Amines Flashcards
Differences between primary, secondary and tertiary amines
Primary: 1 carbon chain attached to nitrogen
Secondary: 2 carbon chains attached to nitrogen
Tertiary: 3 carbon chains attached to nitrogen
Differences in boiling points of primary, tertiary and secondary amines
Primary amines have higher boiling points as they can form hydrogen bonds with each other as well as van der Waals’ and permanent dipole-dipole interactions.
Secondary amines can also form hydrogen bonds but with the amine in the middle of the chain, the permanent dipole is less.
Tertiary amines cannot form hydrogen bonds with each other as there are no hydrogen atoms attached directly to the nitrogen.
Solubility of amines
All of the amines can form hydrogen bonds with water - even the tertiary ones.
Although the tertiary amines don’t have a hydrogen atom attached to the nitrogen and so can’t form hydrogen bonds with themselves, they can form hydrogen bonds with water molecules just using the lone pair on the nitrogen.
Smell of amines
As the amines get bigger, they tend to smell more “fishy”
How do amines act as bases?
The lone pair of electrons on the nitrogen atoms can accept a proton (and form a dative covalent bond)
Amine reactions with acids
The NH2 group gains an H+ leading to NH3+ attached to negatively chrged ion, forming a salt
Reaction of amines with water
React like ammonia, an H+ is taken from water forming an NH3+ ion and an OH- ion
Comparison of strengths as a base of alkylamines, ammonia and primary arylamines
(Stretch and challenge)
Alkylamines tend to be stronger bases than ammonia because the alkyl groups are more electron donating than H atoms so there is a higher electron density around the N atoms and the lone pair of electrons. Thus, a stronger bond is formed with an H+ ion. Primary arylamines are weaker bases than ammonia or alkylamines as the lone pair becomes partly delocalised into the benzene ring and is less available to bond to an H+ ion.
What is one possible problem with the synthesis of alkyl amines and how can it be reduced?
The product has a lone pair of electrons and can react with the halogenoalkane to form hydrogen halide + organic mixture (look at p.38) can be reduced through increasing the pressure/conc. of ammonia.
What is an amino acid?
A compound containing an -NH2 group and a carboxylic acid group
What is an alpha amino acid?
An amino acid with the amino group attached to the carbon atom adjacent to the -COOH groups
What is the general formula of an alpha amino acid?
RCH(NH2)COOH
What is a zwitterion?
A dipolar ionic form of an amino acid that is formed by the donation of a hydrogen ion from the carboxyl group to the amino group. Both charges are present so there is no overall charge.
What the the isoelectric point?
The pH value at which the amino acid exists as a zwitterion
How does R group affect isoelectric point? ***
If you add basic groups such as NH2 to the R side chain, there’s a greater chance of protonation at any given pH as there are now two proton acceptors in the amino acid. As a result, the pH needs to be higher to prevent any charges arising from protonation, hence the isoelectric point is higher.
If you add acidic groups such as COOH to the R side chain, there’s a greater chance of deprotonation at any given pH as there are now two proton donators in the amino acid. As a result, the pH needs to be lower to prevent any charges arising from deprotonation, hence the isoelectric point is lower.
Amino acid in an environment more acidic than isoelectric point
Amino acid behaves as a base and accepts a proton from the acid, forming a positively charged ion
Amino acid as an acid (in more basic environment than isoelectric point)
Amino acid donates a proton to the base forming a negatively charged ion and water
Reaction of alanine (CH3CH(NH2)COOH) with HCl
Cl- + CH3CH(NH3+)COOH formed
Reaction of glycine (CH2(NH2)COOH) and NaOH
Forms H2O + CH2(NH2)COO-Na+
What feature of amino acids allows them to form polymers?
The contain both amine and carboxyl groups so can form peptide links
What is condensation?
A reaction in which two small molecules react together to form a larger molecule with the elimination of a small molecule such as water
What does condensation polymerisation require?
Monomers with two different functional groups
What is a polyester and what groups do the monomers contain?
A polyester is formed when monomer units which contain a carboxyl and hydroxyl group are bonded together through ester linkages
General formula for forming a polyester with one type of monomer
n HO - A - COOH (hydroxycarboxylic acid) -> -[-O-B-CO-]- n + H2O
General formula for the formation of a polyester from different monomer
n HO-A-OH (diol) + n COOH- B - COOH (dicarboxylic acid) -> -[-O - A - O -CO -B -CO-]- n + (2n-1) H2O
How is terylene made?
Ethane -1,2 -diol and benene -1,4- dicarboxylic acid
How is polylatic acid made?
Lactic acid : HO - CH(CH3) - COOH forms a polyester
A bond forms between a hydroxyl group on one lactic acid molecule and a carboxyl group an another lactic acid molecule forming an ester linkage
Uses of polyesters
Makes carpets and clothes, is a strong fibre resistant to stretching, shrinking and chemical attack but burns easily. PLA used for food and drink packaging as it is biodegradable
What is an amide/peptide bond?
-C=O - NH2
What is the bond present in polyamides?
- C=O - NH -
What types of functional groups required to make polyamides?
Carboxyl and amine
Making a polyamide with one type of monomer
Amino acid which contains both COOH and NH2 groups is used
n H2N - B - COOH -> -[-NH - B - CO-]- n + (2n-1) H2O
Making a polyamide with two different monomers
A dicarboxylic acid and a diamine are used
n H2N -A -NH2 + n COOH - B - COOH -> -[-NH-A-NH-CO-B-CO-]- n + (2n-1) H2O
Making Nylon - 6,6
1,6 - diaminohexane is reacted with hexane- 1,6- dioic acid
n H2N - (CH2)6- NH2 + n COOH- (CH2)4 - COOH
n -[-HN- (CH2)6 -NH-CO-(CH2)4-CO-]- + (2n-1) H2O
Making Kevlar
Benzene - 1,4- dioic acid is reacted with benzene -1,4 - diamine
Uses of polyamides
Fibres in clothing, kevlar is very strong and fire resistant so used in bullet proof vests
When amino acids join together what is the name of the structure and what link is present?
Polypeptides and proteins joined by peptide links
Acid hydrolysis of polypeptides
Heat under reflux w. 6 mol.dm^3 HCl for 24 hours. A water molecule breaks each peptide to form a mixture of the amino acids that made up the proteins with positive charge. Polypeptide + H2O + nH+ (from the acid)
Alkaline hydrolysis of polypeptides and proteins
+ NaOH (aq) just above 100 degrees
Polypeptide or protein is broken down into amino acids in the form of their sodium salts
How can condensation polymers be broken down?
Acid or alkali hydrolysis
What is each ester linkage hydrolysed to during alkaline hydrolysis of polyesters
- The sodium salt of a carboxylic acid
- A hydroxyl group
Conditions for hydrolysis of polesters
Hot aqueous acid or alkali
What is each ester linkage hydrolysed to during acid hydrolysis of polyesters
The monomer units of the polyester
Alkali hydrolysis of terylene
Broken down into +Na-OOC-(O)-COO-Na+ and CH2OHCH2OH
Acid hydrolysis of terylene
Broken down into Benzene -1,4- dioic acid and Ethane-1,2-diol
What is formed in acid hydrolysis of polyamides?
Dicarboxylic acid and ammonium salt of the diamine
What is formed in alkali hydrolysis of polyamides?
Sodium salt of dicarboxylic acid and the diamine
Acid hydrolysis of nylon-6,6
Forms n H3+N-(CH2)6-N+H3 + n HOOC-(CH2)4-COOH
Alkaline hydrolysis of nylon-6,6
Forms n +Na-COO-(CH2)4-COO-Na+ + H2N-(CH2)6-NH2
Common property of bonds in biodegradable polymers
Chemical bonds can undergo hydrolysis
What are photo-degradable polymers?
Polymers designed to become weak and brittle when exposed to sunlight for prolonged periods. They are then converted to CO2 and water in the presence of bacteria
How are photo-degradable polymers manufactured?
Blending polymer with light-sensitive additives that catalyse the breakdown of the polymer when exposed to UV radiation. Or incorporating C=O bond which absorb light energy and break.
What is a chiral carbon?
A carbon atom with four different groups attached
How should optical isomers be drawn?
With the geometry around the chiral carbon shown as a tetrahedral shape
Properties of optical isomers
They rotate plane-polarised light differently. One of the optical isomers rotates the light clockwise and the other rotates it anti-clockwise. A racemic mixture has no effect on plane-polarised light because the rotations cancel each other out.
Advantages of production of a single isomer with correct pharmacological activity
Risks from undesirable side effects are reduced.
Drug doses are reduced because half the drug won’t be wasted
Problem with synthesising chiral compounds in a lab
Mixture of optical isomers requires complicated separation techniques as optical isomers usually have very simillar physical or the same physical properties. Techniques include chromatography, electrophoresis and use of enzymes.
Methods to prepare single chiral isomers
Using enzymes as biological catalysts
Use of transition element complexes to produce chiral catalysts
Chiral pool synthesis
Base reactions of amines
—> NH3+A-
