the hexagon, forming rings of delocalised electron density above/below the hexagon

7

What is the effect on benzenes stability of the rings of electron density

Makes benzene very stable, even though it is unsaturated

8

What is the thermochemical evidence that benzene is more stable than cyclohexane-1,3,5-triene

Benzene needs more energy to hydrogenate it

9

Why is cyclohexane-1,3,5-triene not a suitable model for benzene

Not symmetrical like benzene
Would easily undergo addition reactions but benzene does not
Would form two isomers on the addition of Br2 but benzene does not

10

What is the appearance of benzene at 298K

Colourless liquid

11

Why does benzene have a relatively high melting point

Close packing of flat hexagonal molecules when solid

12

Is benzene soluble

No as it is non polar

13

Dangers of benzene

It is a carcinogen

14

Why is benzene attacked by electrophiles

High electron density above/below ring to delocalised electrons

15

What is delocalisation energy and why is the effect of this on benzenes reactions

The large amount of energy that is needed to break the aromatic ring apart
Results in the aromatic ring almost always staying intact

16

What is seen when benzene is combusted

Smokey flame due to soot from unburnt carbon
This is because of the high carbon:hydrogen ratio

17

What ion is used to nitrate benzene

NO2+

18

How is this NO2+ ion generated

H2SO4 + HNO3 -> H2NO3+ + HSO4-
H2NO3+ -> H2O + NO2+

Overall:
H2SO4 + HNO3 -> HSO4- + NO2+ + H2O

19

How is the H2SO4 catalyst regenerated in the nutrition of benzene

HSO4- + H+ -> H2SO4
H+ from benzene ring

20

What are the uses of nitrated arenes

Production of explosives eg TNT

21

How do substituents with a positive inductive effect further substitution

They release electrons into the delocalised electron ring, increasing the electron density and making further substitution reactions more quick

22

How do substituents with a negative inductive effect further substitution

Remove electrons from the delocalised electron ring, decreasing the electron density and making further substitution reactions less quick

23

What type of catalyst is used for Friedel-Crafts reaction

A halogen carrier
AlCl3

24

What is happening when AlCl4- is formed in terms of electrons

Chlorine atoms line pair of electrons is forming a coordinate bond to Al

25

How is the AlCl3 catalyst reformed

AlCl4- + H+ -> HCl + AlCl3

26

In a cyclic compound, what might happen if two double bonds are next to each other

C=C bonds are in close proximity, so electrons in our cloud/p orbitals can partially delocalised and move between the two C=C double bonds

27

What effect would electrons in p orbitals moving between the two C=C double bonds have on the stability of the molecule and it’s enthalpy of hydrogenation

Makes the molecule more stave
Makes enthalpy of hydrogenation more positive