LECTURE 20 REFLECTION: ARENES AND PHENOL PART 1 by Pooganeswari Siteram Pillai

Benedict JC2 T

2022-01-17 07:50:08 UTC

ELECTROPHILIC SUBSTITUTION

- Benzene react with bromine with AlBr3 Catalyst
- Benzene react with chlorine with AlCl3 catalyst
- Mehtylbenzene react with Cl2/Br2 to get mixture of products

FREE RADICAL SUBSTITUTION

- Boiling methylbenzene with halogens will cause the hydrogen molecules in the methylgroup to substitute with halogen molecules

NITRATION OF BENZENE (Electrophilic substitution)

concentrated sulfuric acid reacts with concentrated nitric acid to make NO2+ which will undergo electrophilic substitution with Benzene

Alkylation and Acylation
Friedel Crafts reaction

- substitution of alkyl and carbonyl groups into benzene

Acylation is the substitution of carbnonyl groups with chlorides/bormides with benzene rings. Catalyst will be AlCl3/AlBr3

Alkylation is the substitution of alkyl groups with chlorides/bromides with benzene rings. Catalyst will be AlCl3/AlBr3

Oxidation of the side-chain in arenes

- Alkanes are not usually oxidized by potassium mangante (VII)
- But in alkyarenes, the alkane side chain is oxidised to form carboxylic acid (benzoic acid)
- Methylbenzene is oxidised into benzoic acid when refluxed with alkaline potassium manganate(VII) and then acified with dilute sulfuric acid.

Hydrogenation (Electrophilic Addition) - aromatic stabilisation

- Using H2 and platinum/Nickel catalyst with heat and high pressure (harsher condition)
- Inner benzene ring is broken and each carbon atom is bonded to 2 hydrogen atoms. It forms cyclohexane as the product.

Phenol

- C6H5OH
- Crystalline solid that melts at 43 degrees celcius
- week acid (Lower pKa means it is a better week acid (10 pKa))(more acidic)
- Melting Point is high for an aryl compound because of its hydrogen bonding
- not very soluble in water as polarity is distrbed due to OH bond which disrupts the hydrogen bonding with water.
- Phenol is still a stronger acid than water and alcohol

Preperation of Phenol

- Phenylamine is important in synthesis of dyes
1. phenylamine + HNO2 (nitric (III)acid/nitrous acid)
NaNO2 + HCl -> HNO2 + NaCl (kept under 10 celcius to prevent decomposition to give Nitrogen gas)
2. phenylamine + HNO2 + HCl -> benzenediazoniumchloride
benzenediazoniumchloride reacted with water under warm conditions will form phenol + N2 + HCl

- phenoxide ion has its negative chrages spread all over the whole ion as one of the lone pairs on the oxygen atom overlaps with the pi bonding system in the benzene ring
- phenoxide: C6H5OH <=> C6H5O-(less ngeative) + H+

reactions of phenol

- react with alkali to form salt (sodium phenoxide) and water
- The salt (sodium phenoxide) is soluble in water

Frederic JC2T

2022-01-17 10:17:03 UTC

Phenols are benzene rings with a OH functional group which the electron from the oxygen atom overlaps with the delocalised electron system thus hydrogen can be released more easily making phenol slightly acidic.I also revised substitution reactions with benzene such as Nitration, Oxidation,alkylation,acylation,free radical substitution, electrophilic substitution and hydrogenation.
Preparations of phenol will require phenylamine,nitrous acid and HCl. Product is phenol and water

Arwen JC2 Truth

2022-01-17 10:31:07 UTC

Recall:

Electrophilic substitution
- benzene x bromine (AlBr3 catalyst)
- benzene x chlorine (AlCl3 catalyst)
- methylbenzene x Cl2 or Br2
- nitration of benzene
free radical substitution (boiling methylbenzene x chlorine gas under UV light)
Freidel-Crafts Reactions
- alkylation
- acylation

Learned:

phenols
- properties
- preparation
- reactions
  - x alkali -> salt
  - x NaOH -> H2(g), sodium phenoxide

Michael jc2t

2022-01-17 12:36:32 UTC

Methylbenzene

Methylbenzene can undergo free radical substitution because the carbon is not attached to the benzene directly
Methylbenzene will react with chlorine with the presence of uv rays
Must be boiling methylbenzene
NO2 is the electron withdrawing group

Nitration of benzene

NO2 ion made form concentration nitric acid or concentrated sulfuric acid
Nitrating mixture is refluxed with benzene at 55 degree Celsius to make nitrobenzene.
Stage 1 the electrophile is attracted to the high density of the pi bonding of the benzene
Stage 2 full delocalised ring is restored

Alkylation/Acylation Friedel-crafts reaction

can be used to substitute -CH3 and C2H5
Can be used to introduce acyl group
Friedel-Crafts reactions result in the introduction of side chain into benzene ring
The reaction involve attack on the benzene ring by an electrophile carrying a positive charge on a carbon
The electrophile can be formed by adding AlCl3 catalyst to a halogenoalkane

Oxidation of the side-chain in arenes

alkanes are not usually oxidized by potassium manganate (VII)
But in alklarenes, the alkane side chain is oxidized to form carboxylic acid.
Methylbenzene is oxidized into benzoic acid when refluxed with alkaline potassium manganate (VII) and then acidified with dilute sulfuric acid

Hydrogenation (electrophilic addition)

using H2 and Pt/ Ni catalyst with heat and high pressure (harsher condition)

Phenol

C6H5OH
Crystalline solid that melts at 43 degree
Lower pk indicate that it is a better weak acid
Weakly acid
Position lies to the left-hand side
Phenoxide ion has its negative charge spread all over the whole ion as one of the lone pairs on the oxygen atom overlaps with the pi bonding system in the benzene ring
The delocalisation reduces charge density of the negative charge on the phenoxide ion compared to hydroxide ion or ethoxide ion
Therefore the H ion are not strongly attracted to the phenoxide ion making it more to form dissociated molecules

Preparation of phenol

phenylamine is important in synthesis of dyes
1st step: phenylamine +HNO2 (nitric (III) acid/ nitrous acid)
Nitrous acid is unstable and made in test tube (sodium nitrite, NaNO2 + HCl)
Kept under 10 degree celcius
To prevent decomposition to give N2

sharon jc2t

sharonchristiehalimm — 2022-01-17 13:27:33 UTC

Electrophilic substitution
1. Conditions
  1. ‘Halogen carriers’ catalysts : AlBr3, AlCl3,
  2. Room temperature
2. Can react with Br2 and Cl2

Reaction with Br2
- One of the hydrogen from the benzene ring is removed, substituted with Br
- Creating electrophile (of bromine)
  - FeBr3 + Br2 → FeBr4- + Br+
  - FeBr3 polarises the Br2 molecule
- One of the electron from the delocalised ring → donate → Br+
- Bromine forms dative bond
- FeBr4-
Reaction with Cl2
- –same mechanism with Br2–
Electron donating group → position 2,4,6
- -CH3
- -NH2
- -NHR
- -NR2
- -OH
- -OR
- -Cl
- -NHCOR
Excess chlorine with methyl benzene can form
- 1-methyl-2,4-dichlorobenzene
- 1-methyl-2,6-dichloromethane
- 1-methyl-2,4,6-trichloromethane

Free radical substitution

Boiling methylbenzene + chlorine gas
- Presence of UV light
- No substitution into benzene ring
  - No halogen carriers
- If excess, all 3 hydrogen atoms (in methyl) will be substituted

Nitration of benzene (electrophilic substitution)

Electrophile is NO2+
- HNO3 + 2H2SO4 → NO2+ +2HSO4- + H3O+
Nitrating mixture refluxed with benzene at 55 degree celsius (20 to 60 degree celsius) → nitrobenzene
Mechanism
- Electrophile attack the benzene ring
- New bonds forming with NO2
- H will give the electron back forming H+

Friedel-Crafts reaction (electrophilic substitution)

Can be used to substitute -CH3 and C2H5
Can be used to introduce alkyl group
Alkylation
Acylation
- Catalyst (AlCl3/AlBr3)
- Mechanism
  - Creating electrophile
  - Electrophile attacks benzene ring
  - New bond is being formed with the electrophile
  - Previous bond is retrieved (sending electron back from H)
  - Forming H+ (one of the product)

Hydrogenation (electrophilic addition)

Aromatic stabilisation
High temperature, high pressure
Catalyst of Ni/Pt

Oxidation of side chain arenes

Alklarenes, alkane side chain is oxidised to form carboxylic acid
Methyl benzene is oxidised into benzoic acid
- when refluxed with alkaline potassium manganate
- Then acidified with dilute sulfuric acid

Phenols

C6H5OH
Crystalline solid (melts at 43 degree celsius)
Has hydrogen bonding → melting point is high
Slightly soluble in water → large non polar benzene ring disrupts hydrogen bonding with water
Weakly acidic
Phenol > water > ethanol (acidity)
Preparation of phenol
- Phenylamine + HNO2 (nitrous acid)
  - Nitrous acid is unstable, made in test tube
  - NaNO2 (sodium nitrite + HCl)
- Kept under 10 degree celsius

Ryan JC2Truth

2022-01-17 14:25:14 UTC

I learned about:
- Phenols made up of benzene ring with an OH functional group, where the electron of the oxygen atom overlap with delocalized electron
- Phenols are crystalline solids and it melts at 43 degree celcius
- Phenol has hydrogen bond
- It is weakly acid
- Electrophilic substitution
- Conditions (Halogen carriers catalyst)
- Benzene x Bromine (AlBr3)
- Benzene chlorine (AlCl3)
- Methylbenzene x Cl2 or Br2
- Nitration of Benzene
- Electron donating group only goes to group 2,4,6, while electron withdrawing group goes to group 3,5
- Nitration mixture is refluxed with benzene at 55 degree celius to make nitrobenzene
- Alkylation/Acylation Friedel-crafts reaction
- It produces acyl group, as it involve attacking the benzene ring by an electrophilic carrying a positive charge on carbon

Chris JC2T

2022-01-17 15:35:38 UTC

Learned about:
- Properties of phenol
- How to prepare phenol
- Reactions of phenol (diazotisation)

Gisella JC2 MLG

2022-01-17 17:25:52 UTC

Arenes
- react with Cl2 & Br2 and catalyst to form Halogenoarenes ( Aryl Halides )
- FCA: CH3Cl and AlCl3 and Heat
- FCA: CH3COCl and AlCl3 and Heat
- Nitration: concentrated HNO3 and H2SO4 at room temperature ( 25-60 degree celcius )

Evidences To Reject The Old Benzene Structure
- According to Kekule's structure, there are 3 shorter carbon-carbon double bond and 3 longer carbon-carbon single bonds, the structure should be distorted Hexagonal Shape
- Requires Harsher conditions to go through Addition reaction ( Aromatic Stabilisation )

Naming Aryl Compounds
- C6H5 ( Phenyl )

Reaction Of Arenes
- Delocalized PI bonding electrons remain intact for most reactions ( Aromatic Stabilisation )
- Intial Attact is done by Electrophile ( Attracted to High Density around Benzene Ring )

Electrophile Substitution
- React with bromine with FeBr3 catalyst and created when FeBr3 polarizes Bromine Molecule
- React with Chlorine with FeCl3 catalyst or AlCl3 ( Halogen Carriers )

Free Radical Substitution
- Boiling Methylbenzene and Chlorine gas under UV light
- No substitution
- If excess, 3 H atoms will be substituted

Mechanism

STAGE 1: Electrophile is attracted to High Density of PI bonding of Benzene

STAGE 2: Full delocalised ring is restored

Catherine JC2T

2022-01-18 00:28:01 UTC

Recall on:

Electrophilic substitution (halogenation and nitration)
Free radical substitution
Friedel-Craft’s reaction (alkylation and acylation)
Oxidation
Hydrogenation

Learnt:

Phenol and its properties
Preparation of phenol (from phenylamine and HNO2)
- HNO2 made from test tube (NaNO2 + HCl)
- Kept under 10°C to prevent decomposition of N2
Phenoxide ion vs ethoxide ion
Reactions of phenol (like weak acid)
- reaction w alkali to form salt
- reaction w Na to form salt
- diazotisation (orange dye formed)

Kenneith JC2 MLG

kenneith123wijaya — 2022-01-18 02:00:30 UTC

Reaction of phenylamine (C6H5CN) react with HNO2 or NANO2+HCl.Condition 50 degree and add water.
Reaction of phenol
1.breaking of the OH bond,it react well with alkaline solution(NaOH)
2.substitution
Phenol react more faster than benzene ring because of the overlap of the one pair of electrons in the oxygen group with the pie bonding system which increases the elctron density of the benzene ring
3.bromination
React with bromine,white precipitate form and brown become colourless
4.nitration of phenol
React with dil HNO3 in (2,4,6)

Eugene MLG

2022-01-18 02:01:27 UTC

Phenol
- crystalline solid (melt 43°C)
- C6H5OH
- weak acid
- slightly soluble
- reacts more readily with electrophiles (phrnol has OH which is an elecron donating group, it overlaps with pi bonding system of benzene increasing the electron density, thus more open to electrophilic reactions)
- synthesised from HNO2 and H2O

MLGS JC2 Edward

2022-01-18 02:02:05 UTC

Phenol:
It is benzene with a oh group.
It is solid.
It is weak acid but stronger than water because the lone pair from the oxygen makes the anion stabilise.
It is prepared by phenylamine + NaNO2, HCl, H2O and warm the solution.
It can react with alkali to produce salt and water.
It can react with bromine water to produce 2 4 6 tribromophenol.
It can react with dilute nitric acid to produce 2 nitrophenol and 4 nitrophenol.

Randy mlg

2022-01-18 02:03:55 UTC

Phenol
- C6H5OH
- crystalline solid that melts at 43 C
- weakly acidic, losing an H+ ion from its hydroxyl group
C6H5OH(aq) -> C6H5O–(aq) + H+(aq)
- stronger acid than water or an alcohol
- More acidic because phenol ionises to form a more stable negative ion, so the ionisation of phenol is more likely. This results in the position of equilibrium in the phenol equation in Table 25.3 lying further to the right- hand side (i.e. more molecules donating an H+ ion) than the other equations.
- dissolves well in alkaline solution
- bromine water reacts readily with phenol
- decolorizing the orange solution and forming white precipitate of 2,4,6-tribomophenol

Celine Mlg

2022-01-18 02:06:05 UTC

Phenol C6H5OH

how to prepare:
-NaNO2 +HCl -> HNO2+ NaCl
-use HNO2, add phenylamine
-diazonium salt formed will decompose wit water and gin off nitrogen gas

-reaction with alkali forms salt and water
-phenol react virgorously w sodium metal to form h gas
-reacts more readily than electrophiles because of overlap of lone pair of electron that increases density in pi system

Reaction with bromine
-bromine water
-decolorize orange solution, forms white ppt

nitration
-room temp, dilute nitric acid
-if conc then 2,4,6trinitrophenol

MLG JC2 Axel

2022-01-18 02:07:21 UTC

Phenols
- Formula of C6H5OH

-It is a crystalline solid that has a melting point of 43 degrees celsius.

😳

- more open to electrophilic attacks (Phenol has an OH group which is an electron donating group. this overlaps with the pi bonding system of benzene ring making it more electron dense, thus it is more open to electrophilic attacks)
- synthesized from HNO2 and HCl
- weak acid but better than water and ethanol and me

😔

Mariska MLGS JC2

2022-01-18 02:15:13 UTC

Phenol - C6H5OH (solid)

- Hydrogen bonding causes it’s melting point to be high, 43 degree Celsius

- Slightly soluble in water

- Weakly acidic (still a stringer acid than water/alcohol)

Negative charge is spread over ion as lone pairs of oxygen overlaps with delocalized pi bonding
Delocalization reduces charge density of the negative charge
H+ ions are less attracted to phenoxide ion

Preparation:

NaNO2 is reacted with HCl to form HNO2

Phenylamine C6H5NH2 is reacted with HNO2

Reactions:

React with alkali to form salt and water (phenol acts as an acid)

C6H5OH + NaOH => C6H5O-Na+ +H2O
C6H5OH + 2Na => C6H5O-Na+ +H2O

Electrophilic Substitution

The overlaping of lone pair of electrons with pi bonding increase electron density in pi system, so it attracts electrophiles
C6H5OH + 3Br2 => C6H3Br3O + 3HBr
Observations: Decolourized solution and white percipitate

2. Nitration

Dilute nitric acid at room temperature
C6H5OH + HNO3 => C6H5NO3
Forms 2-nitrophenol and 4-nitrophenol

Charissa JC2 MLG

2022-01-18 03:04:08 UTC

Phenol :

- C6H5OH
- Crystalline solid that melts at 43°C
- Mp is high for an aryl compound because of hydrogen bonding
- Weakly acidic
- Phenol still stronger acid than water or an alcohol because the lone pair from the oxygen makes the anion stabilise.

Preparation of Phenol :

- NaNO2 + HCl = NaCl + HNO2
- HNO2 + C6H5NH2 (Phenylamine)

Reactions :

1.) React with alkali to form salt and water (Phenol behaves as an acid)
- C6H5OH + NaOH = Na+O-C6H5 + H2O
- React vigorously with Na metal

2.) Reaction with bromine water
- Produce 2,4,6 tribromophenol
- Forms white ppt
- Brown become colourless

3.) Nitration
- React with dilute nitric acid at room temperature
- Produce 2-Nitrophenol and 4-Nitrophenol

Thomson JC2T

2022-01-18 04:35:52 UTC

Electrophilic substitution
> With halogens
Need carriers like AlBr3 or FeCl3, bonds to carbon 2,4,6

Free radical substitution
> Boiling and uv, binds to the alkyl group

Nitration
> HNO3 + H2SO4 to produce NO2 which then binds to the benzene at 1,3,5

Acylation or alkylation
> substitution of alkyl or acyl group into the benzene with AlCl3 catalyst and heat

Oxidation
> Produces benzoic acid, water and CO2 (if more than 1 carbon)

Hydrogenation
> benzene becomes cyclohexane when reacted with hydrogen and Ni or Pt catalyst in high heat and pressure

Phenols
> melts at 43C
> dissolves slightly in water due to hydrogen bond even though it is non-polar
> slightly acidic and undergoes neutralization
> preparation of phenols, conditions and reagents
> phenol more acidic than ethanol
> azo dye formation

MLG J

2022-01-18 07:33:12 UTC

- Arenes have considerable energetic stability because of the six delocalised π bonding electrons that lie above and below the plane of the benzene ring
- Phenols are weakly acidic, but are more acidic than water and alcohols. The acidity of phenol is due to delocalisation of the negative charge on the phenoxide ion into the π bonding electron system on the benzene ring

Davis JC2G

2022-01-18 07:49:31 UTC

During the lecture, I learnt about Arenes and Phenols.
- I reviewed the electrophilic substituion of benzene and methylbenzene. As well as the free radical subsitution of boiling methylbenzene and nitration reaction. I also re-learnt alkylation/acylation and the oxidation of the side chain in arenes.

- Then, I was introduced to Phenol (C6H5OH)
It is a crystalline solid that melts at 43 degrees.
It has high mp because of hydrogen bonding, is weakly acidic but is stronger acid that water or alochol.
I also learnt about the preparation of phenol and its conditions/mechanisms.

Lastly, I learnt about the reactions of phenol with alkali to form salt and water/ with sodium metal to form hydrogen and sodium phenoxide, as well as diazotisation (phenylamine) (synthesis of dyes)
(two steps, 2nd step = coupling reaction)

Ella JC2G

2022-01-18 10:23:58 UTC

Brief Overview

Formula: C6H5OH
Melting point: 43°C, relatively high due to H bonding
Large non polar benzene ring disrupts H bonding, reducing its solubility
Weak acid
Acidity: Phenol > Water > Ethanol
- Phenol: Electron pair of O atom overlaps with delocalised pi bonding system, reducing the (-) charge density of the ion. O- is less negatively-charged, hence it is less attracted to H+. The equilibrium lies more to the right and there will be more H+ (more acidic).
- Ethanol: Alkyl groups are electron-donating. Therefore, the O atom will be more negatively-charged, and have greater attraction with H+. Consequently, the equilibrium will lie to the left and there will be less dissociation. Less H+ results in lower acidity.

Phenol Reactions

C6H5OH + NaOH → Sodium phenoxide + water
C6H5OH + Na → Sodium phenoxide + hydrogen gas (vigorous reaction)

Preparation

NaNO2 + HCl → HNO2 + NaCl (below 10°C)
Phenylamine + HNO2 +HCl → Benzenediazonium chloride + water
Benzenediazonium chloride (acts as electrophile) is heated with H2O, forming phenol + HCl + N2

Diazotisation

Benzenediazonium chloride (from previous reactions) + phenol → azo dye (orange) + HCl
With the presence of NaOH
An example of electrophilic substitution

Electrophilic Substitution of Phenols

Bromination: Milder conditions, decolourises bromine water, forms 2,4,6-tribromophenol (white ppt) and HBr, no catalyst needed
Nitration: rtp with dilute HNO3 forms 2 and 4-nitrophenol, and 2,4,6-trinitrophenol if conc. HNO3 is used

Naphthol Reactions

Similar reaction with Na and NaOH to that of phenol
1-Naphthol + Br2 → Br attaches to C2 and C4 since C6 is connected with the next ring
2-Naphthol + Br2 → No substitution in C4 since it is cluttered up with the other ring, so it substitutes the carbon atom between the other ring and the OH group

I think I need to do practice questions to get a better understanding of the chapter and improve my memory on the reaction reagents and conditions. The lesson was clear and concise.

Keira JC2G

2022-01-18 11:51:50 UTC

Reviewed:
- mechanism of electrophilic substitution
- free radical substitution (for methylbenzene)
- nitration of benzene
- alkylation and acylation
- oxidation of side-chains
- hydrogenation

Phenols
- C6H5OH
- weak acid (low pKa)
- slightly soluble with water (non-polar structure)
- can give phenoxide

Phenoxide
- C6H5O-
- negative charge can overlap with pi bonding of benzene ring
- less density of negative charge
- less attracted to H+
- more stable than phenol

1. NaNO2 + HCl → HNO2 + NaCl (at 5°C)
2. Phenylamine + HNO2 + HCl → N2+ Cl- benzene (benzene diazonium salt) + 2H2O

Preparation of phenol
benzene diazonium salt + H2O + heat → phenol + N2 + HCl

Diazotisation
- benzene diazonium salt + alkaline phenol (4th position)

Reaction of phenol
- reacts with alkali to form salt and H2O
- reacts with sodium metal vigorously to form salt and H2
- diazotisation (form orange dye)
- electrophilic substitution

Electrophilic substitution of phenols
- phenol reacts more readily (OH donate electron to benzene ring, increasing density)
- no catalyst needed
- reacts with bromine water with milder condition (gives white ppt.)
- nitration of phenols (room temp + dilute HNO3)

Naphtol
- 1-naphtol and 2-naphtol
- Naphtol + NaOH → O- Na+ + H2O
- Naphtol + Na → O- Na + + ½ H2
- 1-Naphtol + Br2/HNO3 → Br/NO2 will move to position 2, 4
- 2-Naphtol + Br2/HNO3 → Br/NO2 will move to position 1

I still need to memorise the equations and its condition. I also need to do practice questions to further understand the chapter. The lesson was clear and easy to follow.

MLGS JC2 Adel

2022-01-18 14:11:56 UTC

phenol is a weak acid
It is a crystalline that melts at 43°C
It is only slightly soluble in water
Phenol ionizes to form stable negative ion as it has a great acidity
Phenol dissolves well in alkaline solution
Phenol acts as an acid so it can react with alkali and give salt and water
It reacts vigorously with metal especially sodium
Phenol reacts more readily with electrophiles
The electron density of benzene ring increases because there is an overlap of one of the lone pairs of electrons on oxygen
Phenol can react with bromine water in milder conditions and it decolourized orange solution and form white precipitate
Phenol can react with dikute HNO3 to form two products
NO2 will be attached in positions 2 or 4 to the phenol
If use conc nitric acid, the product will we 2,4,6-trinitrophenol which the NO2 attach at the 2,4 and 6 of the phenol

MLGS JC2 Alvin

2022-01-18 14:17:28 UTC

Electrophilic Substitution

-> benzene + bromine ( w/ AlBr3 cat)

-> benzene + chlorine. ( w/ AlCl3 cat)

-> methylbenzene + Cl2/Br2 = mixture of products

NB: requires HBr/AlCl3 as halogen carrier

Free Radical Substitution

Condition: boiled, under UV light

Reactant: Cl2

Nitration of Benzene

Conc of H2SO4 + conc of HNO3 at. 55 degree celcius

Alkylation/ Acylation

Used to:

substitute - CH3 and CH5
Introduce acyl group
Result in side chain

Oxidation of side chain

Alkanes are NOT USUALLY oxidized unlike alkylarenes that CAN BE oxidized to form carboxylic acid

Phenol

Characteristics:

C6H5OH
Solid meltd at 43 degree
Weakly acidic

Facts:

has negative charge spread all over whole ion

delocalised reduced charge density of positive charge

H ion are not strongly attached

Ionization of phenol are more likely

Reactions:

phenol + alkali -> salt (soluble)+ water

phenol+ metal -> Hydrogen (g). + sodium phenoxide

MLGS JC2 jocellyn

2022-01-18 15:05:34 UTC

Phenol

C6H5OH
a crystalline solid
Melts at 43°c. ( high for aryl compounds, due to H-bonds)
Slightly soluble in water. ( due to large non-polar benzene ring that disrupt the H-binds)
Weak acid ( have a high Kpa)
Important in the synthesis of dyes

Reactions:

React with alkali to form sodium phenoxide + H2O
Reacts vigorously with sodium metal
Diazotisation ( to form dyes)
Halogenation (Electrophillic substitution) reacts with bromine water at room temperature. Results in decolorization and forms white precipitate.
Nitration ( room temperature with dilute nitric acid)

MLGS JC2 Yasmin

2022-01-18 15:24:33 UTC

NITRATION OF BENZENE:

The nitration of benzene requires a mixture of concentrated HNO3 and H2SO4 refluxed with benzene at 55^oC.

PHENOL:
-C6H5OH
-Crystalline solid that melts at 43^oC.
-Phenols are only slightly soluble in water due to the large non-polar benzene ring.

-Phenols react more readily with electrophiles compared to benzene.

-Phenol>water>ethanol in regards of acidity.

PREPARATION OF PHENOL:
Phenols can be prepared from phenylamines under the following reaction conditions:

NaNO2 with dilute acid HCl (to form HNO2)
Keep the temperature below 10^oC
The diazonium salt is heated with to form phenol.

-In the phenoxide ion, the negative charge on the oxygen is spread out over the entire ion.
-This is possible as one of the lone pairs on the oxygen atom overlaps with the delocalised π system of the benzene ring.

REACTIONS OF PHENOL:
-Reacts with alkali to form salt(sodium phenoxide) and water.
-Phenol reacts vigorously with sodium metal, sodium phenoxide is formed and hydrogen gas is given off.

Josh JC2G

2022-01-18 15:33:52 UTC

Jacksen JC2T pik

2022-01-18 15:51:45 UTC

revised about
- friedel crafts reaction
- hydrogenation

learned about
- properties and characteristic of phenol
- how to make phenol
- also how to make HNO2 + conditions needed
- phenoxide ion
- reaction with phenol (with alkali and electrophile both nitrile and halogen)
- diazotisation

- need to study bout naphthol
- fill in details of the chapter
- need to stop being in holiday mode
- oh and finish making chem tiktok

Nevan Kho jc2g

2022-01-18 16:08:45 UTC

revised about
- friedel crafts reaction/acylation
- hydrogenation of arene
- properties of phenol and its reactions
- process of making phenol
- conditions and acidification of NaNo2 with HCl
- phenoxide ion and its making, as phenol is reactive as a weak acid
- reaction with phenol ,alkali, nitrile and halogen
- diazotisation
- the double ring structure and properties of naphthol during reaction

Angela JC2G

2022-01-18 16:36:49 UTC

Phenol

C6H5OH
weak acid, low pKa
Crystalline solid that melts at 43°C which is quite high due to hydrogen bonding
Large non polar benzene ring disrupts the hydrogen bonding with water, making it less soluble
Phenol is a better weak acid than water than ethanol
Position of equilibrium lies more to the left because they dont dissociate

Preparation of phenol

To make HNO2: NaNO2 + HCl -> HNO2 + NaCl (kept at 5°C to prevent decomposition to give N2)
Phenylamine + HNO2 + HCl -> Benzenediazonium chloride + 2H2O
Benzenediazonium chloride warmed with water-> phenol + N2 + HCl

Phenoxide ion

C6H5O-
Its negative charge is spread all over the ion as one of the lone pairs overlaps with the pi bond, so the charge becomes less negative.
Phenol: The position of equilibrium shifts more to the right as C6H5O- and H+ will not attract each other as much, theres now more H+ and it is more acidic.
The delocalisation reduces charge density on the phenoxide ion, compared to hydroxide/ethoxide, so the H+ are not attracted to the phenoxide ion and only the dissociated molecule will be formed

Ethanol

alkyl group is electron donating, so the electron from C2H5 will be given to O-, hence more attraction with H+ and forming more C2H5OH

Reactions of phenol

C6H5OH + NaOH -> sodium phenoxide + H2O
2C6H5OH + 2Na -> 2sodium phenoxide + H2 (vigorous)

Diazotisation

2nd step Coupling reaction
Benzene diazonium salt + phenol -> orange dye (4th position) + HCl
Also an electrophilic substitution reaction

Electrophilic substitution of phenols (Bromination)

reacts more readily with electrophiles, as the OH donates electrons to benzene ring, increasing density of electron in benzene ring
Decolourises bromine water but with milder conditions
Forms 2,4,6 tribromophenol (white ppt) + HBr

Electrophilic substitution of phenols (Nitration)

Phenol + dilute nitric acid (rtp) -> 2-nitrophenol + 4-nitrophenol
Phenol + conc. nitric acid (rtp) -> 2,4,6-trinitrophenol

Naphthol + NaOH

1-naphthol + NaOH -> phenoxide ion + H2O
2-naphthol + NaOH -> phenoxide ion (position 2) + H2O

Naphthol + Na

1-naphthol + Na -> phenoxide ion + 1/2H2
2-naphthol + Na -> phenoxide ion (position 2) + 1/2H2

1-naphthol + Br2/HNO3 -> Br/NO2 is attached to position 2 and 4

2-naphthol + Br2/HNO3 -> Br/NO2 is attached to position 1, there cant be any substitution at position 4 because it is cluttered up with the other ring

Ashley JC2G

2022-01-18 18:03:48 UTC

(it's 12:33 pm, technically night)

So we revised a little bit about the last lesson, which had been:
- Alkylation and Acylation, you get the general idea of polarising the would be electrophile, then substitution, broken postive ring of delocalised electrons, etc.
- Oxidation of Side chain alkenes: no matter what, you will always get benzoic acid! from methyl benzene, ethyl benzene, etc.
- Hydrogenation (using NI/Pb as catalyst, with heat and high pressure bc it requires harsher pressures):
- What a phenol is! basically benzene with a hydroxide group attached to it
- How phenol is a weak acid (as it dissociates to produce H+ ions!)
- HOWEVER despite being a weak acid, phenol is still a better weak acid than water or ethanol! This is because it's able to dissociates to a larger extent, poe lies more to the right ! (the benzene group is a large, nonpolar ring, decreases charge density, negatively charged ion and H+ is less attracted to each other than that of, let's say, ethanol!)

Then we learnt about:
- PREPARATION OF PHENOL:
first, create a nitrous acid (and NaCl) is created from NaNO2 and HCl
- COUPLING REACTION: nitrous acid + HCl then reacts with phenylamine, to form an alkaline solution of benzene diazonium salt
- Benzene diazonium salt is then warmed with H2o, forms a phenol!
- REACTIONS WITH NA OR NAOH: yeah it forms sodium phenoxide! it acts like a weak acid, that i will not further elaborate as it is currently 12:49 pm, H2 is produced!
- REACTIONS WITH BR2: jumps immediately to have being bonded to 3 Br molecules in positions 2,4,6. NO MIXTURE
- REACTIONS WITH NO2: with only diluted HNO3, the mixture is produced of 2-nitrophenol, and 2-nitrophenol
BUT IF ITS WITH CONC. HNO3, then 2,4,6-trinitrophenol formed
- REACTION WITH BENZENE DIAZONIUM SALT: Benzene diazonium salt + phenol -> orange dye (4th position) + HCl

*the reason why phenol is so much more reactive than benzene, and therefore does not require as harsh conditions, is because the oxygen's a lone pair overlaps with the pi bonding system, thus making it more open to electrophilic attack! thus more reactive!!

NAPTHOL:
- basically, just reacts the same like phenol for Na, NaOH, Br, and NO2 ion.
- It just reacts normally for 1-napthol ! carbon in 2nd position will be bonded
- FOR 2-NAPTHOL HOWEVER: the ion bonds to the carbon atom ABOVE the 2nd carbon atom. WHY???? bc 2nd carbon is already bonded to OH, can't react with carbon 4 bc it seems like 'too little less', and carbon 6 is already bonded to the other benzene ring.

it's currently 1:00 am! arent you proud that i remembered all this smh

I feel as if the things i need to get reminded of is definitely the observations of the different reactions, like phenol with Br2 with white ppt formed (decolourisation would be kinda obvious though) Though I can understand the logic behind different reactions' considerations, i still can't remember all of them :((

thanks for the lesson sir :D especially for going over the preparation of phenol not once not twice but thrice :>>> psst will we be able to play kahoot again ? :00 not that i particularly enjoy it but it helps with active recall :DD

Jonathan

2022-01-19 00:05:50 UTC

I learned about what a phenol is, its properties, and also how to prepare it. I also learned how to make a phenoxide ion, and its reactions and also diazotisation to create dyes.

Lindsay JC2G

2022-01-19 00:38:00 UTC

Jennifer JC2G

2022-01-19 01:27:46 UTC

Phenol
- C6H5OH
- Crystalline solid
- Melting point is 43C
• Surprisingly high for an aryl compound
- Slightly soluble in water
• Large non-polar benzene ring disrupts hydrogen bonding with water
- Weak acid
- Position is at left-hand side
- Phenol is a stronger acid than water/alcohol
- Phenoxide ion has (-) charge spread all over the whole ion
• A lone pair on Oxygen atom overlaps with π bonding system in benzene ring
- Delocalization reduces charge density of (-) charge on phenoxide than hydroxide/ethoxide
• H ion not strongly attracted to phenoxide ion
- Phenol ionizes to form more stable (-) ion
• Ionization of phenol more likely

Ethanol
- Weaker acid than water
• Alkyl group (electron donating) attached to ethoxide ion
• More (-) charge on Oxygen atom
• Accepts Hydrogen ions more
• Favors undissociated ethanol molecules

Preparation of Phenol
- Phenylalamine + HNO2
• Phenylalamine important in dye synthesis
- Nitrous acid unstable
• Made in test tube
- Kept at 10C
• Prevent decomposition to give N2
- Coupling reaction
• Diazonium reacts with alkaline solution of phenol
• (+) diazonium ion acts as electrophile
- 4th position activated
- Orange dye formed (Diazonium ion)

Reaction of Phenol
- Alkali
• Forms salt (Sodium phenoxide) + water
• The salt is water-soluble
- Sodium metal
• Vigorous reaction
• Forms Hydrogen gas + Sodium phenoxide

Focus : Revise more
Lecture : Good

Justin JC2 Grace

2022-01-19 01:39:27 UTC

We disscussed about phenol and its preperation, the creation of benzene diozonium salt from coupling reation and Diazotation.

Phenol(C6H5OH), Phenoxide(C6H5O-)

, Ethanol(C₂H₆O) are all weak acid.

Learned Friedel crafts reaction Alcylation and Asylation

-I still need to revise on the mechanism and the reactions

Cleantha JC2G

2022-01-19 01:45:07 UTC

Phenol

• C6H5OH

• weak acid

(higher Ka -> more dissociation -> more acidic/ better weak acid)

(lower pH -> more acidic)

• crystalline solid

• melting point: 43 degrees Celsius

• slightly soluble in water

(the ring/ benzene group is non polar structure will disrupt the bonding with the water so disrupt bonding with water)

• position lied on the left hand side

( because they are partially dissociating)

Preparation of phenol

1: phenylamine + HNO2

(nitrous acid is not stable so need to prepare by using NaNO2 and dilute HCl)

(need to be kept under 10 degrees celsius)

(If above 10, the nitrous acid will decompose to form nitrogen gas)

2: NaNO2 + HCl -> HNO2 + NaClb

(below 5 degrees celsius)

Diazotisation

: preparation of dye

Benzenediazonium chloride: reacts with water to give phenol

reacts with phenol to give orange dye

Coupling reaction: couple kne benzene ring with another benzene ring

(no catalysts)

Calvin MLGS JC2

2022-01-19 02:06:59 UTC

Phenol Structure:

C6H5OH
Solid at r.t.p. with a melting point at 43℃ due to hydrogen bonding.
Only slightly soluble in water because the non-polar benzene ring disrupts the H-bonding with water.
Weakly acidic (but stronger than water and alcohol): The negative charge in the phenoxide ion is spread out over the benzene ring as well, so the charge density is lower, which makes it less likely to bond with H+ to reform phenol.

Reactions of phenol:

Formation: (1) Form benzenediazonium chloride from phenylamine and HNO2 (made in situ from NaNO2 and HCl) at T < 10℃. (2) Water is then added and the mixture is warmed to form phenol.
Reactions as acid: React with alkali to form soluble salt, Reacts vigorously with Na to form H2 gas
Diazotisation: Diazonium ion reacts with alkaline solution of phenol. The diazonium ion acts as electrophile and is bound to position 4 which forms an orange dye (azo dye).

MLGS JC2 Michelle

2022-01-19 02:30:12 UTC

Phenol:

C6H5OH
Mp is high for Arya compound (hydrogen bonding)
Large non-polar benzene ring disrupts hydrogen bonding with water (slightly soluble in water)
Weakly acidic (still stronger than water or ethanol)
Position lies to left-hand side (partially dissociating)

Preparation of phenol:

Phenylamine + HNO2 (nitrous acid)

Reactions of Phenol:

+NaOH to form salt (sodium phenoxide, soluble in water) + H2O
+Na metal (vigorously) to form salt (sodium phenoxide) + H2 gas

Diazotisation:

Synthesis of dyes

Coupling Reaction:

Diazonium ion reacts with alkaline solution of phenol
Positive Diazonium acts as electrophile
Activates position 4
Orange die formed

MLGS JC2 Maharani

2022-01-19 02:36:11 UTC

Electrophilic Substitution
Free Radical Substitution
Nitration of Benzene
Substituent Group 2,4, or 6 positions
Substituent Group 3 or 5 positions
Alkylation / Acylation Friedel-Crafts Reaction
Oxidation of the Side-Chain in Arenes
Hydrogenation (Electrophilic Addition)
Phenol
Preparation of Phenol
Reactions of Phenol
Diazotisiation

Dylan JC2G

2022-01-19 03:12:00 UTC

From today's lecture, I’ve learnt about

• Phenols
- C6H5OH
- melting point at 43 °C, this mp is relatively high due to the hydrogen bonding
- weak acid, in terms of acidity, phenol>water>alcohol
- slightly soluble with water (with non-polar structure benzene ring)
- can give phenoxide

• How to prepare phenols
- NaNO2 + HCl → HNO2 + NaCl
- Phenylamine + HNO2 +HCl → Benzenediazonium chloride + water
- Benzenediazonium chloride is then heated with H2O to form phenol + HCl + N2
- to prevent decomposition, kept under 10°C

• Reaction of Phenols
- C6H5OH + NaOH -> sodium phenoxide + H2O
^^salt(sodium phenoxide) is soluble in water
- 2C6H5OH + 2Na -> 2sodium phenoxide + H2 (vigorous)

• Diazotisation
- coupling reaction
- Benzenediazonium salt + phenol → azo dye + H+
(you can use Benzenediazonium chloride and HCl would form instead of H+)
- azo dye (orange dye)
- 4th position of phenol is activated

- electrophilic substitution

• Electrophilic Substitution of Phenols...
- Halogenation
> reacts more readily with electrophiles
> overlap of one of the lone pairs of electrons, increases the
electron density in the pi system
> react with bromine water but milder conditions.
> decolourizing orange solution to form white ppt

- Nitration
> room temp. and dilute HNO3

• Naphthol reactions
- has the same reaction as to how phenol reacts with Na and NaOH
- 1-Naphthol + Br2/HNO3 → Br/NO2
attaches to positions 2 and 4

- 2-Naphthol + Br2/HNO3 → Br/NO2
attached to position 1 as in position 4, there's no substitution since it is cluttered up with other rings

Overall, it was a great, clear and concise lecture as usual, but I feel like to fully remember and understand what we have just learned, I need to practice on doing past year paper questions.

Brian MLGS JC2

2022-01-19 05:54:48 UTC

Bilal MLGS JC2

2022-01-19 06:34:09 UTC

Phenol

C6H5OH
An aromatic organic compound which consists of a phenyl group bonded to a hydroxy group
A white solid crystalline (volatile)
It is a weak acid since a hydrogen ion could easily break from the OH group bonding to another base, after bonding the phenoxide ion would be more stable where the negative charge of the oxygen atom from the OH group would then be delocalised around the ring causing it to be less acidic

Reaction with phenol

Phenylamine + HNO2 and HCl to form benzenediazonium chloride and water
Benzenediazonium chloride would then be heated in a solution to result in phenol with conditions of temperatures less than 15 degrees

Jordan Jc2G

2022-01-19 14:48:01 UTC

In the lecture i learnt about how to prepare phenol and all its reactions.
These reactions include- Electrophilic substitution: halogenation and nitration
I also learnt about naphthol and that it can react with sodium and sodium hydroxide. 1-Naphthol and 2-naphthol also undergoes reaction with bromine water and also dilute nitric acid. The positions where electrophilic substitution differs between 1-naphthol and 2-naphthol.

Gracia MLG

2022-01-19 16:20:30 UTC

Phenol
- C6H5OH
- Crystalline solid
- Melting point is relatively high for an aryl, at 43C
- Slightly soluble in water
- A weak acid but still stronger than water and etanol

Reactions
- Breaking the OH bond: react with an alkali to produce salt and water; reacts vigorousky with sodium metal to produce hydrogen gas
- Subs into benzene ring of phenol:
- Bromination: room temperature, bromine water. Decolorise the orange solution and form a while ppt of 2,4,6-tribromophenol.
- Nitration: dilute nitric acid at rtp, forming 2,4,6-trinitrophenol

Peng Jc2 MLG

2022-01-20 10:25:30 UTC

Phenol
C6H5OH
white crystalline solid
weak acid stronger than water and ethanol
left hand side
PREPARATION
phenylamine+HNO2