6.1 Aromatic Compounds, Carbonyls and Acids (completed) Flashcards
What is the carbonyl group?
Carbon oxygen double bond
C=O
What are examples of carbonyl compounds?
Aldehydes (from primary alcohols)
Ketones (from secondary alcohols)
How do you produce the carbonyl compounds?
Acidified potassium dichromate [O]
Aldehyde distill primary alcohol
Ketone reflux secondary alcohol
Carboxylic acid reflux primary alcohol
What is the test for aldehydes?
Tollen’s reagant Heat in hot water bath Silver compund is reduced to silver metal Forms a silver mirror Aldehyde is reduced to carboxylic acid Also NH4+ ions
What is the test for aldehydes and ketones?
2,4-DNPH Brady’s Reagent
Produce an orange precipitate
How can you find which carbonyl compound has tested positive with Brady’s reagent?
Purify and recrystallise and precipitate
Find its’s melting point and compare with known values
What is the reduction of aldehydes and ketones?
Nucleophilic addition to produce alcohols
How do you reduce aldehyde’s and ketones?
With NaBH4 (sodium tetrahydridoborate) To produce a hydride ion H- with a lone pair
What is the first step in the mechanism of nucleophillic addition?
δ+ and δ- on C=O bond
Curly arrow from hydride ion lone pair to carbon
Curly arrow from C=O bond to oxygen
What is the second step in the mechanism of nucleophillic addition?
Lone pair and negative charge on oxygen
δ+ and δ- on H and O in water
Curly arrow from lone oxygen pair to hydrogen in H2O
Curly arrow from O-H bond to oxygen
What is the third step in the mechanism of nucleophillic addition?
Alcohol produced and OH- ion
What are the reagents and conditions needed to produce a nitrile from a carbonyl?
CN- ions
In dilute acid e.g. H2SO4
Nucleophilic addition
What does adding a cyanide ion do to the carbon chain?
Increases the length
What is the molecular formula of benzene?
C6H6
What was kekulé’s model for benzene?
Cyclic
Planar
Alternating double and single bonds
What were the problems with Kekulé’s model?
All the bonds are same length BUT in Kekulé’s model the C=C bonds will be shorter
Benzene does not behave like an alkene with C=C bonds as it does not easily undergo addition reactions
The enthalpy is not as exothermic as predicted (it’s too stable)
What is the updated benzene model?
π electrons are in delocalised rings of overlapping p orbitals above and below the carbon ring
Planar ring
120° bond angle
Carbon bonds are all the same length
Describe the mechanism for electrophilic substitution
Curly arrow from benzene ring to Electrophile (E+)
Half ring with + inside
H and E bonded to carbon ring
Curly arrow from H bond to +
Electrophile bonded to carbon ring
H+ as other product
What are the reagants of the nitration of benzene?
Conc. nitric acid
Conc. sulphuric acid (catalyst)
Reflux
55°c
What is the nitration of benzene used for?
Explosives, dyes
How is sulphuric acid regenerated as a catalyst in the nitration of benzene?
H2SO4 + HNO3 → HSO4- + NO2+ + H2O
NO2+ is electrophile which generates H+ inmechanism
H+ + HSO4- → H2SO4
What happens if you added bromine water to benzene?
Nothing happens
How does the halogenation of benzene occur?
By using a halogen and a halogen carrier catalyst
e.g. Fe, FeCl3, AlCl3
Reflux
How does the halogen carrier catalyst produce a halogen electrophile?
(use chlorine and AlCl3)
Cl2 + AlCl3 → AlCl4- + Cl+
it’s regenerated so is a catalyst
AlCl4- + H+ → AlCl3 + HCl
What are the two types of Friedal Crafts Reactions?
Alkylation - substitution with an alkane R e.g. CH3Cl
Acylation - substitution with a carbonyl R-CO e.g. CH3COCl
What are the Friedal Crafts Reactions?
Formation of a C-C bond to an aromatic ring
What are the reagants and conditions needed for alkylation?
Alkyl Chloride - RCl
Halogen carrier catalyst e.g. AlCl3
Anhydrous conditions
Electrophilic Substitution Mechanism
What are the reagants and conditions needed for acylation?
C=O RCOCl
Halogen carrier catalyst e.g. AlCl3
Anhydrous conditions
Electrophilic Substitution Mechanism
Why does the hydrogenation of benzene have a higher value?
It’s resistant to hydrogenation becuase it destroys the stable delocalised electron system giving it a high activation energy
What is phenol?
C6H5OH
A very weak acid with an OH group attached directly to the benzene ring
Why is phenol solid at room temperature?
It can form hydrogen bonds which require more energy to break
It’s an almost colourless cyrstaline solid
What does phenol react with?
Metals
Hydroxide
NOT carbonates (it’s too weak an acid)
Why can phenol react with bromine without a halogen carrier?
The lone electron pair on OH
is drawn into the deloclaised benzene ring
increases the electron density of the ring
activating it
able to induce a dipole on Bromine
What is the reaction of phenol with sodium and sodium hydroxide?
Produces Sodium Phenoxide C6H5O-Na+ and H2O (NaOH) or H2 (2Na)
How do 2- 4- directing groups affect the reactivity of the ring when activating it?
Increase it by donating an electron onto the ring
How do 3- directing groups affect the reactivity of the ring when activating it?
Decrease it by withdrawing an electron from the ring
What are examples of 2- 4- directing groups?
OH
NH2
What are examples of 3- directing groups?
NO2
What are the uses of phenols?
TCP
Adhesives
Compact discs
What are nitriles used to make?
Amines
What is the addition of HCN to a carbonyl?
Nucleophilic addition
What is the functional group of carboxylic acids?
-COOH
Are carboxylic acids soluble and if so why?
Yes, they have hydrogen bonding
How does the solubility change as the chain length increases?
Decreases as a result of the increasing nonpolar chain which can’t interact with water molecules
What is the reaction of a metal and a carboxylic acid?
Salt e.g. magnesium ethanoate
Hydrogen 
What is the reaction of a hydroxide and a carboxylic acid?
Salt e.g. potassium propanoate
Water
What is the reaction of a carbonate and a carboxylic acid?
Salt e.g. Calcium methanoate
Water
CO2
What are the uses of esters?
Perfumes, flavourings, essential oils, adhesives
What is the conditions needed for esterification?
Strong catalyst
e.g. concentrated sulphuric acid
What is the reaction of an acid and alcohol?
RCOOH + R’OH → RCOOR’ + H2O
Name these esters
1) CH3CH2COOCH3
2) HCOOCH2CH3
3) CH3OOCCH3
1) Methyl Propanoate
2) Ethyl Methanoate
3) Methyl Ethanoate
What is the reaction between an acid anhydride and an alcohol?
Acid anhydride + alcohol → Ester + carboxylic acid
How can Esters be hydrolysed?
Under acidic or alkaline conditions
Reflux
What is hydrolysis for esters with acidic conditions?
Produces a carboxylic acid and alcohol
Requires reflux
Same conditions as esterification so dynamic equilibrium is formed
What is hydrolysis for esters with alkaline conditions?
Produces a salt E.g. sodium ethanoate
And alcohol
What is the acyl group?
RCOR’
What is an acyl chloride?
RCOCl
How do you produce an acyl chloride?
Carboxylic acid + Thionyl chloride (SOCl2) → Acyl Chloride + SO2 + H2O
What is the reaction of an acyl chloride and water?
Produces carboxylic acid and HCl
What do acyl chlorides react with?
Nucleophiles
What is the reaction of an acyl chloride and alcohol?
Ester + HCl
What is the reaction of an acyl chloride and ammonia?
Primary amide
What is the reaction of an acyl chloride and primary amide? 
Secondary amide
