Chemistry (6.2): Nitrogen compounds, polymers and synthesis

Ammonia formula

NH₃

amines

organic chemicals where one or more of the hydrogen atoms have been replaced with alkyl chains

Primary amine

RNH₂

Secondary amine

RNHR^’

Tertiary amine

RNR^’R^’’

Naming amines suffix

amine

Are amines bases or acids?

weak bases

Lewis base

electron pair donor

Bronsted-Lowry base

proton acceptor

What do amines react with?

dilute inorganic acids (e.g. HCl)

What is produced when HCl reacts with a base?

chloride salt and water

What is produced which primary amines react with HCl?

alkylammonium salt

alkylammonium salt

a compound where the hydrogens on an ammonium ion have been substituted by alkyl chains

Name of salt formed when an amine reacts with HCl

alkylammonium chloride

Name of salt formed when an amine reacts with nitric acid

alkylammonium nitrate

Name of salt produced when amines react with sulfuric aicd

alkylammonium sulfate

What chemicals are used to prepare aliphatic amines?

haloalkane, ammonia and ethanol

ammonia + haloalkane →

ammonium salt

ammonium salt + ammonia →

amine + ammonium salt

quaternary ammonium salt

each hydrogen on the ammonium ion has been replaced with an alkyl chain

How do you prepare aromatic amines?

reduce a nitroarene

What are the conditions for preparing aromatic amines?

Tin, conc HCl, reflux at 100 degrees C, strong alkali (NaOH)

What kind of reaction is the preparation of aromatic amines?

neutralisation

amino acid general formula

RCH(NH₂)COOH

what functional groups do amino acids have?

amine and carboxylic acid groups

What does the amine group on an amino acid act as?

a base

Why does the amine group of an amino acid act as a base?

due to the lone pair of electrons

What does the carboxylic acid group of an amino acid act as?

a weak acid

amphoteric

can act as both an acid and a base

isoelectic point

when there is no net electrical charge due to each zwitterion having an internal balance of charge

What happens when an amino acid is in acidic conditions?

amino acid acts as a base and accepts a proton from the acid and becomes positive

What happens when an amino acid is in alkaline conditions?

amino acid acts as an acid and donates a proton to the hydroxide ion and becomes negative

What does the carboxylic acid functional group of an amino acid react with?

1. metal oxides

2. alkalis

3. carbonates

4. alcohols

acid + amino acid →

ammonium salt

amide

a class of compound with a functional group made of an acyl group which is directly attached to an amine

primary amide general formula

RC(O)NH₂

How are amides related to carboxylic acids?

hydroxyl group has been substituted for an amine group

What is this?

primary amide

What is this?

secondary amide

What is this?

tertiary amide

polyamides

condition polymer made from carboxylic acid and an amine

carboxylic acid + amine →

polyamides

How do you name primary amines?

suffix amide

optical isomers

molecules which are non-superimposable mirror images of each other

chiral carbon

has four different groups attached to it

When are optical isomers formed?

when there is a chiral centre

repeat unit

the arrangement of atoms that occurs many times in a polymer

condensation polymerisation

the chemical reaction to form a long-chain molecule by elimination of a small molecule like water

What does this show?

addition polymerisation

What does this show?

Condensation polymerisation

What are polyesters made from?

dicarboxylic acid and a diol or a molecule that contains both an alcohol and a carboxylic acid group

Types of condensation polymer (2)

1. polyesters

2. polyamides

What are polyamides made from?

dicarboxylic acid and a diamide

Under what conditions do polyesters undergo hydrolysis?

acidic or basic

Products of the acid hydrolysis of polyesters

diol and dicarboxylic acid

Products of the base hydrolysis of polyesters

diol and the salt of the dicarboxylic acid

Under what conditions do polyamides undergo hydrolysis?

acidic or basic

Products of the acid hydrolysis of polyamides

diammonium salt and a dicarboxylic acid

Products of the alkali hydrolysis of polyamides

diamine an

nitrile functional group

-CN

-CN

nitrile functional group

Reactions to extend carbon chain length

1. haloalkane + KCN

2. carbonyl + HCN

3. Friedel-Crafts reactions (acylation and alkylation)

What type of reaction is the reaction between a haloalkane and KCN?

nucleophilic substitution

haloalkane + KCN →

nitrile + halide ion

What type of reaction is the reaction between carbonyl and HCN?

nucleophilic addition

Why is the solvent ethanol when a haloalkane is mixed with KCN and heated under reflux?

ensures that the nucleophile is the cyanide ion

carbonyl + HCN →

hydroxynitrile

Reactions of nitriles (2)

1. reduction

2. hydrolysis

What are the reagents when nitriles undergo reduction?

hydrogen gas, nickel catalyst, increased temp (150) and pressure

What is formed when nitriles undergo reduction?

amines

RCN + 2H₂ →

RCH₂NH₂

What can be used as a reducing agent in the reduction of a nitrile?

LiAlH₄

What are the conditions for the hydrolysis of nitriles?

strong acid catalyst and heating under reflux

What are formed when nitriles undergo acid hydrolysis?

carboxylic acids

What do Friedel-Crafts reactions allow?

electrophilic substitution to occur on an aromatic ring

Friedel-Crafts reactions (2)

1. acylation

2. alkylation

Alkylation

occurs when hydrocarbon chains are added to an organic compound

Reagents for alkylation

aromatic compound, haloalkane and a strong Lewis acid catalyst

What kind of reaction is alkylation?

electrophilic substitution

Acylation

when RCO- is added to an organic compound

What are the reagents of acylation?

benzene, acyl chloride and a strong Lewis acid catalyst

distillation

a technique used to separate miscible liquids or solutions

heating under reflux

used to ensure that volatile compounds are not lost from the reaction mixture

recrystallisation

a method for purifying organic compounds

How are the tubes attached to the condenser in distillation?

water out at the top and cool water in at the bottom

What techniques are used to purify an organic solid? (2)

1. filtration under reduced pressure

2. recrystallisation

How to check purify of an organic compounds

measuring melting points

What kind of funnel is used for pressure filtration?

Buchner funnel

Steps of filtration

1. connect tubing to vacuum pump and check suction

2. put Buchner funnel into top of filter flask

3. connect tubing to filter flask

4. start suction

5. place filter paper into top of funnel and dampen with distilled water

6. poor reaction mixture into centre of funnel

Stages of recrystallisation (4)

1. dissolve product in hot solvent

2. solution undergo gravity filtration

3. hot filtrate allowed to cool

4. purified organic product collected by vacuum filtration

How do you measure melting points?

1. melting po