6.2 Nitrogen Compounds, Polymers And Synthesis Flashcards
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Organic compounds where one or more of the hydrogens of ammonia has been replaced by an alkyl chain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
Describe the acid and base hydrolysis of the amide groups in polyamides
- Polyamides react quickly in strong aqueous acid to form the carboxylic acid groups of the monomers and a diammonium salt
- Polyamides react slowly in hot aqueous NaOH to form the amine groups of the monomers and the salt of the carboxylic acid
Can you predict the repeat unit from a given monomer for addition and condensation polymerisation?
maybe
Can you predict the monomer(s) required for a given section of a polymer molecule for addition and condensation polymerisation
maybe
How are peptides formed?
What is dipeptide and polypepetide?
Amino acids react together to form a peptide in a condensation reaction.
Dipeptide: 2-amino acids
Polypeptide: many amino acids
Suggest two benefits of using single stereoisomers in the synthesis of drugs
no/fewer side effects
increases the (pharmacological) activity/effectiveness
Reduces/stops the need for/cost/difficulty in separating
stereoisomers/optical isomers
State what is meant by a condensation polymer.
monomers join to form polymer
AND small molecule e.g. H2O/HCl
What’s the use of C–C bond formation in synthesis
to increase the length of a carbon chain
formation of C-C=/N by reaction of:
(i) haloalkanes with CN– and ethanol, including
nucleophilic substitution mechanism
R-X + CN- –> R-C=/N + Br-
