Chapter 27 - Amines, amino acids and polymers Flashcards
What are amines?
Organic compounds in which one or more hydrogen atoms in ammonia (NH3) have been replaced by a carbon chain or ring
What is a primary amine?
Amine where the nitrogen atom is only bonded to one alkyl/aryl group, and 2 hydrogens
How do you name primary amines?
If NH2 is at the end of the chain: add suffix -amine to the name of the alkyl chain e.g. ethylamine
If the NH2 group is only any other carbon but carbon-1: use prefix amino- and number used to indicate position of the amine group along that chain e.g. 2-aminobutane
What is a secondary amine?
Amine where nitrogen atom is attached to 2 akyl/aryl groups and 1 hydogen
How do you name a seondary amine?
When amine has 2 of the same alkyl groups: prefixes di- used to indicate the number of alkyl groups attached to the notrogen atom. e.g. (CH3)2NH is dimethylamine
When 2 different alkyl groups attached to the nitrogen: the compound is named as a N-substituted derivative of the larger group. e.g. CH3NHCH2CH2CH3 is N-methylpropylamine
What is a tertiary amine?
Amine where the nitrogen atom is attached to 3 alkyl groups
How do you name tertiary amines?
If it has the same alkyl group: use prefix tri-
If it has 2 or more different alkyl groups attached to the nitrogen atom: the compound is named as a N-substituted derivative of the larger group e.g. CH3N(CH2CH3)CH2CH2CH3 is N-ethyl-N-methylpropylamine
What do amines often behave as?
Bases
How do amines behave as bases?
Lone pair of electrons on the nitrogen atom can accept a proton/H+.
When an amine accepts a proton, a dative covalent bond is formed between the lone pair of electrons on the nitrogen and the proton/H+.
What will a reaction between an amine and an acid make?
A salt (neutralisation reaction)
Write the equation for a reaction between propylamine and hydrochloric acid
CH3CH2CH2NH2 + HCl → CH3CH2CH2NH3+Cl-
forms salt - propylamonnium chloride
For the formation of primary amines, what is reacted together in the two steps?
salt formation:
Haloalkane and ammonia → ammonium salt
amine formation:
Salt and aqueous alkali (sodium hydroxide) → primary amine + ionic solid + water
In primary amine formation, what is in excess and why?
- Ammonia in excess
- Prevents further substitution of the amine group to form secondary and tertiary amines
In primary aliphatic amine formation, what is the purpose of ethanol?
- solvent
- prevents any substituion of the haloalkane by water to produce alcohols
What are the two steps of forming a secondary amine from a primary amine?
Primary amine + haloalkane and ethanol as solvent → ammonium salt
ammonium salt product + NaOH → secondary amine + ionic solid + water
- tertiary amines formed by further reaction of the secondary amine
How is phenylamine (aromatic amine) made from nitrobenzene?
Nitrobenzene heated under reflux with tin and HCl to form ammonium salt (phenylammonium). Ammonium salt reacted with with excess NaOH to produce the aromatic amine, phenylamine
What do tin and HCl act as in formation of phenylamine from nitrobenzene?
Reducing agent
What is an amino acid?
Organic compound containing both amine (NH2) and carboxylic acid (COOH) functional groups
What is an alpha-amino acid?
Amino acids in which the amine group is attached to an alpha carbon (carbon next to the carboxyl group)
What is the general formula for an alpha amino acid?
RCH(NH2)COOH
where R is the side chain attached to the alpha carbon atom
Amino acids are amphoteric, what does this mean?
Have acidic and basic properties
How do amino acids react with acids to form ammonium salts?
Amine group is basic and reacts with acids to make salts
What does an amino acid form when reacted with aqueous alkali such as sodium hydroxide?
- Sodium salt and water
Carboxylic acid can react with alkalis
How is an ester formed fro an amino acid?
Heating with an alcohol in the presence of concentrated sulphuric acid
(acidic conditions also pronate the basic amine group)
What are amides?
Products of reactions of acyl chlorides with ammonia and amines.
CO- NH
What are primary amides?
One carbon atom bonded to nitrogen atom
What are secondary and tertiary amides?
secondary - 2 carbon atoms bonded to the nitrogen atom
tertiary - 3 carbons bonded to the nitrogen atom
What is optical isomerism?
- Type of steroisomerism
- Compounds that are non-superimposible mirror images about a chiral centre
What is a chiral centre?
carbon atom that is attached to 4 different atoms or group of atoms (in organic chemistry)
Any centre that holds attachments that can be arranged as two non-superimposible mirror images
What is an enantiomers?
Pair of non-superimposible mirror image structures/ optical isomers
What do optical isomers do?
Rotate plane-polarised light
How do you draw optical isomers?
Drawn to show the 3D tetrahedral arrangement of the 4 different groups around the central chiral carbon atom. Other isomer is drawn as a mirror image, reflecting the first structure.
How is a chiral carbon atom labelled?
with an asterisk
any carbon atom that is attached to 4 different groups/atoms
What is condenstation polymerisation?
What is required for this?
Joining of monmers with loss of a small molecule, usually water (the condensation) or hydrogen chloride.
2 different functional groups
What is a polyester?
Monomers joined together by ester linkages in a long chain to form a polymer
How can a polyester be made from one monomer?
Monomer contains different functional groups - a hydroxyl (-OH) and a carboxyl group (-COOH)
Carboxylic acid group in one molecule reacts with alcohol group of another molecule
How can a polyster be made from 2 monomers?
- One monomer is a diol (with 2 hydroxyl groups) and one monomer is a dicarboxylic acid (with 2 carboxyl group) or diacyl chloride
a hydroxyl group on the diol reacts with a carboxyl group on the dicarboxylic acid/ diacyl chloride, forming an ester linkage and water/ hydrogen chloride
What are some uses of polyesters?
- Clothing
- Plastics
- electrical insulation
- biodegradables
What are polyamides?
Condensation polymers formed when monomers are joined together by amide linkages in a long chain to form a polymer.
How can polyamides be formed from one monomer?
Amino acids contain both an amine group and a carboxylic acid group. Amino acids undergo condensation polymerisation to form a polypeptide/protein, which contains many different amino acids all linked together by amide bonds - losing water in the process.
How can polyamides be formed from 2 monomers?
Reaction of a carboxylic acid (or acyl chloride) with a diamine
What is required to undergo acid hydrolysis?
Excess hot aqueous HCl
H2O
What is formed from polyester undergoing acid hydrolysis?
- Diol
- Dicarboxylic acid
What is required to undergo base hydrolysis?
Excess hot aqueous NaOH
What is formed from polyester undergoing base hydrolysis?
- Diol
- Salt of dicarboxylic acid
What is formed from acid hydrolysis of polyamide?
- Diammonium salt
- Dicarboxylic acid
What is formed from base hydrolysis of polyamide?
- Diamine
- Salt of dicarboxylic acid
How does addition polymerisation differ from condensation polymerisation with monomers?
Addition - monomer contains C=C bond
Condensation - two monomers with two functional groups or one monomer with two different functional groups
How does addition polymerisation differ from condensation polymerisation with backbone?
Addition - backbone of polymer is -C-C- bond
Condensation - polymer back bone contains ester or amide groups
