Learning The Structure Of Benzene

Question 1

Explain the structure of benzene molecule with reference to delocalized pi electrons

Answer 1

Each carbon atom is bonded to other carbon atoms and one hydrogen atom the final lone pair of electron is in a p orbital which sticks out above and below

Question 2

What is delocalisation

Answer 2

The pi electrons are spread over several Atoms

Question 3

Why are all the carbon-carbon Bonds in the molecule the same length

Answer 3

Due to the delocalized electron structure all the carbon-carbon Bonds in the molecule the same the other same Bond lengths

Question 4

What do the electrons in the P orbitals combine to form

Answer 4

Delocalized ring of electrons

Question 5

Draw the kekule structure of benzene molecule

Answer 5

3 alternating bonds,

Question 6

What is kekule benzene structure wrong

Answer 6

As in benzene all the carbon carbon Bond lengths are equal. Therefore circular structure is wrong as it represents that there are two different types of carbon-carbon bonds in benzene a carbon-carbon double bond and a carbon carbon single Bond.

Question 7

Why is benzene stable and how can we determine stability

Answer 7

We do this by measuring stability of benzene by comparing the enthalpy change of hydrogenation in benzene and cyclohexane 135 triene
The enthalpy change of hydrogenation benzene in experimental factors is much lower in comparison to therapeutically value
Predicted =-360 REAL -280

Energy required to break bonds and energy is required to release bonds so they suggest more energy is required to break bonds in benzene than cyclo hexene 1,3,5 triene
This suggests benzene is more stable than theoretical value with 3 soluble bonds as this stability of greater energy required to break bonds is due to delivalised electrons. Less exothermic and more endo

Question 8

The of phenol and phenyl amine

Answer 8

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Question 9

Why do arenes undergo electrophilic substitution reaction

Answer 9

Benzene has a high electron density . As it has deloclaised electrons. This is attractive to electrophiles- electron loving substances

Question 10

Why does benzene not undergo electrophilic addition like alkenes

Answer 10

This is because benzene a stable so unlike traditional alkenes do not undergo electrophilic addition reactions as this would disrupt the stable ring of electrons

Question 11

How does electrophilic substitution take place in a benzene ring

Answer 11

What about a hydrogen or functional group on the benzene ring is substituted for the electrophile

Question 12

How can benzene be made useful through frediel crafts acylation and what steps are done to allow this to happen?

Answer 12

To add an acyl group (rco) on to the benzene molecule on order to weaken the benzene molecule and make it easier to modify products.

Question 13

What must be done in order to add onto the benzene ring

Answer 13

Electrophile must have very strong positive charge ACYL groups have positive charge , however it is not positive enough therefore we use a halongen carrier to act as the catalyst example aluminium chloride which will produce a much stronger electrophile with a stronger positive charge

Question 14

How do we create our strong positive electrophile in Friedel crafts acylation

Answer 14

We have to react an acyl chloride with the halogen carrier example aluminium chloride to create a strong positive electrophile

Question 15

Explain the reaction of acyl chloride with aluminium chloride

Answer 15

Acyl chloride + aluminium chloride = carbo cation where by the chlorine is removed from the acyl chloride onto the aluminium chloride to form aluminium chloride for

Question 16

Draw the mechanism of fidel crafts acylation , what happens?

Answer 16

For the friedel-crafts acylation what happens is the card and super duper positive so the benzene ring is attracted to therefore an arrow is moved towards the carbo cation this forms a bond with the benzene ring popping the hydrogen out to and breaking the stable molecule into a partial they look like electron there by the chlorine aluminium chloride is a truck to the hydrogen breaking the hydrogen bonds therefore leave the Travelcard on with the benzene ring and hydrogen chloride is formed with The Catalyst aluminium chloride

Question 17

How Can we make the electrophile for nitration of benzene

Answer 17

The first step is to make the electrophile so we react sulfuric acid with nitric acid
HNO3+H2S04= H2N03+HS04

The next step is to decompose the H2N03 rom the nitronium ion
H2N03= N02_+ + H20

Question 18

Draw the mechanism of nitronium ion reacting with benzene

Answer 18

To the benzene ring is attracted to the positively charged nitronium ion because of 18 of a the benzene ring is a high charge density due to the delocalized electron making it electrophilic so Audrey loves electric fan that Tony my on and then this forms and M Newman hydrogen ion parsley breaking the delocalized electron there by the hydrogen carbon halogen Bond is reformed to the delocalized electron the nitronium benzene is formed and a hydrogen is 4 much reacts with hydrogen sulfate from the previous like to make hydrogensulphate agin so had himself it is a catalyst

Question 19

Draw the structure of TNT,

Answer 19

There’s 3 nitrogen oxides and 1 methyl group

Question 20

Explain the mechanism of mono bromination, name the catalyst used and why ?

Answer 20

The Catalyst that can be used is iron bromide or aluminium bromide which are halogen carriers,
Interaction between bromine and halogen carrier occurs through coordinate bond I pair if electrons of bromide to iron. Order to Warners Corton upon deployment has lost some electrons so not it’s trying to receive its electrons once again therefore pull some more of the electrons from the that can bromine molecule there for weakening the bond between the bromine molecules and the bromine molecule the positive one is now able to act as an electrophile . Now that the bromine is attached to the iron it’s able to proceed as normal so you know how the benzene is attracted to the bromine molecule . The hydrogen is removed from the intermediate stage by stage by reacting with the bromine from the Intermediate because only one of the bromine have either interlocked into the benzene ring
This leads to the formation of bromobenzene and hydrogen for me and The Catalyst iron bromide. BR bromine is acting as a halogen carrier catalyst as a gift catalyst back at the end of the reaction.

Question 21

Explain the difference between benzene bromination and alkene bromination

Answer 21

Electron density in cyclohexene is enough to polarize by bromine molecule as a has a double bond the generator electrophile needed to the bromine is attracted to the double bond and therefore whenever therefore whenever the formula of the brahmins having a tractor to the cyclohexene that forms a positive like area in the benzene ring whereby the second bromine which is negatively charge it able to be attracted to the alkene molecule and therefore no chylous is needed as only from one molecule with cyclohexene with the two bromine molecules
Whilst in contrast in the benzene and bromine electrophilic substitution the elctron density are way to spread out there for the charge density is not enough therefore we need a catalyst to generate the positive cation to polarise the bromine molecule

Question 22

Clean the mechanisms of Mona alkylation and the equations for Mona alkylation

Answer 22

Turn order to regenerate the alkali group CH3 you reacted with aluminium chloride,
Ch3cl+ALCL3= ALCL4+ CH3+

CAN BE REGENERATED BY H REACTING WITH CH3

Question 23

What is the name of the electrophile for the bromination of benzene

Answer 23

Bromine is the electrophile which forms of Sigma Bond to the benzene ring

Question 24

What are the electrophile for the nitration of benzene

Answer 24

Electrophiles are the nitronium ion on the sulphur trioxide electrophiles an individual reacts with benzene to give nitrobenzene and benzo sulfinic acid respectively

Question 25

How do we prepare methyl 3-nitrobenzoate

Answer 25

We use nitrate methyl benzoate however this is very creative so we want to form a last course of product therefore we are the nitronium ion onto it and yeah it forms the methyl 3-nitrobenzoate