Chapter 27 Amines

Question 1

How do you name amines?

Answer 1

If primary and the amine is at the end of a chain, alkylamine
If primary and the amine is at another position, 2-aminoalkane
If secondary or tertiary, N-alkyl-N-alkyl-longest alkyl amine
If all substituents are the same, no need for N, e.g triethylamine

Question 2

Why can an amine react with acids?

Answer 2

Amines can act as bases. The lone pair of electrons on the nitrogen can accept a proton, to form a carbammonium ion, and a salt

Question 3

Rank the basicity of different amines? Strongest to weakest

Answer 3

Alicyclic/ Aliphatic amines (more alkyls the stronger the base)
Aromatic amines with another electron donating group
Aromatic Amines - electrons delocalised
Tertiary aromatic amines - no alkyls or hydrogens to donate electrons

Question 4

What are the strongest type of amines in terms of basicity and why?

Answer 4

Tertiary, alkyls are electron donating
Then secondary, then primary, then look at aromatic ones

Question 5

How can you make a primary amine? Conditions?

Answer 5

1.Haloalkane and Ammonia, forms an Ammonium Salt
2. NaOH to deprotonate the salt

Or would the excess mean the second step is not necessary?

Excess ammonia to reduce further substitution, and Ethanol solvent to prevent nucleophilic substitution

Question 6

Why does the NH3/Cl- not deprotonate the salt?

Answer 6

NH3 will but very slowly
Cl- is a weaker base than NH3 so unlikely to
OH- strongest, quickly removes the proton

Question 7

Why does the synthesis of amines with haloalkanes result in multiple products?

Answer 7

Further substitution occur
The amine formed still has a lone pair so can under nucleophilic substitution with more haloalkane
Forms secondary, tertiary amines, and finally carbammonium ions with no lone pairs

Question 8

How do you form phenylamine from benzene? What type of reaction is this?

Answer 8

Nitration with conc H2SO4/HNO3
Reduction :
1. Heat under reflux with Sn/HCl
2. NaOH to deprotonate

Reduction, use brackets H for equation

Question 9

How can you synthesise an amine from an alcohol?

Answer 9

Heat under reflux with NaBr/H2SO4 to form haloalkane
React with NH3 in ethanol solvent, the deprotonate

Question 10

What is an alpha amino acid?

Answer 10

An amino acid where there is one carbon between the COOH and the NH2

Question 11

What types of reactions to amino acids under go?

Answer 11

COOH with Na/NaOH/NaCO3 to form a carboxylate salt
NH2 with HCl to form an ammonium salt
Esterification- forms an ester but also a AMMONIUM SALT as NH2 protonated from the catalyst

Question 12

What is a zwitterion and when does it form?

Answer 12

A form of the amino acid where the COOH’s proton is donated to the NH2, overall neutral molecule
At its isoelectric point , unique as acid/base chemistry of the R groups affects this

Question 13

Why do amino acids have higher melting points than expected/ higher solubilities?

Answer 13

Zwitterion allows for ionic bonding, strong electrostatic force of attraction, lots of energy to overcome in giant ionic lattice
Full charges allow greater interaction with water

Question 14

How does an amino acid act as high/low pHs?

Answer 14

Low pH- acidic environments, so NH2 accepts a proton
High pH- alkaline environments, so COOH donates a proton

Question 15

How do you form amides and what is the side product?

Answer 15

Acyl Chlorides/Acid Anhydrides with NH3 or amines
Forms an amide and an ammonium salt
As the Cl- is a weaker base then NH3

Question 16

What are the main types of isomerism and how can they be split further?

Answer 16

Structural- then Chain, Position, Functional group
Stereoisomerism- Geometric (cis/trans) and Optical

Question 17

What are optical isomers and how do they arise in organic compounds?

Answer 17

Non-superimposable mirror images, in organic, when a chiral carbon is present, a carbon bonded to 4 different groups
In a ring, look for symmetry

Question 18

How do you draw enantiomers of a chiral carbon?

Answer 18

Draw the dots and wedges
Reflect this
And keep the groups the same

Question 19

How do enantiomers differ in their properties? How does a race mic mixture compare to this?

Answer 19

Each enantiomers will rotate plane polarised light into a different direction
As a racemic mixture contains an equal amount of each enantiomers, the rotations will cancel out so the effect is not seen

Question 20

What is the stereochemistry involved with SN1/SN2 and nucleophilic addition?

Answer 20

SN1- Racemic mixtures as equal chance of which side the nucleophilic will attack
SN2- steric inversion, opposite enantiomer to the starting molecule
Nucleophilic addition - Racemic, equal chance of being attacked above of below as a plane

Question 21

What is a monomer?

Answer 21

A small molecule which can react with many other of this molecule to form a polymer

Question 22

What is a polymer? What is a repeat unit?

Answer 22

Polymer- A large molecule formed from many repeating units of smaller molecules
Repeat Unit- simplest unit of a polymer repeated to form the polymer

Question 23

What is a condensation polymer and some examples?

Answer 23

The joining of monomers to form a large molecule of a repeating structure, with the removal of a small molecule such as water
Polyesters, Polyamides

Question 24

How can you make polyesters?

Answer 24

Need the functional groups: alcohol and either an Acyl Chloride or Carboxylic Acid
With the same molecule- one of each, cannot see bond in repeat unit (n-1) water
With two different molecules Diol and Dicarboxylic Acid, Diacyl, see one link, one not seen, (2n-1) water

Question 25

How can you form polyamides?

Answer 25

Need amine and a carboxylic acid derivative (no acid anhydride)
From one monomer- one of each, (n-1) water, cannot see link
From two monomers- diamine… (2n-1)water, see one link, one to form

Question 26

How can you tell the different between an addition polymer and condensation polymer from the back bone?

Answer 26

Addition- only carbon carbon single bonds
Condensation- involve carbon bonds, but also ester/amide links

Question 27

How can you hydrolyse polymers?

Answer 27

Heat under reflux with an Acid Catalyst
Heat under reflux with NaOH

Question 28

For polyamides and polyesters, what forms under acid hydrolysis?

Answer 28

Polyamides- Carboxylic acid and Ammonium Salt, protonate any amine present
Polyesters- Carboxylic Acid and Alcohol

Question 29

For polyamides and polyesters, what forms under base hydrolysis?

Answer 29

Polyamides- amines and carboxylate salt
Polyesters- alcohol and carboxylate salt, react any acid/phenol

Question 30

Why are polyesters/polyamides biodegradable? What happens to the monomers?

Answer 30

The ester/amide bond can be hydrolyses, breaking apart the polymer into monomers again
And if the monomer is also soluble in water, it can form hydrogen bonds and dissolve appearing to disappear

Question 31

How do you calculate the mr of polymers?

Answer 31

If the number of repeat units known, multiple mr of the repeat unit by the number of repeat units
Then add on the end functional groups, usually equivalent to water, but if a diacylchloride used then HCl mass

Question 32

Why is it useful to synthesis a medicine with only one enantiomer?

Answer 32

Reduced risk of side effects
Less money/time needed to be spent into separating the enantiomers e.g using chiral catalysts

Question 33

Why can a singular monomer form a condensation polymer and how?

Answer 33

Contains two different functional groups which can react with each other
Lots of monomer molecules will react with these functional groups to form a long chain molecule with a repeating structure