Chapter 27 - Amines, amino acids Flashcards
Define amines
They are derived from NH3 (ammonia) in which one or more of the hydrogen atoms in ammonia are replaced by a carbon chain or ring.
Define an aliphatic amine
Nitrogen is attached to at least 1 straight chain or branched alkyl chain.
Define aromatic amine
Nitrogen is attached to an aromatic ring. (usually nitrobenzene)
What is a primary amine
NH2R.
Remember to draw the lone pair of electrons above the N
What is a secondary amine
NHR’R’’.
It depends on the number of R groups attached to the N.
Remember to draw the lone pair of electrons on the N.
Examples of amines
Serotonin (acts as a neurotransmitter, controlling appetite, sleep, memory, learning and temperature.)
Pseudoephedrine (an active ingredient in decongestion medicines)
How do you name amines
Add an ‘amine’ to the end.
Secondary and tertiary amines- add ‘di’ or ‘try’ as a prefix.
When there are 2 or more groups attached to the nitrogen atom, name it as an N- substituted derivative of the larger group.
Smell of amines
It smells like rotting fish
Reactions of amines as bases
Due to the lone pair on the nitrogen, they can accept a proton, creating a dative covalent bond.
They can react with acids to give salts.
If it is a NH2, it becomes :
NH3+ X-.
Preparation of aliphatic amines
The lone pair of electrons on Nitrogen allows ammonia to act as a nucleophile.
How can you create a primary amine
- Haloalkane + ammonia -> salt.
Add excess ammonia. (is a nucleophilic substitution) - Salt + NaOH -> primary amine + water + Na-X.
Ethanol can be used as a solvent to prevent substitution of the haloalkane and production of alcohol.
How can you create a secondary amine
- Primary amine + haloalkane -> salt.
2. Salt + NaOH -> Na-X + Secondary amine + water.
Preparation of aromatic amines
Made by the reduction of nitrobenzene.
Nitrobenzene + 6[H+] -> Phenylamine + 2H20.
above the arrow: 1. Sn/ Concentrated HCl.
2. excess NaOH.
what is an amino acid
It contains both amine and carboxylic acid functional groups.
Amino acid + acids
Amino acid + acids -> salt + acid ion.
this is a reaction of the amine group
How many amino acids are there?
20.
Amino acid + alkalis
Amino acid + alkalis -> salt + water
Amino acid + alcohols
Amino acid + alcohols -> esters
Esterification
excess ethanol
and a small amount of sulphuric acid.
Define a zwitterion
It has no charge, because the H+ ion from the COOH group can move to the NH2 group and form a + and a - charge.
Define the isoelectric point
It is the pH at which the zwitterion is formed, and each amino acid has its own unique isolectric point.
If you have a pH above the isolelectric point, then you form a COO- ion.
Define an optical isomer
A chiral carbon with 4 different groups, making it a non-superimposable mirror image.
What is glycine
It is the most simplest amino acid.
Define a chiral centre
a Carbon atom that is attached to 4 different groups or atoms.
How do you name amino acids
The COOH group is always more prioritised, so the Carbon attached to the COOH group is carbon 2.
Define bi-functional
Can behave as an acid or an alkali as it has both functional groups.
Define the racemix mixture
They have equal amounts of left and right handed enantiomers of a chiral molecule.
Define a condensation polymer
Joining of monomers with the loss of a small molecule (usually water or HCl)
What are the 2 ways in which a polyester can be made?
- 1 monomer containing 2 functional groups ( so It should have OH on one side and COOH on the other.)
- 2 monomers that have COOH on both sides or OH on both sides.
What is a monomer that has 2 OH groups
a diol
What is a monomer that has 2 COOH groups
A dicarboxylic acid
Examples of a polyester made from 1 monomer
called PET (Polyethylene terephthalate) it is made using benzene-1,4 di carboxylic acid and ethane-1,2 diol.
How are polyamides formed
By a condensation reaction using a monomer that has both a carboxylic acid functional group (or acyl chloride) and an amine group functional group.
Or by 2 monomers which have 2 COOH functional groups and another which has 2 NH2 functional groups.
What is an ester functional group
COO
What is an amide functional group
COHN
What is a monomer with 2 amine groups called
Diamine
What is nylon made from?
Using hexanedioic acid and 1,6 diaminohexane
or
hexanedioyl chloride and 1,6 diaminohexane
How do you name nylons
The first number is the number of Carbons in the amino group, and then the Carboxylic acid group one next.
Acid hydrolysis of a polyester
Use H2SO4 (hot aqueous)/ H20 Products: Just the monomers
Alkali hydrolysis of a polyester
Use NaOH/H2O
Products: alcohol and carboxylic-salt.
Acid hydrolysis of a polyamide
Use H20 /H+
Products: NH3+ on the amines and a carboxylic acids.
Alkali hydrolysis of a polyamide
Use NaOH/ H2O
Products: COO- Na+ and NH2 amines.
Characteristics of an addition polymer
Contains a C=C bond in the monomer
Contains a backbone of a continuous chain
Characteristics of a condensation polymer
2 monomers with 2 functional groups (on either sides)
1 monomer with 2 different functional groups
Polymer has ester/ amide linkages.
C-N bond
It is polar.
The nitrogen is very electronegative, so it’s quite easy to break this C-N bond as it’s a weaker bond.
Ammonia gas + HCl gas
It creates white smoke.
And NH4+Cl-
Outline how an addition polymer is formed?
The pi-bond breaks and many molecules join together.
Explain why xyz is considered to be a “degradable polymer”?
Because the C=O or the C-N bond can break and it is hydrolysed so that the polymer can be broken into its monomers.
WHENEVER THERE IS ANYTHING ABOUT GREATER MELTING POINT?
ALWAYS INTERMOLECULAR FORCES!!
IS THERE ANY HYDROGEN BONDING? ANY LONDON FORCES? PERMANENT DIPOLE?!
Why are secondary amines stronger bases than primary amines?
Because they have 2 alkyl groups that better stabilize the acid than primary amines, and so making it more basic.
How do amines behave?
They behave as weak bases.
State 2 disadvantages of synthesising something that makes a mixture of optical isomers?
Then 2 methods that are used to synthesis the only wanted optical isomer
One stereoisomer may have adverse side effects, and the cost of separating the stereoisomers can be quite high.
Methods: You have use natural chiral molecules or use enzymes or bacteria.
Diazonium ion
A benzene ring where there is a N=-N attached to one Carbon atom.
How can a polymer be broken down.
Either by hydrolysis or photodegradable
