Chapter 27

• what are amines?


  organic derivatives of ammonia, NH3, in which one or more hydrogen is replaced by a carbon chain or ring
• what is an aliphatic amine?

  - the nitrogen atom is attached to at least one straight or branched carbon chain

  - methylamine is the simplest

  
• what is an aromatic amine?

  - nitrogen atom is attached to an aromatic ring

  - phenylamine is the simplest

  
• how do you classify amines?

  - primary amines, the N will be attached to two hydrogens and one R group

  - secondary amines, the N will be attached to one hydrogen and two R groups

  - tertiary amines, the N will be attached to no hydrogens an three R groups

  
• how do you name amines?

  - primary amines, just add -amine to the name of the alkyl group

  
  

  -primary amines but the amine group is on any other carbon but carbon-1 then prefix amino and number is used e.g. 2-aminobutane

  
  

  - secondary or tertiary amines containing the same alkyl group, prefixes such as di- or tri- are attached to the nitrogen atom. E.g. (CH3)2 NH is dimethylamine

  
  

  - when two or more different groups are attached to a nitrogen atom, the compound is names as N-substituted derivative e.g. CH3NHCH2CH2CH3 is known as N-methylpropylamine

  
• describe the reactions of amines?

  AMINES AS BASES:

  - amines behave as bases because the lone pair on the N can accept a proton

  - when an amine accepts a proton, dative covalent bond is formed between lone pair of electrons and proton

  
• how are salts formed from amines?

  - amines are bases and they neutralise acids to make salts

  - e.g. propylamine reacts with HCl to form the salt propylammonium chloride

  - CH3CH2CH2NH2 + HCl -> CH3CH2CH2NH3+Cl-

  
• how are primary amines formed?

  - ammonia has a lone pair of electrons on the nitrogen atom, which allows it to act as a nucleophile in a substitution reaction with a haloalkane, this produces an ammonium salt, then an aqueous alkali is added to generate the amine from the salt

  
  

  - e.g. salt formation: CH3CH2CH2Cl + NH3 -> CH3CH2CH2NH3+Cl-

  amine formation: CH3CH2CH2NH3+Cl- + NaOH -> CH3CH2CH2NH2 + NaCl + H2O

  
• what are the conditions needed to make a primary amine?

  - ethanol is used as a solvent (prevents substitution of haloalkanes with water to form alcohols)

  - excess ammonia is used, reduces further substitutions into secondary or tertiary amines
• why is the formation of primary amines unsuitable?

  - the product still contains a lone of electrons on the nitrogen atom that can react further with a haloalkane to form a secondary amine
• how can a secondary amine be formed?

  - salt formation (ammonium salt)

  - reacting product (ammonium salt) with NaOH

  
• how can a tertiary amine formed?

  - further reaction of secondary amines
• how are aromatic amines formed?

  - phenyl amines are made by the reduction of nitrobenzene

  - nitrobenzene is heated under reflux with tin and HCl to form phenylammonium chloride (ammonium salt)

  - then it's reacted with excess NaOH to produce phenylamine (tin and HCl act as a reducing agent)
• what does an amino acid look like?

  - hydrogen

  - amino

  - carboxyl

  - r group

  
• how many naturally occurring amino acids are there?

  20
• what is general formula of amino acids?

  RCH(NH2)COOH
• why do amino acids have similar reactions to both carboxylic acids and amines?

  because they have both an acidic COOH and a basic NH2 functional group
• what are the reactions of the amine group in amino acids?

  - amine group is basic and reacts with acids to form salts

  - e.g. 2-aminopropanoic acid reacts with HCl to form an ammonium salt and Cl-

  
• what are the reactions of the carboxylic acid group in amino acids

  with aqueous alkalis?

  - amino acid reacts with an aqueous alkali such as NaOH/KOH to form a salt and water

  - e.g. aminoethanoic acid reacts with NaOH to form a sodium salt

  
• how are amino acids esterified?

  - amino acids are esterified by heating wit an alcohol in the presence of H2SO4

  - e.g. serine is reacted with ethanol and a small amount of H2SO4, producing an ester and water

  
• what are amides?


  products of reactions of acyl chlorides with ammonia and amines
• how do you classify amides?

  - primary, 1 C atom attached to N

  - secondary, 2 C atoms attached to N

  - tertiary, 3 C atoms attached to N

  
• what is optical isomerism?

  - stereoisomers that are non-superimposable mirror images of each other

  - sometimes called enantiomers
• where is optical isomerism found?

  in molecules that contain a chiral centre
• what is a chiral centre?

  a carbon atom with four different atoms or groups attached to it
• how is a chiral centre shown?

  with an asterisk
• examples of chiral centres

  
• what is condensation polymerisation?

  - where monomers with two functional groups join together, usually losing small molecules such as water or hydrogen chloride

  - in condensation reactions, two different functional groups are needed
• how are polyesters formed?

  - monomers are joined together by ester linkages in a long chain to form a polymer

  - need a carboxylic acid group and an alcohol (hydroxyl group) to form an ester linkage
• show the condensation polymerisation of glycolic acid

  
• what are polyamides?


  - condensation polymers formed when monomers are joined together by amide linkages in a long chain to form the polymer

  - it can be made from one monomer containing both a carboxylic acid and an amine group or from two monomers one contain 2 carboxylic acids and the other containing two amine group
• what does an amide linkage look like?

  
• how can polyesters and polyamides be hydrolysed?

  - using hot aqueous alkali such as sodium hydroxide

  - using hot aqueous acid such as hydrochloric acid

  (acid and base hydrolysis)
• show the acid and base hydrolysis of PTT (polyester)

  
• show the acid and base hydrolysis of Nomex (polyamide)

  
• What are amines?

  Organic compounds, derived from ammonia, NH₃, in which one or more hydrogen atoms in ammonia have been replaced by a carbon ring or chain.
• What is an aliphatic amine?

  The nitrogen atom is attached to at least one straight or branched carbon chain.
• What is an aromatic amine?

  The nitrogen atom is attached to an aromatic ring.

  
  

  Phenylamine, C₆H₅NH₂, is the simplest aromatic amine, with a phenyl group attached to the nitrogen atom.
• How do you name a primary amine?

  Add the suffix -amine to the name of the alkyl chain if the -NH₂ group is on the end of the chain.
• How do you name a secondary or tertiary amine when th attached groups are the same?

  The prefixes di- or tri- are used to indicate the number of alkyl groups attached to the nitrogen atom.