Benzene Flahcards Flashcards

1
Q

Nitration of benzene

A

Electrophile substitution
HNO3 + H2SO4 -> HSO4- + NO2 + H2O
H+ + HSO4- -> H2SO4
50°c

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2
Q

Halogenation of Benzene

A

Halogen carrier + halogen -> FeCl4- + Cl+
Electrophile substitution
Halogen+ ion is electrophile
FeCl4- + H+ -> FeCl3 + HCl

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3
Q

Structure of benzene

A

Each of 6C atom is bonded to two other and one H atom.
A p orbital from each c atom with one electron in form pi bonds above and below plane of carbon atoms to form clouds of high electron density
The electrons are delocalised

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4
Q

Kekule

A

Enthalpy change of halogenation is not what is expected
Bond length is between c-c and c=c
Dose not recolour use bromine water under normal conditions

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5
Q

Properties of benzene

A

Colourless liquid
Sweet odour
Highly flammable
Carcinogen ( anaemia, leukaemia)

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6
Q

Where is benzene found

A

Volcanoes
Forest fires
Crude oil, petrol, cigarette smoke

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7
Q

Properties of phenol

A

Solid at room temp + pressure
Slightly soluble
Weak acid
Takes part in acid reactions

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8
Q

Increased reactivity of phenol

A

A lone pair of electrons from oxygen overlaps with the ring and the electrons become delocalised as well
Higher electron density
Polarises bromine so attracted more strongly to the ring structure

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9
Q

Uses of phenols

A

Detergents
Antiseptic
Preparation of pharmaceuticals
Epoxy resins.

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10
Q

Why does the carbonyl group not react the same as an alkene

A

The oxygen atom is more electronegative

So the electrons are attracted more to the oxygen creating a dipole

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11
Q

Reducing aldehydes and ketones

A

Nucleophilic addition
Sodium tetrahydridoborate (III) generates hydride ions
Electron deficient carbon attacked by nucleophile
Pi bond breaks electrons to O
Negatively charges intermediate
Intermediate donates electron pair to hydrogen on water
Hydroxide formed

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12
Q

Detecting carbonyl in ketone and aldehydes using Brady’s reagent

A

Add 2,4-DNP methanol and H2SO4

If aldehyde or ketone an orange/yellow precipitate of 2,4-Dintirophenylhydazone

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13
Q

Using Tollens’

A
NaOH+ AgNO3 
Silver oxide brown precipitate
Dissolve in dilute aqueous ammonia
Aldehydes silver solid
Ketone no reaction / not oxidised
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14
Q

How to identify a carbonyl compound

A
2,4-dinitrohydrazone is impure so filter 
Recrystallise 
Filter again 
Melting point is measured
And compared to table
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15
Q

Base properties in amines with alkyl groups

A

Alkyl groups are slightly electron donating

Called inductive effect the more alkyl chains the more basic

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16
Q

Phenylamine

A

Ring activation
Lone pair delocalise into ring
So weakens lone pair effect
And les basic