Organics 3

Pain

What are arenes

A homologous series of ring structured hydrocarbons containing double bonds

What does the circle inside of a benzene ring represent

The delocalised within the ring structure

How the structure of benzene is proven

Chemists react hydrogen gas with cyclohexene. Delta H value was much lower than expected

Delocalisation enthalpy

The amount of stability delocalisation gives it

How the ring inside a benzene structure is formed

Each carbon only has 3 bonds, with p orbitals. These p orbitals combine and form a delocalised electron ring above and below the carbons

Why is benzene not used in schols

It is toxic and carcinogenic

Combustion of benzene

Burns with a yellow smoky flame, which indicates incomplete combustion. This is because there is a very high % of carbon in the molecule that needs oxidising (50%)

Why is the halogenation of benzene not the usual reaction

The ring does not want to break as it is so stable, and will want to reform again. For this reason it reacts via substitution rather than addition

What is the high electron density in the double bond attractive to and what happens

It is attractive to electrophiles, so it breaks and the substituents add on

It is ... to react via addition

Energetically unfavourable

Electrophilic substitution of benzene occurs in 2 steps

Addition and elimination

The addition to benzene

The electrophile is attracted to the ring, the ring breaks and forms a dative bond between the carbon and the electrophile

The elimination to benzene

In order for the ring to reform, it needs to get rid of a hydrogen, taking its electron and releasing it as a hydrogen

What is needed to break the ring of electrons

A fully charged ion

How is a fully charged ion formed

Using a halogen carrier

What is the halogen carrier for bromine

FeBr3

How is the halogen carrier for bromine created

Warm the benzene in the presence of iron filings

What is the halogen carrier for chlorine

Aluminium chloride, AlCl3

How is the nitration of benzene done

It involves adding a nitro group (-NO2) to a benzene and forming nitrobenzene

Why is the nitration of benzene important

Used in making dyes and explosives

How to generate a nitronium ion for the nitration of benzene

Concenrated nitric and sulfuric acids

How the generation of a nitronium works

Sulphuric acid is a stronger acid and protonates the nitric acid, then the unstable / protonated nitric acid breaks down to form a nitronium ion

Equation for the protonation of nitric acid with sulfuric acid

H2SO4 + HNO3 -> H2NO3+ + HSO4-

Equation for the breakdown of nitric acid to form a nitronium ion

H2NO3+ -> NO+ + H2O

What are the conditions for the formation of a nitronium ion

55 degrees C and reflux

Overall equation for the formation of a nitronium ion

HNO3 + H2SO4 -> NO2(+) + HSO4- + H2O

What does a Friedal-Crafts reaction involve

An alkyl group - alkylation, an acyl group - acylation

The alkylation of benzene

Use a halogen carrier for chlorine, the aluminium chloride takes on the chlorine, leaving a carbo-cation electrophile which reacts in the normal way

Conditions for the alkylation of benzene

Reflux

What halogen carrier is used in acylation

Aluminium chloride, AlCl3

What is an acyl chloride ion called

Acylium ion

What are the conditions for the acylation of benzene

Under reflux with the halogen carrier, H+ ion is used to reform the halogen carrier/catalyst

What is required for the hydrogenation of benzene as an addition reaction

A catalyst

What is the catalyst for the hydrogenation of benzene as an addition reaction

Raney Nickel, as it requires a huge surface area

Conditions for the chlorination of phenol

UV light

What is a phenol

A compound with an -OH group attached / an alcohol group on a benzene ring

Is benzene soluble in water

No

Under what conditions is benzene soluble in water

When there is a phenol group attached, as the -OH is able to hydrogen bond

Will benzene dissolve in an alkali

It will not, but phenol does, it acts as an acid by releasing a hydrogen ion, and forming a soluble ionic compound

What state is benzene at RTP

A colourless / pale yellow liquid

Abilities of benzene

It is unable to hydrogen bond, and can only form London forces between molecules

What state is phenol at rtp

A light pink solid

Abilities of phenol

It is able to hydrogen bond with neighbouring molecules

Phenol reactivity

It is more reactive than benzene

Why is phenol more reactive than benzene

This is due to the non-bonding electrons of the oxygen drawn into the delocalised ring, or activating it. This makes it more attractive to electrophiles + makes electrophilic attack easier

Halogenation of phenol with bromine

Uses bromine water, forms white ppt 2,4,6-tribromophenol

Halogenation of phenol with chlorine

Faster than with bromine, forms white ppt 2,4,6-trichlorophenol

Nitration of phenol

Dilute nitric acid, forms a mixture of 2-nitrophenol and 4-nitrophenol

How can the products of nitration of phenol be seperated

Distillation - 2-nitrophenol can hydrogen bond with everything around it, 4-nitrophenol can hydrogen bond with itself

What are the 3 types of amine and what are their formulas?

Primary - RNH2, Secondary - R2NH, Tertiary - R3N

Are positional isomers possible with primary amines

Yes

When is the prefix amino used

If the amine group is not the most important when naming - alkenes, alkanes + halogenoalkanes

How to name a secondary amine

Name longest chain with nitrogen in it and call it amine, name the shorter chain and add “n” in front

Name of: C-C-C-N-C-C

N-ethylpropananime

How are tertiary amines named

Same way as secondary amines, but have 2 “N” prefixes, when different length alkyl group, list it phonetically

How are amides different to carboxylic acids

NH2 group replaces OH group in a carboxylic acid

Why are amides and amide links important in nature

Make proteins and synthetic polymers, e.g. Nylon

What happens if an alkyl group is added to an amide

Forms an N-substituted amide

How can you form straight-chain / aliphatic amines using halogenoalkanes

Reflux, excess conc ammonia, ethanol

Why is ethanol added when aliphatic amines are formed with halogenoalkanes

Allows both the ammonia + halogenoalkane to mix ad it is immiscible, and therefore react

Why is conc excess ammonia used when aliphatic amines are formed with halogenoalkanes

To prevent the amine product from reacting with the halogenoalkane and producing other products

What could form if excess ammonia was not used when aliphatic amines are formed with halogenoalkanes

Secondary and tertiary amines

What are the 2 ways to form an anime using nitriles

Hydrogenation and reduction

How are amines formed from nitriles in hydrogenation

Using hydrogen and a metal catalyst

What is the equation for hydrogenation of nitriles to form an amine using butanenitrile

CH3CH2CH2C=-N + 2H2 → CH3CH2CH2C2NH2

How are amines formed from nitriles in reduction

LiAlH4 in dry ether + dilute acid

What are the conditions to form nitrobenzene from benzene

Conc h2so4, conc hno3, 50-60 degrees c, reflux

What are the conditions for forming phenylamine from nitrobenzene through reduction of the nitro compound

Reflux, excess conc hcl and tin as a catalyst

What is the equation for forming phenylamine from nitrobenzene through reduction of the nitro compound

C6H5NO2 + 6\[H\] → C6H5NH2 + 2H2O

how are amides made

Reacting ammonia or an amine with an acyl chloride

What does reaction ammonia or an amine with an acyl chloride form?

Misty fumes of HCl

What is the formula for reacting ammonia with an acyl chloride

CH3COCl + NH3 → CH3CONH2 + HCl

Are short chained amines soluble in water

They are as they are able to hydrogen bond

Is phenyl amine soluble

Slightly, as it’s non-polar benzene ring reduces its solubility

WHat happens when a primary aliphatic amine / ammonia reacts with water, + equation

It acts as a base by accepting a proton, NH3 + H2O → NH4+ + OH-

What is formed when a primary aliphatic amine / ammonia reacts with water

A weak acid/base solution

Why does a weak acid/base solution form when a primary aliphatic amine / ammonia reacts with water

The reactions are reversible, and so can only form weak alkali solutions, but not all reactions are the same, as the greater the alkyl group, the greater the inductive effect, making the lone pair more accessible, meaning the PH will increase

Why is phenylamine weaker than ammonia

The lone pair on the nitrogen has become incorporated into the ring system on the benzene, this makes the lone pair less attractive to protons, and so the equilibrium position lies further to the left than ammonia

Why do the longer chain alkyl groups form stronger base solutions

The nitrogen gets better at taking on hydrogen ions. This is due to the alkyl chain acting as an electron releasing group and increasing the electron density of the nitrogen in the amino group. This makes the lone pair more attractive and more available to form dative bonds

What does ammonia form when it reacts with acids

An ammonium salt, e.g. ammonium chloride

Is the reaction of amines faster or slower with acids than water? Why?

The increase of H+ ions of an acid

What forms when an amine reacts with acids

A substituted ammonium salt, e.g. butylammonium chloride

What happens when phenylamine reacts with acids, and what will adding NaOH do?

It will form phenylammonium ions, and adding NaOH removes the H+ ions and reforms the phenylamine

What happens when ammonia/ an amine react with halogenoalkanes

The lone pair of an amino group is attracted to positive ions or a positive centre in a molecule

What is formed when a primary amine reacts with a halogenoalkane

It forms a secondary amine

What are the conditions for an amine reacting with a halogenoalkane and why?

Excess amine must be used in order to prevent further reactions from occurring. These reactions would continue as the secondary amine formed has a much stronger inductive effect that the primary amine, making it more likely to react again.

What happens when amine / ammonia reacts with acyl chlorides

Same as halogenoalkane

What is formed when an amine / ammonia reacts with acyl chlorides

HCl and an N-Substituted amide

What happens when ammonia / amines react with ligands copper (II) ions

When the ammonia / amine is added it displaces 4 of the 6 water molecules attached to the copper, forming a new ion with differing colours

What part of an amino acid changes

The R group, the amino group is always on this carbon

What are Zwitterion forms

A carboxylic acid releases a hydrogen ion and is taken up by the amino group, forming a molecule that is neutral overall, but contains both +ve and -ve charges

What happens with an amino acid in an aqueous solution

The acid group releases hydrogen ions, and the amino group attracts them from neighbouring amino acids

What effect does Ph have on zwitterions and why

They can only exist at certain Ph values, as if the amino group is in an alkali solution the OH- ions will react with all the hydrogen ions released by the carboxylic acid, meaning that there are no H+ ions to join the amino groups, and so only anions will exist. And vice versa

Wtat is the point at which zwitterions exist

Isoelectric point

What reaction can take place between amino acids and why

They contain 2 functional groups, and can therefore undergo a condensation react and form a dipeptide

What are the conditions of condensation polymerisation of amino acids

Refluxing proteins / amino acids in acid or alkali conditions

How can different amino acids be separated

Chromatography

How can a carbon chain be increased by 1

Heat a halogenoalkane in a solution of KCN in ethanol under reflux

How can the chain length be increased by using a grignard reagent

The carbon had a delta - charge and is therefore attractive to electrophiles, such as carbonyl compounds

How stable are grignard reagents

Not very, have to be made just before they are needed