6.2 Nitrogen Compounds, Polymers And Synthesis
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What is an amine?
Organic compounds where one or more of the hydrogens of ammonia has been replaced by an alkyl chain
How do you name tertiary amines?
-Longest carbon chain as stem -Add the other two carbons as prefixes -If there’s more than one of the same chain use di- or tri- Begin the name with N-, N- -e .g . N-, N-dipropylbutamine
Explain the basicity of amines
There’s a lone pair of electrons on the nitrogen atom that’s able to accept protons (H+ ions). So they’re us.
What is formed when amines react with dilute acid? Example: CH3CH2NH2 + HCl –> ethylamine + hydrochloric acid–>
Neutralised to form ammonium salt CH3CH2NH2 + HCl –> CH3CH2NH3+Cl- ethylamine + hydrochloric acid–> ethylammonium chloride
How are aliphatic amines made?
Heating a haloalkane with excess of ethanolic ammonia
What is the problem with making aliphatic amines?
You get a mixture of primary, secondary, tertiary amines and Quaternary ammonium salts as more then one hydrogen likely substituted. Can be separated via fractional distillation
Why is excess ammonia used in making amines?
Drive reaction to the right forming more product
How are aromatic amines made?
Made by reducing a nitro compound. Heat a mix of nitro compound, tin metal and conc. HCl under reflux-this makes a salt. Add sodium hydroxide to neutralise excess acid nitrobenzene + 6[H] –> Phenylamine +2H2O
What is the general formula for α-amino acid?
RCH(NH2)COOH
How does an amino acid react with Acid?
Amino group reacts with acid forming a salt of the conjugate acid. RCH(NH2)COOH + HCl —> RCH(COOH)Cl-H3N+
How does an amino acid react with Alkali?
The carboxylic acid group reacts with an alkali to form a conjugate base. This can combine with a positive ion to form a salt. RCH(NH2)COOH + NaOH —> RCH(NH2)COO-Na+ + H2O
What happens when an amino acid reacts with alcohols?
The carboxylic group reacts with alcohol in the presence of a strong acid catalyst forming an ester
What does amphoteric mean?
Act as acid and base (Amino acid)
What happens when amino acids form zwitterions?
the two groups exchange a proton to from internal salt [A proton (H+) is transferred from the carboxyl group to the basic group->N becomes +]
What is the isoelectric point?
the pH at which a zwitterion forms
In acidic conditions what do amino acids form?
NH3+ (equilibrium driven right)
In alkali conditions what do amino acids form?
COO-Na+ (equilibrium driven left)
Define optical isomerism
Stereoisomers that are non-superimposable mirror images of each other about a chiral centre
How do you identify a chiral center?
Atom (carbon) with 4 different groups attached to it.
What is a racemate?
50:50 mix of each enantiomer, have no effect on plane polarised light
What are enantiomers?
mirror images of eachother that cant be superimposed
Describe condensation polymerisation to form polyesters
Polyesters are formed form monomers that have carboxylic acid and alcohol functional groups Ester link (-COO-) formed between monomers
Describe condensation polymerisation to form polyamides
Polyamides are formed from monomers that have carboxylic acid and amine functional groups amide links (-CONH-) formed between monomers
Describe the acid and base hydrolysis of the ester groups in polyesters
• Polyesters react slowly in strong aqueous acid to reform the carboxylic acid and alcohol groups of the monomers • Polyesters react quickly with hot aqueous NaOH to reform the alcohol groups of the monomers and form the salt of the carboxylic acid