Phenols Flashcards

1
Q

Acidity of phenol
What is pH?
What is the ion produced?
Why its acidic?

A

PH-5/6
Phenoxide ion
Because the negative charge is delocalised onto the ring as the electrons in the P orbital of Oxygen and the Pi electrons of the ring overlap,this gives it stability so likely to donate H+ and is an acid

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2
Q

Acidity of ethanol
Ion produced?
pH?
Why not acidic?

A

Ethoxide ion
PH- 7.3
Not acidic- ethyl group donates electron density as alkyl groups are electron releasing, the negative charge is not delocalised so no extra stability, it’s not likely to donate H+ so not acidic
It’s neutral in aqueous solution

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3
Q

Ethanoic acid
pH?
Ion produced?
Why acidic?

A

Ethane ate ion
pH- 3
It is acidic - the negative charge is delocalised over the O atoms, the delocalisation is stronger than phenol so has more stability, likely to donate H+

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4
Q

Water
Ion produced
pH?
Why?

A

Hydroxide ion
pH-7
Slightly more likely to give up H+ than ethanol so is more acidic, but is still not classed as acidic

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5
Q

What is phenol?

A

An aromatic ring which 1 or more of the aromatic hydrogen atoms are replaced by an OH group

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6
Q

Why is phenol dangerous?

A

It’s a toxic solid so must avoid skin contact

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7
Q

Why doesn’t phenol behave like a typical aliphatic alcohol despite having an OH group?

A

One of the lone pairs of electrons in the P orbital of oxygen overlaps with the delocalised Pi electrons of the ring to form an extended Delocalised Pi system - so C-O bond has Pi character. Meaning the C-O bond is stronger than the C-O in aliphatic alcohols.
The overlaps also reduces the delta + charge on the C attached to O as its spread over the delocalised system. So the c of the c-o in phenol is less subseptible to NUCLEOPHILIC attack than the c-o in aliphatic.
Although it undergoes NUCLEOPHILIC substitution, it is less likely in phenol when compared to ethanol

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8
Q

Reaction of phenol with bromine or bromine water :

What is the type of reaction?

A

Electrophilic substitution

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9
Q

Reaction of phenol with bromine/Br water

What positions are subsituted?

A

2,4,6 positions

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10
Q

Reaction of phenol with bromine / Br water

What is an observation of this?

A

White PPT

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11
Q

Why is phenol more subseptible to Electrophilic substitution than benzene?

A

A catalyst isn’t required e.g FeBr3

Concentrated bromine not required

A mono-substituted product is not produced

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12
Q

Why doesn’t phenol produce an ester with a carboxylic acid and concentrated H2SO4?

A

Because it does not behave like a typical alcohol

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13
Q

What does phenol react with to produce an ester?

What is this reaction called?

A

Ethanoyl chloride

Called an ethanoylation RXN or NUCLEOPHILIC substitution

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14
Q

What does phenol and ethanoyl chloride produce?

A

Phenylethanoate (ester)

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15
Q

Reaction steps in words for preparation of aspirin

A

1- phenol + NaOH

2- sodium phenoxide + CO2/H+

3- salicylic acid

4- ethanoic anhydride + salicylic acid at 90 degrees

5- aspirin + ethanoic acid

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16
Q

What are reagents and conditions for industrial preparation of aspirin?

A

Ethanoic anhydride

90 degrees

17
Q

Reaction test - aqueous iron (III) chloride

What reacts with iron 3 chloride and what does it produce?

A

The phenolic OH group (directly attached to ring) of phenol reacts with iron 3 chloride to produce a PURPLE COLOUR

18
Q

In aqeous iron III chloride why don’t aliphatic alcohols give a purple colour?

A

Because the OH group. Is not phenolic and attached directly to the ring

19
Q

What can also produce a purple colour with aqueous iron III chloride?

A

Other compounds that contain a phenolic OH GROUP such as salicylic acid

20
Q

What are the reagents for Triiodomethane (iodoform) test

And what is seen if the compound is present?

A

I2 / NaOH (aq)

A positive result is seen if the fragment is present

21
Q

What does the positive result consist of in the Triiodomethane iodoform test?

A

A yellow PPT and an antiseptic smell

22
Q

What is the only 1 degree alcohol that gives a positive result in Triiodomethane test?

A

Ethanol.

23
Q

What alcohols don’t give a positive result in Triiodomethane test?

A

Tertiary alcohols

24
Q

Give chemical test for phenol

A

Aqueous iron (III) chloride

25
Q

How can we distinguish phenol?

A

React it with iron (III) chloride and it produces a purple colour- phenolic OH reacts with it

26
Q

What type of reaction is phenol with bromine?

A

Electrophilic substitution

27
Q

Phenol produces an ester in a reaction, but with what reagent?

A

Ethanoyl chloride - NUCLEOPHILIC substitution to produce phenylethanoate

28
Q

What is the positive result seen when phenol reacts with reagents

(Name reagents also)

A

Reagents are sodium hydroxide (aq) and iodine

Positive result is CH3CHOH